Xanthate Adsorption Research Articles

The influence of NaCl on xanthate adsorption on chalcopyrite surface and chalcopyrite flotation

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

Pyrite activation in seawater flotation by copper and lead ions: XPS and in-situ electrochemical investigation

Pyrite, as the main carrier of gold, can be collected via flotation which consumes high volumes of fresh water. Seawater is the promising alternative to fresh water, especially in the fresh water deficient regions. However, pyrite flotation is usually ineffective in seawater, which requires activation prior to recovery. This study mainly focuses on the roles of Cu2+ and Pb2+ on pyrite flotation in seawater. The flotation and contact angle results indicated that Cu2+ and Pb2+ obviously increased pyrite recovery in seawater by enhancing its surface hydrophobicity. Further XPS studies revealed that the formation of Fe-S-Cu(I) and Fe-O-Cu(II) on pyrite surface due to Cu2+ activation while the presence of Fe-O-Pb(II) and Fe-SO-Pb(II) due to Pb2+ activation, thereby improving the active sites and adsorption of xanthate. In addition, the in-situ scanning electrochemical microscopy (SECM) results showed that the formation of Cu2+ and Pb2+ activated products increased the electrochemical reactivity of pyrite surface, which was the main reason for the improved pyrite floatability. Moreover, the current consequence evolution indicated that pyrite activation by Cu2+ was stronger than that by Pb2+. The SECM imaging also showed that the adsorption of xanthate decreased the electrochemical reactivity on pyrite surface, with more significant role observing on the activated surface than that of the un-activated pyrite. It should be noted that the Cu2+/Pb2+ activation and xanthate adsorption were distributed unevenly on pyrite surface. This study therefore provides an in-situ approach to understand the role of inorganic ions and reagents on pyrite flotation in seawater, providing a promising strategy to use seawater for the flotation recovery of gold.

An investigation into the effect of Eh and pH on the adsorption of a xanthate collector on sperrylite (PtAs₂): A surface and solution characterization study

There is evidence of a very weak interaction between sperrylite and xanthate collectors at pH 9, the typical pH used in PGM concentrators. This results in the mineral being hardly hydrophobic when exposed to such collectors. Xanthate collectors adsorb via an electrochemical mechanism which is dependent on pH and Eh. In this study, it was shown that potassium amyl xanthate (PAX) adsorption increases with decreasing pH, with 2.9x10−05 mol/m2 adsorbed at pH 3 compared to only 0.4x10−05 mol/m2 at pH 9. Furthermore, spectroscopic analyses performed in this study showed that PAX is adsorbed as dixanthogen at pH 3 whereas this species was not observed at pH 9. In addition to dixanthogen, the collector may be co-adsorbed as the metal xanthate on sperrylite. However, it is the specific presence of dixanthogen that ultimately strongly promotes the hydrophobicity of the mineral. The adsorption of the collector on sperrylite correlated well with the flotation recovery of this mineral. The microflotation recovery of sperrylite was improved from 22 % at pH 9 to 61 % at pH 3. On the other hand, the use of NaClO to chemically modify Eh was shown to result in excessive oxidation of sperrylite and/or resulted in a reaction between NaClO and PAX which in fact hindered the ability of the collector to impart hydrophobicity. This was found to have a detrimental effect on the floatability of sperrylite. Ultimately, this study provides evidence and insights into the floatability of sperrylite.

Investigation of pullulan polysaccharide as a sphalerite depressant for chalcopyrite separation: Flotation behavior and interfacial adsorption mechanism

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

Synergistic adsorption of ethyl xanthate and butyl xanthate on pyrite surfaces: A DFT study

AbstractPyrite is the most widely distributed sulfide mineral with a wide range of uses, and pyrite is mainly recovered by means of flotation in practical production, and the commonly used flotation collectors are mainly xanthates with good flotation performance. The adsorption behavior of commonly used collectors ethyl xanthate and butyl xanthate on the surface of pyrite is investigated by using the density functional tight bounding theory (DFTB). The results show that when a single reagent acts on the pyrite surface, butyl xanthate has a stronger effect than ethyl xanthate, and the adsorbed mineral surface shows obvious hydrophobicity. The interaction between ethyl xanthate and butyl xanthate had a stronger effect than that of a single reagent, and the simulation of the flotation environment at ordinary temperature using molecular dynamics revealed that the synergistic adsorption of the two different reagents on the surface of pyrite was more hydrophobic, that is, the synergistic adsorption of the combined collector of ethyl xanthate and butyl xanthate on the surface of pyrite was stronger. The results of the study are of great significance for the synergistic effect between the combined collector and the mineral.

First Principle Study of the Relationship between Electronic Properties and Adsorption Energy: Xanthate Adsorption on Pyrite and Arsenopyrite

First Principle Study of the Relationship between Electronic Properties and Adsorption Energy: Xanthate Adsorption on Pyrite and Arsenopyrite

Co-modification of chrysocolla with ammonia and 1,2-diaminopropane and its response to flotation

Chrysocolla is a typical copper oxide with unique structural characteristics and a variable chemical composition, which make its recovery by flotation considerably challenging. A novel ammonia-1,2-diaminopropane-xantahte (NH3·H2O-1,2-DAP-xanthate) flotation method was proposed in this study for its effective recovery. Compared with the 1,2-DAP-xanthate system, the recovery of chrysocolla was substantially increased from 73.43 % to 95.26 % using the NH3·H2O-1,2-DAP-xanthate system. X-ray photoelectron spectroscopy, zeta potential, Fourier transform infrared spectroscopy, xanthate adsorption capacity, and time-of-flight secondary ion mass spectrometry analyses showed that the increase in the chrysocolla flotation recovery was attributed to an increased in the effective xanthate adsorption on the chrysocolla surface. The additional adsorption of xanthate could be attributed to the alteration of the surface properties of the chrysocolla by NH3·H2O, which exposed more copper sites and reduced the hydrophilic component of the surface. This promoted the effective adsorption of more 1,2-DAP on the mineral surface. Thus, more chelated copper formed, which improved the mineral surface activity and increased the number of active sites interacting with the xanthate.

An in-situ study of the interaction mechanism between xanthate and unactivated/Cu-activated sphalerite surfaces at solid–liquid interfaces

The mechanism of surface hydration and xanthate adsorption in the flotation of unactivated/Cu-activated sphalerite is still controversial. Therefore, a study combining in-situ measurement and quantum simulation is employed to investigate the interaction mechanism of ethyl xanthate (EX) and butyl xanthate (BX) on the fully hydrated, unactivated/Cu-activated sphalerite surfaces at solid–liquid interfaces. Density functional based on tight-binding (DFTB+) and molecular dynamics (MD) results suggest that the Cu-activated surface is hydrophobic with the first layer of water being distributed more disorderly on it. This is due to the difficulty of the lone pair electrons of water to interact with Cu. On the unactivated surface, water adsorption is more favorable than xanthates, hence, water molecules are physically adsorbed on it. Whereas the interaction of EX/BX with the hydrated, activated surface is chemisorption. The higher reactivity of Cu+ d orbitals to form π-backbonds with xanthate and the orbital symmetry matching of the Cu dyz orbitals and xanthate pz orbitals contribute to these results. Microcalorimetric results also demonstrate that copper activation enhances the exothermic heat and reaction rate, facilitating the interaction of EX/BX with sphalerite. These are consistent with the flotation and quartz crystal microbalance with dissipation (QCM-D) results.

Influence of pyrite surface defects on xanthate adsorption: A density functional theory perspective

Many scholars have studied the adsorption behavior of various ions and agent molecules on pyrite surfaces based on density functional theory (DFT) calculations, however, the adsorption behavior of pyrite by surface defects has been relatively less studied. In this study, we try to produce defects on the surface of pyrite by hydration and study them systematically. The effects of pyrite surface defects on the molecular adsorption of xanthates were investigated on the atomic scale by combining DFT calculations, and AFM observation methods, respectively. The results indicate that oxygen molecules can indirectly participate in hydration reactions and promote crystal defect generation. In addition, the absence of coordination intensifies the electron transfer of pyrite, which favors the formation of new coordination with xanthates, and the adsorption energy is also reduced. Defects lead to an increase in the number of xanthate molecules at the adsorption site, and the adsorption capacity is also enhanced. The adsorption morphology was analyzed by AFM measurements to confirm the DFT calculation results. The complex interfacial system of sulfide ores was investigated, and it was found that the hydration process of sulfide ores generates surface defects, which further promote xanthate molecules adsorption. The results extend the traditional electrochemical adsorption theory of sulfide ores and provide theoretical support for the study of the molecular dynamics adsorption process on the surface of sulfide ores.

Activation flotation of lime-depressed pyrite with carbon dioxide: Performances, mechanism and pilot-scale application

Activation flotation of lime-depressed pyrite by sulfuric acid (H2SO4) is usually accompanied by safety hazards and environmental pollution. Exploring eco-friendly, economical and effective activator to replace H2SO4 holds great significance for the sustainable development of mining industry. In this study, carbon dioxide (CO2) as a potential activator was applied in activation flotation of lime-depressed pyrite. Micro-flotation experiments results showed CO2 significantly improved the floatability of pyrite, and a maximum recovery of 93.94% was achieved under optimal operating conditions. The activation mechanism was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated the depression of pyrite by lime was attributed to the formation of iron oxide/hydroxide species and calcium film, and CO2 effectively eliminated these hydrophilic compounds from the surface of pyrite, thus promoted the adsorption of xanthate onto the pyrite surface. Moreover, the anodic oxidation of xanthate on pyrite and the influence of CO2 on this process were investigated by cyclic voltammetry measurements. It was found that xanthate oxidation to form dixanthogen was more likely to occur in the presence of CO2, and this reaction replaced pyrite surface oxidation as the dominant anodic process. Finally, pilot-scale experiments were successfully conducted and the recovery of pyrite reached 93.18%, surpassing the ore dressing index of using H2SO4 as activator in actual production at the same period. Moreover, the concentration of sulfate ions in mineral processing wastewater was significantly reduced, and the annual cost of activator can be saved by 0.52 million RMB. The new process of activation flotation pyrite with CO2 has prospects for large-scale application in terms of activation performance, cost-effectiveness and environmental impact.

Experimental and DFT study of modified malachite with 2,5-dimercapto-1,3,4-thiadiazole and its response to sulfidization-xanthate behavior

Malachite is industrially recovered using sulfidization–xanthate flotation. However, due to the instability of the sulfidization effect, it is necessary to strengthen the sulfidization process. To this end, a 2,5-dimercapto-1,3,4-thiadiazole (DMTD) can modify the malachite surface for enhanced sulfidization. Analysis of the sulfidization products indicated that more of highly active Cu2S(Cu(I))species and polysulfides (Sn2−) were found, indicating that the DMTD-modified malachite surface facilitated the adsorption of S components and improved the surface reactivity. Analysis of the sulfidized surface revealed that DMTD and Na2S together increased the ionic strength of S, further confirming that the DMTD-modified malachite surface facilitates S adsorption. Density Functional Theory (DFT) simulates implicate that the intensified sulfidization of malachite surface is due to the resultant of Cu-S products with various degrees of binding and enhanced interactions between S and Cu atoms. Analysis of the sulfidization efficiency of malachite surface confirmed that the DMTD-modified surface adsorbed additional -S components. Changes in the surface potential and contact angle of malachite suggested that the DMTD-modified surface was higher hydrophobic owing to strong adsorption of xanthate. Flotation experiments confirmed that DMTD can improve the sulfidization-xanthate floatability.

Ethyl xanthate adsorption on different surfaces of jamesonite: A DFT study

Adsorption of ethyl xanthate (EX) on jamesonite surfaces with exposing Pb, Fe and Sb (M1), Sb and Pb (M2) and Pb and Fe (M3) was investigated by DFT method. Adsorption energy of EX on M3 is the largest, −236.51 kJ/mol; and then M2, −189.62 kJ/mol; and M1, −65.84 kJ/mol in order. For EX adsorption on M1 surface, S1 and S2 of EX are bonded to Fe1 and Sb1 of jamesonite surface, respectively. However, high spin distribution of d-electrons of Fe2+ leads to the weak interaction between Fe1 and S1. Despite the high polarization rate of Sb3+, the interaction of Sb1 of M1 with S2 of EX is weak, which may be due to the coordination structure of Sb (3-coordination) and structure change of EX. Two sulfur atoms (S1 and S2) of EX are simultaneously bonded to Sb1 (2-coordination) of M2 surface for EX adsorption on M2, leading to the stronger interaction between EX and M2 than that between EX and M1. As for EX adsorption on M3, only S1–Pb1 bond is formed, but the far larger polarization rate of Pb2+ than Sb3+ leads to the stronger interaction between EX and M3 than that between EX and M2.

Effects of seawater on the adsorption of xanthate onto galena and sphalerite

Seawater contains divalent calcium and magnesium cations. Under alkaline conditions, calcium and magnesium ions react with hydroxide ions to form insoluble hydroxyl complexes or hydroxide precipitates. The hydrophilic substances that may be adsorbed on the mineral surface during the flotation process hinder the adsorption of the collector, affecting mineral hydrophobicity, and thus reducing the floatability of the mineral. In this study, the effects of seawater on the adsorption of xanthate onto galena and sphalerite were investigated. The results show that under strong alkaline conditions, seawater has significant and slight adverse effects on sphalerite and galena, respectively. Flotation regulators such as ethylenediamine tetraacetic acid, sodium hexametaphosphate, and sodium silicate can eliminate the adverse effect on galena and sphalerite flotation to a certain extent. The mechanisms were revealed through microflotation experiments, contact angle measurements, bubble-particle attachment tests, zeta potential measurements, and XPS analysis.

Effects of Au doping on the adsorption of xanthate on pyrite surface in presence of H2O: A DFT study

Despite density functional theory (DFT) has been widely applied in the study of Au-doped pyrite, effects of Au doping on the structural properties and floatability of pyrite still remain uncertain. Most of the previous studies were carried out in vacuum disregarding the existence of water molecules, which were inconsistent with the real flotation system. This work aims to study the adsorption behavior of ethyl xanthate on the surface of perfect pyrite and Au-doped pyrite in presence of water molecules through DFT calculations. It was found that the doped Au expanded the lattice of pyrite (100) surface, with enhanced conductivity and chemical reactivity. After Au-doping, the population and covalence level of Fe-S bond of pyrite was reduced, making Fe atoms prone to interact with water molecules and xanthate. The binding energy and density of states (DOS) analysis indicated that Au-doping enhanced the binding ability of xanthate with pyrite surface more significantly than water molecules. Therefore, Au-doping promoted the adsorption of xanthate on pyrite surface in presence of water molecules. This study is of guiding significance for investigating the flotation behavior of Au-doped pyrite and flotation reagents design.

Effect of ammonium carbamate on catalytic sulfidation and flotation of azurite

This study aimed to investigate the effectiveness of catalytic sulfidation using ammonium carbamate and sodium sulfide to achieve satisfactory flotation recovery rates of azurite. The recovery rate of 82.51 % azurite was achieved through catalytic sulfidation. The Cu(II) and S2− species on the pure azurite surface were reduced and oxidized to Cu(I) species, Sn2− or S2− species, respectively. The analyses revealed that the rougher the azurite surface, the higher the atomic concentration of S and the more CuS2 species formed, and the more xanthate adsorption led to the formation of hydrophobic surfaces, promoting the flotation of azurite. The dissociative adsorption of H2O molecules on the (011) surface of azurite hindered further adsorption of HS− species on the (011) surface of azurite. The adsorption energy of HS− species on the (011) surface of azurite was more negative with NH3, indicating that the NH3 enhanced the adsorption of HS− species. In addition, the chemical bond strength of Cu-S formed through catalytic sulfidation of azurite was stronger than the chemical bond strength of Cu-S formed through direct sulfidation. The enhancement between S and Cu bonds greatly improved the stability of sulfide layers after catalytic sulfidation.

The effects of NaCl addition on the particle-bubble interactions of galena in the presence of xanthate

This work investigated the effects of NaCl addition on galena flotation in the presence of xanthate. The micro-flotation experiments were performed using NaCl solutions which also included xanthate, at pH 9 (±0.1). Our results indicated that galena recovery improved for higher NaCl as well as higher xanthate concentrations.A pH-dependent chemisorption model for the galena surface, with the addition of xanthate adsorption was calibrated using measured zeta potential values. We propose that xanthate adsorption on galena can take place via two separate mechanisms. The first mechanism involves direct xanthate chemisorption to specific surface sites. The second mechanism involves lead/xanthate complexes formed in the bulk solution. These lead/xanthate complexes attach on the galena surface as hydrophobic lead xanthate salts.The galena-air bubble interactions are repulsive in 1 mM NaCl, with or without xanthate, consistent with the lower galena recovery measured experimentally. An increase to 100 mM NaCl, irrespective of the xanthate addition, resulted in attractive galena-air bubble total interaction energies. The agreement with the experimental results shows the effectiveness of the charge regulated model for estimating the galena and air bubble behaviours during flotation in NaCl solutions.

Efficient adsorption of butyl xanthate by imidazolium ionic liquid modified fumed silica

Butyl xanthate (BX) usually serve as an available collector in the sulfide mineral flotation. However, it will cause severe pollution and be harmful for living beings when discharged together with beneficiation wastewater. Adsorption, affected by sorbents structure to a great extent, is an effective strategy to treat BX-bearing wastewater. In this paper, ionic liquid-loaded fumed silica (IFS) generated by a simple process was acted as an adsorbent for removing BX from aqueous solution. The ratio of IL loaded onto silicon was about 40 %. The N elements existing in the structure of adsorbents suggested IL loaded onto silica surface successfully. The specific surface area of IFS was 65.25 m2/g, which was smaller than original material. And the total pore volume decreased from 36.75 to 15.22 cm3 g−1 after modification. Different from the virginal silica barely adsorbing BX, ionic liquid (IL) loaded silica had large uptake capacity up to 202.84 mg/g under the combined effect of functional groups modified in the silica particle and the porous structure of nanomaterial. The adsorption kinetics and isotherms are followed with the pseudo-second-order model and Langmuir model, respectively. And the functional groups, charge of adsorbent were analyzed to reveal approaching mechanism. This paper provides an alternative for xanthate and other organic contaminants treatment.

The mechanism of surface activation in sphalerite by metal ions with d10 electronic configurations: Experimental and DFT study

The activation mechanism of metal ions with d10 inert electronic configurations on sphalerite (ZnS) were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS), combined with density functional theory (DFT). Flotation experiments showed that the addition of activators increased sphalerite recovery by 50–70 %. The XPS results indicated that these inert cations with d10 electronic configurations formed stable metal sulfides (Cu2S, CuS, Ag2S, CdS, and HgS) on the sphalerite surface. The FTIR results demonstrated that the activated sphalerite enhanced the adsorption stability of butyl xanthate on the sphalerite surface. DFT studies found that metal ion introduction reduced surface relaxation and decreased the band gap on the sphalerite surface, both of which increased butyl xanthate adsorption. Finally, it was suggested in this study that the energy required for the d10 to d9s1 electron transition and the polarization could be used to predict the potential sphalerite activator.

Synergistic activation of sulfidized hemimorphite with copper-lead species for improving surface hydrophobicity and floatability

In this work, the synergistic effects of Cu2+ and Pb2+ on the flotation behavior, surface properties, and xanthate adsorption of sulfidized hemimorphite were investigated through flotation experiments, surface analysis, and solution determination. The results of the micro-flotation tests indicated that the flotation recovery of sulfidized hemimorphite increased after synergistic activation with Cu2+ and Pb2+, the flotation index can reach about 87%, and superior to that treated with single Cu2+ or Pb2+. Zeta potential, XPS, and ToF-SIMS measurements showed that Cu2+ and Pb2+ were adsorbed onto the sulfidized hemimorphite surface, and multi-metal sulfide species, such as zinc sulfide, copper sulfide, and lead sulfide, were formed. Compared to a single treatment with Cu2+ or Pb2+, the content and activity of sulfidization products became increased after sulfidized hemimorphite was simultaneously activated. The formation of a greater amount of highly active copper and lead species was beneficial for the adsorption of xanthate onto the sulfidized hemimorphite surface, improving surface hydrophobicity. FT − IR, contact angle, and adsorption capacity measurements showed that more xanthate species interacted with the sulfidized hemimorphite surface activated with Cu2+ and Pb2+, and the surface hydrophobicity of the sulfidized hemimorphite was significantly enhanced.

The combination of calcium hypochlorite and fulvic acid as an efficient arsenopyrite depressant in Cu-As separation

In this work, fulvic acid (FA) was tested as a novel arsenopyrite depressant in the flotation separation of chalcopyrite from arsenopyrite with or without calcium hypochlorite (Ca(ClO)2). The flotation behaviors were investigated by single and artificial mixed mineral flotation tests. The depression mechanism of FA and Ca(ClO)2 on mineral surface was uncovered by electrochemical measurement, Zeta potential, contact angle, adsorption capacity, Raman, Fourier Transform Infrared spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS). Flotation tests illustrated that FA had strong depression action on arsenopyrite but hardly influenced the flotation of chalcopyrite with or without Ca(ClO)2. Electrochemical measurement and Raman spectra results showed that the oxidation degree of arsenopyrite surface was higher than that of chalcopyrite. Zeta potential, FTIR and adsorption capacity results illustrated that FA preferred to adsorb on arsenopyrite surface than chalcopyrite surface, and the introduction of Ca(ClO)2 facilitated the adsorption of FA on arsenopyrite surface. XPS results indicated that Ca(ClO)2 promoted the oxidation of arsenopyrite surface to form more iron oxide products. In addition, FA strongly absorbed on arsenopyrite surface via the complexing between hydroxyl groups and Fe oxidized product to form Fe-OH species, preventing the adsorption of sodium isobutyl xanthate (SIBX) on arsenopyrite and rendering it hydrophilic. While FA weakly adsorbed on chalcopyrite surface, which could be substituted by SIBX and regain hydrophobicity.