It is difficult to recover chrysocolla from sulfidation flotation which is closely related to the mineral surface composition.In this study,the effects of fluoride roasting on the surface composition of chrysocolla we...It is difficult to recover chrysocolla from sulfidation flotation which is closely related to the mineral surface composition.In this study,the effects of fluoride roasting on the surface composition of chrysocolla were investigated,its impact on sulfidation flotation was explored,and the mechanisms involved in both fluoride roasting and sulfidation flotation were discussed.With CaF_(2)as the roasting reagent,Na_(2)S·9H_(2)O as the sulfidation reagent,and sodium butyl xanthate(NaBX)as the collector,the results of the flotation experiments showed that fluoride roasting improved the floatability of chrysocolla,and the recovery rate increased from 16.87%to 82.74%.X-ray diffraction analysis revealed that after fluoride roasting,approximately all the Cu on the chrysocolla surface was exposed in the form of CuO,which could provide a basis for subsequent sulfidation flotation.The microscopy and elemental analyses revealed that large quantities of"pagoda-like"grains were observed on the sulfidation surface of the fluoride-roasted chrysocolla,indicating high crystallinity particles of copper sulfide.This suggests that the effect of sulfide formation on the chrysocolla surface was more pronounced.X-ray photoelectron spectroscopy revealed that fluoride roasting increased the relative contents of sulfur and copper on the surface and that both the Cu~+and polysulfide fractions on the surface of the minerals increased.This enhances the effect of sulfidation,which is conducive to flotation recovery.Therefore,fluoride roasting improved the effect of copper species transformation and sulfidation on the surface of chysocolla,promoted the adsorption of collectors,and improved the recovery of chrysocolla from sulfidation flotation.展开更多
Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle...Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle size and settling performance remain unclear.In this study,the growth behavior of CuS particles generated by two sulfide precipitation methods,gas-liquid and liquid-liquid sulfidation,was investigated.The effects of acidity,sulfur-to-copper molar ratio,and temperature on particle size were analyzed.The results showed that increasing the temperature had an adverse effect on CuS particle growth.Additionally,we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system.Based on supersaturation calculations and XPS analysis,it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation,while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge.This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.展开更多
The Zijinshan ore field located in southwestern Fujian Province,China,is a representative porphyry-epithermal ore system hosting diverse mineralization types(Mao et al.,2013).The ore field comprises of the Zijinshan h...The Zijinshan ore field located in southwestern Fujian Province,China,is a representative porphyry-epithermal ore system hosting diverse mineralization types(Mao et al.,2013).The ore field comprises of the Zijinshan highsulfidation Cu-Au deposit,the Luoboling porphyry Cu-Mo deposit,the transitional style Cu deposit(Longjiangting and Wuziqilong)and the Yueyang low-sulfidation Agpolymetallic deposit(Zhang,2013;Zhang et al.,2003)展开更多
Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of v...Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of various fracture surfaces with distinct properties during crushing and grinding,resulting in surface anisotropy.In this study,we explored the surface anisotropy of malachite and further investigated its sulfidation mechanism from the coordination chemistry perspective,considering the influence of the Jahn-Teller effect on malachite sulfidation.Computational results reveal that the penta-coordinated Cu ions on the malachite(201)and(010)surfaces exhibit stronger activity compared to those on the malachite(201)surface.Additionally,the tetra-coordinated structure formed by HS^(−)adsorption on the malachite(010)and(201)surfaces is more stable,with more negative adsorption energy,compared to the hexa coordinated structure formed by HS−adsorption on the(201)surface.The sulfidized malachite surface has an additional pair ofπelectron and smaller HOMO(highest occupied molecular orbital)-LUMO(lowest unoccupied molecular orbital)gap with xanthate molecules,causing strongerπbackbonding with xanthate.This study provides new insights into the surface sulfidation mechanism of malachite and offers a theoretical reference for the design of targeted flotation reagents.展开更多
Flotation behavior of stibiconite after sulfidation roasting with sulfur at a high temperature and the sulfidation mechanisms were investigated by ultraviolet spectrophotometry,X-ray diffraction(XRD)combining with the...Flotation behavior of stibiconite after sulfidation roasting with sulfur at a high temperature and the sulfidation mechanisms were investigated by ultraviolet spectrophotometry,X-ray diffraction(XRD)combining with thermodynamic calculation,X-ray photoelectron spectroscopy(XPS)and electron probe microanalysis(EPMA).The XRD and thermodynamic analyses revealed that the Sb_(3)O_(6)(OH)was reduced into Sb_(2)O_(4)and Sb_(2)O_(3),and was transformed into Sb_(2)S_(3)after introducing sulfur at high temperatures.Flotation test results show that flotation recovery of the stibiconite after sulfidation reaches 90.3%.Ultraviolet spectrophotometry tests confirm that adsorption capacity of sodium butyl xanthate(SBX)on surface of the roasted products has a positive relationship with S/Sb mole ratio.XPS analyses indicate that Sb-bearing species including mainly Sb_(2)S_(3),Sb_(2)O_(3)and Sb_(2)(SO_(4))_(3) are formed at the surface of particle after sulfidation.The EPMA analyses verify that the Sb_(2)S_(3)is generated at the outer layer of sample after sulfidation roasting,but the particle interior is mainly composed of antimony oxides.The sulfur atmosphere induces the outward migration of oxygen to form Sb_(2)O_(4).Then,the Sb_(2)O_(4)is transformed into Sb_(2)O_(3)in two pathways,and the Sb_(2)S_(3)is formed.These findings will provide theoretical support for recovering antimony from antimony oxide ores by xanthate flotation methods.展开更多
In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calc...In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.展开更多
The effects of Y,Ce and La on the sulfidation of alloy Fe-25Cr-40Ni have been investigated. The sulfidation rate of the alloys with RE more than 0.1 wt-% is lower than that of the base alloy.The addition of Y is more ...The effects of Y,Ce and La on the sulfidation of alloy Fe-25Cr-40Ni have been investigated. The sulfidation rate of the alloys with RE more than 0.1 wt-% is lower than that of the base alloy.The addition of Y is more effective than La and Ce in lowering the sulfidation rate. Based on the analyses of the structure and composition of the sulfide seales,the sulfidation mechanism of the alloys with RE has been proposed.展开更多
Zinc leaching residue(ZLR) contains high content of valuable metals such as zinc and iron. However, zinc and iron mainly exist in the form of zinc ferrite, which are difficult to separate and recover. This study propo...Zinc leaching residue(ZLR) contains high content of valuable metals such as zinc and iron. However, zinc and iron mainly exist in the form of zinc ferrite, which are difficult to separate and recover. This study proposed a new process involving sulfidation roasting, magnetic separation and flotation to recover zinc and iron in ZLR. Through sulfidation roasting of ZLR with pyrite, zinc and iron were converted into ZnS and Fe3 O4. The effects of pyrite dosage, roasting temperature and roasting time on the sulfidation of zinc in ZLR were investigated. The results showed that the sulfidation percentage of zinc reached 91.8% under the optimum condition. Besides, it was found that ball-milling was favorable for the separation and recovery of zinc and iron in sulfidation products. After ball-milling pretreatment, iron and zinc were enriched from sulfidation products by magnetic separation and flotation. The grade of iron in magnetic concentrates was 52.3% and the grade of zinc in flotation concentrates was 31.7%, which realized the recovery of resources.展开更多
The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process.The factors such as roasting temperature,roasting time,sulfur content and nitrog...The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process.The factors such as roasting temperature,roasting time,sulfur content and nitrogen flow rate were investigated using XRD,EPMA and SEM-EDS.In a certain range,the sulfur addition has an active effect on the arsenic volatilization because the solid solution phase（（Sb,As）2O3）in the dust can be destroyed after the Sb component in it being vulcanized to Sb2S3 and this generated As2O3 continues to volatile.In addition,an amorphization reaction between As2O（3 ）and Sb2O（3 ）is hindered through the sulfidation of Sb2O3,which is also beneficial to increasing arsenic volatilization rate.The results show that volatilization rates of arsenic and antimony reach 95.36%and only 9.07%,respectively,under the optimum condition of roasting temperature of 350℃,roasting time of 90 min,sulfur content of 22%and N2 flow rate of 70 m L/min.In addition,the antimony in the residues can be reclaimed through a reverberatory process.展开更多
In this study,the biochar (BC) produced from sawdust,sludge,reed and walnut were used to support sulfidation of nano-zero-valent-iron (S-nZVI) to enhance nitrate NO_(3)^(-) removal and investigate the impact on greenh...In this study,the biochar (BC) produced from sawdust,sludge,reed and walnut were used to support sulfidation of nano-zero-valent-iron (S-nZVI) to enhance nitrate NO_(3)^(-) removal and investigate the impact on greenhouse gas emissions.Batch experiment results showed the S-nZVI/BC(sawdust (2:1,500)),S-n ZVI/BC(sludge (2:1,900)),S-n ZVI/BC(reed (2:1,700)),and S-n ZVI/BC(walnut (2:1,700))respectively improved NO_(3)^(-) removal efficiencies by 22%,20%,3%and0.1%,and the selectivity toward N_(2)by 22%,25%,22%and 18%.S-nZVI uniformly loaded on BC provided electrons for the conversion of NO_(3)^(-) to N_(2)through Fe0.At the same time,FeSxlayer was formed on the outer layer of ZVI in the sulfidation process to prevent iron oxidation,so as to improve the electrons utilization efficiency After adding four kinds of S-nZVI/BC into constructed wetlands (CWs),the NO_(3)^(-) removal efficiencies could reach 100%and the N_(2)O emission fluxes were reduced by 24.17%-36.63%.And the average removal efficiencies of TN,COD,TP were increased by 21.9%,-16.5%,44.3%,repectively.The increasing relative abundances of denitrifying bacteria,such as Comamonas and Simplicispira,suggested that S-nZVI/BC could also improve the process of microbial denitrification.In addition,different S-nZVI/BC had different effects on denitrification functional genes (narG,nirk,nirS and nos Z genes),methanotrophs (pmoA) and methanogenesis (mcrA).This research provided an effective method to improve NO_(3)^(-) removal and reduce N_(2)O emission in CWs.展开更多
To recover Zn, Pb, Fe and Si from a low-grade mining ore in the Lanping basin, Yunnan Province, China, a novel technology using the roasting with pyrite and carbon followed by beneficiation and hydrochloric acid leach...To recover Zn, Pb, Fe and Si from a low-grade mining ore in the Lanping basin, Yunnan Province, China, a novel technology using the roasting with pyrite and carbon followed by beneficiation and hydrochloric acid leaching was proposed. Firstly, several factors such as pyrite dosage, roasting temperature, carbon powder dosage, holding time and particle size affecting on the flotation performance of Zn(Pb) and magnetic separation performance of Fe were simultaneously examined and the optimum process parameters were determined. A flotation concentrate, containing 17.46% Zn and 3.93% Pb, was obtained, and the Zn and Pb recoveries were 86.04% and 69.08%, respectively. The obtained flotation tailing was concentrated by a low-intensity magnetic separator. The grade of iron increased from 5.45% to 43.45% and the recovery of iron reached 64.87%. Hydrochloric acid leaching was then carried out for the magnetic separation tailing and a raw quartz concentrate containing 81.05% SiO2 was obtained. To further interpret the sulfidation mechanism of smithsonite, surface morphology and component of the sample before and after reactions were characterized by XRD and EPMA-EDS. The aim was to achieve the comprehensive utilization of the low-grade mining ore.展开更多
In this paper,sulfidation mechanism of cerussite in the presence of sulphur at high temperatures was investigated based on micro-flotation,X-ray powder diffractometry(XRD),electron probe microanalysis(EPMA)and X-ray p...In this paper,sulfidation mechanism of cerussite in the presence of sulphur at high temperatures was investigated based on micro-flotation,X-ray powder diffractometry(XRD),electron probe microanalysis(EPMA)and X-ray photoelectron spectroscopy(XPS).The micro-flotation test results showed that flotation recovery of the treated cerussite increased to above 80%under a suitable flotation condition.It was found that the S/PbCO3 mole ratio and pH obviously affected flotation recovery.XRD analysis results confirmed that the cerussite was decomposed into massicot and then was transformed into mainly PbS and PbO·PbSO4 after sulfidation roasting.EPMA analysis results demonstrated that surface of the obtained massicot was smooth,but surface of the artificial galena was rough and even porous.Content of oxygen decreased,whereas content of sulphur increased with an increase in the S/PbCO3 mole ratio.XPS analysis results revealed that various lead-bearing species,including mainly PbS,PbSO4 and PbO·PbSO4,were generated at the surface.Formation of PbS was advantageous to flotation of the treated cerussite.Based on these results,a reaction model of the cerussite sulfurized with sulphur was proposed.展开更多
Copper and arsenic in acidic wastewater were separated by cascade sulfidation followed by replacement of arsenic in theprecipitates by copper in the solution which was realized by recycling precipitates obtained in th...Copper and arsenic in acidic wastewater were separated by cascade sulfidation followed by replacement of arsenic in theprecipitates by copper in the solution which was realized by recycling precipitates obtained in the first stage into the initial solution.The effects of reaction time,temperature and H2S dosage on copper and arsenic removal efficiencies as well as the effects of solid-toliquidratio,time and temperature on the replacement of arsenic by copper were investigated.With20mmol/L H2S at50°C within0.5min,more than80%copper and nearly20%arsenic were precipitated.The separation efficiencies of copper and arsenic werehigher than99%by the replacement reaction between arsenic and copper ions when solid-to-liquid ratio was more than10%at20°Cwithin10min.CuS was the main phases in precipitate in which copper content was63.38%in mass fraction.展开更多
Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-rela...Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-related oxide semiconductor Bi_(2)O_(2)SiO_(3) nanosheet(BOSO)were largely improved using a surface sulfidation strategy.The experiment and theoretical calculation confirmed that surface sulfidation of the Bi_(2)O_(2)SiO_(3) nanosheet(S-BOSO,6.28 nm)redistributed the charge-enriched Bi sites,extended the solar spectrum absorption to the whole visible range,and considerably enhanced the charge separation,in addition to creating new reaction active sites,as compared to pristine BOSO.Subsequently,surface sulfidation played a switchable role,wherein S-BOSO showed a very high CH_(3)OH generation rate(12.78μmol g^(-1) for 4 h,78.6%selectivity)from low-concentration CO_(2)(1000 ppm)under visible light irradiation,which outperforms most of the state-of-the-art photocatalysts under similar conditions.This study presents an atomic-level modification protocol for engineering reactive sites and charge behaviors to promote solar-to-energy conversion.展开更多
The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate p...The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate precursors in H_2S/H_2 stream at different temperatures were studied by X-ray photoelectron spectroscopy(XPS) and high-resolution transmission electron microscopy(HRTEM). The organic molybdate precursors lead to MoS_2 catalysts with higher sulfidation degree and smaller active phases to demonstrate higher catalytic activity during hydrodesulfurizaiton(HDS) of 4,6-DMDBT.展开更多
ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray dif...ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM),positron annihilation Doppler broadening,and UV-Vis spectrophotometer,respectively.It was found that the(200)-plane preferred orientation of the ZnS thin films changed to(111)-plane with increasing sulfidation temperature.Moreover,a number of large holes were generated at 420?C and eliminated at 440?C.The concentration of defects was lowest when the sulfuration temperature was 440?C.The optical transmission of all samples was maintained at 60%–80%in the wavelength range of 400 nm–800 nm,and the band energy of the ZnS thin films was approximately3.5 e V for all treatment temperatures except 430?C.展开更多
The high temperature corrosion resistance of Ni-25.9Cr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4Cr16.0Al-0.5Y-0.2Hf alloys was assessed in sulfidation/oxidation envi-ronments. In the environment with a sulfur partial press...The high temperature corrosion resistance of Ni-25.9Cr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4Cr16.0Al-0.5Y-0.2Hf alloys was assessed in sulfidation/oxidation envi-ronments. In the environment with a sulfur partial pressure of 1Pa. and an oxygenpartial pressure of 10^(-19)Pa, both these alloys exhibited three distinct stages in theweight gain-time curve when tested at 700℃. In the initial stage, selective sulfidationof Cr suppressed the formation of the other metal sulfides, resulting in lower weightgains. In the transient stage, breakdown and cracking of Cr sulfides and insufficientconcentration of Cr at the outer zone led to the rapid formation of Ni sulfides anda rapid increase in weight. In the steady-state stage, corrosion was controlled by thediffusion of anions and/or cations, which led to a parabolic rate law.展开更多
Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ ca...Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ calculation,X-ray photoelectron spectroscopy(XPS)analysis,time of flight secondary ion mass spectrometry(ToF-SIMS)analysis,and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate((NH_(4))_(2)SO_(4))on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation.The results showed that(NH_(4))_(2)SO_(4)exhibited a positive influence on hemimorphite sulfidation flotation.It was ascribed to the number of zinc components in the form of Zn^(2+)and[Zn(NH_(3))_(i)]^(2+)(i=1–4)increased in the flotation system after hemimorphite treatment with(NH_(4))_(2)SO_(4),which was beneficial to its interaction with sulfur species in solution,resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface.[Zn(NH_(3))_(i)]^(2+)participated in the sulfidation reaction of hemimorphite as a transition state.In addition the sulfidation reaction of hemimorphite was accelerated by(NH_(4))_(2)SO_(4).Thus,(NH_(4))_(2)SO_(4)presents a vital role in promoting the sulfidation of hemimorphite.展开更多
Oxygen fugacity(fO_(2))is a key intensity variable during the entire magmatic-hydrothermal mineralization courses.The redox state and its variations between different stages of the ore-forming fluids of intermediate s...Oxygen fugacity(fO_(2))is a key intensity variable during the entire magmatic-hydrothermal mineralization courses.The redox state and its variations between different stages of the ore-forming fluids of intermediate sulfidation epithermal deposits are rarely deciphered due to the lack of appropriate approaches to determine fO_(2)of the fluids.Here,we reported theδ^(34)S of the sulfides from three different stages(stageⅠ,Ⅱ,Ⅲ)of Zhengguang,an Early Ordovician Au-rich intermediate sulfidation(IS)epithermal deposit,to decipher the redox evolution of the ore-forming fluids.The increasingδ^(34)S values from stageⅠpyrite(pyl,average-2.6‰)through py2(average-1.9‰)to py3(average-0.2‰)indicates a decrease of the oxygen fugacity of the ore-forming fluids.A compilation ofδ^(34)S values of sulfides from two subtypes of IS deposits(Au-rich and Ag-rich)from NE China shows that theδ^(34)S values of sulfides from Au-rich IS deposits are systematically lighter than those of Ag-rich IS Ag-Pb-Zn deposit,indicating the ore-forming fluids of the former are more oxidized than the latter.We highlight that sulfur isotopic composition of hypogene sulfides is an efficacious proxy to fingerprint the oxygen fugacity fluctuations of epithermal deposits and could potentially be used to distinguish the subtypes of IS deposits.展开更多
The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to s...The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to sulfur attack at high temperatures.The alloy is nearly single-phase.containing mostly the intermetallic compound Co17Y2 plus a little amount of the solid solution of Y in cobalt.At 600-700℃ and at 800℃ under 10-2 Pa of S2 the alloy forms multi-layered scales consisting of an outer region of pure cobalt sulfide,an intermediate region of a mixture of the sulfides of the two metals and finally an innermost layer of a mixture of yttrium sulfide with metal cobalt.At 800℃ under 10-3Pa of S2,below the dissociation pressure of cobalt sulfide, the alloy forms only a single layer composed of a mixture of metallic cobalt with yttrium sulfide.Pure Y produces only the oxysulfide Y2O2S, as a result of the good stability of this compound and of the presence of some impurities in the gas mixtures used The corrosion kinetics is generally rather complex and irregular except al 800℃under 10-3 Pa of S2.The addition of yttrium always reduces the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of yttrium sulfide is never achieved.The internal sulfidation of Y in Co-15% Y is not associated with a depletion of Y in the alloy.This kind of diffusionless internal attack is typical of alloys with a very small solubility of the most reactive component Y in the base metal A.which restricts severely the Y flux from the alloy towards the alloy-scale interface.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52374259)the Open Fund of the State Key Laboratory of Mineral Processing Science and Technology,China(No.BGRIMM-KJSKL-2023-11)the Major Science and Technology Projects in Yunnan Province,China(No.202302 AF080004)。
文摘It is difficult to recover chrysocolla from sulfidation flotation which is closely related to the mineral surface composition.In this study,the effects of fluoride roasting on the surface composition of chrysocolla were investigated,its impact on sulfidation flotation was explored,and the mechanisms involved in both fluoride roasting and sulfidation flotation were discussed.With CaF_(2)as the roasting reagent,Na_(2)S·9H_(2)O as the sulfidation reagent,and sodium butyl xanthate(NaBX)as the collector,the results of the flotation experiments showed that fluoride roasting improved the floatability of chrysocolla,and the recovery rate increased from 16.87%to 82.74%.X-ray diffraction analysis revealed that after fluoride roasting,approximately all the Cu on the chrysocolla surface was exposed in the form of CuO,which could provide a basis for subsequent sulfidation flotation.The microscopy and elemental analyses revealed that large quantities of"pagoda-like"grains were observed on the sulfidation surface of the fluoride-roasted chrysocolla,indicating high crystallinity particles of copper sulfide.This suggests that the effect of sulfide formation on the chrysocolla surface was more pronounced.X-ray photoelectron spectroscopy revealed that fluoride roasting increased the relative contents of sulfur and copper on the surface and that both the Cu~+and polysulfide fractions on the surface of the minerals increased.This enhances the effect of sulfidation,which is conducive to flotation recovery.Therefore,fluoride roasting improved the effect of copper species transformation and sulfidation on the surface of chysocolla,promoted the adsorption of collectors,and improved the recovery of chrysocolla from sulfidation flotation.
基金supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.52121004)the National Natural Science Foundation of China(No.52274414).
文摘Sulfide precipitation is an effective method for treating acidic heavy metal wastewater.However,the process often generates tiny particles with poor settling performance.The factors and mechanisms influencing particle size and settling performance remain unclear.In this study,the growth behavior of CuS particles generated by two sulfide precipitation methods,gas-liquid and liquid-liquid sulfidation,was investigated.The effects of acidity,sulfur-to-copper molar ratio,and temperature on particle size were analyzed.The results showed that increasing the temperature had an adverse effect on CuS particle growth.Additionally,we found that acidity and sulfur-to-copper molar ratio had a more significant impact on particle growth in the liquid-liquid sulfidation system than in the gas-liquid sulfidation system.Based on supersaturation calculations and XPS analysis,it is found that particle growth in gas-liquid sulfidation systems is mainly influenced by supersaturation,while particle growth in liquid-liquid sulfidation systems is mainly affected by surface charge.This study provides valuable insights into the factors that influence particle growth in sulfide precipitation and can inform the development of strategies to improve the effective precipitation of sulfide nanoparticles in acidic wastewater.
基金financially supported by Zijin Mining Group(No.01612216)the Ministry of Natural Resources,China(No.ZKKJ202426)。
文摘The Zijinshan ore field located in southwestern Fujian Province,China,is a representative porphyry-epithermal ore system hosting diverse mineralization types(Mao et al.,2013).The ore field comprises of the Zijinshan highsulfidation Cu-Au deposit,the Luoboling porphyry Cu-Mo deposit,the transitional style Cu deposit(Longjiangting and Wuziqilong)and the Yueyang low-sulfidation Agpolymetallic deposit(Zhang,2013;Zhang et al.,2003)
基金Projects(52074356,U22A20170)supported by the National Natural Science Foundation of ChinaProject(2022YFC2904503)supported by the National Key R&D Program of China+4 种基金Project(2023SK2061)supported by the Special Fund for the Construction of Hunan Innovative Province,ChinaProject(2023CXQD002)supported by the Innovation-driven Project of Central South University,ChinaProject(2022RC1183)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(kq2009005)supported by the Changsha Science and Technology Project(Changsha Outstanding Innovative Youth Training Program),ChinaProject supported by the High-performance Computing Centers of Central South University,China。
文摘Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of various fracture surfaces with distinct properties during crushing and grinding,resulting in surface anisotropy.In this study,we explored the surface anisotropy of malachite and further investigated its sulfidation mechanism from the coordination chemistry perspective,considering the influence of the Jahn-Teller effect on malachite sulfidation.Computational results reveal that the penta-coordinated Cu ions on the malachite(201)and(010)surfaces exhibit stronger activity compared to those on the malachite(201)surface.Additionally,the tetra-coordinated structure formed by HS^(−)adsorption on the malachite(010)and(201)surfaces is more stable,with more negative adsorption energy,compared to the hexa coordinated structure formed by HS−adsorption on the(201)surface.The sulfidized malachite surface has an additional pair ofπelectron and smaller HOMO(highest occupied molecular orbital)-LUMO(lowest unoccupied molecular orbital)gap with xanthate molecules,causing strongerπbackbonding with xanthate.This study provides new insights into the surface sulfidation mechanism of malachite and offers a theoretical reference for the design of targeted flotation reagents.
基金Projects(52074139,51964027)supported by the National Natural Science Foundation of ChinaProject(KKS 2202152011)supported by the High-level Talents of Yunnan Province,China。
文摘Flotation behavior of stibiconite after sulfidation roasting with sulfur at a high temperature and the sulfidation mechanisms were investigated by ultraviolet spectrophotometry,X-ray diffraction(XRD)combining with thermodynamic calculation,X-ray photoelectron spectroscopy(XPS)and electron probe microanalysis(EPMA).The XRD and thermodynamic analyses revealed that the Sb_(3)O_(6)(OH)was reduced into Sb_(2)O_(4)and Sb_(2)O_(3),and was transformed into Sb_(2)S_(3)after introducing sulfur at high temperatures.Flotation test results show that flotation recovery of the stibiconite after sulfidation reaches 90.3%.Ultraviolet spectrophotometry tests confirm that adsorption capacity of sodium butyl xanthate(SBX)on surface of the roasted products has a positive relationship with S/Sb mole ratio.XPS analyses indicate that Sb-bearing species including mainly Sb_(2)S_(3),Sb_(2)O_(3)and Sb_(2)(SO_(4))_(3) are formed at the surface of particle after sulfidation.The EPMA analyses verify that the Sb_(2)S_(3)is generated at the outer layer of sample after sulfidation roasting,but the particle interior is mainly composed of antimony oxides.The sulfur atmosphere induces the outward migration of oxygen to form Sb_(2)O_(4).Then,the Sb_(2)O_(4)is transformed into Sb_(2)O_(3)in two pathways,and the Sb_(2)S_(3)is formed.These findings will provide theoretical support for recovering antimony from antimony oxide ores by xanthate flotation methods.
基金Projects(52174269,52374293)supported by the National Natural Science Foundation of ChinaProject(2022RC1123)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.
文摘The effects of Y,Ce and La on the sulfidation of alloy Fe-25Cr-40Ni have been investigated. The sulfidation rate of the alloys with RE more than 0.1 wt-% is lower than that of the base alloy.The addition of Y is more effective than La and Ce in lowering the sulfidation rate. Based on the analyses of the structure and composition of the sulfide seales,the sulfidation mechanism of the alloys with RE has been proposed.
基金Project(2018YFC1900305)supported by the National Key R&D Program of ChinaProject(51825403)supported by the National Science Foundation for Distinguished Young Scholars,China+1 种基金Projects(51634010,51474247,51904354)supported by the National Natural Science Foundation of ChinaProject(2019SK2291)supported by the Key Research and Development Program of Hunan Province,China。
文摘Zinc leaching residue(ZLR) contains high content of valuable metals such as zinc and iron. However, zinc and iron mainly exist in the form of zinc ferrite, which are difficult to separate and recover. This study proposed a new process involving sulfidation roasting, magnetic separation and flotation to recover zinc and iron in ZLR. Through sulfidation roasting of ZLR with pyrite, zinc and iron were converted into ZnS and Fe3 O4. The effects of pyrite dosage, roasting temperature and roasting time on the sulfidation of zinc in ZLR were investigated. The results showed that the sulfidation percentage of zinc reached 91.8% under the optimum condition. Besides, it was found that ball-milling was favorable for the separation and recovery of zinc and iron in sulfidation products. After ball-milling pretreatment, iron and zinc were enriched from sulfidation products by magnetic separation and flotation. The grade of iron in magnetic concentrates was 52.3% and the grade of zinc in flotation concentrates was 31.7%, which realized the recovery of resources.
基金Project(51564034)supported by the National Natural Science Fund for Distinguished Regional Scholars,ChinaProject(2015HA019)supported by the Scientific and Technological Leading Talent Program in Yunnan Province,China
文摘The separation of arsenic and antimony from dust with high content of arsenic was conducted via a selective sulfidation roasting process.The factors such as roasting temperature,roasting time,sulfur content and nitrogen flow rate were investigated using XRD,EPMA and SEM-EDS.In a certain range,the sulfur addition has an active effect on the arsenic volatilization because the solid solution phase（（Sb,As）2O3）in the dust can be destroyed after the Sb component in it being vulcanized to Sb2S3 and this generated As2O3 continues to volatile.In addition,an amorphization reaction between As2O（3 ）and Sb2O（3 ）is hindered through the sulfidation of Sb2O3,which is also beneficial to increasing arsenic volatilization rate.The results show that volatilization rates of arsenic and antimony reach 95.36%and only 9.07%,respectively,under the optimum condition of roasting temperature of 350℃,roasting time of 90 min,sulfur content of 22%and N2 flow rate of 70 m L/min.In addition,the antimony in the residues can be reclaimed through a reverberatory process.
基金supported by the Natural Science Foundation of Shandong Province (Nos. ZR2020MD006, ZR2019MD042)the Science and Technology Support Plan for Youth Innovation of Colleges in Shandong Province (No. DC_(2)000000961)。
文摘In this study,the biochar (BC) produced from sawdust,sludge,reed and walnut were used to support sulfidation of nano-zero-valent-iron (S-nZVI) to enhance nitrate NO_(3)^(-) removal and investigate the impact on greenhouse gas emissions.Batch experiment results showed the S-nZVI/BC(sawdust (2:1,500)),S-n ZVI/BC(sludge (2:1,900)),S-n ZVI/BC(reed (2:1,700)),and S-n ZVI/BC(walnut (2:1,700))respectively improved NO_(3)^(-) removal efficiencies by 22%,20%,3%and0.1%,and the selectivity toward N_(2)by 22%,25%,22%and 18%.S-nZVI uniformly loaded on BC provided electrons for the conversion of NO_(3)^(-) to N_(2)through Fe0.At the same time,FeSxlayer was formed on the outer layer of ZVI in the sulfidation process to prevent iron oxidation,so as to improve the electrons utilization efficiency After adding four kinds of S-nZVI/BC into constructed wetlands (CWs),the NO_(3)^(-) removal efficiencies could reach 100%and the N_(2)O emission fluxes were reduced by 24.17%-36.63%.And the average removal efficiencies of TN,COD,TP were increased by 21.9%,-16.5%,44.3%,repectively.The increasing relative abundances of denitrifying bacteria,such as Comamonas and Simplicispira,suggested that S-nZVI/BC could also improve the process of microbial denitrification.In addition,different S-nZVI/BC had different effects on denitrification functional genes (narG,nirk,nirS and nos Z genes),methanotrophs (pmoA) and methanogenesis (mcrA).This research provided an effective method to improve NO_(3)^(-) removal and reduce N_(2)O emission in CWs.
基金Project(51604131)supported by the National Natural Science Foundation of ChinaProject(2017FB084)supported by the Yunnan Province Applied Basic Research Project,ChinaProject(2018T20150055)supported by the Testing and Analyzing Funds of Kunming University of Science and Technology,China
文摘To recover Zn, Pb, Fe and Si from a low-grade mining ore in the Lanping basin, Yunnan Province, China, a novel technology using the roasting with pyrite and carbon followed by beneficiation and hydrochloric acid leaching was proposed. Firstly, several factors such as pyrite dosage, roasting temperature, carbon powder dosage, holding time and particle size affecting on the flotation performance of Zn(Pb) and magnetic separation performance of Fe were simultaneously examined and the optimum process parameters were determined. A flotation concentrate, containing 17.46% Zn and 3.93% Pb, was obtained, and the Zn and Pb recoveries were 86.04% and 69.08%, respectively. The obtained flotation tailing was concentrated by a low-intensity magnetic separator. The grade of iron increased from 5.45% to 43.45% and the recovery of iron reached 64.87%. Hydrochloric acid leaching was then carried out for the magnetic separation tailing and a raw quartz concentrate containing 81.05% SiO2 was obtained. To further interpret the sulfidation mechanism of smithsonite, surface morphology and component of the sample before and after reactions were characterized by XRD and EPMA-EDS. The aim was to achieve the comprehensive utilization of the low-grade mining ore.
基金Project(51964027)supported by the National Natural Science Foundation of ChinaProject(2017FB084)supported by the Yunnan Province Applied Basic Research Project,ChinaProject(2019J0037)supported by the Education Department of Yunnan Province,China。
文摘In this paper,sulfidation mechanism of cerussite in the presence of sulphur at high temperatures was investigated based on micro-flotation,X-ray powder diffractometry(XRD),electron probe microanalysis(EPMA)and X-ray photoelectron spectroscopy(XPS).The micro-flotation test results showed that flotation recovery of the treated cerussite increased to above 80%under a suitable flotation condition.It was found that the S/PbCO3 mole ratio and pH obviously affected flotation recovery.XRD analysis results confirmed that the cerussite was decomposed into massicot and then was transformed into mainly PbS and PbO·PbSO4 after sulfidation roasting.EPMA analysis results demonstrated that surface of the obtained massicot was smooth,but surface of the artificial galena was rough and even porous.Content of oxygen decreased,whereas content of sulphur increased with an increase in the S/PbCO3 mole ratio.XPS analysis results revealed that various lead-bearing species,including mainly PbS,PbSO4 and PbO·PbSO4,were generated at the surface.Formation of PbS was advantageous to flotation of the treated cerussite.Based on these results,a reaction model of the cerussite sulfurized with sulphur was proposed.
基金Projects(51304251,51504299)supported by the National Natural Science Foundation of ChinaProject(201509050)+1 种基金supported by Special Program on Environmental Protection for Public Welfare,ChinaProject(k1502037-31)supported by Key Project of Changsha,China
文摘Copper and arsenic in acidic wastewater were separated by cascade sulfidation followed by replacement of arsenic in theprecipitates by copper in the solution which was realized by recycling precipitates obtained in the first stage into the initial solution.The effects of reaction time,temperature and H2S dosage on copper and arsenic removal efficiencies as well as the effects of solid-toliquidratio,time and temperature on the replacement of arsenic by copper were investigated.With20mmol/L H2S at50°C within0.5min,more than80%copper and nearly20%arsenic were precipitated.The separation efficiencies of copper and arsenic werehigher than99%by the replacement reaction between arsenic and copper ions when solid-to-liquid ratio was more than10%at20°Cwithin10min.CuS was the main phases in precipitate in which copper content was63.38%in mass fraction.
基金Natural Science Foundation of Hubei Province,Grant/Award Number:2021CFB242Research Project of Hubei Provincial Department of Education,Grant/Award Number:Q20202501+3 种基金China Postdoctoral Science Foundation,Grant/Award Number:2020M682878National Natural Science Foundation of China,Grant/Award Numbers:51971124,52104254,52171217State Key Laboratory of Electrical Insulation and Power Equipment,Xi'an Jiaotong University,Grant/Award Number:EIPE22208National Postdoctoral Program for Innovative Talents,Grant/Award Number:BX20200222。
文摘Unraveling atomic-level active sites of layered photocatalyst towards lowconcentration CO_(2) conversion is still challenging.Herein,the yield and selectivity of photocatalytic CO_(2) reduction of the Aurivillius-related oxide semiconductor Bi_(2)O_(2)SiO_(3) nanosheet(BOSO)were largely improved using a surface sulfidation strategy.The experiment and theoretical calculation confirmed that surface sulfidation of the Bi_(2)O_(2)SiO_(3) nanosheet(S-BOSO,6.28 nm)redistributed the charge-enriched Bi sites,extended the solar spectrum absorption to the whole visible range,and considerably enhanced the charge separation,in addition to creating new reaction active sites,as compared to pristine BOSO.Subsequently,surface sulfidation played a switchable role,wherein S-BOSO showed a very high CH_(3)OH generation rate(12.78μmol g^(-1) for 4 h,78.6%selectivity)from low-concentration CO_(2)(1000 ppm)under visible light irradiation,which outperforms most of the state-of-the-art photocatalysts under similar conditions.This study presents an atomic-level modification protocol for engineering reactive sites and charge behaviors to promote solar-to-energy conversion.
基金the financial support by the National Key Basic Research Development Program "973" Project (2012CB224800) of China
文摘The MoS_2 catalysts were prepared from various molybdate precursors including inorganic and organic molybdate compounds. The sulfidation degree and morphology of active phases of MoS_2 activated by various molybdate precursors in H_2S/H_2 stream at different temperatures were studied by X-ray photoelectron spectroscopy(XPS) and high-resolution transmission electron microscopy(HRTEM). The organic molybdate precursors lead to MoS_2 catalysts with higher sulfidation degree and smaller active phases to demonstrate higher catalytic activity during hydrodesulfurizaiton(HDS) of 4,6-DMDBT.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11705212 and 11675188)
文摘ZnS thin films were prepared by sulfuring zinc thin films at different sulfuration temperatures.The crystal structure,surface morphology,defects,and optical properties of the thin films were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM),positron annihilation Doppler broadening,and UV-Vis spectrophotometer,respectively.It was found that the(200)-plane preferred orientation of the ZnS thin films changed to(111)-plane with increasing sulfidation temperature.Moreover,a number of large holes were generated at 420?C and eliminated at 440?C.The concentration of defects was lowest when the sulfuration temperature was 440?C.The optical transmission of all samples was maintained at 60%–80%in the wavelength range of 400 nm–800 nm,and the band energy of the ZnS thin films was approximately3.5 e V for all treatment temperatures except 430?C.
文摘The high temperature corrosion resistance of Ni-25.9Cr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4Cr16.0Al-0.5Y-0.2Hf alloys was assessed in sulfidation/oxidation envi-ronments. In the environment with a sulfur partial pressure of 1Pa. and an oxygenpartial pressure of 10^(-19)Pa, both these alloys exhibited three distinct stages in theweight gain-time curve when tested at 700℃. In the initial stage, selective sulfidationof Cr suppressed the formation of the other metal sulfides, resulting in lower weightgains. In the transient stage, breakdown and cracking of Cr sulfides and insufficientconcentration of Cr at the outer zone led to the rapid formation of Ni sulfides anda rapid increase in weight. In the steady-state stage, corrosion was controlled by thediffusion of anions and/or cations, which led to a parabolic rate law.
基金Fundamental Research Funds for the Central Universities(No.2023YQTD03,2022JCCX HH09,2022YJSHH01)the Yueqi Outstanding Scholaraward of China University of Mining&Technology(Beijing)+3 种基金the National Natural Science Foundation of China(No.52274283)the National Key R&D Program of China(No.SQ2022YFC2900065)the Ordos Science&Technology Plan(No.202204&2023XM06)the Open Research Fund of State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization(No.CNMRCUKF 2107)。
文摘Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation.In this work,inductively coupled plasma optical emission spectrometer(ICP-OES)measurements,Visual MINTEQ calculation,X-ray photoelectron spectroscopy(XPS)analysis,time of flight secondary ion mass spectrometry(ToF-SIMS)analysis,and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate((NH_(4))_(2)SO_(4))on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation.The results showed that(NH_(4))_(2)SO_(4)exhibited a positive influence on hemimorphite sulfidation flotation.It was ascribed to the number of zinc components in the form of Zn^(2+)and[Zn(NH_(3))_(i)]^(2+)(i=1–4)increased in the flotation system after hemimorphite treatment with(NH_(4))_(2)SO_(4),which was beneficial to its interaction with sulfur species in solution,resulting in a dense and stable zinc sulfide layer generated on the hemimorphite surface.[Zn(NH_(3))_(i)]^(2+)participated in the sulfidation reaction of hemimorphite as a transition state.In addition the sulfidation reaction of hemimorphite was accelerated by(NH_(4))_(2)SO_(4).Thus,(NH_(4))_(2)SO_(4)presents a vital role in promoting the sulfidation of hemimorphite.
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.42202085,42272080)China Postdoctoral Science Foundation(Grant Nos.2020M680666,2021T140660)+1 种基金postdoctoral program of China Scholarship Council(Grant No.202104910161)National Key Research and Development Program of China(Grant No.2017YFC0601305)。
文摘Oxygen fugacity(fO_(2))is a key intensity variable during the entire magmatic-hydrothermal mineralization courses.The redox state and its variations between different stages of the ore-forming fluids of intermediate sulfidation epithermal deposits are rarely deciphered due to the lack of appropriate approaches to determine fO_(2)of the fluids.Here,we reported theδ^(34)S of the sulfides from three different stages(stageⅠ,Ⅱ,Ⅲ)of Zhengguang,an Early Ordovician Au-rich intermediate sulfidation(IS)epithermal deposit,to decipher the redox evolution of the ore-forming fluids.The increasingδ^(34)S values from stageⅠpyrite(pyl,average-2.6‰)through py2(average-1.9‰)to py3(average-0.2‰)indicates a decrease of the oxygen fugacity of the ore-forming fluids.A compilation ofδ^(34)S values of sulfides from two subtypes of IS deposits(Au-rich and Ag-rich)from NE China shows that theδ^(34)S values of sulfides from Au-rich IS deposits are systematically lighter than those of Ag-rich IS Ag-Pb-Zn deposit,indicating the ore-forming fluids of the former are more oxidized than the latter.We highlight that sulfur isotopic composition of hypogene sulfides is an efficacious proxy to fingerprint the oxygen fugacity fluctuations of epithermal deposits and could potentially be used to distinguish the subtypes of IS deposits.
文摘The corrosion properties of a Co-15wt% Y alloy were studied in H_2-H_2S mixtures under a sulfur pressure of 10-3 Pa at 600-800℃ and of 10-2 Pa at 800℃ to examine the effect of Y on the resistance of pure cobalt to sulfur attack at high temperatures.The alloy is nearly single-phase.containing mostly the intermetallic compound Co17Y2 plus a little amount of the solid solution of Y in cobalt.At 600-700℃ and at 800℃ under 10-2 Pa of S2 the alloy forms multi-layered scales consisting of an outer region of pure cobalt sulfide,an intermediate region of a mixture of the sulfides of the two metals and finally an innermost layer of a mixture of yttrium sulfide with metal cobalt.At 800℃ under 10-3Pa of S2,below the dissociation pressure of cobalt sulfide, the alloy forms only a single layer composed of a mixture of metallic cobalt with yttrium sulfide.Pure Y produces only the oxysulfide Y2O2S, as a result of the good stability of this compound and of the presence of some impurities in the gas mixtures used The corrosion kinetics is generally rather complex and irregular except al 800℃under 10-3 Pa of S2.The addition of yttrium always reduces the sulfidation rate of cobalt, even though the formation of a continuous protective external layer of yttrium sulfide is never achieved.The internal sulfidation of Y in Co-15% Y is not associated with a depletion of Y in the alloy.This kind of diffusionless internal attack is typical of alloys with a very small solubility of the most reactive component Y in the base metal A.which restricts severely the Y flux from the alloy towards the alloy-scale interface.
