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Monazite ((Ce, La)PO4) is one of the major types of light rare earth minerals from which the light rare earth elements cerium (Ce) and lanthanum (La) are economically extracted. Flotation is extensively used to recover fine-grained monazite. Sodium oleate (NaOL) is considered as the collector with the strong collecting ability for monazite flotation. However, this study shows that its collecting ability is still limited. In this paper, a phosphonic acid, nonane-1,1-bisphosphonic acid (C9-BPA), was employed as the novel collector in place of NaOL. Flotation experiments show that even when the C9-BPA dosage is less than one-fifth of the NaOL dosage, the monazite recovery using C9-BPA as the collector is approximately 22 wt% higher than that using NaOL. The mechanism by which C9-BPA adsorbs on monazite was investigated using zeta potential, infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements as well as first-principles calculations. Zeta potential measurements show a more significant decrease in the zeta potentials of monazite after the addition of C9-BPA compared to those after the addition of NaOL. For C9-BPA-treated monazite, the characteristic peaks of C9-BPA were observed in the IR and C 1s XPS spectrum, whereas for monazite treated by NaOL, no characteristic peak of NaOL was observed. Experimental results show that C9-BPA has a stronger affinity towards the monazite surface than NaOL as confirmed by the higher adsorption energy of CP-BPA on the monazite surface (‒204.22 kJ/mol) than NaOL (‒48.48 kJ/mol). This study demonstrates an extensive application value and prospect of C9-BPA in monazite flotation and helps design novel collectors with strong collecting ability for monazite flotation.

Neighboring relationships among plants have been extensively reported, but little is known about the effect of waterlogging. In this study, Cleistocalyx operculatus (Roxb.) Merr. and Dalbergia odorifera T. Chen saplings were used in investigating the neighboring relationships between legumes and non-leguminous woody plants under different planting and watering regimes. Results showed that C. operculatus and D. odorifera are waterlogging-tolerant species, and C. operculatus with high proportion of adventitious roots would be at an advantage during waterlogging. The growth performance of D. odorifera was better than that of C. operculatus under well-watered single-planting conditions. However, under well-watered mixed-planting conditions, C. operculatus had an obvious inhibitory effect on the growth traits (increments in stem height and leaf number, total leaf area, and total plant fresh weight) and physiological responses (net photosynthesis rate, stomatal conductance, and transpiration) of D. odorifera, whereas the growth of C. operculatus slightly increased in the presence of D. odorifera. Under waterlogging mixed-planting conditions, the facilitative effect was more intensive; the total leaf area, underground fresh weight, and total plant fresh weight of C. operculatus significantly increased, but a negative effect was found in D. odorifer. These results showed that the neighboring relationship between these two species is predominantly favorable to C. operculatus. This research sheds new light on screening waterlogging-tolerant arbor species and species collocation during vegetation restoration and reconstruction activities in wetland systems.

To improve the magnesia removal effect of collophane and increase the P2O5 grade of phosphorus concentrate, the fatty acid collector mixed with sodium dodecyl sulfate (SDS) was used as the compound collector in reverse flotation for magnesia removal in acid system. Solution surface tension measurement, Zeta potential test and infrared spectrum analysis were conducted to analyze the intensified effect of compound collector for dolomite removal. The results showed that under the conditions of grinding fineness -0.074 mm accounted for 89.8%, sulfuric acid dosage 12.0 kg/t, phosphoric acid dosage 3.0 kg/t, SDS compound proportion 3%, collector dosage 1.0 kg/t, the P2O5 grade of concentrate is increased from 25.7% to 29.94%. SDS can reduce the surface tension of slurry, which is conducive to the formation and stability of flotation foam. Zeta potential became negative due to the compound collector adsorbed on the mineral surface. Moreover, the -CH2 antisymmetric stretching vibration peak originated from fatty acid and SDS were detected after the interaction of collectors with dolomite. The compound collector was effectively adsorbed on the surface of dolomite, enhancing the magnesium removal effect of collophane.

Based on the 2012 and 2018 China Family Panel Studies (CFPS) data, this paper explores the influence mechanism between rural social security, precautionary savings, and the upgrading of rural residents’ consumption structure in China from theoretical and empirical perspectives. The results show that China’s rural social security can significantly promote the upgrading of rural residents’ consumption structure, and 1.79% of the positive effect of China’s rural social security on the upgrading of rural residents’ consumption structure in China is realized through the mediating effect of precautionary saving; the robustness of the regression results is tested by a placebo test and substitution matching method. Through further research, it is found that the promotion effect of China’s rural social security on the upgrading of rural residents’ consumption structure in China varies by region and age. In order to promote the sustainable upgrading of rural residents’ consumption structure, rural social security policies should be further improved, and new rural social pension insurance policies should be formulated according to local conditions, which will ultimately promote the economic development of rural areas.

Based on the Peking University Digital Financial Inclusion Index and 2011–2018 provincial panel data, this paper discusses the mechanism of digital financial inclusion on agricultural green total factor productivity from both theoretical and empirical perspectives. The result shows that digital financial inclusion can significantly increase China’s agricultural green total factor productivity, and the optimization of the agricultural industry structure can bring a significant “structural growth effect”. A total of 8.42% of the positive effects of digital financial inclusion on agricultural green total factor productivity are realized through the intermediary effect of agricultural industrial structure optimization. Through further research, it is found that digital financial inclusion has regional heterogeneity in the improvement of agricultural green total factor productivity. At the same time, digital financial inclusion of different dimensions will also have a differential impact on the improvement of agricultural green total factor productivity. In order to promote the green development of agriculture, it is necessary to further improve the financial development environment, optimize the structure of the agricultural industry, and formulate development policies for digital inclusive finance in accordance with local conditions.

Probing the interaction mechanism between organic molecules and material surfaces in the presence of metal ions is of great importance in many fields, such as mineral flotation. The collectability ...

Due to their excellent physical and chemical stability and long-term cycling, insertion anodes are becoming increasingly important in energy storage. However, insertion anodes still suffer from low energy density and large irreversible capacity. Systematically controlling the macroscopic structure and microscopic crystal parameters are effective ways of improving the energy density, cycle capacity, and rate performance of carbonaceous materials. In this work, a series of nonporous, microporous, and mesoporous carbon nanosheets was designed and fabricated from balsa waste by thermal infiltration, and displayed high disorder and abundant surface functional groups. The sample with the best performance (BC-8) had a large pore size centred at 2.5–4.5 nm, accompanied by a highly disordered crystallite structure, expanded carbon interlayers, a large number of active sites, and small particle sizes. The results revealed that mesoporous carbon nanosheets deliver a large capacity, and that the ion storage capacity of carbon nanosheets could be increased by optimizing the pore size. As an ion storage anode, sample BC-8 exhibited higher reversible capacity (630 mA h g−1 at a rate of 0.2 A g−1 after 100 cycles), longer cycling stability, and better rate performance (150 mA h g−1 at 5 A g−1 after 1000 cycles) than the other samples. Kinetic analysis confirmed that porous carbon nanosheet materials show a synergistic effect between capacitor-like and diffusion-controlled behavior; the excellent electrochemical properties of mesoporous carbon nanosheets are dominated by diffusion-controlled behavior; and the capacity of the micropores is mainly governed by surface capacitance-controlled contributions. Our work helps explain the improved ion storage behavior of carbon with a two-dimensional nanosheet structure and provides an effective strategy for designing higher energy density carbon materials for advanced energy storage systems.

The self-assembly behaviors of sodium oleate (NaOL), dodecylamine (DDA), and their mixtures in aqueous solution were systematically investigated by large-scale molecular dynamics simulations, respectively. The interaction mechanisms between the surfactants, as well as the surfactants and solvent, were revealed via the radial distribution function (RDF), cluster size, solvent-accessible surface area (SASA), hydrogen bond, and non-bond interaction energy. Results showed that the molecules more easily formed aggregates in mixed systems compared to pure systems, indicating higher surface activity. The SASA values of DDA and NaOL decreased significantly after mixing, indicating a tighter aggregation of the mixed surfactants. The RDF results indicated that DDA and NaOL strongly interacted with each other, especially in the mixed system with a 1:1 molar ratio. Compared to van der Waals interactions, electrostatic interactions between the surfactant molecules were the main contributors to the improved aggregation in the mixed systems. Besides, hydrogen bonds were found between NaOL and DDA in the mixed systems. Therefore, the aggregates in the mixed systems were much more compact in comparison with pure systems, which contributed to the reduction of the repulsive force between same molecules. These findings indicated that the mixed NaOL/DDA surfactants had a great potential in application of mineral flotation.

Utilization of large doses of inorganic reagents in mineral industry not only leads to high cost but also increases the toxicity in the environment. This research provides a new, environmentally friendly, biodegradable, and cost-effective depressant reagent, namely tricarboxylate sodium starch (TCSS), in chalcopyrite and pyrrhotite flotation systems. The selective depression and adsorption mechanism of TCSS on the two minerals were studied through the laboratory based measurements such as microflotation experiments, XPS spectral analysis, IR spectral analysis, adsorption amount analysis and zeta potential measurements. The addition of TCSS exhibited a much better depressive performance towards pyrrhotite than chalcopyrite in a wide pH range. Binary mineral flotation experiments indicated that an effective separation between the two minerals could be possible at a low concentration of TCSS, at which an improved recovery and grade of chalcopyrite of more than 75% could be achieved. All of the analytical measurements justified the flotation results and revealed that TCSS behaved differently with the two minerals. TCSS showed significantly much greater affinity towards pyrrhotite, the reason of which may be the presence of large amount of metal hydroxyl species on its surface. Keywords: Organic depressant, Flotation, Pyrrhotite, Chalcopyrite, Tricarboxylate sodium starch

Apatite (Ca10(PO4)6F2) is the most important phosphate mineral, and flotation is the main beneficiation method to separate apatite from its major gangue mineral calcite (CaCO3). Till date, ...

Since the excessive dosage of Pb2+ ions could facilitate the gangue mineral quartz activation and cause serious environmental problems, this work has an attempt to examine the performance of cupferron as a new alternative collector in selective separation of cassiterite from quartz with low dose of Pb2+ ions. Microflotation results show the improved selectivity of cupferron towards cassiterite as compared to quartz. Accordingly, its selective adsorption mechanism has been investigated by zeta potential measurements, X-ray photoelectron spectroscopy (XPS) analysis and first-principle density functional theory (DFT) calculations. The results of zeta potential measurements demonstrate the stronger adsorption of cupferron on cassiterite surface than quartz whether Pb2+ ion was added or not. The XPS analysis and first-principle DFT calculations consistently show that Sn4+ ions on the hydrated cassiterite surface exhibit much stronger reactivity towards cupferron adsorption than Si atoms on the hydrated quartz surface, resulting in a remarkable difference between the collecting ability of cupferron towards cassiterite and quartz. This work should shed new light on the discovery of cleaner flotation reagents for cassiterite beneficiation.

In the flotation of copper sulfides, pyrite is often activated by Cu2+ ions dissolved from copper-bearing minerals in alkaline media (pH ˃ 9), which results in pyrite entering the copper concentrate. To reduce the floatability of pyrite, we designed a novel functionally modified biopolymer, tricarboxylate sodium starch (TCSS), that showed superior depression selectivity towards pyrite in low pH solutions when employed in Cu–Fe flotation separation in the presence of sodium butyl xanthate (SBX) as a collector. TCSS depressed the floatability of pyrite more strongly than that of chalcopyrite in single mineral flotation in the pH range 4–6. The most selective separation was achieved at pH ∼ 6; the recovery of Cu in the concentrate was over 77%, and the grade was improved to 24.50% compared to the initial feed grade of 12.50%. Surface characterization analyses, including zeta potential, X-ray photoelectron spectroscopy (XPS) analysis, and Fourier transform infrared (FTIR) spectroscopy, confirmed the different degrees of interaction of TCSS with the two minerals. TCSS was adsorbed on the pyrite surface, possibly via a chemisorption mechanism, as reflected in the FTIR and XPS analyses. The adsorption of TCSS passivated the pyrite surface, which inhibited the adsorption and oxidation of the collector. On the other hand, the adsorption and oxidation of the collector on chalcopyrite surface were effective even in the presence of TCSS, attesting to the weak interactions between chalcopyrite and TCSS.

Molecularly imprinted polymers (MIPs) are typically prepared using a single template molecule, which allows selective separation and enrichment of only one target analyte. They are not suitable for determination of complex real samples containing multiple analytes. In order to expand the practical application of MIPs, novel dual-template molecularly imprinted mesoporous silica (DMIMS) was prepared by a simple and facile hybrid dual-template imprinting strategy using bisphenol A (BPA) and diethylstilbestrol (DES) as templates for simultaneous selective recognition and extraction of the two endocrine disruptors in environmental water samples. The structure and morphology of the synthesized DMIMS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and N2 sorption analysis. The results showed that DMIMS exhibited a spherical morphology, mesoporous structure and favorable thermal stability. More importantly, DMIMS was verified to exhibit fast kinetics, high rebinding capacity and excellent selectivity towards BPA and DES. DMIMS can reach equilibrium within 30 min and the saturated adsorption capacities of DMIMS for BPA and DES are 66.8 mg g−1 and 43.9 mg g−1, respectively. The selectivity coefficients of DMIMS are all far more than 1.0. Theoretical analysis showed that the experimental data fitted well to the pseudo-second-order model, indicating that chemical adsorption might be the rate-limiting step. Furthermore, the high adsorptive capability and selectivity of DMIMS were maintained almost constant after six runs. Finally, water samples were successfully analyzed with DMIMS and high recoveries (95.0–107.1%) and relative standard deviation (1.18–5.63%) were obtained. The limits of detection (3σ) of 3.4 × 10−4 mg L−1 and 5.6 × 10−4 mg L−1 were obtained for BPA and DES, respectively. Overall, these results demonstrated that DMIMS possesses great potential for simultaneous rapid and efficient detection of BPA and DES in environmental water samples.

Novel magnetic dummy molecularly imprinted mesoporous silica particles (m-DMIMSP) were prepared using a hybrid dummy imprinting approach combined with magnetic nanoparticles to obtain a magnetic material highly selective towards bisphenol A (BPA). The structure and morphology of synthesized m-DMIMSP were characterized by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometry, X-ray diffraction and N2 sorption analysis. The results showed that m-DMIMSP exhibited a mesoporous structure and favorable magnetic properties with saturation magnetization of 4.87 emu g−1. More importantly, m-DMIMSP displayed fast binding kinetics, high rebinding capacity of 76.8 mg g−1, excellent imprint factor of 4.9 and extremely high selectivity towards BPA over 4,4′-biphenol, diethylstilbestrol and hydroquinone, with selectivity coefficients all above 3.80. Moreover, the adsorptive capacity of m-DMIMSP was 2.0, 4.6 and 4.9 times higher than those of controlled magnetic molecularly imprinted mesoporous silica particles, magnetic dummy non-imprinted mesoporous silica particles and magnetic non-imprinted mesoporous silica particles, respectively, thus indicating the superiority of dummy molecular imprinting. Theoretical analysis showed that the experimental data fitted well to the pseudo-second-order model and Langmuir adsorption isotherm, indicating that chemical adsorption might be the rate-limiting step. Furthermore, the high adsorptive capacity and selectivity of m-DMIMSP remained almost constant after 8 runs. Finally, water samples were successfully analyzed with m-DMIMSP and high recoveries in the range of 95.6–106.2% were obtained. Overall, these results demonstrate that m-DMIMSP possesses great potentials for rapid and highly effective extraction of BPA from water samples.

Probing the interaction mechanism between organic molecules and material surfaces in the presence of metal ions is of great importance in many fields, such as mineral flotation. The collectability of benzohydroxamic acid (BHA) to a spodumene (LiAl(SiO

In this paper, a novel collector, dodecyl dimethyl betaine (BS-12), was used in the selective separation of ilmenite from titanaugite. The flotation performance and associated adsorption mechanism were studied by micro-flotation experiments, particle size analysis, Fourier-transform infrared (FT-IR) spectroscopy analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The micro-flotation results indicated that BS-12 exhibited a stronger collecting ability towards ilmenite than titanaugite within an acidic pH range, and that the recovery of ilmenite was about 50% higher than that of titanaugite under the optimum flotation conditions. Particle size analysis demonstrated that BS-12 could selectively agglomerate ilmenite to a certain extent and then contribute to the flotation difference between ilmenite and titanaugite. FT-IR results showed some characteristic bands of BS-12 on treated ilmenite, and on titanaugite with BS-12. The XPS analysis further confirmed that BS-12 chemisorbed onto ilmenite and titanaugite in a similar way, but the limited active sites on titanaugite in comparison with ilmenite accounted for their differences in flotation.

Metal ions are widely used as activators in the flotation of oxidised minerals. At the same dosage of collector, the recovery of target minerals (cassiterite, scheelite, wolframite and ilmenite) can be evidently improved with the addition of metal ion activator. Adsorption of metal ions and their hydroxides can provide attractive sites for collector attachment, contrary to bare minerals that exhibit considerably low affinity towards the collector. Iron complexes of benzohydroxamic acid (BHA) are formed during the reaction of ferric chloride with BHA in the solution. These complexes also exhibit strong collecting ability towards cassiterite in the flotation, which contradicted the classical theory that the activator must be added before the collector. However, the major active component and the underlying adsorption mechanism of the Fe-BHA complexes are still unknown. In this study, the solution chemistry calculation has been used to identify the major active components of the Fe-BHA complexes. Accordingly, a preferred adsorption model of the Fe-BHA complexes onto the cassiterite surface has been proposed and proven effective, through first-principles calculations based on density functional theory, flotation experiments and adsorption tests. Our results might shed new light on the activation mechanism of metal ions in mineral flotation.

Using microflotation experiments, this study investigated the effect of Pb2+ ions on flotation performance of cassiterite (SnO2) by using benzohydroxamic acid (BHA) as collector. Flotation results showed that floatability of cassiterite significantly improved after addition of Pb2+ ion to the process. Adsorption behaviour and mechanism of BHA on the inactivated and Pb-activated cassiterite surface were further explored by adsorption experiments, zeta potential measurements, X-ray photoelectron spectroscopy analysis and first-principle density functional theory calculations. Experimental and computational results consistently suggested that the adsorbed Pb atoms can coordinate with two O atoms of the two hydroxyl groups on the cassiterite surface. BHA molecules can form two coordination bonds with one Pb ion adsorbed on the cassiterite surface, resulting in a five-membered chelating ring. The proposed adsorption mechanism can be extended to the vast majority of interface assembly systems.

To improve the floatability of tungsten minerals, lead ions (lead nitrate) were used to modify the surface properties of the minerals and benzohydroxamic acid (BHA) was used as a collector in the flotation system. Pb 2+ -BHA complexes are inevitably present in this process and the role of it is unclear. This investigation is going to describe a new approach and the mechanism of catalyzing BHA adsorption onto scheelite by lead ions. Chemical speciation, zeta potential, FTIR, and XPS studies were conducted to establish the important role of lead ions. Indeed, Pb 2+ -BHA complexes were shown to be the active species responsible for flotation. The speciation and zeta potential results showed the presence of the adsorbed Pb 2+ -BHA complexes on the scheelite. The XPS results for atomic composition and binding energies confirmed Pb 2+ -BHA species adsorbed on the scheelite surface, which contributed to more adsorption of BHA. The new method would increase the recovery of scheelite, simplify the flowsheet and reduce the processing cost.

Pb2+ ions are commonly used as the activator in the flotation of cassiterite. However, lead pollution of surface water has attracted more concern and attention. In this study, the effect of Fe3+ ions as an activator on the flotation performance of cassiterite using benzohydroxamic acid (BHA) as the collector was investigated by the micro-flotation tests. The results of the flotation experiments showed that the addition of Fe3+ ions significantly increased the recovery of cassiterite in the presence of BHA collector. In the BHA flotation of cassiterite, there was a direct relationship between the recovery of cassiterite and the adsorption amount of BHA on the cassiterite surface. The adsorption mechanism of BHA on un-activated and Fe-activated cassiterite surfaces was studied by the adsorption experiments, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. The results of the adsorption and zeta potential experiments indicated that the adsorption amount of BHA on the cassiterite surface increased significantly in the presence of Fe3+ ions. The XPS analysis also revealed that terminal hydroxyl group oxygen atoms of the cassiterite surface were the dominant reactive sites for Fe3+ ion adsorption. Furthermore, BHA anions can react with Fe atoms adsorbed on the cassiterite surface to form Fe-BHA complexes, thus improving the hydrophobicity of the cassiterite surface.

Hollow mesoporous silica surface dummy molecularly imprinted polymers (HM-DMIPs) were prepared via surface dummy molecular imprinting combined with a hybrid strategy for the highly selective recognition and rapid separation of trace bisphenol A (BPA) from environmental water samples. The obtained materials were well characterized using TEM, SEM, FT-IR, TG and N2 sorption analysis. Moreover, the proper binding and selective recognition ability were also investigated by a batch rebinding assay. As a control, hollow mesoporous silica surface molecularly imprinted polymers (HM-MIPs), silica surface dummy molecularly imprinted polymers (SiO2-DMIPs) and hollow mesoporous silica surface dummy non-imprinted polymers (HM-DNIPs) were also synthesized. Results showed that HM-DMIPs possessed a fast kinetics, high rebinding capacity of 69.6 mg g−1, 3.0, 2.2 and 4.7 times higher than that of SiO2-DMIPs, HM-MIPs and HM-DNIPs, respectively. Moreover, an extremely high selectivity toward BPA over 4,4′-biphenol, diethylstilbestrol and hydroquinone was obtained and the selectivity coefficients were all above 6.96. The HM-DMIPs could be reused for ten runs, indicating their excellent stability and reusability. The results of theoretical analysis indicated a chemical adsorption process. Furthermore, real water samples were successfully analyzed with HM-DMIPs and high recoveries in the range of 98.7–101.7% were obtained. These results demonstrated that HM-DMIPs could serve as an efficient sorbent for rapid separation of trace BPA from environmental water samples.

This paper presents an efficient COD reduction from sulfide minerals processing wastewater using Fenton process, and the COD of the tailings dam wastewater is largely reduced from 130 mg/L to 30 mg/L, so as to meet the emission limit (COD

Galena (PbS) is an important and abundant source of lead (Pb) metal. It often coexists with other sulphide minerals such as sphalerite (ZnS). Flotation has been extensively used to separate galena and sphalerite. Herein, a reagent scheme comprising aerofloat collectors and Zn2+ and SO32− depressants is developed for the flotation separation of galena from sphalerite-rich sulphide ore. The flotation results demonstrate that Zn2+ and SO32− provide a synergistic depression effect on sphalerite and the aerofloat collectors exhibit more selectivity towards galena. Static calculations and ab initio molecular dynamics simulations were employed to investigate the mechanism of the adopted reagent scheme on galena/sphalerite flotation separation at the atomic scale. The reagent scheme used here has great potential for beneficiating other galena-containing sulfide ores. The calculation and simulation results can help in the design of novel collectors and depressants exhibiting excellent selectivity for the flotation separation of galena/sphalerite.

Lead ions (lead nitrate) were introduced to modify the surface properties of tungsten minerals, effectively improving the floatability, with benzohydroxamic acid (BHA) serving as the collector. Flotation tests indicated that Pb-BHA complexes were the active species responsible for flotation of the tungsten minerals. The developed Pb-BHA complexes and the novel flotation process effectively increased the recovery of scheelite and wolframite, simplified the technological process, and led to reduced costs. Fourier transform infrared spectra data showed the presence of adsorbed Pb-BHA complexes on the surface of the minerals. The characteristic peaks of BHA shifted by a considerable extent, indicating that chemical adsorption plays an important role in the flotation process. Zeta potential results confirmed physical adsorption of the positively charged Pb-BHA complexes on the mineral surfaces. The synergistic effect between chemical and physical adsorption facilitated the maximum flotation recovery of scheelite and wolframite.

Benzohydroxamic acid (BHA) has been widely used as the collector for cassiterite flotation, whereas low collecting ability of BHA need to be improved. It is shown through flotation that BHA exhibits weak collecting capacity to cassiterite even in the case of using lead nitrate as the activator, but the superior floatation performances of lead(II)–BHA complexes is observed. The adsorption isotherms of BHA onto cassiterite reveal a higher adsorption density around pH 9 using lead(II)–BHA complexes as the collector. The complexation of lead(II) by BHA has been studied by differential pulse voltammetry. In weak alkaline solution, [Pb(HL)]+ and [Pb(OH)(HL)] species with significantly collecting power are well predominant. Zeta potential studies demonstrate a stronger affinity to the mineral surface of Pb2+/Pb(OH)+–BHA complexes. XPS and FTIR studies indicate that chemisorption with the similar formation of Sn–O–Pb bond is the main interaction between the two kinds of collector and cassiterite.

The flotation response of chalcopyrite and molybdenite when using a novel compound, acetic acid-[(hydrazinylthioxomethyl)thio]-sodium (AHS), as the depressant was investigated through micro-flotation and batch flotation in this study. The depressing mechanisms were studied by means of zeta potential, FTIR and XPS measurements. The micro and bench flotation results indicated that AHS exhibited a strong influence on the depression of chalcopyrite and had little effect on the flotation of molybdenite minerals; these results might be attributed to the significant improvement of the molybdenite/chalcopyrite selectivity index after the addition of AHS. The results of the FTIR spectra, zeta potential and XPS measurements indicated that AHS chemisorbs onto the chalcopyrite surface through its S and N atoms, forming a five-membered cheat ring. A possible depressant mechanism along with a postulated adsorption mode for the surface interaction between AHS and chalcopyrite are provided.

A scientific and rigorous study on the adsorption behavior and molecular mechanism of collector sodium oleate (NaOL) on a Ca2+-activated hydroxylated &alpha, quartz surface was performed through experiments and density functional theory (DFT) simulations. The rarely reported hydroxylation behaviors of water molecules on the &alpha, quartz (101) surface were first innovatively and systematically studied by DFT calculations. Both experimental and computational results consistently demonstrated that the adsorbed calcium species onto the hydroxylated structure can significantly enhance the adsorption of oleate ions, resulting in a higher quartz recovery. The calculated adsorption energies confirmed that the adsorbed hydrated Ca2+ in the form of Ca(H2O)3(OH)+ can greatly promote the adsorption of OL&minus, on hydroxylated quartz (101). In addition, Mulliken population analysis together with electron density difference analysis intuitively illustrated the process of electron transfer and the Ca-bridge phenomenon between the hydroxylated surface and OL&minus, ions. This work may offer new insights into the interaction mechanisms existing among oxidized minerals, aqueous medium, and flotation reagents.

The separation of sylvite (KCl) and halite (NaCl), two main minerals in potash ores, is difficult because of the high ion concentration, fine particles of NaCl, and aggregation of KCl and NaCl in the saturated system. This study employed ammonium chloride (NH4Cl) as a new depressant and dodecyl morpholine as a collector in the reverse flotation process. The depressing mechanisms were studied by adsorption capacity experiments, infrared spectral analysis, and molecular dynamics simulations. The flotation tests showed that NaCl recovery increased to 97% after the addition of NH4Cl, while KCl recovery was reduced to &lt, 1%. Notably, NH4Cl not only acted as a selective KCl depressant, but also activated NaCl flotation. The FTIR measurements showed that NH4Cl was physically adsorbed onto the KCl and NaCl surfaces. Adsorption capacity experiments and molecular dynamics simulations confirmed more favorable NH4Cl adsorption on the KCl surface than on the NaCl surface. Moreover, the KCl mineral surface was more hydrophilic, while that of NaCl was more hydrophobic. Relative concentration analysis revealed that &gt, 90% ammonium and chloride ions were distributed 2&ndash, 10 &Aring, away from the KCl surface but were dispersed on the NaCl surface, indicating that NH4Cl exhibited stronger intermolecular interactions with KCl than with NaCl.

Sphalerite (ZnS), galena (PbS) and pyrite (FeS2) are the important metallic sulphide minerals. These three sulphide minerals are often associated with each other, and large amounts of sphalerite and pyrite are lost in the galena flotation tailings. In this study, the flotation method was employed to recover sphalerite and pyrite from a galena flotation tailing waste. The reagent scheme, including Cu2+ activator and butyl xanthate (BX) collector, can efficiently recover sphalerite and pyrite to obtain a two-mineral mixed concentrate with the Zn and Fe grades of ∼17 % and ∼26 %, respectively, in the sphalerite-pyrite bulk rough flotation. Quicklime (CaO) depressant in combination with BX collector can efficiently separate sphalerite and pyrite to obtain the two products in the sphalerite/pyrite separation rough flotation: the sphalerite concentrate with the Zn grade of ∼33 % and the pyrite concentrate with the Fe grade of ∼36 %. The first-principles calculations were employed to study the interaction mechanism of the adopted reagents in the recoveries of sphalerite and pyrite from the galena flotation tailing. This study provides an important reference for the recoveries of sphalerite and pyrite from similar galena tailings.

The selective separation of molybdenite from chalcopyrite is difficult because of their similar floatability in the presence of a collector. In this study, rhodanine-3-acetic acid (3-Rd) was first applied in molybdenite flotation as a novel chalcopyrite depressant, and its depression effect and mechanism were systematically investigated by flotation tests, density functional theory (DFT) calculation, zeta potential measurements, and X-ray photoelectron spectroscopy (XPS) analysis. Single mineral flotation results indicated that 3-Rd can selectively depress chalcopyrite flotation, whereas its effect on molybdenite is negligible. Mixed mineral and bench flotation tests further proved that 3-Rd is an efficient chalcopyrite depressant. The first-principle periodic calculations based on DFT predicted that 3-Rd prefers to adsorb onto Fe rather than Cu because of the more negative adsorption energy of the COO or CSS group on Fe in the chalcopyrite surface. Zeta potential measurements demonstrated that 3-Rd is adsorbed on chalcopyrite surface more selectively, and its adsorption strength is higher than that on molybdenite surface. XPS analysis further confirmed that 3-Rd is chemisorbed on chalcopyrite surface by binding with Fe active site and is adsorbed on molybdenite surface through hydrogen bonding and electrostatic interactions.

Native starch has a complex molecular structure that limits its ability as a selective depressant in sulfide flotation separations. This research study was conducted primarily to develop a series of starch-based molecules of different molecular weights with the aim of obtaining the most selective depressant of pyrite in chalcopyrite flotation. Five low molecular weight molecules were produced by the oxidative treatment of starch using H2O2 as the oxidant and FeSO4·7H2O as the catalyst. Oxidation treatment resulted in molecular modification of starch, producing low molecular weight molecules of grafted polar groups with increased reaction time. The molecules developed were investigated by microflotation to obtain the most selective and effective depressant for pyrite than chalcopyrite. The optimal and most selective depressant was named tricarboxystarch (sodium salt), also known as TCSS, based on the results of characterization measurements. The inhibitory effect of tricarboxystarch on pyrite was far more selective and effective than native starch. Good selective separation between pyrite and chalcopyrite was achieved by adding tricarboxystarch to a low pH solution. Tricarboxystarch contained three –COOH and several –OH groups in the skeleton, providing excellent depression of pyrite. This study is a basic research that sheds new light on the development and optimization of organic polymers for flotation technology.

In this work, the interfacial microstructures and adsorption mechanisms of benzohydroxamic acid (BHA) on Pb2+-activated cassiterite (1 1 0) surface were investigated by means of Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM) and density functional theory (DFT) calculations. AFM images showed that the roughness value of the natural cassiterite surfaces decreased after the treatment of Pb2+ and BHA with respect to the clean surface. The experimental high-resolution XPS spectra and the DFT calculated spectral lines consistently showed that the major surface species was the Pb-BHA complex on the cassiterite surface. The new peak of N1s at 401.88 eV in the X-ray photoelectron spectroscopy of cassiterite surface treated by BHA showed that BHA could be also chemically adsorbed on the surface. The Raman spectra revealed that the peak around 268 cm−1 should be attributed to the Pb-O bonds in the interface bonding structure of BHA-Pb-O≡. HR-TEM images of the clean, Pb2+ and Pb2+||BHA (adding BHA after Pb2+)-treated interfaces further demonstrated the interfacial microstructures. This work showed a new light on the understanding of the interface adsorption mechanism of flotation reagent and the activation mechanism of metal ion on oxidized mineral.

Tin and its compounds have a variety of applications. It is recovered as cassiterite from ore deposit by flotation. Traditionally, the use of fatty acids and their derivatives with limited selectivity of cassiterite over calcite (the main gangue mineral) has been replaced by benzohydroxamic acid (BHA). BHA shows poor collecting ability to cassiterite, even when lead nitrate (LN) is added as the activator. In this work, the flotation results show that cassiterite can be separated efficiently from cassiterite-calcite binary mixed minerals using a mixture of LN/BHA as collector and carboxymethyl cellulose (CMC) as depressant. The separation performance of the mixture of LN/BHA is much better compared with adding LN and BHA in sequence at the same dosage. Zeta potential measurements indicate that the mixture of LN/BHA exhibits much stronger ability to adsorb on cassiterite compared with adding LN and BHA in sequence even in the presence of CMC.

Metal indium (In) and its alloys have been widely used in semiconductor industries. In a Canadian sulfide ore, metal In mainly occurs as substitutes in stannite and sphalerite, and a sulfide mineral (i.e., roquesite), which accounts for 65% and 20% of the total In, respectively. In this work, the flotation method was adopted to pre-enrich the In in the Canadian sulfide ore due to its low cost, simple operation and high separation efficiency for fine particles. The findings of this research can provide a basis for the pre-treatments of In-bearing sulfide ores.

In this work, the activation mechanism of calcium species on the α-quartz surface was investigated. Microflotation, zeta potential measurements, first-principle calculation based on density functional theory (DFT), time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements and atomic force microscope (AFM) were conducted in this investigation. Sample preparation methods for minerals without a complete cleavage plane and reagent adsorption determination were introduced. Results revealed that quartz could be activated by calcium ions at the pH above 10, and calcium ion concentrations at pH below 10 slightly affected quartz recovery. Ca2+ could repel the hydration shell and hydroxylation on the quartz and be preferentially adsorbed onto the quartz surface at an alkaline pH. However, the coverage thickness and density of Ca2+ and the relevant coverage density of sodium oleate increased as the pH increased. The adsorbed amounts in the horizontal and vertical directions were also not uniform. The surface coverage thickness and density of Ca2+ and the corresponding amount of adsorbed sodium oleate played an important role in the activation of quartz. When the pH was above 10, the thickness and density of Ca2+ coverage on the quartz surface was sufficient, and Ca2+ could subsequently react with sodium oleate forming C18H33O2Ca. Thus, the quartz hydrophobicity was improved.

The depression of pyrite (FeS2) through an organic depressant is not only ineffective but also nonselective which causes poor selectivity. In this research, the depression effect of an organic polymer ‘poly-γ-glutamic acid (γ-PGA, a widely available class of polysaccharides)’ on pyrite flotation was improved by the addition of lime (CaO). The most encouraging flotation results were received at relatively lower concentrations of CaO and γ-PGA. The addition of CaO and γ-PGA had a synergistic inhibitory effect on pyrite flotation with a minor compromise in terms of the chalcopyrite grade at low alkaline conditions (pH 9). Adsorption studies and zeta potential measurements revealed that both CaO and γ-PGA were greatly adsorbed onto the pyrite surface than chalcopyrite. The addition of CaO and γ-PGA underwent a two-step depression effect on pyrite surface: (1) calcium species dissolved from CaO prefrentially adsorbed onto the pyrite surface and decreasing its negative charges; (2) pre-adsorbed calcium hydroxyl species promoted the adsorption of γ-PGA onto the pyrite surface. The XPS and FT-IR measurements revealed that γ-PGA formed the chemical coordination bonds with Ca-species on pyrite surface. Based on these measurement analyses, a two-step depression mechanism of CaO and γ-PGA on pyrite was also proposed. The envisaged scheme has its own benefits of environmental friendliness and cost-effective characteristics in Cu S flotation systems.

Novel collector lead(II)-benzohydroxamic acid (Pb(II)&ndash, BHA) complexes in aqueous solution were characterized by using experimental approaches, including Ultraviolet-visible (UV-Vis) spectroscopy and electrospray ionization-mass spectrometry (ESI-MS), as well as first-principle density functional theory (DFT) calculations with consideration for solvation effects. The Job plot delineated that a single coordinated Pb(BHA)+ should be formed first, and that the higher coordination number complexes can be formed subsequently. Moreover, the Pb(II)&ndash, BHA species can aggregate with each other to form complicated structures, such as Pb(BHA)2 or highly complicated complexes. ESI-MS results validated the existence of Pb-(BHA)n=1,2 under different solution pH values. Further, the first-principles calculations suggested that Pb(BHA)+ should be the most stable structure, and the Pb atom in Pb(BHA)+ will act as an active site to attack nucleophiles. These findings are meaningful to further illustrate the adsorption mechanism of Pb(II)&ndash, BHA complexes, and are helpful for developing new reagents in mineral processing.