Sphalerite Surface Research Articles

Selective depression mechanism of combination of lime and sodium humate on arsenopyrite in flotation separation of Zn–As bulk concentrate

Lime (CaO) and sodium humate (NaHA) were used as the combined depressant for arsenopyrite pre-treated by CuSO4 and butyl xanthate. Micro-flotation tests show that the combined depressant CaO and NaHA achieved the selective depression of arsenopyrite. Closed-circuit lab-scale test results indicate that the synergistic effect of CaO+NaHA achieved a satisfactory flotation separation of sphalerite and arsenopyrite, for which the Zn grade and recovery of Zn concentrate were 51.21% and 92.21%, respectively. Contact angle measurements, adsorption amount measurements and X-ray photoelectron spectroscopy analysis indicate that the dissolved calcium species (mainly as Ca2+) were adsorbed on the mineral surfaces, thereby promoting NaHA adsorption. Moreover, the surface of the arsenopyrite absorbed more amount of calcium species and NaHA than that of the sphalerite, thereby accounting for the strong hydrophilic surface of arsenopyrite. The adsorption of NaHA on arsenopyrite was mainly chemical adsorption through its carboxyl groups and Ca atoms, whereas that on sphalerite surface was relatively weak.

Effect of Magnesium on the Hydrophobicity of Sphalerite

The use of untreated recycled water has negative effects in the flotation of zinc sulfide ores due to the presence of dissolved species, such as magnesium and calcium. Although it has been found that magnesium is a more potent depressant than calcium, it has not been investigated in this role or for the effect of adding sodium carbonate. The results of an investigation to evaluate the effect of magnesium on the hydrophobicity of Cu-activated sphalerite conditioned with Sodium Isopropyl Xanthate (SIPX) are presented. Zeta potential of natural and Cu-activated sphalerite as a function of the conditioning pH and Cu(II) concentration, respectively, was first evaluated. Later, the effect of pH and presence of magnesium on the contact angle of Cu-activated sphalerite conditioned with SIPX was studied; it was also evaluated the effect of sodium carbonate to counteract the effect of magnesium. Cu-activation enhances the zeta potential of sphalerite up to a concentration of 5 mg/L. Contact angle tests, thermodynamic simulation, and surface analysis showed that magnesium hydroxide precipitates on the sphalerite surface at pH 9.6, decreasing its hydrophobicity. Addition of sodium carbonate as alkalinizing agent precipitates the magnesium in the form of a species that remained dispersed in the bulk solution, favoring the contact angle of Cu-activated sphalerite and, consequently, its hydrophobicity. It is concluded that the use of sodium carbonate as alkalinizing agent favors the precipitation of magnesium as hydromagnesite (Mg5(OH)2(CO3)4∙4H2O) instead of hydroxide allowing the recovery of sphalerite.

Electronic simulations of alanine and water coadsorption over Defect-free and Sulfur-depleted sphalerite surfaces

Understanding the interactions of amino acids with minerals is crucial for selecting the peptide-based reagents of interest in environmentally friendly ore separation applications. This study aimed to simulate archetypal alanine/water/ZnS complexes through DFT by including explicit water molecules on defectless and sulfur-deficient sphalerite. Swarms of water molecules up to a multilayer were introduced into the simulation cells in order to examine the different types of surface interactions in the solvated mode. Using the grand canonical Monte Carlo method, an efficient strategy was also proposed to diversify the highly plausible initial configurations. Our results revealed that solvated alanine disinclines to form a covalent bond with the defect-free sphalerite surface, thereby the higher affinity toward the neighboring water molecules. On the contrary, sulfur-depleted ZnS surfaces were the siege of stable monodentate bonds between the solvated alanine and Zn atoms around the pruned vacancy site. In particular, our study suggests that the level of interactions between solvated alanine and ZnS can be controlled by tuning the density of sulfur vacancy on the ZnS surface.

Evaluation of 1-hydroxyethylidene-1,1-diphosphonic acid as an efficient and low-toxic sphalerite depressant in the selective flotation of galena from sphalerite

In this work, an environment-friendly sphalerite depressant 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) was exploited in the flotation separation of sphalerite and galena. The flotation performances of sphalerite and galena treated by HEDP were investigated by mineral flotation tests. The depression mechanisms of HEDP on sphalerite were investigated by various characterization techniques such as zeta potential tests, Fourier Transform Infrared Spectrometer (FTIR), X-ray Photoelectron Spectroscopy (XPS) analysis, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and density functional theory (DFT) calculation. Flotation tests showed that HEDP selectively depressed sphalerite but almost did not influence the flotation of galena in sodium isobutyl xanthate (SIBX) system, which achieved effective flotation separation results. zeta potential tests and FTIR results proved the preferential adsorption of HEDP on sphalerite surface, but the pre-adsorbed of HEDP on galena could be replaced by SIBX easily. XPS, ToF-SIMS analysis and DFT calculation demonstrated that HEDP was coordinated with Zn atom through two different phosphonic acid group, forming a six membered chelating ring.

An environmental-friendly sphalerite depressant (2-Hydroxyphosphonoacetic Acid) for the selective flotation separation of sphalerite from galena

In this work, HPAA (2-Hydroxyphosphonoacetic Acid) was explored as a novel sphalerite depressant for the selective flotation of sphalerite and galena. The depression performances and mechanisms were investigated through micro-flotation tests and various characterization techniques. Micro-flotation tests showed that HPAA selectively inhibited sphalerite but barely affected the flotation of galena at board pH range in Sodium Isobutyl Xanthate system (SIBX). Zeta potential, Fourier Transform Infrared Spectrometer (FTIR) and XPS results suggested that HPAA was tended to adsorb on sphalerite surface chemically in the form of a six-membered chelating ring through the complexation of PO3-2 and COO– with Zn atoms on sphalerite surface. Moreover, SIBX could substitute HPAA from galena surface while almost didn’t influence the adsorption of HPAA on sphalerite surface, which rendered galena surface hydrophobic and sphalerite surface hydrophilic. HPAA had potential application prospect because of the good selectivity and environmental compatibility.

Synthesis of trimethylacetyl thiobenzamide and its flotation separation performance of galena from sphalerite

A novel surfactant trimethylacetyl thiobenzamide (TTBA) was synthesized and first conducted as flotation separation collector for galena and sphalerite. The flotation performance of TTBA and traditional collector sodium isobutyl xanthate (SIBX) was investigated by micro-flotation, which displayed that TTBA possessed stronger collecting ability than SIBX for galena, as well as better selectivity than SIBX for sphalerite. Zeta potential tests indicated that TTBA possessed superior selectivity to adsorb onto galena surfaces against sphalerite surfaces. FTIR and XPS results showed that TTBA chemisorbed onto galena surfaces with the formation of new chemical bonds. However, before and after treatment by TTBA, there was no obvious change on sphalerite surfaces, indicating no chemisorption occurred. DFT calculations revealed that C = S and C = O groups were the main reaction sites of TTBA, meanwhile, TTBA adsorbed onto galena surfaces by the formation of Pb-S and Pb-O bonds.

The Evaluation of Sphalerite Surface Formed During Oxidative Leaching in Acidic Ferric Sulfate Media

The Evaluation of Sphalerite Surface Formed During Oxidative Leaching in Acidic Ferric Sulfate Media

The utilization of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) as a novel sphalerite depressant in the selective flotation of galena from sphalerite

In this work, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) was explored as a novel sphalerite depressant in the selective flotation of galena from sphalerite. The separation performances were investigated by single and synthetic flotation tests. The depression mechanism was examined by Fourier Transform Infrared spectroscopy (FTIR), zeta potential and X-ray Photoelectron Spectroscopy (XPS) analysis. The flotation test results showed that PBTCA was an effective sphalerite depressant with good selectivity at broad pH range, which could achieve satisfactory separation results. Zeta potential and FTIR results indicated that PBTCA was more prone to adsorb on sphalerite surface than that of galena. In addition, SIBX could replace adsorbed PBTCA on the galena surface while it was impossible to substitute that on the sphalerite surface, which rendered sphalerite surface hydrophilic and enlarged the floatability difference. XPS analysis manifested that PBTCA was adsorbed on sphalerite surface through the strong complexation between carboxyl, phosphonic acid groups and Zn sites on sphalerite surface, forming C-O-Zn or P-O-Zn bond.

The flotation separation of sphalerite from pyrite through a novel flotation reagent system of FeCl3-CuSO4-aminotriazolethione

To reduce the consumption of lime in mineral processing means reducing CO2 emission. Herein, a novel FeCl3-CuSO4-APTT (4-amino-5-pentyl-1,2,4-triazole-3-thione) approach was first developed to replace the common CaO-CuSO4-xanthate technology during flotation separation of sphalerite from pyrite. APTT exhibited a stronger collecting power towards pyrite than sphalerite, while the attendance of ferric chloride significantly depressed the floatability of pyrite and sphalerite, and its inhibition against pyrite was stronger than that to sphalerite. The addition of cupric sulfate not only removed the inhibition of ferric chloride against sphalerite, but also promoted its floatability. Nevertheless, the floatability of the FeCl3-depressed pyrite was hardly recovered by cupric sulfate. Using FeCl3 as the depressor against pyrite and CuSO4 as the activator for sphalerite, APTT realized a selective and efficient flotation recovery of sphalerite from pyrite in the weakly-acidic medium. FTIR (Fourier Transform Infrared Spectroscopy) and contact angle indicated that the pretreatment with FeCl3 and CuSO4 in sequence significantly weakened APTT adsorption on pyrite, while benefited sphalerite adsorption towards APTT, resulting in creating a dramatical difference of surface hydrophobicity and flotation recovery between the two minerals. XPS (X-ray photoelectron spectroscopy) elucidated that after modifying sphalerite surface successively through FeCl3, CuSO4 and APTT, the Cu-APTT complexes were detected on sphalerite, which were of significance to hydrophobizing its flotation.

Influence of high concentration Zn2+ on floatability of sphalerite in acidic system

The influence of high concentration Zn2+ on the floatability of sphalerite in an acidic system was investigated via flotation experiments, zeta potential measurements, contact angle measurements, and X-ray photoelectron spectroscopy. The results indicated that Zn2+ was adsorbed on the sphalerite surface and a Zn-hydroxyl complex was formed at a pH of 4 and a Zn2+ concentration of 4×10−2 mol/L. The zeta potential increased and the contact angle decreased from 84.80° to 36.48°, strongly inhibiting the floatability of sphalerite. When S2− or Cu2+ activator was used alone, sphalerite was not activated after Zn2+ was adsorbed, and its contact angle did not change significantly. However, by using a combination of S2− and Cu2+ activators, its floatability was realized after Zn2+ adsorption. This result was attributed to the removal of the Zn-hydroxyl complex on the surface of sphalerite by S2−. After this removal, Cu2+ was adsorbed on the sphalerite surface to form a Cu2S·S0 hydrophobic film.

Selective depressive effect of pectin on sphalerite flotation and its mechanisms of adsorption onto galena and sphalerite surfaces

In this work, pectin was investigated as a non-toxic and eco-friendly sphalerite depressant in the flotation separation of galena and sphalerite. The selective adsorption of pectin on sphalerite surfaces was predicted by molecular dynamics simulations, and its depressive effect was evaluated by single- and mixed-mineral flotation tests. The relevant adsorption characteristics and associated interaction mechanisms were further investigated by electrokinetic studies, adsorption density analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The flotation results demonstrated that pectin exerts a selective depressive effect on sphalerite flotation and could achieve the separation of galena from sphalerite. Electrokinetic and adsorption studies confirmed that pectin is adsorbed on both mineral surfaces. However, pectin is adsorbed much less extensively on the galena surface than on the sphalerite surface and could be displaced by xanthate. FTIR and XPS results revealed that the interactions between pectin and galena are physical interactions, the most likely of which is hydrophobic interactions based on the “salting-out” effect. The strong adsorption of pectin on the sphalerite surface was attributed to chemical complexation, and it could not be displaced by xanthate through competitive adsorption. Specifically, pectin is chemisorbed on the sphalerite surface through the O atoms of its –OH and –COOH groups, while Zn atoms on the sphalerite crystals function as adsorption sites.

Selective depression of copper-activated sphalerite by polyaspartic acid during chalcopyrite flotation

Environmentally friendly flotation reagent, polyaspartic acid (PAPA), was tested as a potential selective depressant in the flotation separation of chalcopyrite and Cu-activated sphalerite. The depression mechanism of PAPA was revealed by contact angle measurements, Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR) analysis and inductively coupled plasma (ICP) measurement. The micro-flotation tests with single minerals showed that PAPA selectively depressed Cu-activated sphalerite, while chalcopyrite remained floatable. Moreover, a concentrate containing 31.40% Cu with a recovery of 92.43% was obtained in flotation tests of artificially mixed minerals. Results of contact angle measurements, Zeta potential measurements and FT-IR spectrum revealed that PAPA exerted a much stronger adsorption on Cu-activated sphalerite surface than on chalcopyrite surface, preventing the further adsorption of sodium diethyl dithiocarbamate (DDTC) on its surface. ICP measurements indicated that PAPA had an excellent complexing ability with Cu2+ in flotation pulp, weakening the activation of Cu species on sphalerite surface and producing selective depression.

Adsorption of DTC-CTS on sphalerite (1 1 0) and Cu-activated sphalerite (1 1 0) surfaces: A DFT study

Density functional theory (DFT) was used to simulate the adsorption of dithiocarbamate chitosan (DTC-CTS) on sphalerite (110) and Cu-activated sphalerite (110) surfaces in the presence and absence of water molecules. The results show that the adsorption of DTC-CTS on sphalerite (110) and Cu-activated sphalerite (110) surfaces in the absence of water are physical adsorption and chemical adsorption, respectively. It indicates that the adsorption capacity of DTC-CTS on sphalerite surface is enhanced obviously after being activated by Cu. That’s because DTC-CTS is easier to adsorb on Cu. Besides, the replacement of Zn by Cu on sphalerite (110) surface further enhanced the adsorption ability of DTC-CTS onto S of sphalerite surface. However, the presence of water molecules has little effect on the adsorption of DTC-CTS on sphalerite (110) and Cu-activated sphalerite (110) surfaces. The results of Density of states (DOS) and Mulliken population analysis also confirmed that the adsorption of DTC-CTS on Cu-activated sphalerite (110) surface is easier and more stable than that of sphalerite (110) surface.

Steric hindrance effect on adsorption of xanthate on sphalerite surface: A DFT study

The influence of steric hindrance effect on xanthate adsorption on sphalerite surface has been studied by adopting density functional theory (DFT). On the relaxed sphalerite (110) surface, one surface zinc atom coordinates with three sulfur atoms and is located in the center of a planar triangular structure. The sulfur atom with a large atomic radius could spatially hinder the zinc atom, which subsequently results in steric hindrance effect. Consequently, the interaction of xanthate S atoms with surface Zn has to overcome a potential barrier caused by steric hindrance effect. In addition, the DFT simulation and LST search confirmed that the replacement of surface Zn atom by Cu atom could decrease the energy barrier caused by steric hindrance effect, which is favorable for the adsorption of xanthate. The results could explain why ethyl xanthate with short chain length is hard to adsorb on the clean sphalerite surface, but can strongly adsorb on the Cu-activated sphalerite surface.

Depression mechanism of environment-friendly depressant dithiocarbamate chitosan in flotation separation of Cu-Zn sulfide

The depressant performance and mechanism of dithiocarbamate chitosan (DTC-CTS) in flotation separation of chalcopyrite and sphalerite were investigated by micro-flotation experiment, UV–vis (UV–vis) spectrophotometer determination, time of flight secondary ion mass spectrometry (ToF-SIMS) test and local electrochemical impedance spectroscopy test (LEIS). The flotation results of Cu-Zn (1:1) mixed sulfide showed that chalcopyrite can be effectively separated from sphalerite using DTC-CTS as depressant and butyl xanthate as collector. The optimum conditions for flotation separation of chalcopyrite from the Cu-Zn sulfide were as follows: the dosage of DTC-CTS of 0.4 mg/L, butyl xanthate of 1 × 10−5 mol/L and flotation pH of 10. Copper concentrate with Cu grade of 31.93% and recovery of 85.97%, Zn grade of 4.82% and recovery of 4.18% can be obtained under the above conditions in the Cu-Zn sulfide flotation system. The results of ToF-SIMS showed that DTC-CTS can adsorb on both chalcopyrite and Cu-activated sphalerite surfaces, and the adsorption capacity on the two surfaces is roughly equivalent. UV–vis Spectrophotometric determination and LEIS results indicated that DTC-CTS strongly blocks the subsequent collector adsorption of butyl xanthate on sphalerite surface, but has little effect on the adsorption of butyl xanthate on chalcopyrite. Such difference of collector adsorption on chalcopyrite and sphalerite surfaces differs the surface hydrophobic and further results in the selective separation of chalcopyrite from Cu-Zn sulfide ore.

The synergistic depression of lime and sodium humate on the flotation separation of sphalerite from pyrite

Pyrite depression in flotation separation of Zn-S mixed concentrate has become a difficult and serious problem. This work introduces a non-toxic and efficient depressant reagent scheme in selective flotation separation of spalerite from pyrite with pretreatment by CuSO4 and butyl xanthate (BX). Micro-flotation experiments showed that the combined depressant lime (CaO) and sodium humate (NaHA) depressed the floatability of pyrite more strongly than that of the sphalerite within at pH 11.5–12.0. Moreover, the inhibitory effect of NaHA on pyrite was significantly promoted by calcium-species dissolved from CaO. Real ore sample flotation separation tests showed that the mixed depressant CaO and NaHA acted better than single depressant CaO or NaHA, and the best results were obtained by addition of 850 g/t CaO and 30 g/t NaHA at pH 11.5, with 46.01% Zn grade and 90.11% Zn operating recovery. The synergistic depressing mechanism of CaO and NaHA was revealed through adsorption amount measurements, contact angle measurements, fourier infrared spectroscopic (FT-IR) analysis and X-ray photoelectron spectroscopy (XPS) analysis. Mechanism experiments indicated that the addition of calcium species (mainly as Ca2+ and Ca(OH)+) promoted the adsorption of NaHA on mineral surfaces, and the pyrite surface adsorbed much more calcium-species and NaHA than that of the sphalerite. The chemical adsorption of NaHA on pyrite was mainly through its carboxyl groups and Ca atoms on pyrite surface, while the NaHA adsorption on sphalerite surface was relatively weak.

Influence of Terpenic Oil on Flotation Behavior of Sphalerite and Implication for the Selective Separation

Terpenic oil (TO) is commonly used as a flotation frother for the selective separation of sulfide minerals. As a frother, most reports have mainly focused on its effect on froth stability and froth entrainment, whereas its influence on the floatability of sulfide minerals has received little attention. In this work, the influence of TO on the flotation behavior of sphalerite was investigated by using microflotation tests, contact angle and zeta potential measurements, and FT-IR and SEM-EDS analyses. Microflotation tests conducted in a modified Hallimond tube indicated that compared with the collector potassium butyl xanthate (KBX), the flotation recovery of sphalerite was significantly increased when TO was added to the pulp, but the recovery of Cu-activated sphalerite with the addition of TO was lower than that with the addition of KBX. Contact angle measurements demonstrated that the contact angle of sphalerite was distinctly increased by the addition of TO, but the contact angle of sphalerite treated with TO was lower than that treated with KBX after Cu activation. Zeta potential measurements demonstrated that the zeta potential of sphalerite particles was slightly decreased when treated with TO, and the isoelectric point (IEP) was decreased from 3.3 to 3.1 due to the interaction of TO with sphalerite particles. FT-IR and SEM-EDS confirmed that TO could be adsorbed on the sphalerite surface on the formation of the oil film due to its low solubility, thereby increasing the surface hydrophobicity of the sphalerite. In addition, the TO absorbed on the surface acts as a bridging role and promotes the hydrophobic agglomeration of sphalerite particles. These results suggest that except for froth entrainment, the influence of TO on the flotation behavior of sphalerite may be another reason for the misreporting of sphalerite in concentrates.

Study on the depression mechanism of calcium on the flotation of high-iron sphalerite under a high-alkalinity environment

Although numerous studies on the flotation depression of sphalerite by calcium have been reported, certain issues warrant further investigation. Previous research works did not examine the role that the iron content of iron-bearing sphalerite plays in calcium depression and did not obtain direct and convincing microscopic evidence of calcium adsorption to support the depression of calcium-containing ions on iron-bearing sphalerite’s flotation. In this paper, the effects of iron content and the presence of calcium on iron-bearing sphalerite’s flotation depression under high alkalinity environment are studied using flotation tests, adsorption amount measurements, surface extraction, zeta potential measurements, time-of-flight secondary-ion mass spectrometry (TOF-SIMS) and density functional theory (DFT) calculations. The results show that increasing iron content or the presence of calcium will lead to an increase in the degree of flotation depression and will reduce the adsorption of copper and xanthate. Increasing iron content will cause the surface of iron-bearing sphalerite to adsorb more metal hydroxides (especially iron hydroxide) and calcium. The TOF-SIMS results confirmed the trend of calcium adsorption at the atomic level. DFT calculations show that the adsorption energy of CaOH+ on the surface of iron-substituted sphalerite is lower than that on the surface of ideal sphalerite. The following conclusions can be obtained through analysis of the aforementioned: Increase in the adsorption of hydroxides (especially iron hydroxide) and calcium significantly hinder the adsorption of copper and xanthate, and increase the hydrophilicity of high-iron sphalerite surface, which ultimately leads to an increase in the degree of flotation depression of high-iron sphalerite with increasing iron content.

Chemical transformation and dissociation of amino acids on metal sulfide surface: Insights from DFT into the effect of surface vacancies on alanine-sphalerite system

The affinity of amino acid species toward mineral surfaces is a favorable phenomenon in green material science applications. To this end, we performed a DFT calculation to study adsorption of alanine on the sphalerite (ZnS) surface, focusing on the role of surface vacancy defects by removing single sulfur, single zinc and double neighboring congruent atoms from the outermost layer. Removal of single sulfur or zinc atom led to surface reconstruction by forming favorable local Zn-Zn and S-S bonds around the defect sites, respectively. The presence of double neighboring congruent vacancies and their relative positions altered the adsorption configuration to more complicated modes. The lowest-energy configuration was predicted when both sulfur and zinc atoms were removed from the upper hill of the surface. In this case, alanine was dissociatively adsorbed on the surface, and a tridentate bond was formed between alanine and two zinc atoms on the surface. The alanine affinity was also significantly more stable than the defect-free surface with an energy difference of about 55 kcal/mol. In another special case with two Zn and S vacancies, respectively, on the downward and upper hills, alanine underwent a chemical transformation from neutral to zwitterionic form according to an intramolecular dissociation reaction.

Synergistic depression mechanism of zinc sulfate and sodium dimethyl dithiocarbamate on sphalerite in Pb−Zn flotation system

Abstract The depression mechanism of zinc sulfate (ZnSO4) and sodium dimethyl dithiocarbamate (DMDC) as the combined depressant on sphalerite was investigated by micro-flotation experiments, ion complexing tests, contact angle tests and X-ray photoelectron spectroscopy (XPS) analysis. The micro-flotation tests revealed that ZnSO4+DMDC had a better selective depression effect on sphalerite than using single ZnSO4 or DMDC. Ion complexing tests confirmed that DMDC had a strong complexing capacity with lead ions or hydroxy complexes. Contact angle tests illustrated that ZnSO4+DMDC makes the sphalerite surface more hydrophilic than ZnSO4 or DMDC. XPS analysis indicated that the combined depressant could prevent collector adsorbing on the Pb-activated sphalerite surface by a competitive adsorption method, while the combined depressant and collector were co-adsorbed on galena surface.