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The recovery of scheelite from calcium-bearing carbonate ores by foam flotation is challenging due to its low separation efficiency. This study investigated the effect of pentasodium diethylenetriaminepentaacetate (PD) on the surface properties of scheelite and fluorite. For this purpose, we performed micro-flotation tests and carried out zeta potential measurements, as well as Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopic measurements, in order to analyze the surface properties of these minerals. The addition of PD as a novel depressor significantly improved the effect of fluorite and sodium oleate (NaOl) on the flotation-based scheelite recovery and separation from fluorite. PD was spontaneously adsorbed onto fluorite through electrostatic and chemical adsorption. By contrast, PD did not appear on the scheelite because of the reaction conditions, surface site, and steric hindrance. X-ray photoelectron spectroscopy measurements and a solution chemistry analysis were used for the determination of the PD-selective adsorption mechanism and key factors derived from multi-layer adsorption onto fluorite, which completely hindered that of NaOl. [ABSTRACT FROM AUTHOR]

In the study, a novel compound of dodecyliminodimethylenediphosphoinc acid was synthesized, and its adsorption mechanism onto ilmenite surface was investigated by zeta potential, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscop (XPS) measurements. The zeta potential measurement results indicated that dodecyliminodimethylenediphosphoinc acid (DDDA) could adsorb onto ilmenite surface, and the optimum pH range for adsorption was 4–8 (similar to the flotation behavior). The FTIR analyses further confirmed that DDDA chemisorbed onto ilmenite surface and formed metal–DDDA complex, rendering the hydrophobic media for flotation. The XPS results provided strong evidences that DDDA species chemisorbed onto ilmenite surface and reacted with Fe ions rather than Ti ions. [ABSTRACT FROM AUTHOR]

Pyrite depression in copper ore flotation often requires large doses of inorganic depressants that lead to high toxicity, high costs, and low selectivity. Thus, this study offers a novel pyrite depressant, polyglutamic acid (PGA), in the selective flotation of chalcopyrite with xanthate as a collector. The flotation and adsorption mechanism on chalcopyrite and pyrite were systematically studied using a series of flotation tests, zeta potential measurements, adsorption analysis, infrared spectral (IR) analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The addition of PGA depressed the flotation of pyrite more strongly than chalcopyrite in the wide pH range of 8–12. In the presence of PGA, selective separation between the two minerals was achieved at pH 9, and the recovery of chalcopyrite was over 85% and that of pyrite was less than 20%. All of the surface analysis techniques indicated that PGA interacted differently with the two minerals and the surface of pyrite adsorbed a much greater amount of PGA than that of chalcopyrite. Prior addition of PGA significantly reduced the adsorption of the collector on the pyrite surface and thus depressed its flotation. However, the significant adsorption of the collector and its oxidation to dixanthogen on the chalcopyrite surface caused its improved flotation even in the presence of PGA. Therefore, PGA, which is a non-hazardous, biodegradable, and renewable reagent, could be used as an alternative pyrite depressant in Cu–Fe conventional flotation circuits. • PGA achieves improved selective separation of chalcopyrite (Clp) and pyrite (Pyr). • Polyglutamic acid (PGA) is a nontoxic and degradable depressant of Pyr flotation. • Clp adsorbs much greater amount of xanthate than Pyr in the presence of PGA. • PGA could be an alternative depressant in Cu–Fe conventional flotation circuits. [ABSTRACT FROM AUTHOR]

Highlights • TCSS achieves improved selective separation of chalcopyrite (Clp) from pyrite (Py). • Tricarboxylate sodium starch (TCSS) is a biodegradable depressant of Py flotation. • Clp adsorbs more xanthate collector than Py in the presence of TCSS depressant. Abstract 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. [ABSTRACT FROM AUTHOR]

In previous studies, by regulating the Pb/BHA ratio and pH, lead complexes of benzohydroxamic acid (Pb-BHA) have been proven to be selective for the separation of scheelite from calcium minerals. In this study, sodium silicate (Na 2 SiO 3 ) and Al-Na 2 SiO 3 polymer were used as depressants for the further separation of scheelite from calcite. Flotation results indicated that both scheelite and calcite were depressed by Na 2 SiO 3 , while Al-Na 2 SiO 3 polymer gave good selectivity. The depressing ability of Na 2 SiO 3 for calcite was significantly improved due to the formation of some Al-Na 2 SiO 3 species with aluminum ions, while the reverse was true for scheelite. Zeta potential results indicated that both colloidal Na 2 SiO 3 and Al-Na 2 SiO 3 particles were negatively charged and difficult to adsorb on the negative scheelite surface through electrostatic attraction, especially for Al-Na 2 SiO 3. X-ray photoelectron spectroscopy analysis results showed that the Al-Na 2 SiO 3 adsorbed amount on the scheelite surface was less than the Na 2 SiO 3 adsorbed amount, while the reverse was true on the calcite surface. Binding energy analysis results indicated that calcium cations of scheelite and calcite surfaces could bond to oxygen atoms of Na 2 SiO 3 /Al-Na 2 SiO 3 through chemisorption. However, compared with Na 2 SiO 3 , Al-Na 2 SiO 3 showed weaker chemisorption on the scheelite surface, but adsorbed more powerfully onto the calcite surface. Therefore, Al-Na 2 SiO 3 showed excellent selectivity for scheelite and calcite, which has been successfully applied at the Shizhuyuan mine. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The adsorption behaviors and the activation mechanism of calcium ions (Ca 2+ ) on sericite surface have been investigated by Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR), Micro–flotation tests and First principle calculations. Zeta potential tests results show that the sericite surface potential increases due to the adsorption of calcium ions on the surface. Micro-flotation tests demonstrate that sericite recovery remarkably rise by 10% due to the calcium ions activation on sericite surface. However, the characteristic adsorption bands of calcium oleate do not appear in the FT-IR spectrum, suggesting that oleate ions just physically adsorb on the sericite surface. The first principle calculations based on the density functional theory (DFT) further reveals the microscopic adsorption mechanism of calcium ions on the sericite surface before and after hydration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: The flotation behavior of kaolinite was investigated using a series of tertiary amines (DRN, DEN, DPN and DBN). Maximum recoveries of kaolinite were 93%, 88% and 84% for DEN, DPN and DRN, respectively. The recovery for DBN was very low. On the basis of the Zeta potential and FT-IR spectra, the ionization of surface hydroxyl and the isomorphic exchange of surface ions accounts for the charging mechanisms of the kaolinite surface. The adsorption mechanism of tertiary amines onto the kaolinite surface was mainly electrostatic. We determined that the IEP of kaolinite increased from 3.4 to higher values after the interaction of kaolinite with the four tertiary amines. FT-IR spectra of kaolinite changed to include sharp peaks of tertiary amines. Inductive electronic effects and space-steric effects of –CH3, –C2H5, –C3H7 and –C7H7 bound to the N atom result in different collecting powers for the four tertiary amines. [Copyright &y& Elsevier]

The effect of chemical composition of diaspores on their electrokinetics was studied. Increasing SiO2 content in a diaspore sample was found to decrease its isoelectric point. The X-ray diffraction and SEM microanalysis showed the absence of distinct SiO2 phases. A linear correlation was found to exist between the measured isoelectric point and alumina to silica mass ratio in diaspore samples. The linear regression analysis of the experimental data suggests a more significant impact of silicon content than aluminum content, indicating a preferential adsorption of dissolved silicon on diaspore samples and/or preferential dissolution of aluminum from diaspore samples. [Copyright &y& Elsevier]

Collecting properties of a new amphoteric collector (α-benzol amino benzyl phosphoric acid, BABP) for calcium-containing minerals were studied by micro-flotation tests and measuring mineral electrokinetic potentials and collector adsorption. The collector adsorption was confirmed by infrared spectroscopic characterization and adsorption determination. The results were interpreted based on solution chemistry calculations. BABP collector exhibited selectivity for fluorite and calcite in a weak alkaline medium. The increasing collecting power of BABP is apatite≪scheelite

This study presents a highly selective reagent system that utilizes sodium hexametaphosphate (SHMP) to improve the separation of scheelite from calcite and fluorite using an anionic–nonionic collector. The recoveries of calcite and fluorite decreased to 20% as the SHMP dose exceeded 6 × 10−6 mol/L, whereas that of scheelite remained at 85%. The interaction mechanisms of minerals with SHMP were investigated through equilibrium speciation, Zeta potential, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy analyses. SHMP exists as hydrogen phosphate anion in the aqueous solution with a pH of 7–12. Moreover, it may be adsorbed intensively on the positively charged surfaces of calcite and fluorite via electrostatic force or chelation with calcium ion to impede further adsorption of the assembled collector. By comparison, the adsorption of SHMP is feeble on the scheelite surface because of its negative charge. The roughing grade of low-grade scheelite ore is substantially improved from 0.74% to 1.65% compared with that in the contrast test in the absence of SHMP. [ABSTRACT FROM AUTHOR]

The flotation separation of scheelite from calcite is problematic, where sodium silicate modified by polyvalent metal ions has shown some advantages for selective depression. In this study, an Al-Na2SiO3 polymer was used as the depressant for the flotation separation of scheelite from calcite using a lead complex of benzohydroxamic acid (Pb-BHA) as the collector. Furthermore, a number of measurements were conducted to investigate the structure of the Al-Na2SiO3 polymer and its adsorption behavior with Pb-BHA complexes on the mineral surface. Flotation experiments indicated that the Al-Na2SiO3 polymer shows good selectivity for the flotation separation of scheelite from calcite at pH 8, where the optimum ratio of sodium silicate to aluminum sulfate was 2:1. Fourier-Transform Infrared (FTIR) and solution chemical analyses revealed that aluminum hydroxide complexes and the hydroxy moiety of silicic acid are able to self-assemble via condensation affording an Al-Na2SiO3 polymer, i.e., a composite aluminosilicate polymer. The zeta potential measurements and adsorption capacity measurements indicated that, upon adsorption of the Al-Na2SiO3 polymer and Pb-BHA complexes on the mineral surface, the Al-Na2SiO3 polymer had less influence on the adsorption of Pb-BHA complexes on the scheelite surface, while the opposite was true for calcite. Therefore, more Pb-BHA complexes and fewer Al-Na2SiO3 polymers were deposited on the scheelite surface, while fewer Pb-BHA complexes and more Al-Na2SiO3 polymers were adsorbed on the calcite surface. The selective separation of scheelite from calcite was attributed to the cooperative selectivity of the Pb-BHA complexes and Al-Na2SiO3 polymer. [ABSTRACT FROM AUTHOR]

A portion of dodecyl amine (DDA) in a muscovite flotation system was replaced with alcohols with different carbon-chain lengths. These alcohols included octanol (OCT); decanol (DEC); dodecanol (DOD); and tetradecanol (TER). The muscovite adsorption behavior of the mixed DDA and alcohol systems were investigated through zeta potential; contact angle; and adsorption quantity tests. Single-mineral flotation tests showed that the muscovite-collecting power of the mixed DDA/alcohol (OCT, DEC, or DOD) system was stronger than that of the pure DDA system. The muscovite-collecting power of the collector systems decreased in the following order: DDA/DEC > DDA/OCT > DDA/DEC > DDA > DDA/TER. Zeta potential and contact angle analysis indicated that when combined with DDA; alcohols physically adsorbed on the surfaces of muscovite. This behavior improved the hydrophobicity of muscovite. Furthermore, adsorption analysis revealed that synergy between DDA and alcohol enhanced the adsorption of alcohol on muscovite. DDA has a dominant role in synergistic adsorption; whereas alcohol has a supporting role. Among all tested alcohols; DDA and DOD exhibit the highest synergetic adsorption effect because of their similar carbon-chain lengths. This similarity promotes the formation of a compact adsorption layer on the muscovite surface. [ABSTRACT FROM AUTHOR]

Selective adsorption of tannic acid (TA) on calcite surfaces and the implications of this process for the separation of fluorite ore were studied by microflotation tests, surface adsorption experiments, zeta potential measurements, UV–vis analysis, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation tests indicated that TA, when added before sodium oleate (NaOl), could selectively depress calcite from fluorite at pH 7. Surface adsorption experiments revealed that TA hinders the interaction of NaOl with calcite. The zeta potential of calcite became more negative with TA than with NaOl. However, the characteristic features of TA adsorption were not observed on fluorite, suggesting that the dominant adsorption sites are dissimilar on the fluorite and calcite surfaces in the pulp. UV–vis spectroscopy, XPS, and solution chemistry analysis were utilized to obtain a better understanding of the mechanism for selective adsorption of TA as well as the key factors determined by the Ca 2+ and Ca(OH) + components on the mineral surfaces. A possible adsorption mechanism along with an adsorption mode is proposed for the surface interaction between TA and calcite. [ABSTRACT FROM AUTHOR]

In this work, the adsorption behavior of dodecylamine (DDA) on scheelite and calcite mineral surfaces were investigated by molecular dynamics (MD) simulation, zeta potential measurement, AFM observation, contact angle measurement, and flotation test. The results implied that, the different adsorption behavior of DDA on scheelite and calcite surfaces was mainly attributed to cationic species RNH 3 + of DDA. The adsorption of neutral species RNH 2 and complex precipitates produced by the reactions between RNH 3 + and anionic species released by both mineral surfaces, also played important roles. In a DDA solution (1 × 10 −4 mol/L, pH 7.5–8.0), a handful of RNH 2 of DDA adsorbed on both scheelite and calcite surfaces through N–Ca bonding and hydrogen bonding between hydrogens of –NH 2 group and mineral surface oxygens. On positively charged calcite surface, RNH 3 + adsorbed on a moderate number of CO 3 2 − sites through electrostatic attraction and hydrogen bonding, which caused a moderate zeta potential increase for calcite. On negatively charged scheelite surface, a large number of cationic species RNH 3 + could easily adsorb on abundant WO 4 2 − sites, which caused a significant increase of zeta potential for scheelite. The different adsorption behavior led to a heavier monolayer coverage of DDA species on scheelite surface, and thus a more hydrophobic surface and a better flotation recovery of scheelite. The present work helps propose a new adsorption model of DDA on scheelite and calcite. [ABSTRACT FROM AUTHOR]

Highlights: [•] A first study applying mixture of thermophiles in nickel–copper sulfide bioleaching. [•] A first study on community succession during nickel–copper sulfide bioleaching. [•] l-Cysteine contributed to higher ORP, zeta potential, cell amount and lower pH value. [•] Ni recovery was always higher than that of Cu and l-cysteine promoted them both. [•] Without l-cysteine, S. m dominated while A. m dominated when l-cysteine added. [Copyright &y& Elsevier]

A selective organic depressant was investigated to promote the separation of scheelite from calcite and fluorite. 1-Hydroxyethylidene-1, 1-diphosphonicacid (HEDP) could efficiently reduce the recoveries of calcite and fluorite to less than 20%, while that of scheelite remained above 85%. The selective interaction mechanism was demonstrated via Zeta potential and X-ray photoelectron spectroscopy (XPS) analyses. The conceivable adsorption models of reagents on mineral surfaces were constructed to explain their adsorption mechanism. HEDP exhibited an excellent ability to selectively depress calcite and fluorite attributed to the intense adsorption on their surfaces, whereas its adsorption on scheelite surface was feeble. The technology feasibility of using HEDP to improve the scheelite flotation performance was verified through laboratory and industrial tests. The roughing grade was dramatically improved from 1.22% to 1.68%, and the product grade was enhanced from 24.66% to 28.26% with a noteworthy improvement of cleaning recovery by 6.93%, which would produce a considerable economic benefit. [ABSTRACT FROM AUTHOR]

Pb 2+ 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 Fe 3+ 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 Fe 3+ 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 Fe 3+ ions. The XPS analysis also revealed that terminal hydroxyl group oxygen atoms of the cassiterite surface were the dominant reactive sites for Fe 3+ 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. [ABSTRACT FROM AUTHOR]

The effects of Pb 2+ ions on ilmenite flotation and adsorption of benzohydroxamic acid (BHA) as a collector were investigated using microflotation tests, zeta potential measurements, adsorption analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The microflotation results indicate that the addition of Pb 2+ significantly improves the recovery of ilmenite using BHA as a collector. A maximum recovery of 88.46% is obtained at pH 8.12 in the presence of Pb 2+ ; a maximum recovery of 45% is obtained at the same pH using BHA alone. At pHs below 8.0, lead nitrate are mainly present in the solution as Pb 2+ and PbOH + , while at pHs above 8.0, the predominant components are Pb(OH) 2(s) and Pb(OH) 3− . The adsorption of these lead species influences the zeta potential of ilmenite and the number of activated sites on the ilmenite surface. FTIR and XPS analyses reveal that lead species and BHA react with the metal sites on the ilmenite surface. The lead species in solution are either adsorbed onto the ilmenite surface, which increases the surface activity of ilmenite, or react with BHA in solution to form complexes of lead and BHA. [ABSTRACT FROM AUTHOR]

The anisotropic adsorption of sodium oleate (NaOL) on feldspar surfaces was investigated to elucidate the different flotation properties of feldspar particles of four different size ranges. Microflotation experiments showed that the feldspar flotation recovery of particles with sizes spanning different ranges decreased in the order 0–19 > 19–38 > 45–75 > 38–45 μm. Zeta potential and FTIR measurements showed that NaOL was chemically adsorbed on the Al sites of the feldspar surface. The anisotropic surface energies and broken bond densities estimated by density functional theory calculations showed that, although feldspar mostly exposed (0 1 0) and (0 0 1) surfaces, only the (0 0 1) surfaces contained the Al sites needed for NaOL adsorption. The interaction energies calculated by molecular dynamics simulations confirmed the more favorable NaOL adsorption on (0 0 1) than (0 1 0) surfaces, which may represent the main cause for the anisotropic NaOL adsorption on feldspar particles of different sizes. SEM measurements showed that the main exposed surfaces on coarse and fine feldspar particles were the side (0 1 0) and basal (0 0 1) ones, respectively. A higher fraction of Al-rich (0 0 1) surfaces is exposed on fine feldspar particles, resulting in better floatability compared with coarse particles. XPS and adsorption measurements confirmed that the Al content on the feldspar surface varied with the particle size, explaining the different NaOL flotation of feldspar particles of different sizes. Therefore, the present results suggest that coarsely ground ore should be used for the separation of feldspar gangue minerals. Further improvements in the flotation separation of feldspar from associated valuable minerals can be achieved through selective comminution or grinding processes favoring the exposure of (0 1 0) surfaces. [ABSTRACT FROM AUTHOR]

The flotation behaviors of ilmenite untreated or treated with lead ions using sodium oleate as a collector were studied. The results of micro-flotation experiments reveal that ilmenite shows good floatability at pH 6–8. Compared with the flotation recovery of ilmenite untreated with lead ions, ilmenite floatability can be enhanced, and the resulting increase in recovery can surpass 30% after the addition of lead ions. The results of zeta potential tests show that the isoelectric point of ilmenite can change from 5.2 (untreated) to 7.8 (treated), which is beneficial for the interaction between ilmenite and the collector and increases its floatability. Adsorption measurements show that the adsorption amounts of ilmenite treated with lead ions are higher than those of untreated ilmenite. XPS tests show that after activation with lead ions, the relative contents of iron and titanium on the ilmenite surface, which play leading roles in ilmenite flotation, increase by 5.9% and 4.6%, respectively. At the same time, changes in binding energy are more visible after ilmenite is pretreated with lead ions and subsequently treated with sodium oleate. Within the optimal flotation pH range, oleate species (RCOO − , ( RCOO ) 2 2 - , (RCOO) 2 H − ) can mainly react with iron on the ilmenite surface through chemical adsorption in addition to electrostatic effects. [ABSTRACT FROM AUTHOR]

Sodium oleate (NaOl) has been widely used as a collector for the scheelite flotation. However, low selectivity of NaOl and large amount of sodium silicate (SS) needed remain tough problems. In this study, octyl hydroxamic acid (HXMA-8) was used as an associate collector with NaOl in scheelite flotation. The flotation tests showed that a novel reagent scheme, i.e., a lower dosage of SS (300 mg/L) and mixed collectors of HXMA-8 + NaOl (total concentration 4.5 × 10 − 4 mol/L, preferred mass ratio of 1:2) achieved the selective separation of scheelite from calcite. Zeta potential measurements indicated that the depressant, SS, adsorbed more strongly on calcite surface than on scheelite surface. HXMA-8 adsorbed significantly on scheelite surface either in the absence or presence of SS by chemical bonding between oxygens of HXMA-8 and surface metal ions. NaOl also adsorbed on both mineral surfaces by chemisorption, but the adsorption on calcite surface was influenced adversely by the presence of SS. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trisodium nitrilotriacetate (TN) was a novel depressant during fluorite separation from calcite. • TN showed excellent depressing performance on calcite at pH 7.9. • The multi-dentate neutralization reaction between TN and calcite surface occurred. • An adsorption model is finally obtained. The recovery of fluorite from calcium-bearing carbonate ores by foam flotation is challenging due to low separation efficiency. Herein, we studied the effect of trisodium nitrilotriacetate (TN) addition on the surface properties of calcite and fluorite. For this purpose, we performed micro-flotation tests and carried out zeta potential measurements as well as Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopic measurements to analyze the surface properties of these minerals. The addition of TN as a novel depressor significantly improved the effect of calcite and sodium oleate (NaOl) on the flotation-based fluorite recovery and separation from calcite. TN interacted with fluorite via an electrostatic interaction according to the zeta-potential and XPS analyses. The interaction of TN with calcite was via electrostatic attraction and chemical adsorption. Preferential chemical adsorption of NaOl replaces TN from the fluorite surface. However, calcite preferentially adsorbs TN due to the chemical bonding between carboxyl of TN and the hydrated calcite surface layer, which chemically modifies the original calcite surface. This work also suggests interaction and adsorption mechanisms between TN and calcite. [ABSTRACT FROM AUTHOR]

This paper presents a study on the relation between bacterial adhesion force and bioleaching rate of chalcopyrite, which sheds light on the influence of interfacial interaction on bioleaching behavior. In our research, Acidithiobacillus ferrooxidan s ( A . ferrooxidan s) were adapted to grow with FeSO 4 ·7H 2 O, element sulfur or chalcopyrite. Then, surface properties of Acidithiobacillus ferrooxidans and chalcopyrite were analyzed by contact angle, zeta potential and Fourier transform infrared spectroscopy (FTIR). Adhesion force between bacteria and chalcopyrite was measured by atomic force microscopy (AFM). Attachment and bioleaching behaviors were also monitored. The results showed that A . ferrooxidan s adapted with chalcopyrite exhibited the strongest adhesion force to chalcopyrite and the highest bioleaching rate. Culture adapted with sulfur bacteria took second place and FeSO 4 ·7H 2 O-adapted bacteria were the lowest. Bioleaching rate and bacterial attachment capacity were positively related to bacterial adhesion force, which is affected by the nature of energy source. According to this work, the attachment of bacteria to chalcopyrite surface is one of the most important aspects that influence the bioleaching process of chalcopyrite. [ABSTRACT FROM AUTHOR]

In this study, flotation behavior of scheelite and calcite was investigated using mixed cationic/anionic collectors of dodecylamine (DDA) and sodium oleate (NaOL). Individual NaOL or DDA was also tested for comparison. The flotation results of single mineral and mixed binary minerals demonstrated a high selectivity and recovery for the flotation of scheelite from calcite at pH 7 using mixed DDA/NaOL collectors. The adsorption mechanism of the selective separation was analyzed through zeta potential measurement. [ABSTRACT FROM AUTHOR]

Abstract: Highly branched waxy maize starch (WMS) was used to separate diaspore from artificial mixtures of diaspore and kaolinite by microflotation using dodecylamine (DDA) as collector. It was found that WMS depressed the diaspore flotation while activated the kaolinite flotation more or less. The adsorption of WMS on diaspore was examined through adsorption test, zeta potential measurement, infrared spectroscopy, and atomic force microscopy. It is suggested that both chemical interaction and intermolecular hydrogen bonding by hydroxyl groups of starch with surface Al–OH moieties occurred in the adsorption. Results obtained from the adsorption of DDA and WMS on diaspore showed that starch virtually enhanced the DDA adsorption. The depressant action of WMS can be rationalized primarily by the formation of hydrophilic adsorption layer enveloping the surface of diaspore and covering the collector. [ABSTRACT FROM AUTHOR]

Abstract: The variation of surface properties of pyrrhotite after biological conditioning with Leptospirillum ferriphilum and Acidithiobacillus caldus was evaluated by zeta-potential, adsorption and contact angle measurements. Previous work showed that the pyrrhotite isoelectric point (IEP) shifts towards the cell isoelectric point after interacting with bacterial cells, indicating the adsorption of cells on the pyrrhotite surface. The degree of interaction of pyrrhotite with A. caldus was observed to be much more pronounced than that of L. ferriphilum, because of the different affinity of A. caldus and L. ferriphilum to pyrrhotite. After treatment by A. caldus, the pyrrhotite surface formed a membrane of sulfur, which was shown by X-ray diffractograms (XRD) and the energy dispersion spectrum (EDS), which explains the increasing hydrophobicity of pyrrhotite. However, the contact angle and surface hydrophobicity of pyrrhotite treated by the L. ferriphilum kept decreasing during bioleaching. The results indicate that the energy source for the microorganism growth determines its function mechanism in the bioleaching system. The iron-oxidizing bacteria offer an indirect mechanism function during bioleaching of pyrrhotite and the sulfur-oxidizing bacteria offer a direct mechanism function. [Copyright &y& Elsevier]

The effect of l-cysteine in different concentrations on the bioleaching of Ni–Cu sulfide and marmatite were studied with a moderately thermophilic, sulfur-oxidizing bacterium, strain of Acidithiobacillus caldus. X-ray diffraction (XRD) observations showed the change of bioleached solid residues and the effect of l-cysteine on the surface charges of minerals. It was found that adding certain amounts of l-cysteine to the leaching system of Ni–Cu sulfide largely enhanced the leaching rate, while l-cysteine inhibited the bioleaching of marmatite by A. caldus. The mechanism of l-cysteine interaction with mineral surfaces was studied by means of zeta potential determination and IR spectra. [Copyright &y& Elsevier]

The depression of pyrite (FeS 2) 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. A two-step depression mechanism of CaO and γ-PGA reagents on pyrite flotation. Unlabelled Image • Depression effect of γ-PGA polymer on pyrite was improved by addition of CaO. • Selective separation of FeS 2 and CuFeS 2 was achieved at low doses of CaO and γ-PGA. • Addition of CaO and γ-PGA had synergistic inhibitory effect on pyrite flotation. • Scheme has benefits of environment friendliness and cost-effective characteristics. [ABSTRACT FROM AUTHOR]

• Ultrasound treatment improves separation of ilmenite from titanaugite & olivine. • Treatment condition for maximum difference in floatability was identified. • Effect of ultrasound on different minerals is due to change in mineral dissolution. • Ultrasound converts Fe(II) to Fe(III) and promotes dissolution of Ca and Mg. • Fe(OH) 3 precipitate on ilmenite enhances collector adsorption in floatation. Selective separation of ilmenite from gangue minerals after ultrasonic preconditioning was studied in terms of surface dissolution. After preconditioning, ilmenite exhibited better single-mineral flotation capacity while titanaugite and olivine had lower recoveries. Significant separation could be obtained at pH 6.0 after ultrasonic treatment (500 W, 5 min). Zeta potentials of preconditioned titanaugite and olivine shifted positively compared to those of raw titanaugite and olivine treated with sodium oleate (NaOL), respectively. Meanwhile, the zeta potential of ilmenite was similar before and after NaOL adsorption. Mineral dissolution results indicate that ultrasonic preconditioning promotes the dissolution of Mg and Fe species but not the Ca species. The dissolution of Ca and Mg is much higher than that of Fe. According to solution chemistry calculation, Fe(OH) 3 precipitate is dominant at pH greater than 2.5, and Ca2+, Mg2+, Fe2+, and Fe(OH)+ are dominant under acidic conditions. Microcalorimetric measurements demonstrate that the preconditioned ilmenite releases more heat during NaOL adsorption than titanaugite and olivine do. XPS results reveal that ultrasonic treatment facilitates the conversion of Fe2+ to Fe3+. After preconditioning, Fe species interacted with NaOL to promote the latter's chemisorption on ilmenite and olivine, while Ca2+ was more likely to interact with NaOL on titanaugite. [ABSTRACT FROM AUTHOR]

A schematic representation of the adsorption mechanism of CaO and TCSS on pyrite surface. • Study offers novel depressant scheme combining CaO and TCSS for pyrite flotation. • Synergistic effect of CaO and TCSS achieves separation of chalcopyrite from pyrite. • Addition of CaO significantly promotes the adsorption of TCSS on pyrite surface. • Use of CaO and TCSS can reduce consumption of lime reagent in copper ore industry. • Use of CaO and TCSS can reduce potential environmental impacts of processing. Pyrite depression in xanthate flotation of multiple sulphide minerals has become a serious problem in every mineral industry. The present study introduces a novel and non-hazardous depressant reagent scheme in selective flotation of chalcopyrite from pyrite with sodium butyl xanthate (SBX) as the collector. The combined inhibitory effect of an organic polymer, tricarboxylate sodium starch (TCSS), and calcium oxide (CaO) depressed the flotation of pyrite more strongly than that of the chalcopyrite in a wide pH range of 7–12. The synergistic effect of CaO and TCSS achieved an improved selective flotation separation of chalcopyrite from pyrite at low alkaline pH of 9, for which the recovery of chalcopyrite was over 80% and that of pyrite was less than 19%. The IR spectral, XPS spectral, UV–vis spectral and zeta potential measurements indicated that the surface of pyrite adsorbed significantly more amount of CaO and TCSS than that of the chalcopyrite. The dissolved calcium species preferentially adsorbed on the pyrite surface decreasing its negative charge and promoting TCSS adsorption. The findings of this research are of great significance in reducing the consumption of larger doses of lime in conventional Cu–Fe flotation circuits of the copper industry. [ABSTRACT FROM AUTHOR]

• HEDP was for the first time applied in the separation of chalcopyrite from pyrite. • HEDP exhibited a higher selectivity than widely used ethyl xanthate (EX). • HEDP showed a weaker adsorption on pyrite but a stronger one on chalcopyrite. Ethyl xanthate (EX) is a widely used collector in the flotation of sulfide minerals. However, it also has the disadvantages of low selectivity and harm to human health. Screening and/or designing more selective and green collectors is a 'hot topic' in mineral processing field. In this work, 1-Hydroxyethylidene-1, 1-diphosphonic acid (HEDP), a cheap green reagent widely used in water treatment, was for the first time, applied in the flotation separation of chalcopyrite from pyrite. In addition, a comparative test of the traditional EX collector was also carried out. Flotation results of single mineral and binary mineral mixture showed that HEDP possessed a better selectivity for the separation of chalcopyrite from pyrite than EX. Zeta potential measurement results indicated that HEDP exhibited a stronger adsorption on chalcopyrite and a weaker interaction with pyrite. Hence, HEDP is a promising collector that possesses the potential to replace EX in future chalcopyrite flotation practice. [ABSTRACT FROM AUTHOR]