Synergistic activation of smithsonite with copper–ammonium species for enhancing surface reactivity and xanthate adsorption

Feng Q., Wang M., Zhang G., Zhao W., Han G.

In the flotation of zinc oxide minerals, unavoidable lead ions (Pb2+) in the pulp interact with the mineral surface, sulfidizing reagents, and collectors. This interaction affects the sulfidization characteristics and xanthate adsorption on the surfaces of zinc oxide minerals. In this study, the mechanism of the interaction between Pb2+ and smithsonite surfaces, its effect on the surface sulfidization of smithsonite, and its response to xanthate adsorption were investigated. The flotation results showed that the addition of 5 × 10−4 mol/L Pb2+ in the pulp greatly increased the smithsonite flotation recovery. Pb2+ can interact with smithsonite surfaces to form a significant layer of lead-containing species. The amount of sulfide species on the smithsonite surface significantly increased after Pb2+ pretreatment and sulfidization. This shows that Pb2+ pretreatment promoted the reaction between the mineral surface and sodium sulfide because of the newly generated lead-containing species on the smithsonite surface. Infrared spectroscopy showed that the amount of xanthate adsorbed on the smithsonite surface in the Pb2+–sulfidization–xanthate system was larger than that in the sulfidization–xanthate system. An appropriate concentration of Pb2+ in the pulp before sulfidization could therefore promote sulfidization of smithsonite surfaces and improve xanthate adsorption. This would enhance the hydrophobicity of the smithsonite surfaces and increase the smithsonite flotation recovery.

Feng Q., Yang W., Wen S., Wang H., Zhao W., Han G.

Copper oxide minerals are important copper resources, which include malachite, azurite, chrysocolla, cuprite, etc. Flotation is the most widely used method for the enrichment of copper oxide minerals in the mineral processing industry. In this paper, the surface properties of copper oxide minerals and their effects on the mineral flotation behavior are systematically summarized. The flotation methods of copper oxide minerals and the interaction mechanism with reagents are reviewed in detail. Flotation methods include direct flotation (using chelating reagents or a fatty acid as collector), sulfidization flotation (using xanthate as collector), and activation flotation (using chelating reagents, ammonium/amine salts, metal ions, and oxidant for activation). An effective way to realize efficient flotation of copper oxide minerals is to increase active sites on the surface of copper oxide minerals to enhance the interaction of collector with the mineral surface. Besides, various perspectives for further investigation on the efficient recovery of copper oxide minerals are proposed.

Zhao W., Yang B., Liu D., Feng Q.

This work proposed a promising method to increase the flotation recovery of smithsonite in the sulfidization xanthate system by activation with copper ions prior to addition of Na 2 S. The effect of copper ions on surface properties, sulfide adsorption, and floatability of smithsonite was examined using micro-flotation experiments, solution composition determination, and surface measurements. The flotation recovery of smithsonite activated by copper ions was superior to that in the direct sulfidization system, along with a maximum increase by approximately 19%. It was ascribed to an increase in active sites on smithsonite surfaces due to the formation of –O–Cu complexes. Cu 2+ in the pulp solution bonded to O sites on smithsonite surfaces, and Cu(OH) + interacted with –OH species through dehydration reaction to form activation products. It was beneficial to the interaction of sulfide species with smithsonite surfaces, and more sulfidization products formed on the mineral surface. The sulfidization products were composed of copper sulfide and zinc sulfide species in the enhanced sulfidization system, and copper sulfide species exhibited higher affinity to xanthate than zinc sulfide. It greatly improved the surface hydrophobicity of smithsonite after enhanced sulfidization with copper ions, thereby promoting the flotation recovery of smithsonite, which is significant for the sustainable production of refractory zinc oxide ores. • Copper species could interact with O sites on smithsonite surfaces to produce –O–Cu complexes. • Both copper sulfide and zinc sulfide species formed on smithsonite surfaces after enhanced sulfidization. • More sulfide species adsorbed on smithsonite surfaces with copper ions. • Flotation recovery of smithsonite was significantly increased after activation by copper ions.

Zhao W., Wang M., Yang B., Feng Q., Liu D.

• Copper–ammonium species exhibited superior activation performance than individual copper ions. • The activity of sulfidization products on smithsonite surfaces enhanced after activation with copper–ammonium species. • Addition of copper–ammonium species significantly enhanced the surface hydrophobicity of smithsonite. • Smithsonite floatability greatly increased in the synergistic activation system of copper–ammonium species. Copper–ammonium species were introduced in this work to improve the surface sulfidization and flotation performance, and the mechanism was revealed by solution composition determination and surface measurements. Results showed that copper–ammonium species exhibited superior activation performance compared to individual copper ions, and more copper ions were transferred onto the smithsonite surface to increase the mineral surface reactivity with sulfide and xanthate species. Compared with the individual activation system of copper ions, a superior sulfidization of smithsonite was obtained in the synergistic activation system of copper–ammonium species. The activation of smithsonite surfaces with copper–ammonium species not only increased the content of copper sulfide species, but also enhanced the activity of sulfidization products on the surface of smithsonite. Accordingly, a greater amount of xanthate species adsorbed on the surface of smithsonite, and the surface hydrophobicity significantly was enhanced after smithsonite was activated with copper–ammonium species. Compared with treatment in the direct sulfidization system, the flotation recovery of smithsonite increased by approximately 30% under the optimum flotation conditions after treatment in the synergistic activation system of copper–ammonium species. The research results provide a potential technology for promoting the efficient recovery of zinc oxide minerals through sulfidization xanthate flotation.

Wang H., Wen S., Han G., He Y., Feng Q.

Malachite is one of the main minerals used for the industrial enrichment and recovery of copper oxide resources, and copper ions are unavoidable metal ions in the flotation pulp. The microflotation, contact angle, and adsorption experiments indicated that pretreatment with an appropriate concentration of copper ions could improve the malachite recovery, and the addition of excess copper ions reduced the hydrophobicity of the malachite surface. The results of zeta potential tests indicated that sodium sulfide and butyl xanthate were also adsorbed on the surface of malachite pretreated with copper ions. X-ray photoelectron spectroscopy (XPS) results indicated that —Cu—O and —Cu—OH bonds were formed on the surface of the samples. After pretreatment with an appropriate concentration of copper ions, the number of —OH groups on the mineral surface decreased, whereas the number of Cu—S groups on the mineral surface increased, which was conducive to the sulfidization of malachite. After adding a high concentration of copper ions, the —OH groups on the mineral surface increased, whereas the number of Cu—S groups decreased, which had an adverse effect on the sulfidization flotation of malachite. Time-of-flight secondary ion mass spectrometry showed that pretreatment with copper ions resulted in a thicker sulfidization layer on the mineral surface.

KURSUNOGLU S., TOP S., KAYA M.

The recovery of zinc and lead from Yahyali non-sulphide flotation tailing using sulfuric acid followed by sodium hydroxide leaching in the presence of potassium sodium tartrate was experimentally investigated. In the acidic leaching stage, the effects of pH, solid-to-liquid ratio and temperature on the dissolution of zinc from the tailing were explored. 82.3% Zn dissolution was achieved at a pH of 2, a temperature of 40 °C, a solid-to-liquid ratio of 20% and a leaching time of 2 h, whereas the iron and lead dissolutions were determined to be less than 0.5%. The sulfuric acid consumption was found to be 110.6 kg/t (dry tailing). The leaching temperature had no beneficial effect on the dissolution of zinc from the tailing. The acidic leach solution was subjected to an electrowinning test. The cathode product consisted of 99.8% Zn and 0.15% Fe. In the alkaline leaching stage, the Pb dissolution increased slightly in the presence of potassium sodium tartrate. More than 60% of Pb was taken into the leach solution when the leaching temperature increased from 40 to 80 °C. The final leach residue was analyzed by XRD and XRF. The XRD results indicated that the major peaks originated from the goethite and quartz while minor peaks stem from smithsonite and cerussite. The XRF analysis demonstrated that the residue contained 70.3% iron oxide. Based on the sequential leaching experiments, the zinc and lead were excellently depleted from the flotation tailing, leaving a considerable amount of iron in the final residue.

Bai X., Liu J., Wen S., Wang Y., Lin Y.

The sulfidization–xanthate method is an important method for recovering smithsonite. As the sulfidization time increases, the newly formed sulfidization layer on the smithsonite surface is unstable, which causes attenuation and affects the recovery efficiency. We studied the stability of the sulfidization layer of smithsonite and the effect of ammonium chloride on the sulfidization layer by microflotation experiments, sulfur adsorption test, X-ray photoelectron spectroscopy and time-of-flight secondary mass spectrometry. Microflotation experiments results showed that ammonium-chloride addition can increase the recovery efficiency of the smithsonite by ~10%. Sulfur adsorption test results showed that after ammonium-chloride addition, more sulfur components were formed on the smithsonite surface. XPS results showed that after ammonium-chloride addition, the atomic concentration of the surface sulfur component increased from 0.09% to 2.38%. ToF-SIMS results showed that the newly formed sulfide component was more evenly distributed and the surface of the sulfide layer was smoother. The sulfur composition and sulfide layer thickness increased significantly, which increased the sulfide layer stability and improved the recovery efficiency of the smithsonite. All these details have established that the ammonium chloride has a good promoting effect on the sulfidization of smithsonite and increases the sulfidization layer stability.

Luo B., Liu Q., Deng J., Li S., Yu L., Lai H.

In this study, microflotation experiments, as well as inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), localized electrochemical impedance spectroscopy (LEIS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to understand the influence of lead ions on smithsonite flotation during sulfidation processing and determine the lead sulfur species formed on the mineral surface. Lead ions significantly improve smithsonite recovery in microflotation experiments. The depletion of lead ions and the clear reduction in the concentration of sulfur ions in solution indicate that lead ions act as activators that greatly modify the smithsonite surface during sulfidation processing. XPS showed that lead-sulfide complexes and PbCO3 form on the mineral surface. These lead-sulfide complexes exist in the forms of lead monosulfide and lead polysulfide. PbS+, PbS2﹣, and PbS3﹣ species were detected on the smithsonite surface by TOF-SMIS, and the increase in the level of CO3– observed by TOF-SMIS further indicates that PbCO3 was formed after lead-ion activation of the smithsonite. The increased impedance observed by LEIS is due to the formation of PbCO3 and lead-sulfide complexes on the smithsonite surface and the formation of large amounts of lead-sulfide complexes promote smithsonite flotation.

Bai S., Yu P., Ding Z., Li C., Xian Y., Wen S.

NH3-based promoting sulfidation have attracted attention for smithsonite surface sulfidation, but the role of the NH3/zinc/sulphur interface in promoting this chemistry remains under debate. Herein, we combined Visual MINTEQ models, ToF-SIMS and DFT to elucidate the impact of this interface on smithsonite surface sulfidation. The results demonstrated that the addition of ammonium chloride caused the CZnT in the pulp solution to increase. After the sulfidation reaction between zinc ammonium complex ions and HS− ions, accompanying the deeper conversion from ZnS(aq), Zn2S32− and Zn4S64− ions to sphalerite, more sphalerite was formed. ToF-SIMS analysis provided strong evidence for an increase in the zinc sulfide species on the smithsonite surface with the addition of NH4Cl, and the thickness of formed zinc sulfide species was approximately 26.66 nm. DFT study confirmed that NH3 acted a catalytic role during the smithsonite surface sulfidation processing including ion-exchange reaction and sphalerite precipitation adsorption. The presence of NH3 changed the reaction pathway from Zn(OH)2 + HS− → ZnS to Zn(OH)2 → Zn(NH3)42+ + HS− → ZnS and decreased the total energy barriers from 90.46 kcal/mol to 65.31 kcal/mol. Additionally, the NH3 promoted the sulphur migration from HS− to Zn with a lower energy barrier to form the ZnS spontaneously.

Bai S., Li C., Fu X., Ding Z., Wen S.

The sulfidation-flotation method is commonly used for the treatment of zinc oxide minerals. However, few studies have been conducted on the promoting sulfidation-flotation behavior and mechanism of smithsonite. In this paper, we investigate the promoting sulfidation of smithsonite by zinc sulfide species increase with addition of ammonium chloride (NH4Cl) and its effect on flotation performance. The micro-flotation experiment results concluded that the addition of the ammonium chloride improved smithsonite flotation recovery by ∼17%. Zinc ion adsorption experiments and Visual MINTEQ model analysis showed that more zinc sulfide species were produced in the presence of NH4Cl. Zeta potential analysis indicated that additional sulfide ion species and isoamyl xanthate ions (IX−) from the pulp solution adhered to the smithsonite surface as NH4Cl was added, and the SEM-EDS study and the contact angle results further confirmed the positive influence of NH4Cl on the smithsonite sulfidation process. The TOF-SIMS results provided strong evidence for an increase in zinc sulfide species on the smithsonite surface and an increase in the sodium isoamyl xanthate (NaIX) molecular adsorption on the surface of sulfidized smithsonite with the addition of NH4Cl. The thickness of zinc sulfide species formed after promoting sulfidation was ∼29.20 nm, and the thickness of xanthogenate species formed was a few nanometers. The promotion in sulfidation may be due to the combined effect of the improvement of sphalerite precipitation adsorption and the ion-exchange reaction between the sulfide ions and the carbonate ions on the surface of the smithsonite.

Jia K., Feng Q., Zhang G., Ji W., Zhang W., Yang B.

Smithsonite is a readily dissolvable carbonate mineral that is naturally hydrophilic, making recovery of this ore by flotation difficult. The flotation results showed that conditioning with only sodium sulfide (Na2S) did not successfully allow the smithsonite samples to float, whereas treatment with a combination of S(II), Pb(II) and xanthate (with Na2S as the sulfurizing reagent, lead ions (Pb(II)) as the activator, and xanthate as the collector) improved the flotation of smithsonite, achieving a mass recovery of 95.8%. A combination of analytical techniques, including X-ray diffraction (XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), in conjunction with depth profiling, was used to investigate the chemical nature of the sulfur and lead species on the smithsonite surface. For S(II)-conditioned smithsonite, a layer of ZnS formed on the smithsonite (ZnCO3) substrates; this newly formed ZnS coating was amorphous or poorly crystallized. For smithsonite samples conditioned with S(II) and Pb(II), the microstructures and the phase constituents, obtained by AFM and XRD analyses, confirmed the formation of the PbS species with a cubic galena structure on the surface. XPS depth profiling showed that the PbS layer was 18-nm thick, which corresponds to 30 PbS molecular layers. This study presents direct evidence that the coating of the activation product, PbS, on the smithsonite surface was similar to a relatively thick galena layer, which led to successful flotation.

Feng Q., Zhao W., Wen S.

In this study, the surface modification of malachite with ammonia was developed as a promising method to enhance the adsorption of sulfide species onto the mineral surface. The flotation recovery of the ammonia-modified malachite was significantly improved under the same flotation condition compared with that of bare malachite. This result can be ascribed to the fact that the adsorbed amount of S species on the mineral surface increased because of the considerable affinity of the ammonia-modified malachite for sulfide ion species in the pulp solution. The negativity of the zeta potential of malachite increased, which implied that more S species was adsorbed onto the surface of the ammonia-modified mineral. This phenomenon facilitated the attachment of the collector. XPS analysis confirmed the enhancement of sulfide ion species adsorption onto the ammonia-modified malachite surface. In addition, the amount of cuprous sulfide species on the modified surface increased. The mechanism by which ammonia modification enhances the sulfidization of malachite was further studied by solution chemistry calculation. The hydrophilic Cu(OH) 2 coated on the malachite surface was detrimental to the adsorption of sulfide ion species, whereas the involvement of Cu ( NH 3 ) 2 2 + changed the surface species distribution and improved the sulfidization of malachite, thereby facilitating its flotation recovery.

Wu D., Ma W., Wen S., Deng J., Bai S.

Sodium sulfosalicylate was used for the first time to enhance the sulfidation–flotation of smithsonite. Sodium sulfosalicylate could facilitate the flotation of smithsonite, and increase the flotation recovery by ∼28%. Inductively coupled plasma analysis indicated that the surface dissolution of the enhanced sulfurized smithsonite decreased significantly. X-ray photoelectron spectral analysis revealed that smithsonite can be sulfurized easily by using sodium sulfide with sodium sulfosalicylate. The effect of sodium sulfosalicylate on zinc-oxide ore flotation has been verified. Compared with the direct sulfidation–flotation of zinc-oxide ore, enhanced sulfidation–flotation can improve the concentrate grade by 3.83% and the concentrate recovery by 7.63%. Therefore, the addition of sodium sulfosalicylate played a significant role in smithsonite sulfidation, which improves the flotation performance.

Medas D., Podda F., Meneghini C., De Giudici G.

Hemimorphite, Zn 4 Si 2 O 7 (OH) 2 ·H 2 O, one of the most common minerals in non-sulfide Zn deposits, together with smithsonite and hydrozincite, is one of the most abundant minerals in the “calamine” deposits in SW Sardinia. In spite of their importance for the development of ore genesis models, the stability properties of hemimorphite are poorly known. This paper presents solubility experiments on two different types of hemimorphite: a “geological” hemimorphite from a supergene non-sulfide Zn deposit, of supposed abiotic origin, and a hemimorphite precipitated by bacterial activity. Both specimens were characterized, before and after the experiment, by Synchrotron Radiation X-ray powder diffraction, Scanning Electron Microscopy, and X-ray Absorption Spectroscopy. The calculated solubility product constants (logK s ) are similar for both “geological” and biogenic hemimorphite (30.3 ± 0.4 and 30.5 ± 0.1, respectively). During the solubility experiment, biological hemimorphite undergoes an amorphous to crystalline phase transition, and the distinctive features (mineralized bacterial sheaths and organic filaments), that allowed us to demonstrate its biological origin, are no longer recognizable by Scanning Electron Microscopy. The results of this study may be useful for developing ore genesis models, including evolution in a supergene environment, and in general for performing geochemical speciation and equilibrium calculations. Moreover, our findings open the way for a new interpretation of hemimorphite-forming processes, and suggest the possibility that bacteria may have played a role in the formation of this mineral in ore deposits.

Feng Q., Wen S.

The interaction between sulfide-ion species and smithsonite surfaces and its response to flotation performance were investigated by means of microflotation experiments, surface-adsorption tests, zeta-potential determination, and X-ray photoelectron spectroscopy (XPS) analysis. The microflotation experiments results indicated that addition of Na2S elicited a positive effect on the smithsonite floatability within an appropriate concentration range (

Yang W., Tang Y., Han G., Miao Y., Zhao W., Feng Q.

Yang W., Tang Y., Huang B., Han G., Feng Q.

An M., Liu D., Nie Q., Liu Z., Xu L., Shao P., Wen S.

Xu L., Liu D., Sun R., Liu Z., An M., Luo F., Wen S.

Kong N., Wu D., Zuo Q., Cao J., Wu F., Feng K., Li J.

Zhang Y., Zhao W., Han G., Feng Q.

Smithsonite is a typical zinc oxide mineral, and the flotation index is not ideal for the recovery of smithsonite via sulfidization–xanthate flotation. In this study, Pb2+ was used as an activator for the stepwise activation of smithsonite in a sulfidization–xanthate flotation system. Micro-flotation tests and various surface analytical assays were employed to investigate the effects of Pb2+ stepwise activation on the flotation behavior and surface properties of smithsonite. The micro-flotation tests revealed that the flotation recovery of smithsonite reached 90.26 % after the stepwise activation of Pb2+ at an appropriate concentration. X-ray photoelectron spectroscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, atomic force microscopy, and time-of-flight secondary ion mass spectrometry indicated that abundant active sites of Pb components appeared on the smithsonite surface after Pb2+ stepwise activation, which promoted the adsorption of S ions on the smithsonite surface. The increase in the proportion of the PbS component after sulfidization effectively enhanced the reaction activity of the mineral surface. Fourier-transform infrared spectroscopy and contact angle measurements showed that xanthate could be stably adsorbed on the smithsonite surface after Pb2+ stepwise activation, thereby enhancing the surface hydrophobicity and flotation behavior of smithsonite. Therefore, Pb2+ stepwise activation can promote sulfidization on the smithsonite surface, improve the reactivity and hydrophobicity of the mineral surface, and substantially increase the flotation index of smithsonite.

Jung M., Tadesse B., Dick C., Logan A., Dyer L., Albijanic B.

Water quality has been found to significantly influence the flotation operations due to the alteration of surface properties of minerals. The effect of cations on the flotation of RE minerals has been studied, however, there are still very limited information regarding the effect of anions. The present study examined the impact of specific anions such as Cl−, SO42−, and HCO3− on the flotation performance of rare earth (RE) ore. This study integrates flotation experiments, rheology measurements, entrainment experiments, zeta potential measurements and settling experiments. It is observed that an increase in the concentration of these anions lead to a decrease in the recovery of RE minerals and an increase in the recovery of FeO minerals and thus negatively affecting flotation efficiency. This adverse effect is most pronounced with Cl− and least noticeable with HCO3−. An increase in the non-selective entrainment of gangue minerals is observed when the flotation pulp has higher viscosity. The reduction in the zeta potential of fine particles in the presence of these results in a higher pulp viscosity due to increased attractive forces between particles. These findings were verified by settling experiments and calculations based on the DLVO theory.

Feng Q., Lu W., Wang H., Zhang Q.

Malachite is a common copper oxide mineral that is often enriched using the sulfidization–xanthate flotation method. Currently, the direct sulfidization method cannot yield copper concentrate products. Therefore, a new sulfidization flotation process was developed to promote the efficient recovery of malachite. In this study, Cu2+ was used as an activator to interact with the sample surface and increase its reaction sites, thereby strengthening the mineral sulfidization process and reactivity. Compared to single copper ion activation, the flotation effect of malachite significantly increased after stepwise Cu2+ activation. Zeta potential, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF–SIMS), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS), and atomic force microscopy (AFM) analysis results indicated that the adsorption of S species was significantly enhanced on the mineral surface due to the increase in active Cu sites after Cu2+ stepwise activation. Meanwhile, the proportion of active Cu–S species also increased, further improving the reaction between the sample surface and subsequent collectors. Fourier-transform infrared spectroscopy (FT-IR) and contact angle tests implied that the xanthate species were easily and stably adsorbed onto the mineral surface after Cu2+ stepwise activation, thereby improving the hydrophobicity of the mineral surface. Therefore, the copper sites on the malachite surface after Cu2+ stepwise activation promote the reactivity of the mineral surface and enhance sulfidization flotation of malachite.

Zhang S., Liang G., Xian Y., Wen S.

Triethanolamine (TEA) is a promising eco-friendly alternative to inorganic ammonia for enhancing surface sulfidization and flotation recovery of smithsonite. Micro-flotation experiments revealed an enhancement in smithsonite recovery to 95.21% with TEA modification, comparable to the results obtained using ammonia. The mechanisms behind the ability of TEA to enhance the sulfidization process were investigated through surface analysis and molecular dynamics simulations. TEA modification increased the content of sulfidization products, the proportion of crucial S22− in adsorbed products, and the thickness and size of the sulfidization product layer. The complexation of TEA with Zn sites formed positively charged Zn–TEA complexes that adsorb onto the smithsonite surface. These complexes promoted negatively charged HS− adsorption, creating a multi-layered adsorption structure. Moreover, TEA modification reduced the total energy required for the sulfidization. These findings open up new possibilities for using eco-friendly reagents in mineral processing, highlighting the potential of TEA in green mineral processing practices.

Yu X., Yu B., Wang H., Shen P., Liu D.

Peng R., Wang H., Wei Z., Fang J., Zhang X., Shen P., Liu D.

Jia K., Ding R., Chen Y., Lu T., Li G., Cao Y., Wang C.

Zinc oxide ore containing smithsonite is a refractory ore, and it is difficult to separate smithsonite and calcite with traditional flotation collectors. A new collector was developed in this study, the multiligand biodegradable biosurfactant sodium myristoyl glutamate (SMG), which used calcium lignosulfonate (CLS) as a calcite depressant for the flotation of smithsonite. Microflotation experiments showed that SMG was an effective smithsonite flotation collector, with a recovery of more than 95 % after it reached a specific concentration. Adding CLS could achieve a considerable difference in flotation recovery rates between smithsonite and calcite. Adsorption of the collector on the mineral surface was analyzed. The contact angle, zeta potential, Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectra (XPS), and atomic force microscopy (AFM) results confirmed that SMG was strongly adsorbed on smithsonite. Moreover, the depressant CLS was strongly adsorbed on the surface of calcite, and less was adsorbed on the surface of smithsonite. Density functional theory (DFT) calculations confirmed that the amino group in SMG promoted the binding of adjacent carboxyl groups to metal sites on the mineral surface. These results indicated that SMG, which is a biodegradable biosurfactant, is a promising collector for the selective recovery of smithsonite from calcite through flotation.

Yang X., Mu Y., Liu S.

Despite being a major cyanide species in the process water, it is unclear how iron cyanide influences pyritic gold ore flotation as well as how lead ions influence pyritic gold ore flotation in the presence of iron cyanide. This study aims at revealing the interaction of Fe(CN)63− and lead ions in pyrite flotation to investigate the strong depressing effect of Fe(CN)63− on pyritic gold ore flotation and the significant activating effect of lead ions on pyritic gold ore flotation in the presence of Fe(CN)63− using flotation, zeta potential measurement and surface analysis methods. The flotation results showed that upon 5 × 10−5 mol/L Fe(CN)63− addition, pyrite recovery drastically decreased from about 51.3% to 8.6%, while the subsequent addition of 9.5 × 10−4 mol/L lead ions significantly activated pyrite with the recovery increasing from 8.6% to 91%, which demonstrated that Fe(CN)63− strongly depressed pyrite flotation, while lead ions completely activated pyrite in the presence of Fe(CN)63−. Zeta potential measurement, surface analysis using Cryogenic X-ray photoelectron spectroscopy (Cryo-XPS) and electrochemical impedance spectroscopy (EIS) revealed that Fe(CN)63− depression was attributed to the chemical adsorption of Fe(CN)63− on iron sites of pyrite as Prussian Blue (Fe[Fe(CN)6]); however, this hydrophilic layer could be covered totally by lead ions which adsorbed on as lead hydroxide/oxide through electrostatic interactions, which resulted in the significant activation effect of lead ions. The results from this study will lead to improved flotation of gold associated with pyrite in gold flotation plants.

Teng Y., Wu Q., Sun Y., Wang C., Zhang R., Lu Z.

Mixed matrix membranes (MMMs) containing fluorescent coordination polymers (CPs) showed high sensitivity and stability for detecting Cr2O72− in water.

Liao R., Wen S., Bai S., Liu J., Zhang Q., Feng Q.

The flotation research of zinc oxide ores has been paid more and more attention with the increasing demand for zinc resources. In this particular study, micro-flotation tests were carried out using a mixed ternary collector comprising dodecylamine (DDA), potassium isoamyl xanthate (KAX), and ammonium dibutyl dithiophosphate (ADD), along with pre-sulfidization treatment using Na2S to improve the flotation efficiency of smithsonite. Micro-flotation experimental results showed that the flotation recovery significantly increased by over 40 % when employing the ternary mixed collector of DDA-KAX-ADD, as compared to using DDA alone. Through the measurement of the adsorption and surface potential of each collector on the mineral surface, the synergistic effect of DDA, KAX, and ADD was confirmed. The phenomenon was discovered that the ternary collector effectively reduced the solution's surface tension in the surface tension tests, which enhanced the adsorption efficiency of ternary collector on mineral surface. Additionally, the verification of the chemisorption and physisorption between the ternary collector and the mineral surface was accomplished through the utilization of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The measurement results of contact angles demonstrated that the ternary collector significantly enhanced the hydrophobicity of sulfidized smithsonite, a finding that was further supported by molecular dynamics (MD) simulation. Finally, the MD simulation revealed that DDA, KAX, and ADD exhibit multilayer adsorption on the mineral surface.