Chemical leaching techniques have been proven effective in removing heavymetal contaminants fromsoil using various leaching agents.Previous research has shown that both singleagent and composite leaching systems have ...Chemical leaching techniques have been proven effective in removing heavymetal contaminants fromsoil using various leaching agents.Previous research has shown that both singleagent and composite leaching systems have been applied for the remediation of chromiumcontaminated soils,with varying degrees of success depending on soil type and contaminant form.However,the removal rate of total chromium(Cr)and hexavalent chromium(Cr(Ⅵ))often fluctuates based on the chemical composition of the leaching agents,as well as the soil’s physicochemical properties,such as pH and Cr speciation stability.Therefore,this study investigates the effectiveness of 20 composite leaching systems,including deionized water,lime water,calcium chloride,sodium carbonate,and sodium phosphate,through soil column leaching tests.The aim was to evaluate their impact on soil pH,total Cr,and Cr(Ⅵ)removal,and to examine the transformation of various Cr species during the leaching process.Results reveal that lime water and sodium phosphate were particularly effective in stabilizing Cr(Ⅵ)and neutralizing soil pH,while total Cr removal amount ranged from 197.4 mg/kg to 1671.6 mg/kg and Cr(Ⅵ)removal amount ranged from 113.2mg/kg to 316.8mg/kg.We also find that using 0.2 mol/L citric acid,0.1 mol/L hydrochloric acid,and 1.2 mL/g lime solution adjusted soil pH to 7.37,with average removal efficiencies of 34.6%.for total Cr and 72.7%for Cr(Ⅵ).Overall,our results suggest that the combined use of lime water and sodium phosphate is an effective strategy for remediating chromium-contaminated soil,particularly for stabilizing unleached Cr and adjusting soil pH.展开更多
This study addresses the global problem of the detoxification of cadmium(Cd)-containing solid waste by developing an eco-friendly thiosulfate system for extracting the negative electrode materials from spent Ni–Cd ba...This study addresses the global problem of the detoxification of cadmium(Cd)-containing solid waste by developing an eco-friendly thiosulfate system for extracting the negative electrode materials from spent Ni–Cd batteries and proposing an ultraviolet(UV)photolysis technology for the green recycling of the Cd in the resultant leached solution.Cd extraction is performed using both simple thiosulfate and cuprous thiosulfate systems,with the cuprous thiosulfate system exhibiting a superior leaching performance(80%),as compared with that of the simple thiosulfate system(36%).X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)analyses reveal the formation of copper sulfide on the surface of the Ni–Cd batteries leaching residue,which is confirmed by Cdleaching kinetics fitting using the shrinking-core model.Following UV exposure,95%of the Cd precipitates from the leaching solution to form CdS.Transmission electron microscopy(TEM)characterization and particle size distribution reveal that the CdS contains 100–150 nm-diameter spherical particles with compact surface structures.Electrochemical performance tests and UV–visible diffuse reflectance spectra(UV–Vis DRS)analyses demonstrate that the UV-photolysis product exhibits excellent photoelectric conversion characteristics.Photocatalytic activity tests of the recovered CdS confirm that the photocatalytic degradation ratio of methyl orange is 87%,indicating the successful green recycling of Cd from spent Ni–Cd batteries,which improves its potential application in the field of photocatalysis.展开更多
The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied....The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm-1 and 1193 cm-1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.展开更多
Oxidation pressure leaching was proposed to selectively dissolve Li from spent LiFePO_(4)batteries in a stoichiometric sulfuric acid solution.Using O_(2)as an oxidant and stoichiometric sulfuric acid as leaching agent...Oxidation pressure leaching was proposed to selectively dissolve Li from spent LiFePO_(4)batteries in a stoichiometric sulfuric acid solution.Using O_(2)as an oxidant and stoichiometric sulfuric acid as leaching agent,above 97%of Li was leached into the solution,whereas more than 99%of Fe remained in the leaching residue,enabling a relatively low cost for one-step separation of Li and Fe.And then,by adjusting the pH of leachate,above 95%of Li was recovered in the form of the Li_(3)PO_(4)product through iron removal and chemical precipitation of phosphate.展开更多
The study is focused on the extraction of valuable metals from automotive shredder residue(ASR)by different leaching solutions.First,ASR samples were roasted at 600°C to simulate a thermal treatment processing.Di...The study is focused on the extraction of valuable metals from automotive shredder residue(ASR)by different leaching solutions.First,ASR samples were roasted at 600°C to simulate a thermal treatment processing.Distilled water,citric and sulphuric acid were preliminarily investigated,thus two further full factorial systems entailing H2SO4–H2O2and H2SO4–H2O2–Fe3+were tested.The preliminary experimental results showed that0.1 mol·L-1H2SO4solution extracted 100%of Cu,Fe and Zn,whereas citric acid leached 100%of Zn and Pb,59%of Fe and 62%of Cu;whereas,H2SO4–H2O2and H2SO4–H2O2–Fe3+(Fenton's)leaching media showed that Cu,Fe and Zn can be extracted simultaneously and completely from the ASR ashes before final disposal.展开更多
The extraction of gold from refractory gold ores(RGOs)without side reactions is an extremely promising endeavor.However,most RGOs contain large amounts of sulfide,such as pyrite.Thus,investigation of the influence of ...The extraction of gold from refractory gold ores(RGOs)without side reactions is an extremely promising endeavor.However,most RGOs contain large amounts of sulfide,such as pyrite.Thus,investigation of the influence of sulfide on the gold leaching process is important to maximize the utilization of RGOs.In this work,the effects of pyrite on the stability of the thiourea system were systematically investigated under different conditions.Results showed that the decomposition rate of thiourea was accelerated sharply in the presence of pyrite.The effect of pyrite on gold recovery in thiourea leaching systems was then confirmed via a series of experiments.The decomposition efficiency of thiourea decreased by 40%and the recovery efficiency of gold increased by 56%after the removal of sulfide by roasting.Under optimal conditions,the efficiency of the gold recovery system increased to 83.69%and only 57.92%of thiourea decomposition was observed.The high consumption of thiourea by the leaching system may be attributed to not only adsorption by mineral particles but also catalytic decomposition by some impurities in the ores,such as pyrite and soluble ferric oxide.展开更多
The kinetics of the catalytical oxidation acid leaching of arsenopyrite is studied in the HNO<sub>3</sub>-H<sub>2</sub>SO<sub>4</sub>-O<sub>2</sub> aqueous system. In ad...The kinetics of the catalytical oxidation acid leaching of arsenopyrite is studied in the HNO<sub>3</sub>-H<sub>2</sub>SO<sub>4</sub>-O<sub>2</sub> aqueous system. In addition to the effect of reaction time on the extraction of arsenopyrite and distribution of products, the effects of operation factors and several additives on the reaction rate are also investigated. The experi mental results show that the oxidation rate is greatly dependent on nitric acid concentration, average radius of samples and acid concentration. The elemental sulphur produced does not interfere with the progress of the reacation process. It is found that a shrinking core model with chemical reaction controlling, which is expressed as 1-（1-α）<sup>1/3</sup>=kt, may be adopted to describe the kinetics results. The apparent activation energy is tested to be 23. 6 kJ/mol.展开更多
The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosi...The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosite(Pb-J)were 130℃,30 g/L H_(2)SO_(4),15 g/L Fe^(3+),and an oxygen partial pressure of 0.4 MPa.Furthermore,increased Fe^(3+)concentration and oxygen partial pressure did not enhance jarosite formation.Conversely,lowering the temperature and increasing the H_(2)SO_(4) concentration facilitated PbSO_(4) formation and inhibited its further conversion to Pb-J.Additionally,the effects of potassium sulfate,sodium sulfate,and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests,XRD,SEM-EDS,and FT-IR analyses.All three sulfates inhibited the conversion of galena to Pb-J.Among these,potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite.However,high concentrations of zinc sulfate facilitated the crystallization of both PbSO_(4) and Pb-J,which altered the morphology of the product.Zinc ions coprecipitated with Pb-J,thereby integrating into the product.展开更多
In view of the difference in coordination capacity of the glycine ion(Gly−),a selective leaching process for treating with spent lithium-ion batteries(LIBs)in the alkaline glycinate system was proposed.The effects of ...In view of the difference in coordination capacity of the glycine ion(Gly−),a selective leaching process for treating with spent lithium-ion batteries(LIBs)in the alkaline glycinate system was proposed.The effects of retention time,leaching temperature,concentration of glycine ligand,liquid-solid ratio(L/S),pH,stirring speed,and H_(2)O_(2) dosage on the leaching efficiency of valuable metals and the dissolution of impurities were investigated.When the spent LIBs were leached in 3 mol/L glycine aqueous solution with pH of 8,L/S of 5 mL:1 g and H_(2)O_(2) dosage of 5 vol.%at 90℃and stirring speed of 400 r/min for 3 h,lithium,cobalt,nickel,and manganese recoveries were 96.31%,83.18%,91.56%,and 31.16%,respectively,but Ca,Al,Fe,and Cu were almost insoluble.Meanwhile,the kinetic study showed that the activation energies for the leaching of Li,Co,Ni,and Mn were all in the range of 45−61 kJ/mol.The results indicate that the leaching process is all controlled by chemical reactions.展开更多
In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under...In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under different influencing factors was designed with the aid of ICP-OES,XRD,and SEM-EDS.The experimental results show that,with the extension of leaching time,the continuous hydration reaction in the system enables the leaching amount of Si,Al,Mg,and Ca elements to show an overall downward trend.In the alkaline environment,the more sufficient hydration reaction consumes more soluble elements,resulting in a significantly smaller leaching amount than that in the neutral environment.Temperature is also an important factor affecting the leaching of elements.The rise of temperature promotes the dissolution of amorphous phases Si,Al,and Mg in the system,leading to increased leaching amount and higher consumption of C_(2)S and C_(3)S,generating more reaction products.In addition,the content and fineness of FETNS also have a significant effect on the element leaching of the composite cementitious system.More importantly,this paper clarifies the leaching safety of internal heavy metal elements when FETNS is used under the above conditions,which provides a scientific guarantee for the safe and efficient application of FETNS in building materials.展开更多
Microwave roasting self-leaching is an innovative method for recovering gold from high-sulfur refractory gold concentrates,without using deadly toxic cyanide reagents.However,the mechanism of gold self-leaching,which ...Microwave roasting self-leaching is an innovative method for recovering gold from high-sulfur refractory gold concentrates,without using deadly toxic cyanide reagents.However,the mechanism of gold self-leaching,which relies on lixiviants prepared using volatilized sulfur obtained from roasting,has not been fully elucidated.This study employs the response surface methodology to optimize processing parameters,resulting in an increased gold extraction rate of 96.18%.Analytical factorization and the Tafel curve indicate that CuSO_(4) and NH_(3)·H_(2)O significantly influence the self-leaching process.Furthermore,X-ray photoelectron spectroscopy(XPS)analysis reveals that S^(2−),S_(2)^(2−),polysulfides(S_(n)^(2−)),and thiosulfate(S_(2)O_(3)^(2−))are involved in the gold leaching reaction,with S^(2−),S_(2)^(2−),and S_(n)^(2−) serving as primary ligands for gold complexation.The role of S_(2)O_(3)^(2−) in the early stages of the gold-leaching reaction is also noteworthy.The copper–ammonia complex catalyzes the self-leaching gold reaction;however,an improper addition ratio can lead to copper-sulfur compound precipitates,reducing the extraction rate.展开更多
Ida2--H2O system（iminodiacetate aqueous solution） was used to leach a low grade zinc oxide ore for Zn extraction.The effects of leaching time,liquid-solid ratio（L/S）,total concentration of Ida2-（[Ida2-]T）,leachi...Ida2--H2O system（iminodiacetate aqueous solution） was used to leach a low grade zinc oxide ore for Zn extraction.The effects of leaching time,liquid-solid ratio（L/S）,total concentration of Ida2-（[Ida2-]T）,leaching temperature and pH on Zn leaching recovery and the dissolution of impurities such as Ca,Mg,Cu,Ni,Fe,Pb and Cd were investigated.Results show that Ca,Mg and Fe in ores were hardly dissolved in alkalescent iminodiacetate aqueous solution,while valuable metals such as Cu,Ni,Pb and Cd were partly dissolved into leaching liquor with Zn.The recovery of Zn reaches 76.6% when the ores were leached for 4 h at 70 ℃ by 0.9 mol/L iminodiacetate aqueous solution with pH of 8 and L/S of 5：1.展开更多
To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures rangi...To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.展开更多
Gold bearing pyrite leaching was conducted in H2SO4-Fe2（SO4）3 system at different reaction temperatures,with different ferric ion concentrations,sulfuric acid concentrations and stirring speeds.The leaching kinetics...Gold bearing pyrite leaching was conducted in H2SO4-Fe2（SO4）3 system at different reaction temperatures,with different ferric ion concentrations,sulfuric acid concentrations and stirring speeds.The leaching kinetics and mechanism were studied.When the temperature ranged between 30-75 °C,the pyrite leaching was mainly controlled by chemical reaction with positive correlation to the ferric ion concentration.The activation energy obtained from Arrhenius empirical formula is 51.39 k J/mol.The EDS and XPS analyses suggest that the oxidation of sulfur within pyrite is through a series of intermediate stages,and eventually is oxidized to sulphate accompanied with the formation of element sulfur.This indicates a thiosulfate oxidation pathway of the gold bearing pyrite oxidation in H2SO4-Fe2（SO4）3 system.展开更多
DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and e...DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and enzyme activities involved in N cycling is largely unknown. Therefore, an on-farm experiment, for two years, has been conducted, to elucidate the effects of DMPP on mineral N （NH4^＋- N and NO3^--N） leaching, nitrifying organisms, and denitrifying enzymes in a rice-oilseed rape cropping system. Three treatments including urea alone （UA）, urea ＋ 1% DMPP （DP）, and no fertilizer （CK）, have been carded out. The results showed that DP enhanced the mean NH4^＋-N concentrations by 19.1%-24.3%, but reduced the mean NO3^--N concentrations by 44.9%-56.6% in the leachate, under a two-year rice-rape rotation, compared to the UA treatment. The population of ammonia oxidizing bacteria, the activity of nitrate reductase, and nitrite reductase in the DP treatment decreased about 24.5%-30.9%, 14.9%-43.5%, and 14.7%-31.6%, respectively, as compared to the UA treatment. However, nitrite oxidizing bacteria and hydroxylamine reductase remained almost unaffected by DMPP. It is proposed that DMPP has the potential to either reduce NO3^--N leaching by inhibiting ammonia oxidization or N losses from denitrification, which is in favor of the N conversations in the rice-oilseed rape cropping system.展开更多
A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station （116.3°E, 39.9°N） in the North China Plain. The objective ...A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station （116.3°E, 39.9°N） in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize （Zea mays L.）： sole maize （CK）, maize ＋ soybean （CST）, maize ＋ groundnut （CGT）, maize ＋ ryegrass （CHM）, and maize ＋ alfalfa （CMX）. Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK〉CST〉CMX〉CHM〉CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9- 174.8 （CGT）, 35.2-130.8 （CHM）, 60.4-122.0 （CMX）, and 30.6-82.4 kg ha-1 （CST）. The results also suggested that intereropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.展开更多
[Objective] The aim was to seek effective soil remediation technologies suitable for soils slightly or moderately polluted. [Method] In-situ leaching-immobi- lization was used to research remediation soil and vegetabl...[Objective] The aim was to seek effective soil remediation technologies suitable for soils slightly or moderately polluted. [Method] In-situ leaching-immobi- lization was used to research remediation soil and vegetable contaminated by lead in vegetable bases in Chongqing. [Result] By tartaric acid-based leaching-sodium sulphide-based immobilization, vegetable Pb reduction rate was 46.4%, soil Pb reduction rate was 8.45% and Pb immobilization rate was 9.3% in deeper horizons. EDTA leaching did reduce lead content in vegetables, but reduced vegetable yield simultaneously. [Conclusion] The coupling remediation technology brought heavy metal contents down in vegetables without affecting productions. Therefore, it guarantees vegetable safety and reduces vegetable farmer＇s economic loss. It is a remediation technology suitable for soils slightly or moderately contaminated by heavy metals.展开更多
The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching effic...The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69 μm, holding at 80 ℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2-1, and the ratio (g/mL) of solid to liquid being 1-10.展开更多
In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O...In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O,As-N-Na-H2Osystems at ionic mass concentration of0.1mol/kg and temperatures of298,373,423and473K were established according tothermodynamic calculation.The results show that the existence forms of arsenic are associated with pH value,which mainly exists inthe forms of H3AsO4,24H AsO-,24HAsO-,H2AsO2-and As2O3in lower pH region,while it mainly exists in the form of3AsO4-when pH>11.14.High alkali concentration and high temperature are advantageous to the arsenic leaching.The alkaline pressureoxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis resultsobtained from theφ-pH diagrams of As-N-Na-H2O system,and the highest leaching rate of arsenic reaches95.85%at453K.展开更多
基金supported by the National Key Research and Development Program of China(No.2023YFC3707902)China Postdoctoral Science Foundation(No.2024M752168)+1 种基金Jiangsu Funding Programfor Excellent Postdoctoral Talent(No.2024ZB393)the National Natural Science Foundation of China(No.42407126).
文摘Chemical leaching techniques have been proven effective in removing heavymetal contaminants fromsoil using various leaching agents.Previous research has shown that both singleagent and composite leaching systems have been applied for the remediation of chromiumcontaminated soils,with varying degrees of success depending on soil type and contaminant form.However,the removal rate of total chromium(Cr)and hexavalent chromium(Cr(Ⅵ))often fluctuates based on the chemical composition of the leaching agents,as well as the soil’s physicochemical properties,such as pH and Cr speciation stability.Therefore,this study investigates the effectiveness of 20 composite leaching systems,including deionized water,lime water,calcium chloride,sodium carbonate,and sodium phosphate,through soil column leaching tests.The aim was to evaluate their impact on soil pH,total Cr,and Cr(Ⅵ)removal,and to examine the transformation of various Cr species during the leaching process.Results reveal that lime water and sodium phosphate were particularly effective in stabilizing Cr(Ⅵ)and neutralizing soil pH,while total Cr removal amount ranged from 197.4 mg/kg to 1671.6 mg/kg and Cr(Ⅵ)removal amount ranged from 113.2mg/kg to 316.8mg/kg.We also find that using 0.2 mol/L citric acid,0.1 mol/L hydrochloric acid,and 1.2 mL/g lime solution adjusted soil pH to 7.37,with average removal efficiencies of 34.6%.for total Cr and 72.7%for Cr(Ⅵ).Overall,our results suggest that the combined use of lime water and sodium phosphate is an effective strategy for remediating chromium-contaminated soil,particularly for stabilizing unleached Cr and adjusting soil pH.
基金financially supported by the National Natural Science Foundation of China(No.52104349)Henan Provincial Science and Technology R&D Plan Joint Fund Project(No.232103810032)+1 种基金the Funds for HAUST Young Cadre Teacher(No.400213450022)supporting by China Postdoctoral Science Foundation(No.2022M721031)。
文摘This study addresses the global problem of the detoxification of cadmium(Cd)-containing solid waste by developing an eco-friendly thiosulfate system for extracting the negative electrode materials from spent Ni–Cd batteries and proposing an ultraviolet(UV)photolysis technology for the green recycling of the Cd in the resultant leached solution.Cd extraction is performed using both simple thiosulfate and cuprous thiosulfate systems,with the cuprous thiosulfate system exhibiting a superior leaching performance(80%),as compared with that of the simple thiosulfate system(36%).X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)analyses reveal the formation of copper sulfide on the surface of the Ni–Cd batteries leaching residue,which is confirmed by Cdleaching kinetics fitting using the shrinking-core model.Following UV exposure,95%of the Cd precipitates from the leaching solution to form CdS.Transmission electron microscopy(TEM)characterization and particle size distribution reveal that the CdS contains 100–150 nm-diameter spherical particles with compact surface structures.Electrochemical performance tests and UV–visible diffuse reflectance spectra(UV–Vis DRS)analyses demonstrate that the UV-photolysis product exhibits excellent photoelectric conversion characteristics.Photocatalytic activity tests of the recovered CdS confirm that the photocatalytic degradation ratio of methyl orange is 87%,indicating the successful green recycling of Cd from spent Ni–Cd batteries,which improves its potential application in the field of photocatalysis.
基金Project (41271330) supported by the National Natural Science Foundation of China
文摘The effects of moderately thermophilic bacteria on the extraction of metals from zinc smelting slag and electrochemical characteristics of zinc smelting slag carbon paste electrode in bioleaching process were studied. The results show that the extraction rates of Fe, Cu and Zn from the slag reach 86.7%, 90.3% and 66.7% after adsorbed bacteria sterilize, while those with adsorbed bacteria are 91.9%, 96.0% and 84.5% in conditions of pulp density 2%, pH 1.0, temperature 65 °C and stirring rate 120 r/min, respectively. Some stretching peaks of functional groups from bacterial secretes on the bioleached residue surface, such as 1007 cm-1 and 1193 cm-1, turn up through FI-IR analysis and indirectly reveal the presence of the adsorbed bacteria on the slag particles surface. Besides, the corrosion of zinc smelting slag is enhanced by bacteria according to the characteristics of cyclic voltametry and Tafel curves in bioleaching system.
基金the financial supports from the National Natural Science Foundation of China(Nos.51804083,52104395,21906031)the Natural Science Foundation of Guangdong Province,China(No.2019A1515011628)+1 种基金the Science and Technology Planning Project of Guangdong Province,China(No.2017B090907026)the Special Program of Guangdong Academy of Sciences,China(Nos.2019GDASYL-0103069,2020GDASYL-0104027,2020GDASYL-0302004,2020GDASYL-0302009,2021GDASYL-0302004)。
文摘Oxidation pressure leaching was proposed to selectively dissolve Li from spent LiFePO_(4)batteries in a stoichiometric sulfuric acid solution.Using O_(2)as an oxidant and stoichiometric sulfuric acid as leaching agent,above 97%of Li was leached into the solution,whereas more than 99%of Fe remained in the leaching residue,enabling a relatively low cost for one-step separation of Li and Fe.And then,by adjusting the pH of leachate,above 95%of Li was recovered in the form of the Li_(3)PO_(4)product through iron removal and chemical precipitation of phosphate.
文摘The study is focused on the extraction of valuable metals from automotive shredder residue(ASR)by different leaching solutions.First,ASR samples were roasted at 600°C to simulate a thermal treatment processing.Distilled water,citric and sulphuric acid were preliminarily investigated,thus two further full factorial systems entailing H2SO4–H2O2and H2SO4–H2O2–Fe3+were tested.The preliminary experimental results showed that0.1 mol·L-1H2SO4solution extracted 100%of Cu,Fe and Zn,whereas citric acid leached 100%of Zn and Pb,59%of Fe and 62%of Cu;whereas,H2SO4–H2O2and H2SO4–H2O2–Fe3+(Fenton's)leaching media showed that Cu,Fe and Zn can be extracted simultaneously and completely from the ASR ashes before final disposal.
基金This work was financially supported by the National Natural Science Foundation of China(No.51922108)the Hunan Natural Science Foundation(No.2019JJ20031)the Hunan Key Research and Development Program(No.2019SK2061).
文摘The extraction of gold from refractory gold ores(RGOs)without side reactions is an extremely promising endeavor.However,most RGOs contain large amounts of sulfide,such as pyrite.Thus,investigation of the influence of sulfide on the gold leaching process is important to maximize the utilization of RGOs.In this work,the effects of pyrite on the stability of the thiourea system were systematically investigated under different conditions.Results showed that the decomposition rate of thiourea was accelerated sharply in the presence of pyrite.The effect of pyrite on gold recovery in thiourea leaching systems was then confirmed via a series of experiments.The decomposition efficiency of thiourea decreased by 40%and the recovery efficiency of gold increased by 56%after the removal of sulfide by roasting.Under optimal conditions,the efficiency of the gold recovery system increased to 83.69%and only 57.92%of thiourea decomposition was observed.The high consumption of thiourea by the leaching system may be attributed to not only adsorption by mineral particles but also catalytic decomposition by some impurities in the ores,such as pyrite and soluble ferric oxide.
基金Financially supported by the National Natural Science Foundation of China
文摘The kinetics of the catalytical oxidation acid leaching of arsenopyrite is studied in the HNO<sub>3</sub>-H<sub>2</sub>SO<sub>4</sub>-O<sub>2</sub> aqueous system. In addition to the effect of reaction time on the extraction of arsenopyrite and distribution of products, the effects of operation factors and several additives on the reaction rate are also investigated. The experi mental results show that the oxidation rate is greatly dependent on nitric acid concentration, average radius of samples and acid concentration. The elemental sulphur produced does not interfere with the progress of the reacation process. It is found that a shrinking core model with chemical reaction controlling, which is expressed as 1-（1-α）<sup>1/3</sup>=kt, may be adopted to describe the kinetics results. The apparent activation energy is tested to be 23. 6 kJ/mol.
基金Projects(2023AG05008,202302AB080012)supported by the Yunnan Major Scientific and Technological Program,ChinaProject(202405AC350015)supported by the Science and Technology Talent Programme of Yunnan Province,China。
文摘The phase transformation of galena in H_(2)SO_(4)-Fe_(2)(SO_(4))_(3) system under oxygen pressure was investigated.Results indicated that the critical conditions for the phase transformation of galena into lead jarosite(Pb-J)were 130℃,30 g/L H_(2)SO_(4),15 g/L Fe^(3+),and an oxygen partial pressure of 0.4 MPa.Furthermore,increased Fe^(3+)concentration and oxygen partial pressure did not enhance jarosite formation.Conversely,lowering the temperature and increasing the H_(2)SO_(4) concentration facilitated PbSO_(4) formation and inhibited its further conversion to Pb-J.Additionally,the effects of potassium sulfate,sodium sulfate,and high concentrations of zinc sulfate on the phase transformation of galena were examined through leaching tests,XRD,SEM-EDS,and FT-IR analyses.All three sulfates inhibited the conversion of galena to Pb-J.Among these,potassium sulfate prevented Pb-J formation and converted it more thoroughly into potassium jarosite.However,high concentrations of zinc sulfate facilitated the crystallization of both PbSO_(4) and Pb-J,which altered the morphology of the product.Zinc ions coprecipitated with Pb-J,thereby integrating into the product.
基金Projects(51974137,52274299)supported by the National Natural Science Foundation of ChinaProject(2023M733190)supported by the China Postdoctoral Science Foundation。
文摘In view of the difference in coordination capacity of the glycine ion(Gly−),a selective leaching process for treating with spent lithium-ion batteries(LIBs)in the alkaline glycinate system was proposed.The effects of retention time,leaching temperature,concentration of glycine ligand,liquid-solid ratio(L/S),pH,stirring speed,and H_(2)O_(2) dosage on the leaching efficiency of valuable metals and the dissolution of impurities were investigated.When the spent LIBs were leached in 3 mol/L glycine aqueous solution with pH of 8,L/S of 5 mL:1 g and H_(2)O_(2) dosage of 5 vol.%at 90℃and stirring speed of 400 r/min for 3 h,lithium,cobalt,nickel,and manganese recoveries were 96.31%,83.18%,91.56%,and 31.16%,respectively,but Ca,Al,Fe,and Cu were almost insoluble.Meanwhile,the kinetic study showed that the activation energies for the leaching of Li,Co,Ni,and Mn were all in the range of 45−61 kJ/mol.The results indicate that the leaching process is all controlled by chemical reactions.
基金Funded by the Science and Technology Program of Gansu Province(Nos.23JRRA799 and 24JRRA213)the National Natural Science Foundation of China(Nos.52178216,52008196,and U21A20150)。
文摘In order to explore the leaching law of different elements in the composite cementitious system composed of ferrous extraction tailing of nickel slag(FETNS)and ordinary Portland cement(OPC),element leaching test under different influencing factors was designed with the aid of ICP-OES,XRD,and SEM-EDS.The experimental results show that,with the extension of leaching time,the continuous hydration reaction in the system enables the leaching amount of Si,Al,Mg,and Ca elements to show an overall downward trend.In the alkaline environment,the more sufficient hydration reaction consumes more soluble elements,resulting in a significantly smaller leaching amount than that in the neutral environment.Temperature is also an important factor affecting the leaching of elements.The rise of temperature promotes the dissolution of amorphous phases Si,Al,and Mg in the system,leading to increased leaching amount and higher consumption of C_(2)S and C_(3)S,generating more reaction products.In addition,the content and fineness of FETNS also have a significant effect on the element leaching of the composite cementitious system.More importantly,this paper clarifies the leaching safety of internal heavy metal elements when FETNS is used under the above conditions,which provides a scientific guarantee for the safe and efficient application of FETNS in building materials.
基金supported by the National Natural Science Foundation of China(No.51974016).
文摘Microwave roasting self-leaching is an innovative method for recovering gold from high-sulfur refractory gold concentrates,without using deadly toxic cyanide reagents.However,the mechanism of gold self-leaching,which relies on lixiviants prepared using volatilized sulfur obtained from roasting,has not been fully elucidated.This study employs the response surface methodology to optimize processing parameters,resulting in an increased gold extraction rate of 96.18%.Analytical factorization and the Tafel curve indicate that CuSO_(4) and NH_(3)·H_(2)O significantly influence the self-leaching process.Furthermore,X-ray photoelectron spectroscopy(XPS)analysis reveals that S^(2−),S_(2)^(2−),polysulfides(S_(n)^(2−)),and thiosulfate(S_(2)O_(3)^(2−))are involved in the gold leaching reaction,with S^(2−),S_(2)^(2−),and S_(n)^(2−) serving as primary ligands for gold complexation.The role of S_(2)O_(3)^(2−) in the early stages of the gold-leaching reaction is also noteworthy.The copper–ammonia complex catalyzes the self-leaching gold reaction;however,an improper addition ratio can lead to copper-sulfur compound precipitates,reducing the extraction rate.
基金Project (2007CB613604) supported by the National Basic Research Program of China
文摘Ida2--H2O system（iminodiacetate aqueous solution） was used to leach a low grade zinc oxide ore for Zn extraction.The effects of leaching time,liquid-solid ratio（L/S）,total concentration of Ida2-（[Ida2-]T）,leaching temperature and pH on Zn leaching recovery and the dissolution of impurities such as Ca,Mg,Cu,Ni,Fe,Pb and Cd were investigated.Results show that Ca,Mg and Fe in ores were hardly dissolved in alkalescent iminodiacetate aqueous solution,while valuable metals such as Cu,Ni,Pb and Cd were partly dissolved into leaching liquor with Zn.The recovery of Zn reaches 76.6% when the ores were leached for 4 h at 70 ℃ by 0.9 mol/L iminodiacetate aqueous solution with pH of 8 and L/S of 5：1.
基金Project(2007CB613504)supported by the National Key Basic Research Program of ChinaProjects(51004033,50974035,51074047)supported by the National Natural Science Foundation of ChinaProject(2008BAB34B01)supported by National Science and Technology Support Plan of China during the 11th Five-Year Plan
文摘To analyze the thermodynamic characteristics of leaching process of converter slag, φ-pH diagram of V-Ti-H2O system at oxygen partial pressure of 0.5 MPa, ionic mass concentration of 0.1 mol/kg and temperatures ranging from 60 to 200 ℃ was obtained by recently published critically assessed standard Gibbs energies and activity coefficients of various species. When pH2, stable regions of V3＋, VO2＋ and VO2＋ exist in the stable region of TiO2. The pH values of stable regions of vanadium and titanium decrease and redox potentials become more positive with the temperature increasing. Vanadium and titanium could be separated by one-step leaching based on thermodynamics. The experiment results of pressure acid leaching of converter slag show that leaching rates of vanadium and titanium are 96.87% and 8.76% respectively, at 140 ℃ of temperature, 0.5 MPa of oxygen partial pressure, 0.055-0.075mm of particle size, 15：1 of liquid to solid ratio, 120 min of leaching time, 500 r/min of stirring speed and 200 g/L of initial acid concentration. Vanadium and titanium could be selectively separated in the pressure acid leaching process, and the experiment result is in agreement with thermodynamic calculation result.
基金Project(51474075)supported by the National Natural Science Foundation of China
文摘Gold bearing pyrite leaching was conducted in H2SO4-Fe2（SO4）3 system at different reaction temperatures,with different ferric ion concentrations,sulfuric acid concentrations and stirring speeds.The leaching kinetics and mechanism were studied.When the temperature ranged between 30-75 °C,the pyrite leaching was mainly controlled by chemical reaction with positive correlation to the ferric ion concentration.The activation energy obtained from Arrhenius empirical formula is 51.39 k J/mol.The EDS and XPS analyses suggest that the oxidation of sulfur within pyrite is through a series of intermediate stages,and eventually is oxidized to sulphate accompanied with the formation of element sulfur.This indicates a thiosulfate oxidation pathway of the gold bearing pyrite oxidation in H2SO4-Fe2（SO4）3 system.
文摘DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and enzyme activities involved in N cycling is largely unknown. Therefore, an on-farm experiment, for two years, has been conducted, to elucidate the effects of DMPP on mineral N （NH4^＋- N and NO3^--N） leaching, nitrifying organisms, and denitrifying enzymes in a rice-oilseed rape cropping system. Three treatments including urea alone （UA）, urea ＋ 1% DMPP （DP）, and no fertilizer （CK）, have been carded out. The results showed that DP enhanced the mean NH4^＋-N concentrations by 19.1%-24.3%, but reduced the mean NO3^--N concentrations by 44.9%-56.6% in the leachate, under a two-year rice-rape rotation, compared to the UA treatment. The population of ammonia oxidizing bacteria, the activity of nitrate reductase, and nitrite reductase in the DP treatment decreased about 24.5%-30.9%, 14.9%-43.5%, and 14.7%-31.6%, respectively, as compared to the UA treatment. However, nitrite oxidizing bacteria and hydroxylamine reductase remained almost unaffected by DMPP. It is proposed that DMPP has the potential to either reduce NO3^--N leaching by inhibiting ammonia oxidization or N losses from denitrification, which is in favor of the N conversations in the rice-oilseed rape cropping system.
基金the Key Technologies R&D Program of China during the 11th Five-Year Plan period (2007BAD89B01)the Key Technologies R&D Program of China during the 12th Five-Year Plan period(2011BAD16B15)the Project of Collaboration between Henan Province and Chinese Academy of Agricultural Sciences Program (102106000034)
文摘A 2-yr field experiment was conducted on a calcareous alluvial soil with four summer maize intercropping systems at Shangzhuang Experiment Station （116.3°E, 39.9°N） in the North China Plain. The objective was to determine nitrate leaching from intercropping systems involving maize （Zea mays L.）： sole maize （CK）, maize ＋ soybean （CST）, maize ＋ groundnut （CGT）, maize ＋ ryegrass （CHM）, and maize ＋ alfalfa （CMX）. Intercropping greatly reduced nitrate accumulation in the 100-200 cm soil layers compared with maize monoculture. Nitrate accumulation under intercropping systems decreased significantly at the 140-200 cm soil depth; the accumulation varied in the order CK〉CST〉CMX〉CHM〉CGT. However, compared to the CK treatment, nitrate leaching losses during the maize growing period were reduced by 20.9- 174.8 （CGT）, 35.2-130.8 （CHM）, 60.4-122.0 （CMX）, and 30.6-82.4 kg ha-1 （CST）. The results also suggested that intereropping is an effective way to reduce nitrogen leaching in fields with N fertilizer over-dose.
基金Supported by Chongqing Key Technologies R&D Program(CSTC2011AC101)Technology Supporting Program in 2013 of Chongqing Agriculture Committee~~
文摘[Objective] The aim was to seek effective soil remediation technologies suitable for soils slightly or moderately polluted. [Method] In-situ leaching-immobi- lization was used to research remediation soil and vegetable contaminated by lead in vegetable bases in Chongqing. [Result] By tartaric acid-based leaching-sodium sulphide-based immobilization, vegetable Pb reduction rate was 46.4%, soil Pb reduction rate was 8.45% and Pb immobilization rate was 9.3% in deeper horizons. EDTA leaching did reduce lead content in vegetables, but reduced vegetable yield simultaneously. [Conclusion] The coupling remediation technology brought heavy metal contents down in vegetables without affecting productions. Therefore, it guarantees vegetable safety and reduces vegetable farmer＇s economic loss. It is a remediation technology suitable for soils slightly or moderately contaminated by heavy metals.
基金Project(2007CB613604) supported by the Major State Basic Research Development Program of ChinaProject(50674104) supported by the National Natural Science Foundation of ChinaProject(GJJ08279) supported by the Department of Education of Jiangxi Province
文摘The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69 μm, holding at 80 ℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2-1, and the ratio (g/mL) of solid to liquid being 1-10.
基金Project(51564031) supported by the National Natural Science Foundation of ChinaProject(0201352042) supported by the Cooperation between School and Enterprise of China
文摘In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O,As-N-Na-H2Osystems at ionic mass concentration of0.1mol/kg and temperatures of298,373,423and473K were established according tothermodynamic calculation.The results show that the existence forms of arsenic are associated with pH value,which mainly exists inthe forms of H3AsO4,24H AsO-,24HAsO-,H2AsO2-and As2O3in lower pH region,while it mainly exists in the form of3AsO4-when pH>11.14.High alkali concentration and high temperature are advantageous to the arsenic leaching.The alkaline pressureoxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis resultsobtained from theφ-pH diagrams of As-N-Na-H2O system,and the highest leaching rate of arsenic reaches95.85%at453K.
