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Experimental investigation of the fractionation behavior of Cu isotopes during the replacement of pyrite by Cu-bearing sulfides (chalcopyrite, bornite, and chalcocite) was conducted under hydrothermal conditions. At the initial stages of the replacement reaction, small mounds of product formed on the pyrite surface; these mounds then grew and coalesced, progressively covering the pyrite grains as the reaction proceeded. Chalcopyrite, bornite, and chalcocite formed sequential monomineralic zones from the pyrite reaction front towards the solution. During the early stage of the reaction, Cu isotope fractionation between the solids and the aqueous solution (Δ65Cu solid-aqueous , Δ65Cu solid-aqueous = δ65Cu solid – δ65Cu aqueous) was approximately –0.6 ‰, similar to the calculated equilibrium Cu isotope fractionation factors between Cu-bearing sulfides (chalcopyrite, bornite, and chalcocite) and CuCl 2 –. However, the Δ65Cu solid-aqueous moved progressively further from equilibrium with prolonged reaction time, with fractionation factors ranging from approximately –0.6 ‰ to –1.2 ‰. We found that significant fractionation of Cu isotopes between the solid products and aqueous solution was mainly controlled by the amount of chalcopyrite that formed in the product layers. We interpret that the Δ65Cu solid-aqueous was controlled by the diffusion of aqueous Cu(I) species among the product layers and the changes in Cu redox state during the precipitation of chalcopyrite. These results imply that the δ65Cu values measured in sulfides from low-temperature hydrothermal deposits may be controlled by the local chemistry of the fluids in product layers that precipitate sulfides. This study highlights the importance of local fluid characteristics, such as redox conditions, metal speciation, and diffusion, in controlling isotope fractionation pathways during non-equilibrium mineral replacement. [ABSTRACT FROM AUTHOR]

The alkaline hydrogen evolution reaction is a promising solution to meet future energy demand due to the sustainable production of hydrogen via water electrolysis. The development of copper nickel sulfide (CuNiS) electrocatalysts for hydrogen evolution reaction (HER) relies on robust active sites without degradation. However, the performance of CuNiS depends on the nature of sulfur precursors and complexing agents since the copper and sulfur oxidation states determine the adsorption and release of H 2. The CuNiS synthesized with thioacetamide and 3-mercaptopropionic acid as sulfur source and complexing agent, respectively, at 100°C for 10h delivered a lower overpotential of −96 mV to achieve a current density of −10 mA cm−2 in 1 M KOH electrolyte. The positive and negative shifts in binding energy peaks of Ni and S, respectively, caused charge redistribution and charge transfer between metals and S. The transfer of electrons from Ni to Cu atoms decreases the hydrogen binding energy and accelerates the H ad desorption process, which leads to the subsequent formation of H 2. Moreover, the negative shift in S improves the electron occupation, which helps with proton adsorption and the release of H 2. [Display omitted] • Pyrite CuNiS grown on nickel foam (NF) by chemical bath deposition (CBD) method. • CuNiS with thioacetamide and 3-mercaptopropionic acid has high catalytic activity. • For HER, CuNiS/NF electrode requires only 96 mV overpotential to reach 10 mA cm−2. • Tafel slope was evaluated from the steady state chronoamperometry (CA) technique. • CuNiS/NF-100oC-10h catalyst shows excellent HER stability at 100 mA cm−2 in 1 M KOH. [ABSTRACT FROM AUTHOR]

• POCA has initially proven to be effective in separating chalcopyrite from galena. • The stronger interaction of POCA with Pb sites on the galena surface than Cu sites on the chalcopyrite surface. • The adsorption of SBX on the galena surface was hindered following treatment with POCA. The research proposes an innovative galena depressant, known as Phosphonyl carboxylic acid copolymer (POCA), to enhance the efficiency of flotation separation between chalcopyrite and galena. Mineral flotation tests were conducted to investigate the flotation performance of chalcopyrite and galena. The inhibition mechanism of POCA on galena was studied using multiple characterization techniques including Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) testing, Zeta potential testing, X-ray photoelectron spectroscopy (XPS) analysis, atomic force microscopy (AFM) testing, contact angle testing, time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, and density functional theory (DFT) calculations. In the flotation test, at a concentration of 10 mg/L sodium butyl xanthate (SBX) and pH 9, adding 50 mg/L POCA can reduce the flotation recovery of galena from 83.50 % to below 5 %, whereas the recovery of chalcopyrite was almost influenced. The testing conducted via ICP-OES revealed that POCA promotes the dissolution of Pb2+ from the galena surface. The adsorption of POCA on the galena surface was confirmed through zeta potential testing, XPS testing, contact angle, AFM testing, and ToF-SIMS analysis, it was noted that POCA exhibited high levels of adsorption on the galena surface. Density Functional Theory (DFT) calculations suggest that the chemical interaction between the sulfonic acid present in POCA and the Pb2+ active site of galena is regarded as the primary inhibition mechanism. [ABSTRACT FROM AUTHOR]

• Temperature-controlled sulfuric acid pre-oxidation enhances the separation of galena and chalcopyrite. • Sulfuric acid recycling reduces acid consumption and environmental impacts. • Increased pre-oxidation temperature decreases galena floatability. • Explain the relationship between the independent variable temperature and thermodynamic and electrochemical processes. Galena and chalcopyrite pose challenges in their separation owing to their similar surface chemistry. The flotation separation of galena and chalcopyrite significantly depends on the use of depressants. However, conventional depressants are often associated with several drawbacks, such as toxicity and inefficiency. Hence, exploring efficient and environmentally friendly techniques to separate galena and chalcopyrite is vital. This study investigated the use of sulfuric acid as a surface oxidant for the pre-oxidation treatment of galena and chalcopyrite at high temperatures. This approach facilitated acid recycling and eliminated the need for multiple flotation chemicals. The floatability of galena and chalcopyrite was investigated through micro-flotation. The results revealed that at a pre-oxidation temperature of 100℃, galena exhibited a recovery rate of only 9.98 %, while chalcopyrite maintained a recovery rate of 96 % across the temperature range. The selective depressant mechanism of sulfuric acid in the flotation separation of galena and chalcopyrite was investigated through scanning electron microscopy, zeta potential measurements, X-ray photoelectron spectroscopy, thermodynamic calculations, and electrochemical analyses. The results indicated that the high temperature facilitated the dissolution of the sulfide layer on the galena surface. Consequently, S2− ions underwent oxidization into SO 4 2− to form a stable oxide film on the galena surface through interaction with Pb2+. Conversely, the high-temperature pre-oxidation had a minimal effect on the surface of chalcopyrite, indicating selective oxidation benefits. Findings from the pre-oxidation floatation separation test of galena–chalcopyrite mixtures revealed the efficient and thorough separation of the two minerals under high-temperature pre-oxidation conditions. The lead concentrate obtained from the floatation process exhibited a Pb grade of 79.38 % and a recovery rate of 97.17 %, while the Cu concentrate featured a Cu grade of 32.14 % and a recovery rate of 97.06 %. Additionally, the sulfuric acid solution was recycled. Overall, this study provides a sustainable and cost-effective approach for the green separation of copper–lead sulfide ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • PMA was used as an eco-friendly Pb-affinity depressant in copper-lead sulfide minerals flotation separation. • PMA selectively attenuated the floatability of galena in a weakly alkalized pulp. • Adsorption density of PMA on galena was greater than that on chalcopyrite. • PMA significantly weakened the adsorptive activity of SBX on galena. Utilization of novel and highly efficient organic depressants in separation of various minerals in flotation is always a research hotspot. Herein, polymaleic acid (PMA) was utilized as an eco-friendly depressant with high affinity for lead to effectively separate chalcopyrite from galena via the flotation method. Flotation trials showed that PMA, added at low dosages, could considerably depress galena, while chalcopyrite was minimally affected, thereby achieving the separation of both minerals. Adsorption tests indicated that PMA strongly and selectively adsorbed on galena than on chalcopyrite, which significantly reduced the reactive activity of xanthate on galena. These findings were supported by contact angle measurements. Surface properties investigations also corroborated the stronger adsorption of PMA observed on galena. Molecular dynamic simulations suggested that the introduction of PMA into an aqueous system resulted in the accumulation of water molecules on galena. Simultaneously, the adsorption strength of PMA on galena increased during the interaction process between PMA and galena. These effects altered the surface characteristics of galena and increased its surface hydrophilicity. The present work provides mechanistic insights into the separation of metallic sulfide minerals in the presence of organic acid via the flotation method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pb was well selectively leached with Fe(MS) 3 -MSA solution. • Fe(MS) 3 -MSA solution could be regenerated for next time leaching. • The galvanic effect mechanism of selective leaching was proposed. • Cu was more effectively extracted from the obtained residues. The selective leaching of lead from complex polymetallic sulfide secondary concentrate (CPSSC) with the solution mixed by ferric methanesulfonate and methanesulfonic acid (Fe(MS) 3 -MSA) was investigated by leaching experiments, analysis of solids, and electrochemical characterizations. The leaching results showed that stirring rate, liquid–solid ratio, temperature, and ferric concentration greatly influenced Pb extraction rate. At the optimum leaching conditions, 93.1 % Pb, while 3.8 % Cu and 18.8 % Fe were extracted. The selective leaching mechanism was related to the activity of PbS in Fe(MS) 3 -MSA solution and the galvanic effect between sulfides. XRD and SEM-EDS results of leaching residues verified the selective decreases in PbS, and retainment of most Cu, Fe, and Zn. Electrochemical characterizations demonstrated a more stable and higher open-circuit potential, and an increase/decrease in A 0 peak potential/current in LSV curve for the residue's electrode, suggesting the selective decreases in active components (e.g. PbS). After selective leaching, Cu could be easily extracted from residues by pressurized water leaching, and Fe(MS) 3 -MSA solution could be regenerated for recycling used in leaching. These results indicate the great potential of Fe(MS) 3 -MSA solution to selectively leach and separate Pb from CPSSC, and unveil a method to effectively treat refractory CPSSC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calcium lignosulfonate depressed molybdenite with little effect on chalcopyrite. • The chelation/complexation between oxygen-contained groups in lignosulfonate and metal sites of chalcopyrite occurred. • The physical adsorption between molybdenite and calcium lignosulfonate occurred. • KEX competitively adsorbed much more on chalcopyrite than on molybdenite. This study investigated the potential mechanisms by which lignosulfonate selectively depresses the flotation of fine molybdenite during Cu–Mo flotation separation using ethyl potassium xanthate as a collector. The flotation tests confirmed that molybdenite was significantly depressed by calcium lignosulfonate, whereas chalcopyrite flotation was only slightly affected. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to explore the distinct interaction of lignosulfonates with the mineral surfaces: chelation/complexation occurred between the deprotonated oxygen-contained groups in calcium lignosulfonate with the exposed metal sites on the surface of chalcopyrite, whereas the hydrophobic interaction between calcium lignosulfonate and molybdenite was the main driving force of adsorption. Additionally, the adsorption experiments suggested that the calcium lignosulfonate previously adsorbed on chalcopyrite could be removed by treatment with ethyl potassium xanthate while there was a relatively small effect on the calcium lignosulfonate previously adsorbed on the surface of molybdenite. Therefore, depressing molybdenite and floating chalcopyrite achieved by using calcium lignosulfonate as the depressant and ethyl potassium xanthate as the collector. [ABSTRACT FROM AUTHOR]

[Display omitted] • The combined depressants containing Ca(ClO) 2 and polysaccharide OCMC selectively depressed the pyrite. • The combined depressants facilitated the selective flotation separation of CuFeS 2 -FeS 2 at pH=8. • Interaction mechanism between the combined depressant and mineral surfaces was well illustrated. • Ca(ClO) 2 combined with OCMC exhibited synergy effects on the selective depression of pyrite. Flotation separation of copper-sulfur at low alkalinity has attracted soaring interest in the beneficiation of copper sulfide ore. In this work, application of calcium hypochlorite (Ca(ClO) 2) and carboxymethyl chitosan (OCMC) as combined depressants for selective flotation separation of chalcopyrite from pyrite was investigated. A maximum recovery difference of 71.35 % between both minerals is observed under the recommended conditions ([Ca(ClO) 2 ] = 60 mg/L, [OCMC] = 400 mg/L and 40 mg/L SBX at pH=8). Besides, the copper-sulfur flotation separation indexes were assessed by the artificial mixed-mineral tests. Results of contact angle measurement, zeta potential and adsorption amount analysis reveal that the combined depressants severely impede the collector adsorption onto pyrite surfaces, and has a light effect on the chalcopyrite. OCMC exhibits a stronger complexing ability on Ca2+ and Fe2+ ions than Cu2+ ions. XPS results confirm that the combined depressant interact with pyrite surfaces intensively, and prompt a deep conversion of S 2 2- and S n 2-/S0 into S2- and SO 4 2- species, as well as a deep transformation of Fe(II)-S into Fe(III)-O/OH on the pyrite surface. ToF-SIMS and thermodynamic calculation results afford the favorable evidence for the selective suppression of the pyrite with added the combined depressant. Thereby the selective oxidation and intense complexation on the pyrite stemming from the combined depressant synergy are responsible for the selective separation of chalcopyrite from pyrite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recovery of chalcopyrite of 84.7 % was at pH 9.4 in presence of Mg. • Xanthomonas campestris is potential pyrite depressants. • Adsorption of both anionic polysaccharides decreased with increase in pH. • Zeta potential of chalcopyrite decreased in presence of polysaccharides. • Molecular potential of Mg species is more than that of Ca species. The surface chemistry of chalcopyrite (Cpy) and pyrite (Py) in presence of water containing with Mg and Ca was studied using gum acacia (GA), xanthomonas campestris (XC) and guar gum (GG) as depressants. The adsorption density of XC and GA beyond IEP of Cpy and Py in absence of metal ions was nil, whereas that of GG increased with increase in pH till at pH 9.4. However, in presence of Mg and Ca, the adsorption of XC was higher than that of GA and that of GG was higher onto mineral-metal than onto mineral. Further, the adsorption of XC, GA and GG onto mineral-Mg was more than that onto mineral-Ca and this was due to higher maximum molecular electrostatic potential (MESP) of Mg species (413.3 kcal/mol) relative to Ca species (253 kcal/mol). Additionally, the polysaccharides' adsorption onto Py-Ca and Py-Mg was higher than onto Cpy-Mg and Cpy-Ca. On Cpy and Py with metal ions, the adsorption of XC and GA decreased with increase in pH attesting to polysaccharides anionicity. Theoretical analysis of complexes formed on Py and Cpy surfaces containing Mg and Ca, and polysaccharides was due to conventional hydrogen bonding, non-covalent and partially covalent bonding. Flotation of synthetic mixture of Py and Cpy (1:1) in presence of Mg at pH 9.5 performed better than other systems yielding Cu grade and recovery of 31.1 % and 85.6 % after 80 g/t of XC. Therefore, XC is a potential Py depressant in presence of Ca and Mg species. [ABSTRACT FROM AUTHOR]

• Increased ionic strength by NaCl enhanced xanthate oxidation and adsorption on chalcopyrite. • More hydrophobic xanthate compounds formed on chalcopyrite in NaCl solutions. • True chalcopyrite flotation could be improved by NaCl at low xanthate concentrations. • Strong froth destabiliation occurred at high concentrations of both xanthate and NaCl. • Froth destabiliation led to low water recovery and low true flotation recovery of chalcopyrite. Due to freshwater scarcity, mineral flotation plants have been using alternative water resources including seawater together with water recycling, resulting in the accumulation of salts in process water. However, how salts affect the adsorption of xanthates on the surfaces of sulphide minerals and subsequent sulphide mineral flotation is unclear. To address the knowledge gap, this study investigated how NaCl affected the adsorption of potassium amyl xanthate (PAX) on chalcopyrite surface and chalcopyrite flotation. Cyclic voltammetry (CV) tests identified that NaCl increased the oxidation of PAX and its adsorption on chalcopyrite surface due to elevated ionic strength and electrical conductivity of water, facilitating charge transfer among PAX, chalcopyrite surface and oxygen. NaCl also increased chalcopyrite surface oxidation to produce more CuS, facilitating the formation of copper-xanthate complexes. Flotation tests identified that the increased adsorption of PAX by NaCl was only translated into improved true flotation of chalcopyrite at a low PAX concentration such as 50 ppm in NaCl solutions with low and medium concentrations (0.1 and 0.7 M, respectively). At a high PAX concentration such as 150 ppm, the coexistence of high concentrations of PAX and NaCl led to strong froth destabilisation, resulting in a dramatic reduction in water recovery and true flotation recovery of chalcopyrite. The findings from this study will be able to guide the flotation plants to maximise mineral flotation by choosing collector dosage based on the ionic strength of process water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three novel dithiocarbamates HPD-2, HPD-3 and HED-2 were synthesized and used to float chalcopyrite. • HPD-3 had superior flotation ability for chalcopyrite than HED-2 and HPD-2. • HED-2 possessed a higher chemical reactivity owing to the C O C group. • HED-2 chemisorbed on chalcopyrite surface by the formation of C O Cu and C S Cu structures. Three novel dithiocarbamate surfactants including 2-hydroxypropyl diethyldithiocarbamate (HPD-2), 3-hydroxypropyl diethyldithiocarbamate (HPD-3), and 2-(2-hydroxyethoxy)ethyl diethyldithiocarbamate (HED-2) were prepared and characterized by FTIR, 1H/13C NMR and HRMS. They were first employed as collectors to float chalcopyrite. DFT calculations were performed to anticipate the structure–reactivity of the novel dithiocarbamates, revealing that the reaction sites were primarily distributed in C S and OH groups. Compared with HPD-2 and HPD-3, HED-2 possessed a higher chemical reactivity owing to the C-O-C group. Microflotation results indicated that the collecting ability of the three dithiocarbamate collectors towards chalcopyrite followed as HPD-3 > HED-2 > HPD-2. FTIR and XPS demonstrated that HED-2 chemisorbed onto the surface of chalcopyrite through newly generated Cu S and Cu O bonds. [ABSTRACT FROM AUTHOR]

It is difficult to realize an effective separating of chalcopyrite and pyrite without using any depressants due to their similar physicochemical properties. Herein, a cyclic oligosaccharide carboxymethyl-β-cyclodextrin (CMCD) with carboxyl and hydroxyl groups was introduced for the first time as a novel environmentally friendly depressant for separating chalcopyrite from pyrite. The depression performance and adsorption mechanism of CMCD in the flotation separation of chalcopyrite and pyrite were investigated through micro-flotation experiments, molecular dynamics (MD) simulations, and a series of characterization tests. The flotation findings manifested that under weakly acidic conditions (pH=6.5±0.2), a high-quality copper concentrate with a copper recovery of 73.15 % and a grade of 28.06 % was obtained. CMCD exhibited superior inhibition of pyrite compared with other traditional inhibitors. The adsorption density of CMCD onto the pyrite surface was significantly higher than that of chalcopyrite, and the pre-treatment with CMCD hindered the attachment of sodium butyl xanthate (SBX) on pyrite but had a minor effect on chalcopyrite, as confirmed by contact angle, adsorption amount, and Atomic Force Microscope analyses. Moreover, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses robustly demonstrated that the carboxyl and hydroxyl groups in the CMCD molecule primarily reacted with the metal hydroxides on the pyrite surface through hydrogen bonding, leading to a more hydrophilic surface. MD simulations further confirmed at the molecular level that the affinity of CMCD for the pyrite surface was much greater than for chalcopyrite. In summary, CMCD shows promising potential as a depressant for separating chalcopyrite from pyrite. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • SDD selectively improves chalcopyrite hydrophobicity to achieve copper and arsenic separation. • The feedback π and positive σ bonds between SDD and arsenopyrite are weak. • SDD is stronger than BX and Z-200 regarding selective collection ability. • SDD breaking the CaOH+ adsorption barrier on the chalcopyrite surface. • The CaOH+ expands the selective collection capability of SDD. The efficient separation of chalcopyrite and arsenopyrite is significant for preventing and controlling arsenic pollution. Herein, sodium diisobutyl dithiophosphate (SDD) selectively improves chalcopyrite hydrophobicity to achieve copper and arsenic separation in low alkali. The flotation test results show that SDD is stronger than butyl xanthate and ethyl thiocarbamate regarding selective collection ability. SDD accurately separates chalcopyrite and arsenopyrite under low alkali conditions. Frontier orbit analysis shows that the feedback π and positive σ bonds between SDD and arsenopyrite surface are the weakest among the three collectors. Surface wettability, adsorption capacity, FTIR, XPS, and adsorption simulation calculations reveal more detailed collecting mechanisms. Analysis shows that SDD can selectively improve the hydrophobicity of the chalcopyrite surface. The above results were attributed to SDD breaking the CaOH+ adsorption barrier on the chalcopyrite surface. On the contrary, the interaction between SDD and arsenopyrite is weak, resulting in SDD being unable to break through the cover of CaOH+ on the surface of arsenopyrite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four generations of pyrite and three types of chalcopyrite were identified at Shuanglong. • Core-to-rim elemental and sulfur isotope changes in Py1 and Py2 show increasing temperature and oxygen fugacity. • Isotopic evolution from Py3 to Py4 and chalcopyrite indicates mixing of magmatic and non-magmatic sulfur during copper mineralization. Geochemistry of sulfides is widely used to constrain sources and ore-forming processes of various mineral deposits. However, its application on Fe–oxide Cu–Au (IOCG) deposits is not well constrained due to multiphase pyrite and Cu minerals and their complex inheritance relationships. The Shuanglong deposit is an IOCG-like deposit in the Eastern Tianshan characterized by abundant Py1 and Py2 in the Fe mineralization stage (II) and Py3 and Py4 in the Cu mineralization stage (III). Chalcopyrite is divided into three types where Ccp1 is formed by replacing Py1 and Py2, Ccp2 coexists with Py4, and higher grade Ccp3 is in quartz–hematite–chalcopyrite veins without pyrite. Py1 and Py2 are associated with multiphase magnetite in stage II Fe mineralization, whereas Py3 coexists with the early epidote replaced by the late calcite–hematite–Py4–Ccp2 assemblage in stage III Cu mineralization. The increasing Co contents and Co/Ni ratios and decreasing δ34S values (∼8‰ to 4 ‰) from core to rim in Py1 and Py2 indicate temperature and oxygen fugacity increases during the input of magmatic-hydrothermal fluids. Decreasing Co/Ni, increasing Au, and δ34S fluid (from ∼ 6 ‰ to 30 ‰) from Py3 to Py4 show fluid mixing between the magmatic-hydrothermal fluid and oxidized non-magmatic sulfur such as seawater or basinal brine sulfate during the stage III Cu mineralization. Ccp1 inherited its sulfur and certain trace elements such as Pb and Zn from pyrite, whereas the addition of external sulfur contributed to local high-grade Cu mineralization. Such external sulfur may be from the seawater or basinal brine sulfate, with an increasing contribution during precipitation of Ccp2 and Ccp3 shown by fluid δ34S values (from 26 ‰ to 36 ‰). Combined with the decreasing Cd/Zn ratios from Ccp1 to Ccp3 caused by increasing total sulfur in fluids, this suggests that the sulfate sulfur contribution may have played a significant role in the high-grade Cu mineralization in IOCG deposits. This study also highlights the importance of the detailed texture of pyrite using acid etching, coupled with in-situ sulfur isotope and trace elements of pyrite and chalcopyrite for IOCG deposit research. [ABSTRACT FROM AUTHOR]

• The S 2 O 8 2−/Fe2+ system selectively depressed PbS in the PbS-CuFeS 2 mixture. • The S 2 O 8 2−/Fe2+ process decreased the hydrophobicity of the PbS surface. • The S2− on the PbS surface was oxidized to SO 4 2− by the S 2 O 8 2−/Fe2+ system. • The SO 4 − radicals are the primary oxidants in the S 2 O 8 2−/Fe2+ system. • The S 2 O 8 2−/Fe2+ process could not efficiently oxidize the CuFeS 2 surface. The separation of galena (PbS) from chalcopyrite (CuFeS 2) requires strong oxidants for the depression of PbS, due to the excellent hydrophobicity of PbS. In this work, an advanced oxidation process, i.e., S 2 O 8 2−/Fe2+ treatment, was employed to selectively depress PbS. The parameters of the S 2 O 8 2−/Fe2+ process were determined via flotation tests as follows: pH 3, 1:1 S 2 O 8 2−: Fe2+ molar ratio, and 10 min reaction time. The S 2 O 8 2−/Fe2+ treatment selectivity decreased the hydrophobicity of the PbS surface. UV–vis spectroscopy results revealed that SO 4 − (major species) and OH radicals were produced in solution by the activation of Fe2+. The SO 4 −/OH radicals reacted with the PbS surface, generating the SO 4 2− and PbSO 4 species. These species coated the PbS surface, forming a hydrophilic PbS surface and inhibiting the PbS flotation. By contrast, the S 2 O 8 2−/Fe2+ treatment generated only a minimal amount of SO 4 2− (5.98 % of the total S species) on the CuFeS 2 surface. Therefore, the CuFeS 2 surface was hydrophobic and CuFeS 2 particles could still be floated into the foam phase. This study provides a promising method for the selective depression of PbS in the PbS-CuFeS 2 mixture. [ABSTRACT FROM AUTHOR]

• MCA along with Fe and Fe 2 O 3 addition enhance the leachability and leaching rate. • The MCA with Fe promotes leachability and leaching rate more than MCA with Fe 2 O 3. • The leaching mechanism changed to chemical control due to MCA with Fe. • Except for microstrain, all microstructural changes always are effective. The influence of mechanical activation (MA) and mechanochemical activation (MCA) with Fe and Fe 2 O 3 on the microstructural changes, leachability and leaching rate of natural chalcopyrite was investigated and compared. MCA pretreatments were carried out by chalcopyrite co-milling with Fe and Fe 2 O 3 for 20 and 50 min. The XRD analysis indicated that even after 50 min MA and MCA, constituent phases of chalcopyrite, Fe and Fe 2 O 3 could be detectable beside the newly formed bornite. Regarding the peak broadening and peak intensity reduction, MCA generally intensified the microstructural changes of chalcopyrite in comparison with MA. The microstructural study performed by the Rietveld method also proved that all microstructural parameters changed in favor of reactivity, such that the amorphization degree and microstrain were increased to 96 % and 0.164 (%), respectively, while crystallite size was reduced to 14.6 nm after 50 min MCA of chalcopyrite with Fe 2 O 3. It could be concluded from the leaching tests that MCA along with Fe and Fe 2 O 3 addition could promote the leachability and leaching rate of chalcopyrite, as compared to MA and nonactivated chalcopyrite. Although both the MCA of chalcopyrite with Fe and Fe 2 O 3 could enhance copper extractions in the 1 M sulfuric acid leaching tests at 80 °C, Fe addition was slightly more effective than Fe 2 O 3. The results obtained from the kinetic study also revealed that the leaching mechanism of nonactivated chalcopyrite, mechanically activated chalcopyrite and mechanochemically activated chalcopyrite with Fe 2 O 3 changed from diffusion control to chemical control due to MCA with Fe. Finally, the combination of kinetic and microstructural studies proved that all microstructural parameters, except for the microstrain parameters of chalcopyrite MCA with Fe 2 O 3, could be effective in chalcopyrite reactivity promotion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Al3+ (aq) leads to the formation of AlSO 4 + (aq) species and alunite at pH 1–3. • Al-sulphate phases lower the sulphate activity for jarosite and sideronatrite. • Al-rich phases formed in AlCl 3 -rich lixiviants are amorphous and porous. • The Fe-diffusion rate to Cu mineral surfaces is highest in AlCl 3 lixiviants. • The initial rate of Fe3+ (aq) -promoted copper release is fastest in AlCl 3 lixiviants. Copper (Cu) extraction from low-grade ores is limited by the formation of secondary minerals that can passivate the surfaces of Cu-sulphide minerals in these ores. Hence, a novel approach utilizing AlCl 3 as a lixiviant was developed to modify coupled dissolution-reprecipitation processes at the mineral interface. The formation of Al-rich phases instead of Fe-hydroxysulphates enhanced Cu extraction through combined ferric-iron and proton-promoted dissolution. AlCl 3 accelerated chalcopyrite and bornite dissolution by forming soluble intermediate Cu-phases (e.g., covellite) at consistently high Eh (550–650 mV) and acidity due to the Lewis acid property of AlCl 3. X-ray diffraction analysis revealed that Na-bearing jarosite [(K 0.61 Na 0.41) Fe 3 (SO 4) 2 (OH)] and sideronatrite [Na 2 Fe(SO 4) 2 (OH)(H 2 O)] formation in lixiviants without AlCl 3 decreased Fe3+ (aq) availability for Cu-sulphide minerals dissolution. In contrast, significant amounts of AlSO 4 + (aq) formed in the AlCl 3 -rich lixiviant at pH 1–3, which reduced the sulphate activity and decreased the saturation state of the Fe-hydroxysulphates. Further, AlCl 3 promoted the formation of amorphous, porous Al-rich phases, facilitating quick Fe diffusion through the passivating layer and improving Cu recovery compared to lixiviants containing CaCl 2 , NaCl, or acid-only. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pullulan polysaccharide (PP) was used as sphalerite depressant for Cu–Zn separation. • PP can be chemisorbed onto the Zn sites on sphalerite surfaces via C−O−H groups. • PP effectively prevent the adsorption of the collector onto sphalerite surfaces. • The Fe sites on chalcopyrite surfaces can adsorb PP, but the Cu sites remain exposed. • PP cannot prevent the adsorption of the collector onto chalcopyrite surfaces. The remarkable differences in the metallurgical processes of copper and zinc require their host minerals to be separated as far as possible during beneficiation. For chalcopyrite and sphalerite, the primary host minerals of copper and zinc, their green and efficient separation in the beneficiation stage remains a great challenge. This work is the first to employ environmentally friendly pullulan polysaccharide (PP) as a sphalerite depressant to assist in the concentration of chalcopyrite. Flotation experiments have revealed that PP possesses a selective depression action on sphalerite without having a large influence on the recovery of chalcopyrite. Characterization analysis has revealed that PP can be adsorbed onto chalcopyrite and sphalerite surfaces, but with a different response to subsequent sorption collectors. PP adsorbs to the Zn atoms on sphalerite surfaces via its O atoms in the C−O−H group and thus prevents the adsorption of sodium butyl xanthate (BX). The Fe sites on the chalcopyrite surface can adsorb PP, but this process does not affect the BX adsorption as the Cu sites remain exposed. Hence, PP can enhance the hydrophilicity of sphalerite without interfering with the hydrophobicity of chalcopyrite, resulting in a desirable separation effect. Overall, this work offers a promising scheme for the concentration of chalcopyrite from sphalerite during beneficiation, thereby contributing to the efficient exploitation of copper and zinc resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carrageenan was utilized for the selective separation of chalcopyrite from pyrite. • Carrageenan showed selective depression towards pyrite as opposed to chalcopyrite. • Carrageenan bonds with Fe sites on pyrite through sulfuric acid and hydroxy groups. In this study, an eco-friendly compound, carrageenan, was employed as a depressant for the selective separation of chalcopyrite and pyrite. The depressant performance and mechanism were comprehensively investigated. The results of the flotation experiments demonstrated that carrageenan exhibited selective depression towards pyrite as opposed to chalcopyrite, achieving flotation recoveries of 88.57 % for chalcopyrite and 9.57 % for pyrite with the combination of 2 × 10-5 mol/L SIBX and 20 mg/L carrageenan. The results of AFM and contact angle measurements revealed that carrageenan exhibited selective adsorption on pyrite surface, resulting in an enhancement in surface hydrophilicity. In contrast, the adsorption of carrageenan on chalcopyrite surface was found to be negligible. Zeta potential and XPS analyses further confirmed the chemisorption of carrageenan on the pyrite surface, indicating the reaction involving sulfuric acid and hydroxyl groups on carrageenan and Fe sites on pyrite. Therefore, carrageenan holds potential as a promising depressant for the selective separation of chalcopyrite from pyrite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of the effect of PA addition chalcopyrite and molybdenite surfaces. • The Cu OH and Fe OH species that facilitate the separation of chalcopyrite and molybdenite after treatment with PA. • Recoveries of chalcopyrite and molybdenite differ after PA addition. • Strong and weak adsorption of PA on CuFeS 2 and MoS 2 surfaces, respectively. Chalcopyrite and molybdenite are the primary minerals from which copper and molybdenum are extracted. However, the separation of chalcopyrite and molybdenite is restricted because of their inherent floatability. This study explores the separation effects of the addition of a green depressant, pyrogallic acid (PA), on chalcopyrite and molybdenite. The feasibility of flotation separation was verified by flotations tests with chalcopyrite and molybdenite under weak acid conditions at pH 6. The zeta potential and total organic carbon (TOC) illustrated that PA could have strong chemical adsorption on the surface of chalcopyrite and weak adsorption on the surface of molybdenite. Fourier-transform infrared (FTIR) spectroscopy illustrated that PA had a strong redox reaction at the surface of chalcopyrite. X-ray photoelectron spectroscopy (XPS) results illustrated that the reaction occurred through the generation of Cu/Fe-OH complexes covered on the chalcopyrite surface to reduce the active adsorption sites, which led to a decrease in the collection capacity for chalcopyrite. Moreover, time-of-flight secondary ion mass spectrometry (ToF-SIMS) results showed that the Cu and Fe sites on the surface of chalcopyrite were oxidized by PA. The intensities of FeOH− and CuOH− were found to be enhanced in the fragmentation peaks. Accordingly, a new selective adsorption model of PA on chalcopyrite and molybdenite was proposed. [ABSTRACT FROM AUTHOR]

• TA can realize the selective separation of chalcopyrite and talc. • TA adsorption on the talc surface is stronger than that on the chalcopyrite surface. • TA and SBX create various shaped adsorbates on the surfaces of chalcopyrite and talc. • Compared to TA, SBX adsorption on the chalcopyrite surface exhibits more selectivity. A key strategy for achieving the selective separation of talc and chalcopyrite is the development of chemical depressants with high solubility and strong selectivity. Tannic acid (TA), a polyphenol found in green plants and has good solubility, contains abundant phenolic hydroxyl groups. Moreover, the adsorption mechanism of TA with chalcopyrite and talc was examined after TA was chosen as the separation depressant for chalcopyrite and talc. Single-mineral flotation test results found that at optimal pH and TA and sodium butyl xanthate (SBX) dosages, the flotation recoveries of talc and chalcopyrite were 9% and 92.17%, respectively, and the difference in recovery between them was 83.17%. Results from real ores and artificially mixed minerals tests also confirmed that TA can achieve selective separation of chalcopyrite and talc. Since chalcopyrite has distinct electrochemical properties, the results of atomic force microscope and electrochemical tests demonstrated that there are significant differences in the adsorption behavior of TA on the surface of chalcopyrite and talc. And the adsorption selectivity of SBX on the chalcopyrite surface is better than that of TA on the chalcopyrite surface, which is an important reason for the selective separation of chalcopyrite and talc. [ABSTRACT FROM AUTHOR]

In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. A previous paper presented the results of a largely electrochemical study of the behaviour of NBS during cyanidation of gold. The results confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action. This paper explores the corresponding oxidation of sulfide minerals, that inevitably are contained in gold concentrates, by either dissolved oxygen or NBS. Using electrochemical techniques it was found that dissolved oxygen is effective in the oxidation of several sulfide minerals at pH values between 9 and 11. The effect of cyanide on both the anodic and cathodic processes has been studied. NBS has been found to be ineffective as an oxidant for all minerals tested except galena, even in the presence of cyanide. • Effect of oxygen and NBS on mineral mixed potential good indicator of the rate of mineral oxidation. • Cathodic reduction of NBS occurs at potentials too negative to oxidise the sulfide minerals. • Relative rates of oxidation of minerals by dissolved oxygen in absence and presence of cyanide. • The presence of cyanide results in reduced rates of oxidation of most minerals except chalcopyrite and galena. [ABSTRACT FROM AUTHOR]

• A predicting model based on Fluid Dynamics Coupling with Flotation Kinetics Models was built. • The optimal combination of flotation kinetics models for the prediction of flotation rate constant is obtained. • The predicted flotation rate constant is only 8.44% different from the experiment. CFD (computational fluid dynamics) simulation plays an important role in flotation prediction research and application. The flotation process of chalcopyrite in a three-dimensional mineralized tube was simulated coupled with flotation kinetic model. Regarding kinetic prediction model in the flotation process is explored at gas flow rate of 0.06 m3/h, slurry flow rate of 0.4 and 0.5 m3/h, including collision probability model, attachment probability model, detachment probability model and bubble slip velocity model. Flotation experiments of chalcopyrite is performed, and the simulation of flotation process is realized by adding UDF (user-defined function). Furthermore, the flotation rate constant is taken to verify the validity of the model. The prediction error of flotation rate constant is 19 % and 17 % between flotation experiments and simulations at slurry flow rate of 0.4 and 0.5 m3/h, respectively. According to the combinations of flotation kinetic model, it's found that the prediction results of Yoon-Luttrell collision probability model, Yoon-Luttrell attachment probability model, Schulze detachment probability model and Kostoglou bubble slip velocity model are superior to other combinations. the prediction error of flotation rate constant is 8 % at the slurry flow rate of 0.4 m3/h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chalcopyrite was separated effectively from pyrite by Ca(ClO) 2 oxidated in AMD system. • Ca(ClO) 2 reduced pyrite surface hydrophobicity and had little effect on chalcopyrite. • Pyrite treated by AMD and Ca(ClO) 2 formed numerous hydrophilic species on the surface. • Characterization tests confirmed the presence of CaOH+, Fe(Ⅲ)–OOH, Fe 2 (SO 4) 3 species. Efficient and clean flotation separation of copper-sulfur has attracted soaring interest in the beneficiation of sulfide ore. The objective of this work was to examine the influence of calcium hypochlorite (Ca(ClO) 2) oxidative modification on the flotation separation of chalcopyrite from pyrite in acid mine drainage (AMD) system. A maximum recovery difference of 69.70 % between both minerals was observed under the recommended conditions (initial pH = 8.5 ± 0.2, [Ca(ClO) 2 ] = 100 mg/L, [EX] = 32 mg/L, and the volume ratio of AMD to pure water = 1:1). A high-grade concentrate with 77.35 % Cu recovery and 29.01 % Cu grade was obtained, demonstrated by mixed-mineral micro-flotation experiments. Analysis of Cu and Fe ions influence indicated that low concentrations of Fe3+ and Cu2+ favored the selective separation of pyrite and chalcopyrite. Moreover, analysis of the pulp ion concentrations showed that Ca(ClO) 2 promoted the dissolution of iron ions on the pyrite surface compared to chalcopyrite, thereby enhancing pyrite oxidation. The Ca(ClO) 2 interacted more intensively with the pyrite surface, forming a passivated layer that impeded the adsorption of collector, as demonstrated by Zeta potential and contact angle results. The generation of hydrophilic products caused by oxidation on the pyrite surface, such as CaSO 4 , CaOH+, Fe(Ⅲ)–OOH, and/or Fe 2 (SO 4) 3 was confirmed by XPS analysis, further reducing the floatability of pyrite. Furthermore, local electrochemical impedance spectroscopy and scanning electron microscopy analyses further afforded favorable evidence for selective inhibition of pyrite by Ca(ClO) 2 in the AMD system. This study provides a new approach to achieve cleaner separation of pyrite and chalcopyrite and offers new perspectives for AMD treatment solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The FBF system is capable of rejecting tailings with yield of 48% and Cu grade of 0.06%. • The FBF system improving Cu grade for 1.65 times for subsequent grinding and froth flotation. • The separation of coarse particles relies on the existence of a fluidized bed. • The fluidized bed facilitates the attachment of bubbles and particles during separation. Coarse particle separation is important in mineral processing. In this study, the performance of coarse chalcopyrite ore separation (−600 μm, Cu grade 0.375 %) by fluidized bed flotation (FBF) was investigated and the basic function of fluidized bed on the particle separation is discussed. The chalcopyrite grain size distribution mainly ranges from 50 to 300 μm, with over 80 % of the grains being liberated. The results indicate that the FBF system can reject tailings with a yield of 48 % and a Cu grade of 0.06 %. Additionally, concentrate Cu grade reaches 0.62 %, which is around 1.65 times higher than feed, resulting in a total Cu recovery of 91.55 %. The introduction of a fluidized bed increases Cu recovery of −600 + 300 μm from 50 % to73%, as it improves the possibility of bubble-particle attachment, but the variation of bed height has little influence. Particles with a size of −300 + 74 μm can obtain a 96 % Cu recovery in the bubbly flow, while particles with a size of −74 μm lose their separation effect due to hydraulic entrainment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The copper flotation mechanism in the presence of ultrafine bubbles was investigated. • Freshly generated bubbles had a size of 600 nm, increasing to 5 μm after 25 days. • MNBs enhanced chalcopyrite and ore recoveries by 24.5 % and 7 %, respectively. • MNBs improved SIPX collector adsorption and kinetics by 73.8 % and 69.44 %. • SIPX sorption on chalcopyrite was chemisorption and physicochemical with and without MNBs. The present study systematically explores the relationship between chalcopyrite mono-mineral and copper-bearing ore flotation in the presence and absence of micro- and nano-bubbles (MNBs). Ultrafine bubbles were generated through a cavitation mechanism, and their stability, size, and zeta potential were monitored over a period of 0–25 days. Micro-flotation and batch rougher kinetic flotation experiments were carried out with and without ultrafine bubbles using a modified Hallimond tube and 2.5 L Denver® flotation cell, respectively. The results showed that the presence of MNBs improved the recovery of chalcopyrite mono-mineral and its ore by 24.5 % and 7 %, respectively. Furthermore, the adsorption behavior of sodium isopropyl xanthate (SIPX) collector at various concentrations was analyzed in the presence and absence of stable MNBs using UV–visible spectroscopy, FTIR analysis and kinetic models. The adsorption studies supported the micro-flotation findings, demonstrating that the presence of MNBs not only boosted collector adsorption on the chalcopyrite surface (by an average of 73.8 %) but also improved the adsorption kinetics (by 69.44 %). The sorption kinetics followed the pseudo 2nd order model in the presence of MNBs, while in the absence of MNBs, both pseudo 1st order and pseudo 2nd order models were observed. The sorption of SIPX onto chalcopyrite was identified as a chemisorption process in the presence of MNBs, whereas it was a physicochemical sorption in the absence of MNBs. [ABSTRACT FROM AUTHOR]

• A novel collector MIBATC was synthesized and applied in the chalcopyrite flotation. • MIBATC effectively separated chalcopyrite from sphalerite and pyrite. • MIBATC chemisorbed on chalcopyrite, whereas physisorbed on sphalerite and pyrite. • MIBATC spontaneously reacted by S atom at Cu site on chalcopyrite surface. In this study, a novel collector, named O-methylisobutyl-N-allyl thionocarbamate (MIBATC) was synthesized and characterized by Fourier Transform Infrared Spectrometer (FTIR), 13C NMR, 1H NMR analysis. The flotation behavior of MIBATC was investigated by flotation experiments and interaction mechanism was conducted by adsorption amount, zeta potential, FTIR, X-ray photoelectron spectroscopy (XPS) measurements and density functional theory (DFT) calculation. Flotation results demonstrated that MIBATC appeared powerful collecting ability to chalcopyrite against sphalerite and pyrite. The recovery of chalcopyrite was more than 80 % with pH of 9.5–10 and MIBATC concentrate of 30–40 mg/L. Adsorption amount and zeta potential measurements showed a tendency that MIBATC exhibited more affinities for the chalcopyrite compared with sphalerite and pyrite. FTIR and XPS analysis provided the evidence that MIBATC chemisorbed on chalcopyrite surface of Cu site, whereas physisorbed on sphalerite and pyrite surface. Specially, DFT reconfirmed the fact that S atom in MIBATC donated electrons to Cu on chalcopyrite surface and the adsorption energy was −21.67 kcal/mol, regarding as an exothermic reaction. These findings provided evidence for superior separating chalcopyrite from sphalerite and pyrite in the presence of MIBATC. [ABSTRACT FROM AUTHOR]

• The HPMA showed impressive selectivity for depressed galena, resulting in an outstanding separation of Cu and Pb. • The adsorption of HPMA on chalcopyrite's surface is negligible and does not affect SBX adsorption. • The pre-adsorption of HPMA hinders the adsorption of SBX on galena, leading to the depression of galena. • The –COO- functional group within the HPMA molecule exhibits a strong affinity towards Pb atoms on the galena surface. • HPMA has the potential to be an effective, non-toxic alternative to traditional galena depressants. The similar flotation properties of chalcopyrite and galena present a significant challenge for achieving efficient and environmentally sustainable separation via flotation. The present study investigates the application of hydrolyzed polymaleic anhydride (HPMA) as a safe and effective galena depressant, aiming to effectively separate chalcopyrite from galena without any toxic effects. The flotation performance of chalcopyrite and galena was evaluated through flotation tests to determine the influence of HPMA in a sodium butyl xanthate (SBX) flotation system. Various characterization techniques were employed to examine the inhibitory mechanism of HPMA on galena, including zeta potential determination, contact angle measurements, x-ray photoelectron spectroscopy (XPS) analyses, and density functional theory (DFT) calculations. The flotation test results demonstrate that HPMA exhibits exceptional depression efficacy towards galena, while exerting minimal impact on chalcopyrite. The successful separation of chalcopyrite from galena was accomplished in artificial mixed ore flotation by employing HPMA as a depressant. The zeta potential and contact angle measurements demonstrated a pronounced augmentation in the adsorption affinity of HPMA towards the galena surface as opposed to chalcopyrite, consequently hindering subsequent collector attachment onto galena. Nevertheless, negligible influence of HPMA was noted regarding subsequent collector adsorption onto chalcopyrite. XPS and DFT analyses unveiled that HPMA can form a stable chemical bond with Pb atoms through its carboxylic acid group, thereby facilitating effective adsorption onto the galena surface. In conclusion, these findings suggest that HPMA exhibits promising potential for practical implementation in flotation separation processes involving Cu-Pb ore. [ABSTRACT FROM AUTHOR]

[Display omitted] • PA was introduced as a high-efficiency and environment-friendly galena depressant in chalcopyrite flotation. • PA exhibited stronger adsorptive capacity on galena than on chalcopyrite. • Surface properties of galena were markedly altered following exposure to PA. • Interaction between galena and SBX was attenuated with participation of PA. Novel eco-friendly organic depressants with high selectivity are attracting ever-growing interests. The selective inhibition effect of pyrogallic acid (PA) on galena in chalcopyrite flotation was investigated in this study. Flotation trials showed that PA markedly depressed galena with only a small effect on chalcopyrite, which contributed to the separation of chalcopyrite and galena by flotation after adding a low dosage of PA. Surface hydrophobicity tests suggested that PA strongly adsorbed on galena but not on chalcopyrite, which attenuated the adsorption activity of collector on galena, thus rendering galena highly hydrophilic. Conversely, chalcopyrite still retained favorable floatability. These findings were corroborated by the results obtained from infrared and surface adsorption measurements. Results of time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy measurements also validated the strong adsorption of PA on galena. This behavior promoted the generation of other hydrophilic species on galena. In addition, molecular dynamic simulations demonstrated that PA tended to adsorb on galena, and water molecules accumulated on galena following PA adsorption, which would decrease the floatability of galena. [ABSTRACT FROM AUTHOR]

[Display omitted] • In situ Cu isotope data show large fractionation between Sn-rich and Cu-rich ores. • Cu isotopes and modeling show water–rock interaction crucial in Sn-Cu mineralization. • Cu source of the Sn-Cu coexisting deposit may be the Cu-rich country rocks. This study presents high-resolution in situ Cu isotope data for chalcopyrite from the Jinkeng Sn-Cu deposit, Guangdong Province, China, with the aim of understanding how the Sn-Cu mineralization was formed. Results show that early chalcopyrite (quartz-cassiterite stage) has the lowest δ65Cu values (–0.01 to +0.02 ‰), similar to δ65Cu values (∼0‰) in most granites. In contrast, chalcopyrite from the subsequent cassiterite-sulfide stage exhibits the highest δ65Cu values (+0.90 to +0.97 ‰), comparable to those of the volcanic country rocks (+0.87 to +1.00 ‰). δ65Cu values in late chalcopyrite gradually decrease (from +0.79 to +0.45 ‰) across the latest ore-forming stages, from quartz-sulfide to quartz-calcite-sulfide mineral assemblages. Observed variation in δ65Cu is explained by water–rock interaction. Quantitative geochemical modeling also demonstrates that the Cu isotopic compositions of chalcopyrite record variable degrees of water/rock ratios during water–rock interactions. Therefore, our results suggest that water–rock interaction plays a critical role in providing Cu for Sn-Cu ore systems. The study further indicates that in situ Cu isotope analysis provides an accurate and efficient tool for diagnosis of magmatic-hydrothermal processes. [ABSTRACT FROM AUTHOR]

The separation of polymetallic sulfide ores by flotation is a difficult task in the mineral processing industry. In this investigation, a small-molecule organic compound, mercaptosuccinic acid (MSA), was used as a new depressant for inhibiting galena in chalcopyrite flotation. Micro-flotation and surface wettability tests indicated that MSA pronouncedly weakened the floatability of galena but not chalcopyrite, resulting in marked differences in their flotation recovery. Findings of Fourier transform infra-red (FT-IR) spectroscopy measurements and reagent adsorption trials showed that MSA was strongly adsorbed on galena, resulting in the inability of the collector to effectively interact with galena. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses further corroborated that MSA showed a greater affinity for galena than chalcopyrite, this behavior markedly altered the superficial chemical environment of galena. Molecular dynamic simulations (MDS) showed that MSA increased the concentrations of H 2 O molecules on galena, which enhanced the surface hydrophilicity of galena. [Display omitted] • MSA was used as a new organic depressant to inhibit galena in chalcopyrite flotation. • MSA markedly degraded the floatability of galena under alkaline conditions. • MSA had a greater adsorption affinity to galena than to chalcopyrite. • MSA promoted the accumulations of H 2 O molecules on galena surface. • Amounts of SBX adsorbed on MSA-treated galena significantly reduced. [ABSTRACT FROM AUTHOR]

Numerous investigations into the northern Mid-Atlantic Ridge (the NMAR), a typical slow-spreading mid-ocean ridge, have revealed that NMAR is favorable for the development of long-lived detachment faults and the formation of oceanic core complexes (OCCs). OCCs are often conducive to the development of ultramafic-hosted hydrothermal deposits with significant resource potential. However, as a counterpart of the NMAR on the Southern Hemisphere, the southern Mid-Atlantic Ridge (SMAR), also belonging to the class of slow-spreading ridges, has only received very limited investigation. This prompts the inquiry as to whether the SMAR, like the NMAR, can foster the development of OCC and associated hydrothermal deposit. To address this issue, we present the identification of an OCC (named as Kaifeng OCC) at the intersection of the SMAR and the Martin Vaz transform fault (∼23°S). This discovery is accompanied by evidence detailing a new detachment fault breakaway on an old detachment footwall. Collected samples reveal indications of hydrothermal activity, encompassing (1) residual sulfide containing chalcopyrite within honeycomb-like structures, (2) reddish-brown Fe oxides and atacamite, partially concretized by dolomite, and (3) a dark gray Mn-oxide crust. These mineralogical features indicate the presence of gossans, commonly iron oxide-dominated cover layers that envelope the outer surface of weathered seafloor sulfide deposits, which subsequently undergo modifications due to subsequent hydrothermal activities. Our work proves the existence of OCC and associated hydrothermal deposits at a ridge-transform intersection of the SMAR. • An OCC was discovered at the intersection of the Southern Mid-Atlantic Ridge and the transform fault around 23°S. • Gossan, resulting from the weathering of an early hydrothermal deposit, was identified on the OCC. • Mineralogical studies suggest that this gossan underwent alterations due to subsequent hydrothermal activity. [ABSTRACT FROM AUTHOR]

Bulk and nanoparticles of n -type CuFeS 2 Chalcopyrite have been synthesized using vacuum melting reaction and conventional hydrothermal method, respectively. The powder XRD pattern of both the samples has confirmed phase formation, and the crystallite size was calculated to be ∼30 nm for nano-CuFeS 2. FE-SEM micrographs illustrate the cuboid morphology of nano-CuFeS 2 with particles sizes in the range of 50–200 nm, and EDS analysis confirms the nominal composition. The elemental composition and electronic states of Cu1+, Fe3+, and S2− present in CuFeS 2 are further confirmed by XPS studies. The weak ferromagnetic nature of both bulk and nano-CuFeS 2 with magnetic saturation of ∼0.075 emu/g and ∼0.036 emu/g, respectively, has been observed from VSM measurements. The bulk n -type CuFeS 2 exhibits the Seebeck coefficient of −160 μV/K at room temperature, increasing to −187 μV/K for nano-CuFeS 2. Interestingly, a huge reduction in total thermal conductivity of ∼0.69 W/mK is observed in nano-CuFeS 2 compared to the bulk sample (∼4.18 W/mK) at room temperature, resulting in an overall enhanced thermoelectric figure of merit, zT of ∼0.28 at 623 K for nano-CuFeS 2. Mid-to-long wavelength phonon scattering from the increased grain boundaries and reduced grain sizes of nano-CuFeS 2 and their corresponding reduction in lattice thermal conductivity as a function of temperature. [Display omitted] • Bulk and nano CuFeS 2 samples have been successfully synthesized using vacuum melting and hydrothermal method, respectively. • The mean particle size of nano-CuFeS 2 was calculated to be ∼130 nm. • An increase in Seebeck co-efficient (S) of −305 μV/K at 623 K was observed for nano-CuFeS 2. • Ultra-low thermal conductivity of ∼0.69 W/mK at 623 K was observed for nano-CuFeS 2. • Overall, a maximum figure of merit (zT) of 0.28 at 623 K is achieved for nano-CuFeS 2. [ABSTRACT FROM AUTHOR]

Reactions among minerals occur via solid-state diffusion or fluid-induced, interface-coupled dissolution-reprecipitation (ICDR). Both mechanisms can coexist under conditions where the rates of both processes are similar, depending mainly on the nature of the mineral, temperature, and fluid composition. To clarify the synergies between these reaction mechanisms, we investigated the replacement and recrystallization reactions of chalcopyrite in the presence of a 65Cu-enriched aqueous fluid. The replacement of chalcopyrite by secondary copper sulfides follows a paragenetic sequence, whereby chalcopyrite is initially replaced by covellite, and then by digenite, with some of the digenite replacing covellite in longer duration experiments. The replacement reactions proceed via ICDR along with solid-state diffusion of 65Cu from the fluid into product minerals, with both mechanisms occurring at similar rates. Over time, chalcopyrite is completely replaced, and the secondary copper sulfides attain isotopic equilibrium with the fluid. Depending on temperature, thermal history, and fluid-mineral ratio, the reaction products may preserve kinetic or equilibrium signatures. We have identified a new geochemical process of ' porosity-aided recrystallization ', which may result in a re-equilibration or perturbation of mineral isotopic/trace element compositions due to exchanges between the mineral and fluid facilitated by extensive micro- to nano-scale porosity created by ICDR reactions. Porosity-aided recrystallization will affect any mineral-fluid system where mass transfers via solid-state diffusion and ICDR operate at similar rates, causing rapid (days-weeks) 'resetting' of the original isotopic abundances and trace element contents of the affected minerals. In copper sulfides, porosity-aided recrystallization occurs at lower temperatures (<300 °C) due to fast cation diffusion rates (log 10 D ≈ –13.6, 300 °C), but also takes place across other mineral systems where diffusion rates are faster at high temperatures. The open-system isotopic and trace element exchanges associated with porosity-aided recrystallization could lead to erroneous petrological interpretations, especially where these markers are used as a proxy for reconstructing geological evolution. [ABSTRACT FROM AUTHOR]

• A new mode of hydrothermal mineral replacement reactions has been proposed. • Solid-state diffusion & coupled dissolution-reprecipitation (CDR) operate together. • Surface dissolution induce bulk solid-state diffusion, a mechanism called FI-SSD. • The synergy between FI-SSD & CDR result in complex reaction pathways and textures. • Correct interpretation of mineral texture needs process-specific textural criteria. Mineral replacement reactions are one of the most important phenomena controlling the geochemical cycle of elements on Earth. In the early years, solid-state diffusion was proposed as the main mechanism for mineral replacement reactions, but over the past 20 years the importance of the coupled dissolution-reprecipitation (CDR) mechanism has been recognized. In the presence of a fluid phase and at low temperatures (e.g., <300 °C), CDR is the predominant mineral replacement process compared to relatively slow solid-state diffusion. However, in the present case study, we show that the rate of solid-state diffusion is comparable to the rate of CDR processes during the replacement of bornite (Cu 5 FeS 4) by copper sulfides at 160–200 °C. The experiments initially produced chalcopyrite lamellae homogeneously distributed in the entire bornite grain, and each lamella was enveloped by digenite. The lamellae were formed by removing Fe3+ from bornite via solid-state diffusion, since there was no evidence for fluid entering the bornite grains during lamellae formation. An interesting discovery is that solid-state exsolution of chalcopyrite lamellae was induced by the bulk hydrothermal fluids surrounding the mineral grains, because in the absence of fluids under otherwise identical conditions, no exsolution occurred, and because the exsolution rate and lamellae size were sensitive to the composition of hydrothermal fluids. We hypothesize that this fluid-induced solid-state diffusion (FI-SSD) mechanism is made possible by the similar topology of the crystal structure of these phases. The solid-state diffusion of Fe3+ within bornite and across the resultant chalcopyrite and digenite phase boundaries is facilitated by the near-identical S framework. Parallel to and after lamellae exsolution, CDR reactions proceeded from the surface to the interior of the grains or along fractures, replacing chalcopyrite by digenite, and digenite by covellite and/or chalcocite, depending on experimental conditions. The synergy between FI-SSD and CDR resulted in complex reaction pathways for reactions in five acidic hydrothermal fluids with or without added Cu2+, Cu+, Cl−, SO 4 2−, and SO 3 2−. The outcomes of these experiments imply that (1) under conditions where cation diffusion rates are of the same order of magnitude as dissolution and precipitation rates, hydrothermal fluids can induce and control solid-state diffusion processes, e.g., exsolution; (2) mineral replacement can be a result of the synergy between FI-SSD and CDR mechanisms; this happens at low temperatures (≤200 °C) in chalcogenide systems, but could affect silicate and oxide systems at amphibolite to granulite to eclogitic metamorphic grade; and (3) the synergy between FI-SSD and CDR mechanisms can lead to complex reaction pathways that cannot be easily predicted empirically. [ABSTRACT FROM AUTHOR]

[Display omitted] • SP was used as a novel depressant to inhibit galena in chalcopyrite flotation. • SP reduces the surface hydrophobicity and floatability of galena and maintains the floatability of chalcopyrite. • SP significantly weakened the adsorptive activity of SBX on galena. • Advanced analytical techniques reveal SP induced surface modifications and propose a selective flotation mechanism. The successful separating galena and chalcopyrite by flotation presents difficulties owing to their analogous surface chemical properties. This study investigated sodium periodate (SP) as a novel depressant for selectively oxidizing and modifying chalcopyrite and galena surfaces, enabling successful flotation separation. In micro-flotation tests were carried out at pH 8.5 and SP concentration of 5 × 10−4 mol/L. The grades of Cu and Pb in the copper concentrate were 27.87 % and 23.13 % with recoveries of 81.22 % and 27.78 %, respectively. SP selectively inhibited galena floatability while preserving chalcopyrite floatability. The selective depression mechanism research of SP in flotation separation process showed that galena surface hydrophobicity was significantly reduced by SP, which in turn prevented the collecting agent from adhering to galena. In the presence of SP, hydrophilic species such as PbSO 4 and Pb(OH) 2 were generated on the surface of galena, which decreased its ability to float. Conversely, on the chalcopyrite surface, hydrophobic products such as CuS 2 , CuS n , and S0 were formed, having little effect on its floatability. A model was developed to elucidate the mechanism underlying the selective flotation separation of the chalcopyrite and galena using SP. [ABSTRACT FROM AUTHOR]

The schematic diagram and adsorption mechanism of the depressant-free Cu/Zn sulfides flotation separation by using DEHTT as the collector. [Display omitted] • A novel triazine-thiol collector DEHTT was used in flotation of Cu/Zn sulfides. • DEHTT efficiently separated chalcopyrite from sphalerite at pH∼9.5. • DEHTT chemisorbed the surface Cu atoms through its S or O atoms. The depressant-free flotation separation of chalcopyrite from sphalerite in the lower alkaline (pH<10) environment will contribute to reduce carbon emission and benefit the recovery of precious metal minerals. However, it is almost impossible for traditional collectors such as xanthates due to their weak selectivity for chalcopyrite against sphalerite. In this paper, a novel triazine-thiol collector, 2-diethylamine-4-hydroxy-1,3,5-triazine-6-thiol (DEHTT), was first introduced in flotation separation of chalcopyrite from sphalerite. The micro-flotation results elucidated that in the absence of depressants, the recoveries of chalcopyrite and sphalerite from their mixture with 2.0 × 10−6 mol/L DEHTT at pH 9.45 (Na 2 CO 3 as regulator) were 91.83 % and 28.84 %, respectively, while those with sodium isobutyl xanthate (SIBX) were 96.11 % and 78.00 % under the same conditions. In situ AFM and contact angle exhibited that DEHTT assembled on chalcopyrite surface to form lots of aggregates which increased its hydrophobicity, while an insignificant change of sphalerite surface was observed. FTIR, zeta-potential and XPS explored that DEHTT chemisorbed the Cu sites of chalcopyrite surface through its S or O atoms. The specific flotation affinity of DEHTT to chalcopyrite might contribute the cleaner recovery of copper sulfide ores with the lower carbon emission. [ABSTRACT FROM AUTHOR]

As an antiferromagnetic material, chalcopyrite CuFeS 2 has both magnetic and semiconductor properties, which brings great prospects for the application of spintronics devices. Here, chalcopyrite CuFeS 2 nanoplates were successfully synthesized through a template mediated method. The CuFeS 2 exhibits a tetragonal phase while largely maintaining the hexagonal morphology of the CuS template, with particle sizes ranging between 90 and 120 nm. Specifically, the magnetic properties of CuFeS 2 can be tuned by varying the Fe content. The strong room-temperature ferromagnetism is attributed to the coexistence of the ferromagnetic Fe 7 S 8 and the antiferromagnetic CuFeS 2 , as well as to the unsaturated spin states of Fe on the surfaces of the nanoplates. Furthermore, the photoresponses of CuFeS 2 nanoplates were confirmed by I-V measurements under dark and light illumination. The stable photoresponse capability is attributed to its semiconductor properties. This novel room-temperature ferromagnetism and photoelectric effect promotes the development of CuFeS 2 nanoplates, and has great significance for the synthetic pathways of other ternary magnetic compounds. • CuFeS 2 nanoplates were successfully synthesized by template mediated method. • CuFeS 2 are of tetragonal phase and almost maintains the hexagonal morphology of CuS template. • CuFeS 2 exhibits room-temperature ferromagnetic property. • The stable photoresponse capability of CuFeS 2 is attributed to its semiconductor properties. [ABSTRACT FROM AUTHOR]

Galena separation from chalcopyrite poses a notable challenge in mineral processing, owing to the involvement of high dosages of traditional process reagents and substantial environmental impact. This study addresses this challenge by introducing 2,5-dimethoxy-1,3,4-thiadiazole (DMTD) as a chalcopyrite depressant using sodium ethyl xanthate (NaEX) as a collector. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses showed that DMTD can be adsorbed on the surfaces of chalcopyrite and galena, but the adsorption on chalcopyrite is stronger than that on galena. UV–vis, zeta potential and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses revealed that DMTD impeded the adsorption of NaEX on chalcopyrite; moreover, NaEX could desorb the DMTD adsorbed on galena and re-adsorb it on galena. Surface hydrophilicity tests revealed that DMTD significantly enhanced the hydrophilicity of chalcopyrite in the presence of NaEX, and galena was selectively separated from chalcopyrite using 1×10− 4 mol/L DMTD at pH exceeding 5. The recovery of galena remained >90 %, while that of chalcopyrite drastically decreased to <5 %. Furthermore, artificial-mixing experiments confirmed the separation effect of DMTD as a chalcopyrite depressant. Notably, this study avoids environmental pollution caused by traditional depressants, offering a potential green approach to achieve effective flotation separation of copper–lead sulfide ore. [Display omitted] [ABSTRACT FROM AUTHOR]

Amorphous silica has been recently recognized for its adverse effects on copper flotation, but its impact remains poorly understood. This study investigates the effects of varying amorphous silica content on the kinetics and selectivity of copper flotation. Results show a significant reduction in chalcopyrite from approximately 99 % to 86 % with increasing amorphous silica content, attributed to increased pulp viscosity and slowed flotation kinetics. The classical first-order kinetic model provided the best fit for the flotation kinetics data, revealing that higher amorphous silica content prolongs the time required to achieve ultimate recovery. Results also show that amorphous silica deteriorated flotation selectivity and increased gangue recovery via entrainment, with complex variations depending on amorphous silica content. A small amount of amorphous silica was identified to significantly impair flotation kinetics and selectivity, leading to a deterioration in overall flotation performance. Effects of amorphous silica on the flotation kinetics of a copper ore comprising chalcopyrite and a mixture of quartz and amorphous silica (based on the classical first-order model). [Display omitted] • Amorphous silica increases pulp viscosity by forming aggregate structures. • Classical first-order kinetic model best describes flotation kinetics. • Amorphous silica adversely affects flotation kinetics and selectivity. • minor amorphous silica content poses challenges in copper flotation performance. [ABSTRACT FROM AUTHOR]

Carrollite is often associated with chalcopyrite, and their natural floatability is similar, which makes it difficult to separate the two minerals by flotation in industrial production. In this study, the depression behavior and mechanism of flaxseed gum (FG) introduced as carrollite depressant on carrollite and chalcopyrite in PBX flotation system was investigated through micro-flotation, zeta potential, total organic carbon (TOC), fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The flotation results indicated that FG was a highly effective depressant to separate 92.39 % chalcopyrite from the mixture with carrollite at pH 9.0 with a reagent scheme of 50 mg/L of FG and 8.0 × 10−5 mol/L of PBX. The zeta potential and TOC analysis results demonstrated that both carrollite and chalcopyrite exhibited a favorable affinity to FG, and pre-treated FG significantly hindered the adsorption of PBX on carrollite, while only slightly decreased that on chalcopyrite, resulting in the considerable difference in floatability between carrollite and chalcopyrite. In addition, FT-IR spectra and XPS detection results further confirmed that the affinity of FG towards carrollite superior to PBX might be due to the bidentate coordination of the carboxyl groups in FG with Co sites on carrollite surface, whereas the interaction between its carboxyl groups and Cu sites on both minerals was very weak or did not happen. Therefore, FG was promising in flotation separation of copper-cobalt sulfide minerals as a new friendly efficient depressant. [Display omitted] [ABSTRACT FROM AUTHOR]

The floatation of target minerals is often severely deteriorated in highly muddy mineral flotation systems. In this study, it was shown that the chalcopyrite recovery was significantly decreased due to the slime-coating of the serpentine fines. To enhance the floatability of chalcopyrite in the presence of serpentines, two phosphonic acids of 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) and ethylenediamine tetramethylene phosphonic acid (EDTMP) were applied as dispersants in the floatation process. The micro-flotation tests indicated that HEDP and EDTMP could well eliminate the adverse effect of coated serpentine on the floatability of chalcopyrite. Adsorption tests and X-ray photoelectron spectra (XPS) analysis demonstrated that HEDP and EDTMP could selectively adsorb on the serpentine surface due to the chelation of phosphonic acid groups with the magnesium atoms on the serpentine surface, which was confirmed by the flight secondary ion mass spectrometry (TOF-SIMS) characterization. The zeta potential measurements showed that the adsorption of dispersants on serpentine changed the surface charges from positive to negative, while the zeta potential of chalcopyrite became more negative due to the dissolution of copper and iron cations from the chalcopyrite surface. Therefore, the electrostatic repulsion effectively prevented the slime-coating of serpentine on the chalcopyrite surface, which was also supported by the atomic force microscope (AFM) force measurements. As a result, the use of dispersants eliminated the adverse effects of serpentinite and greatly improved the floatability of chalcopyrite. The findings in this work indicate that the phosphonic acids of HEDP and EDTMP might find their application as effective dispersants to improve the floatability of target minerals in highly muddy mineral flotation systems. [Display omitted] • The chalcopyrite recovery was significantly influenced by the slime-coating of the serpentine fines. • The application of phosphonic acid dispersants enhanced the floatation recovery of chalcopyrite from 16 % to 86 %. • TOF-SIMS confirmed the adsorption of dispersants on serpentine via chelation of phosphonic groups with magnesium atoms. • AFM force measurements indicated that the force between chalcopyrite and serpentine changed from attractive to repulsive. [ABSTRACT FROM AUTHOR]

[Display omitted] • STG effectively separates chalcopyrite and molybdenite bulk concentrates. • STG chemisorption layer containing Cu(I)-S and Fe(III)-S forms on chalcopyrite surfaces. • Adsorption density of STG on chalcopyrite is higher than that on molybdenite. • STG desorbs the previously adsorbed xanthate from the chalcopyrite surface. The pivotal roles of Cu and Mo in industrial applications accentuate the importance of effectively separating and recovering chalcopyrite and molybdenite. They commonly exist together in natural environments, necessitating their segregation prior to engaging in smelting processes. The separation is mainly accomplished through flotation. The inadequate comprehension of the mechanisms of thiol depressants, commonly used in the separation of chalcopyrite and molybdenite, poses challenges to both resource recovery and the development of depressants. Based on the bulk flotation practice of copper-molybdenum sulfide minerals, this study investigated the separation effect and mechanism of sodium thioglycolate (STG) on xanthate-treated chalcopyrite and molybdenite. Flotation and contact angle tests validate that STG enhances the hydrophilicity of chalcopyrite surfaces, leading to an 83.79% flotation separation efficiency for molybdenite. Various methodologies were employed to explore the mechanism of the depressant, encompassing open-circuit potential measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, infrared and ultraviolet spectroscopy, time-of-flight secondary ion mass spectrometry, classical molecular dynamics and ab initio molecular dynamics simulations. The stable adsorption layer of STG is established by the interaction of thiol groups from STG with Cu and Fe sites on the chalcopyrite surface, resulting in the formation of Cu(I)-S and Fe(III)-S structures. The adsorption density of STG layer on the chalcopyrite surface is four times greater than that on molybdenite. Additionally, following the adsorption of STG, the previously adsorbed xanthate chalcopyrite surface is desorbed with an efficiency of 65.88%. These findings contribute to the elucidation of the mechanistic understanding of thiol-containing depressants in the flotation separation process of copper-molybdenum sulfide minerals and establish a basis for the prospective advancement of mineral processing reagents. [ABSTRACT FROM AUTHOR]

• Designed a flotation equipment to simulate atmosphere at different altitudes. • The flotation inhibition behavior of chalcopyrite was studied at high altitude. • Adsorb less collectors at high altitude are favorable for the separation process. • Study of chalcopyrite interface and inhibition mechanisms at high altitude. Given the scarcity of conventional low-altitude high-quality copper–molybdenum resources, people gradually explore mining opportunities in elevated regions. Molybdenite in high-altitude ores is initially recovered with chalcopyrite, which is then separated and floated to produce refined molybdenite. There are few studies on the influence of the sulfide ore flotation process under high-altitude and low dissolved low-dissolved oxygen (DO) environments. In the present study, a flotation plant is designed and assembled to simulate the flotation of chalcopyrite at high altitudes by controlling the partial pressures of N 2 /O 2 and DO under different altitude conditions, using the DO value as a standard. UV/VIS, electrochemical, and contact angle measurements were used to reveal the effect of conditions at 4600 m DO = 4.0 mg/L at altitude on chalcopyrite–molybdenite separation. Pure mineral flotation results indicate that a low DO environment at high altitudes favors the separation process and reduces the number of inhibitors. The mechanism of chalcopyrite inhibition at high altitudes still relies on the adsorption of large amounts of Fe(Ⅲ)-O/OH and hydrophilic polysulfides on the surface. Results reveal the reason for the relatively low inhibitor dosage in the chalcopyrite–molybdenite separation flotation process under low DO conditions at high altitudes. The findings also confirm that enhanced collector removal at high altitude altitudes is conducive to implementing a pathway toward a more efficient separation flotation process. [ABSTRACT FROM AUTHOR]

[Display omitted] • ADD degradation efficiency of 91.15% and TOC removal rate of 85.41% were achieved. • The main reactive radicals were identified as SO 4 ∙ - , •OH, and O 2 ∙ -. • S2− as electron donors in the CuFeS 2 surface promoted the reduction of Fe3+ and Cu2+. • Degradation pathways of ADD in CuFeS 2 -PMS system were proposed. The effects of natural chalcopyrite (CuFeS 2) as a peroxymonosulfate (PMS) activator on ammonium dibutyl dithiophosphate (ADD) degradation from mineral processing wastewater were systematically investigated in this study. Under the optimal operating conditions, a degradation efficiency of 91.15 % for ADD and a removal rate of 85.41 % for total organic carbon (TOC) were achieved through the CuFeS 2 -PMS system, which was significantly superior to CuFeS 2 alone and PMS alone systems because of the synergetic effects between chalcopyrite and PMS. Radicals (S O 4 ∙ - , •OH, and O 2 ∙ -) could be simultaneously generated in the CuFeS 2 -PMS system, implied by electron paramagnetic resonance tests and quenching tests. Among these species, S O 4 ∙ - emerged as the predominant participant in the degradation of ADD. Leaching metal ions tests and cycling experiments demonstrated that CuFeS 2 possessed a degradation efficiency of over 75 % for ADD even after five cycles of use. Additionally, X-ray photoelectron spectroscopy and comparative experiments suggested that reducible sulfur species were crucial in facilitating the recycling of Fe3+/Fe2+ and Cu2+/Cu+ on CuFeS 2 surfaces. Meanwhile, the presence of Fe and Cu bimetallic active sites on the surface synergistically enhanced PMS activation. The S6 and S7 atoms in ADD molecule were more susceptible to be attacked by active species, as calculated by density functional theory. Finally, the proposed degradation pathway and mechanism of ADD in the CuFeS 2 -PMS system were established based on identification of intermediates. In the end, the CuFeS 2 -PMS system still showed excellent degradation performance when applied to the treatment of ADD in actual water systems and the treatment of other flotation agents. This paper provides new insights into the effective treatment of organic contaminants from mineral processing wastewater. [ABSTRACT FROM AUTHOR]

During froth flotation, the separation of chalcopyrite from molybdenite is hindered by their similar surface properties. Therefore, it is imperative to develop an efficient selective collector with innovative minerophilic groups and reduce the use of inhibitors. In this study, 5-methyl diethyl dithiocarbamate-1,3,4-oxadiazole-2-thione (MDCODT) was first introduced as a collector in chalcopyrite flotation separation from molybdenite. Micro-flotation experiment results expressed that the selectively separation of chalcopyrite from molybdenite could be realized without the addition of inhibitor. Wettability tests, ζ-potential analyses and UV spectrum demonstrated that MDCODT specifically adsorbed on the surface of chalcopyrite rather than molybdenite. And the adsorption mechanism was future explored by AFM scan, electrochemical tests, FTIR spectrum, XPS spectrum and DFT calculation. The active centers of MDCODT are concentrated in dithiocarbamate and oxadiazole thione groups, and MDCODT-Cu(I) complexes can be covered on the chalcopyrite surface with formation of Cu-S and Cu-N bonds. The di-minerophilic group oxadiazole-thione collector, MDCODT, exhibits the advantages of cost-effectiveness and environmental friendliness, rendering it suitable for a wide range of industrial applications. [Display omitted] • 5-methyl diethyl dithiocarbamate-1,3,4-oxadiazole-2-thione (MDCODT) was synthesized. • MDCODT provided effective flotation separation of chalcopyrite from molybdenite. • MDCODT-Cu chemisorption layer is selectively formed on chalcopyrite surface. • MDCODT-Cu surface complexes hydrophobized chalcopyrite surface. • MDCODT was chemisorbed on chalcopyrite by establishing Cu(I)-S and Cu(I)-N bonds. [ABSTRACT FROM AUTHOR]

• Multimodal assessment of the leaching variability at the micro- and macroscale. • Tracking of hundreds of thousands of grains over time. • Able to couple porosity network development and microcrack formation to leaching variability. • Leaching in chloride media is more selective for copper sulphides, evidencing virtually no pyrite dissolution. Understanding the variability of leaching kinetics is extremely challenging due to the nature of leaching processes. Common experimental setups, such as column leaching experiments, only allow for quantification of apparent leach kinetics at the macroscale (e.g. at the particle or column level), failing to capture grain-scale variability. In this paper, we study variability in leaching kinetics at the micro- and macroscale using a combination of 4D imaging and standard chemical measurements. The impact of chloride ions on leaching performance was evaluated using column leaching experiments. Micro-computed tomography (micro-CT) was combined with SEM/EDX to isolate chalcopyrite from pyrite dissolution. Using in-house algorithms, the leaching behaviour of hundreds of thousands of grains was quantified and tracked over time. Morphological changes at the agglomerate level were assessed, coupling porosity network development and microcrack formation to leaching variability. It was concluded that a decrease in internal macro porosity does not significantly impact macro-scale leaching performance. Grain size had an impact, although grain location does not influence mass transport resistance. Another key finding was that leaching in chloride media is more selective for copper sulphides, evidencing virtually no pyrite dissolution. This study not only provides new understanding of the factors influencing the leach behaviour of chalcopyrite ore, but also generates data that represents the process more accurately and allows for better planning. [ABSTRACT FROM AUTHOR]