The principle for the electro-generative leaching was applied to simultaneous leaching of sphalerite-MnO2. A galvanic system for the bio-electro-generative leaching was set up. The effects of grain size and temperatur...The principle for the electro-generative leaching was applied to simultaneous leaching of sphalerite-MnO2. A galvanic system for the bio-electro-generative leaching was set up. The effects of grain size and temperature on rate of zinc extraction from sphalerite under the conditions of presence and absence of Acidithiobacillus ferrooxidans (A.ferrooxidans) were studied, respectively. The results show that with bacteria, the maximum extraction of zinc from the ores with grain size of 16.6 μm can reach 32.01% after leaching for 12 h, while to obtain the same extraction ratio in the traditional bio-leaching route (i.e. not electro-generative one) 10 d is needed to ore granules with same size. The unreacted shrinking core model was used for describing the reaction-relative and diffusion-relative phenomena presented in the process of the electro-generative leaching with and without bacteria, which is considered to be diffusion controlled. The activation energies of the anodic reaction for leaching system in the presence and absence of bacteria are 11.97 and 14.39 kJ/mol, respectively, indicating that leaching rate can be decreased by A. ferrooxidans. SEM was used to study the effect of A. ferrooxidans on the ores in the simultaneous electro-generative leaching, which indicates that the produced sulfur on the surface of the sulfides can be oxidized by A. ferrooxidans after bio-electro-generative leaching for 24 h, and the transferred charge due to the bacterial oxidation is up to 17.86%, which is an important part of the output electric quantity.展开更多
The efficient extraction and separation of valuable metal elements from coal gasification fine slag(CGFS)are crucial for the comprehensive high-value utilization of its constituents.This study focused on the carbon-ri...The efficient extraction and separation of valuable metal elements from coal gasification fine slag(CGFS)are crucial for the comprehensive high-value utilization of its constituents.This study focused on the carbon-rich components of CGFS(CGFS-H)and systematically investigates the selective leaching behavior of Fe^(3+),Al^(3+)and Ca^(2+)using three organic acid extractants,i.e.,citric acid,tartaric acid,and tetrasodium iminodisuccinate.Additionally,the stepwise leaching of iron,aluminum and calcium from CGFS-H is explored.The selective dissolution mechanisms of these metals by different organic acids are elucidated through X-ray diffraction(XRD),X-ray fluorescence(XRF),and scanning electron microscopy(SEM)analyses.The results indicate that tetrasodium iminodisuccinate exhibits the highest leaching selectivity for Fe^(3+),while tartaric acid demonstrateds a comparable affinity for both Fe^(3+)and Al^(3+).In contrast citric acid shows superior selectivity toward Ca^(2+).The leaching yield of Fe^(3+),Al^(3+)and Ca^(2+)after sequential leaching with the three organic acids were 79.8%,65.08%and 78.6%,respectively.These findings confirm that effective and selective separation of Fe^(3+),Al^(3+)and Ca^(2+)from CGFS-H can be achieved via optimized organic acid-based leaching strategies.This advancement provides a critical foundation for developing Ca/Fe/Al hydrotalcite materials using CGFS-H as a sustainable feedstock,thereby facilitating the transformation of waste residue into high-value functional materials and promoting resourceefficient utilization of coal gasification fine slag.展开更多
Phosphogypsum,an industrial solid waste,is an effective binder for partially replacing cement in stabilizing dredged sediments.Acid rain,as a worldwide ecological problem,also affects the long-term stability and susta...Phosphogypsum,an industrial solid waste,is an effective binder for partially replacing cement in stabilizing dredged sediments.Acid rain,as a worldwide ecological problem,also affects the long-term stability and sustainability of geotechnical materials and structures.However,the research on leaching effects and long-term durability of phosphogypsum-stabilized soils under acid rain conditions is limited and remains a significant challenge for practical applications.This study investigates the leaching effects and long-term durability of phosphogypsum-stabilized soils by simulating acid rain erosion through semi-dynamic leaching tests.Key parameters,including leached Ca^(2+)concentration,leachate pH,and unconfined compressive strength after leaching,were evaluated.Microscopic analyses with X-ray diffraction(XRD)and scanning electron microscopy(SEM)were also conducted to explore the underlying mechanisms.The results indicate that the presence of phosphogypsum in stabilized soil with high water content shows a significant improvement in leaching resistance subjected to acid ions,evidencing a lower Ca^(2+)concentration and pH value in the leachate,and a higher strength after leaching compared to those samples without phosphogypsum.SEM images and XRD analysis revealed that samples with higher phosphogypsum content possess denser structures due to more needle-shaped ettringite and other minerals in the soil matrix,contributing to improved strength and leaching resistance.The enhanced strength and leaching resistance of phosphogypsum-stabilized soil can be attributed to additional gel formation,a rise in swelling potential,ettringite bridging,and a denser microstructure,which reduces Ca^(2+)availability for leaching in acidic environments.展开更多
The leaching mechanism of gallium(Ga)and germanium(Ge)from zinc powder replacement residue(ZPRR)was investigated through ultrasonic-assisted sulfuric acid leaching.Characterization via XRD,SEM,XPS,and FT-IR revealed t...The leaching mechanism of gallium(Ga)and germanium(Ge)from zinc powder replacement residue(ZPRR)was investigated through ultrasonic-assisted sulfuric acid leaching.Characterization via XRD,SEM,XPS,and FT-IR revealed that ultrasonic treatment promotes the dehydration of H_(4)SiO_(4)colloids,thereby reducing their adsorption capacities for Ga and Ge complexes.Additionally,ultrasound enhances the dissolution of CaS in H_(2)SO_(4),increasing H_(2)S production,which aids in the reduction of Fe^(3+)and mitigates iron precipitate formation.Process parameters including ultrasonic power(0-450 W),temperature(100-120℃),and leaching time(30-120 min)were systematically optimized,achieving optimal leaching efficiencies of Ga and Ge at 95.7%and 94.5%,respectively.展开更多
The leaching process and kinetic behavior of lepidolite in hydrochloric acid were explored systematically.The influence of leaching conditions on the leaching efficiency of valuable metals in lepidolite was investigat...The leaching process and kinetic behavior of lepidolite in hydrochloric acid were explored systematically.The influence of leaching conditions on the leaching efficiency of valuable metals in lepidolite was investigated.Under optimized conditions,the leaching efficiencies of Li,K,Rb,Cs and Al are 92.02%,93.31%,88.59%,86.75%and 81.07%,respectively.Kinetics research results show that the leaching process conforms to the shrinking core model that is under the mixed control of chemical reaction and diffusion through the solid product layer.In addition,the contribution of solid product layer diffusion to the leaching gradually expands as the temperature rises,but it is still significantly less than the contribution of chemical reaction.Cost saving in the neutralizing agent and leaching processes makes hydrochloric acid an economical leaching agent for lepidolite.Finally,the Li2CO3 product with a purity of 99.89%was synthesized from the hydrochloric acid leachate.展开更多
Phosphorus(P)leaching in alkaline soils,exacerbated by excessive fertilizer application,represents a significant pathway for P loss.While soil pore structure and texture critically regulate P transport,mechanisms gove...Phosphorus(P)leaching in alkaline soils,exacerbated by excessive fertilizer application,represents a significant pathway for P loss.While soil pore structure and texture critically regulate P transport,mechanisms governing P loss in texturally diverse alkaline soils remain unclear.This study investigated P leaching dynamics and transport parameters across four alkaline soil textures(silty clay,clay loam,loam,sandy loam)using a one-dimensional convective-diffusion equation(CDE)based on column experiments.Results indicated that phosphorus leaching kinetics were predominantly governed by diffusion transport,evidenced by low Peclet numbers(P_(e))(ranged from 0.02 to 0.31)across varying textures and initial P concentrations(C_(0)).Comparative analysis of transport parameters revealed significant textural effects on dispersion coefficient(D),retardation factor(R),pore water velocity(V),P_(e),and diffusion coefficient(λ)(F>523.42,p<0.001).Among these,only D,P_(e) andλexhibited substantial differences in response to variations in C_(0)(F>89.47,p<0.001).Saturated hydraulic conductivity(K_(s))(R^(2)=62.9%,p<0.01)and total pore area(A)(R^(2)=12.4%,p<0.01)emerged as primary regulators of P leaching.Enhanced clay content increased total pore area while reducing average pore diameter,concurrently decreasing pore water velocity and saturated infiltration rates.These textural modifications amplified diffusive P transport within soil matrices.The findings provide mechanistic insights into texturedependent P mobility in alkaline environments,informing targeted strategies for agricultural phosphorus management.展开更多
Heavy metal contamination of soil is one of the major challenges to sustainable agriculture.This contamination can be transmitted through the soil food chain and poses a serious threat to human health.In this study,we...Heavy metal contamination of soil is one of the major challenges to sustainable agriculture.This contamination can be transmitted through the soil food chain and poses a serious threat to human health.In this study,we found that freeze-thaw leaching(FTL)effectively complements the low removal rate of chemical leaching,and investigated the effects of different numbers of FTL on Cd contamination,soil chemical properties and microbial communities.The results showed that repeated FTL significantly reduced(P<0.05)the total Cd content in the top soil(19.02%-49.35%)and subsoil(0.41%-21.13%)and promoted the transformation of Cd to a more stable form,mainly through various removal mechanisms such as complexation,ion-exchange,and chemical precipitation.This finding was supported by reductions in several soil properties,including pH,available potassium(AK),and available phosphorus(AP).FTL treatment initially increased the bioavailability of Cd compared to chemical leaching,but bioavailability of Cd progressively decreased as the number of freeze-thaw cycles increased.Additionally,FTL reduced the richness and diversity of bacteria communities,destabilized ecological symbiotic networks,while increasing the richness and diversity of fungi in the soil.Various model analyses indicated that FTL treatment,available Cd,soil pH,AP and AK were the key drivers influencing the changes in microbial community structure.This study provides new insights and scientific bases for the effective management of heavy metal pollution in agricultural soils,the restoration of ecosystem health,and the improvement of soil sustainability.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
A dual cell system was used to study the output power, output voltage, galvanic polarization of anode and cathode, and the relationship between the electric quantity(Q) and some factors, such as the dissolved Fe2+ mag...A dual cell system was used to study the output power, output voltage, galvanic polarization of anode and cathode, and the relationship between the electric quantity(Q) and some factors, such as the dissolved Fe2+ magnitude, the time in the electro- generative simultaneous leaching with bacteria(BEGSL) and without bacteria(EGSL). A three-electrode system was adopted to study their individual self-corrosion current, which was smaller compared with the galvanic current. The results show that the output power and voltage in BEGSL are higher than those in EGSL. The accumulated sulfur on the surface of sulfides produced in BEGSL can be oxidized by A. ferrooxidans, and the ratio of biologic electric quantity reaches 51.50% in 72 h. The first stage both in EGSL and in BEGSL is the dissolution of pyrite on the surface to ferrous ion and sulfur element, which was oxidized by A. ferrooxidans in the further procedure.展开更多
To clarify the role and mechanism of Acidithiobacillus ferrooxidans (A. ferrooxidans) in bio-electro-generative-leaching (BEGL), an experiment was made on the electro-generative leaching of chalcopyrite-MnO2 in the pr...To clarify the role and mechanism of Acidithiobacillus ferrooxidans (A. ferrooxidans) in bio-electro-generative-leaching (BEGL), an experiment was made on the electro-generative leaching of chalcopyrite-MnO2 in the presence of the bacteria which grew respectively in Fe(Ⅱ) and S0 media. A dual cell system with chalcopyrite anode and MnO2 cathode was used to study the relationship between time and both of electric quantity and dissolved rate of the two minerals in BEGL. The results show that the dissolved rates for Cu2+ and Fe2+ under the action of the bacteria cultivated by S0 medium are almost 2 times faster than those by Fe(Ⅱ). And the leaching ratio for Mn2+ and the electric output increase by near 3 times. The oxidation residue of chalcopyrite was characterized by SEM and XRD, whose patterns are similar to those of raw ore in BEGL. The mechanism of anodic reaction for CuFeS2-MnO2 leaching in the presence of A. ferrooxidans cultivated by S0 medium is proposed as a successive reaction of two independent sub-processes. The first stage is the dissolution of chalcopyrite to produce Cu2+, Fe2+ and sulfur, and the second stage is bio-oxidation of sulfur, which is the control step of the process. However, dissolution of MnO2 lasts until the reaction of chalcopyrite stops or the ores exhaust in two types of leaching.展开更多
To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the character...To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the characteristics of low-tempe rature sulfuric acid deco mposition.When a single monazite was leached using 75 wt% H_(2)SO_(4) solution with phosphoric acid,the size and number of monazite particles in the washing slag gradually decrease with the increase in phosphoric acid content in the leaching solution.The monazite phase can hardly be found in the slag when the phosphoric acid content reaches 70 g/L,which indicates that phosphoric acid is favorable for monazite decomposition.The mixed rare earth concentrate was leached by 75 wt% H_(2)SO_(4) containing 70 g/L phosphoric acid,the mineral compositions of the washing slag are only gypsum and unwashed rare earth sulfuric acid.After cyclic leaching of75 wt% H_(2)SO_(4),the mineral compositions of the primary leaching washing slag are mainly undecomposed monazite,rare earth sulfate and calcium sulfate.However,monazite is not found in the mineral phase of the second and third leaching washing slag.The leaching rates of rare earth and phosphorus gradually increase with the increase in cyclic leaching times.In addition,the phosphoric acid content in the leaching solution increases with the increase in the number of cyclic leaching time.However,the rising trend decreases when the phosphoric acid content reaches 50 g/L by adsorption and crystallization of phosphoric acid.A small amount of water can be used to clean the leaching residue before washing to recover the more soluble phosphorus acid according to the difference of dissolution between phosphoric acid and rare earth sulfuric acid.展开更多
The efficient recycling of spent lithium iron phosphate(LiFePO_(4),also referred to as LFP)should convert Fe(Ⅱ)to Fe(Ⅲ),which is key to the extraction of Li and separation of Fe and is not well understood.Herein,we ...The efficient recycling of spent lithium iron phosphate(LiFePO_(4),also referred to as LFP)should convert Fe(Ⅱ)to Fe(Ⅲ),which is key to the extraction of Li and separation of Fe and is not well understood.Herein,we systematically study the oxidation of LiFePO_(4)in the air and in the solution containing oxidants such as H_(2)O_(2)and the effect of oxidation on the leaching behaviors of LFP.In the air,O_(2)breaks down the LFP olivine structure at 550℃for 1 h by oxidizing Fe(Ⅱ)to Fe(Ⅲ)in terms of converting LFP to Li_(3)Fe_(2)(PO_(4))_(3)and Fe_(2)O_(3).After that,Li is leached in 0.5 M sulfuric acid solution and is further recycled as Li_(3)PO_(4)with a Li recovery efficiency of 97.48%.Meanwhile,Fe is recovered as FePO_(4)and Fe_(2)O_(3).Compared with H_(2)SO_(4)-H_(2)O_(2),the air oxidation saves H_(2)O_(2)but increases the leaching efficiency of Fe and H_(2)SO_(4)consumption.The discrepancy of Fe leaching efficiency can be attributed to the different leaching mechanisms involving the solid-to-solid and solid-to-liquid-to-solid conversions.Furthermore,the results of the Everbatt model analysis show that the air roasting-H_(2)SO_(4)leaching method has low emission and potentially high income,which is simple and safe.Overall,this work will deepen the understanding of acid leaching of LFP and favorably stimulate the maturation of the LFP recycling technique.展开更多
The rare earth elements(REEs)extraction by chemical leaching from ion-adsorption type rare earth ores(IAREO)has led to serious ecological and environmental risks.Conversely,demand for bioleaching is on the rise with t...The rare earth elements(REEs)extraction by chemical leaching from ion-adsorption type rare earth ores(IAREO)has led to serious ecological and environmental risks.Conversely,demand for bioleaching is on the rise with the advantage of being environmental-friendly.As one of the organic acids produced by biological metabolism,citric acid was used to leach REEs and explore the performance and process.The results demonstrate that citric acid exhibits higher leaching efficiency(96.00%)for REEs at a relatively low concentration of 0.01 mol/L compared with(NH_(4))_(2)SO_(4)(84.29%,0.1 mol/L)and MgSO_(4)(83.99%,0.1 mol/L).Citric acid shows a preference for leaching heavy rare earth elements,with 99%leaching efficiency in IAREO,which shows higher capacity than(NH_(4))_(2)SO_(4)and MgSO_(4)(as inorganic leaching agents).Kinetic analysis indicates that the leaching process of REEs with citric acid is controlled by both the internal diffusion kinetics and chemical reaction kinetics,which is different from inorganic leaching agents.Visual Minteq calculations confirm that RE-Citrate is the main constituent of the extract solution in the leaching process of the IAREO,thereby enhancing the leaching efficiency of REEs from the IAREO.It suggests that citric acid may be used as a promising organic leaching agent for the environmentalfriendly extraction of REEs from IAREO.展开更多
The leaching of sulfuric acid converted product of scheelite in NH_(3)·H_(2)O−NH_(4)HCO_(3)solution was systemically studied to improve sulfuric acid conversion−ammonium salts leaching technology route for ammoni...The leaching of sulfuric acid converted product of scheelite in NH_(3)·H_(2)O−NH_(4)HCO_(3)solution was systemically studied to improve sulfuric acid conversion−ammonium salts leaching technology route for ammonium paratungstate production.The results showed that the WO_(3)leaching efficiency was about 99%under optimal conditions of 350 r/min,liquid-to-solid ratio of 3 mL/g,1 mol/L NH_(4)HCO_(3),4 mol/L NH_(3)·H_(2)O,25℃,and 15 min.During the leaching,CaSO_(4)almost had no change and was still in a banding or rod-like shape in short leaching time,while conglobate CaCO_(3)was gradually formed on the CaSO_(4)surface.A secondary reaction might occur between CaSO_(4)and WO_(4)^(2−),which could be restrained by a certain amount of CO_(3)^(2−)in the solution.There was no CaCO_(3)phase determined by XRD in leaching residue of converted product for scheelite concentrate under optimal conditions,which was different from that for synthetic scheelite.The leaching process could be explained by neutralization reaction of H_(2)WO_(4)and solid transformation of CaSO_(4)in NH_(3)·H_(2)O−NH_(4)HCO_(3)solution.展开更多
Co-associated rare earth elements(lanthanide and yttrium,REY)in coal and its by-products have been considered important potential nontraditional rare earth sources.In this study,a coal gangue sample collected from a c...Co-associated rare earth elements(lanthanide and yttrium,REY)in coal and its by-products have been considered important potential nontraditional rare earth sources.In this study,a coal gangue sample collected from a coal processing plant in Jinsha County of Guizhou Province,southwest China,was used as the research object.The content,modes of occurrence,and extraction(acid leaching after pretreatment of selective grinding,tailings discarding,and alkali roasting)of REY from the sample were analyzed.The result shows that the content of REY(1038.26μg/g)in pyrite and quartz is low but mainly enriched in kaolinite.Under the following conditions of a filling ratio of 40%(grinding media steel ball)and grinding time of 8 min,selective grinding pretreatment is applied to achieve 176.95μg/g(yield 24.08%)and 1104.93μg/g(yield 75.92%)of REY in+2 mm and-2 mm fractions,respectively.Thus,the-2 mm coal gangue fraction is selected,used as the feed,and roasted and leached with HCl.When Na_(2)CO_(3)and NaCl are separately used as roasting activators,the REY leaching ratios are 91.41%and 68.88%,respectively,under the optimum conditions.The contents of REY in the final leachate are 1010.02 and 761.08μg/g when Na_(2)CO_(3)and NaCl are used,respectively.The two REY contents are relatively higher than the impurity ions in the leachate,which facilitates further REY separation.The mechanism study reveals that high-temperature roasting increases the pore size and the total pore area of the gangue,which promotes leachate penetration and improves reaction efficiency.In addition,roasting facilitates the reaction between the sodium salt activator and kaolinite and other aluminosilicate minerals in the coal gangue to generate soluble salts,thus releasing REY into the solution.The appropriate roasting temperature transforms the activator into a molten state.Thus,the reaction between coal gangue and activator is a solid-liquid reaction rather than a solid-solid reaction,which improves the efficiency of the chemical reaction.展开更多
Selenium distillation slag(SDS)is a high-value-added secondary resource with a high recovery value.This paper aims to investigate the leaching behavior and kinetics of selenium,tellurium,and copper in the SDS acid oxi...Selenium distillation slag(SDS)is a high-value-added secondary resource with a high recovery value.This paper aims to investigate the leaching behavior and kinetics of selenium,tellurium,and copper in the SDS acid oxidation leaching process with H_(2)SO_(4) and H_(2)O_(2).The experimental results showed that under the optimum conditions,the contents of selenium,tellurium,and copper in the SDS were reduced from 22.13 wt%,3.58 wt%,and 6.42 wt%to 3.06 wt%,0.27 wt%,and 0.33 wt%,respectively.Correspondingly,the recovery rates are 87.08%,97.15%and 99.7%.The leaching processes of selenium and tellurium were controlled by diffusion and chemical reactions,and the leaching behavior of copper was controlled by chemical reactions.Below 45℃,the activation energies for selenium,tellurium,and copper were found to be 26.47,62.18 and 19.67 kJ/mol,respectively.In addition,the contents of lead,silver and gold in the leaching residue are increased to 46.8 wt%,8.35 wt%and 0.27 wt%,respectively.These substances can be utilized as raw materials for the recovery of these valuable metals.Importantly,the entire process does not generate toxic or harmful waste,making it a green and environmentally friendly method for resource recovery.展开更多
The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solu...The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.展开更多
Neodymium-iron-boron(Nd-Fe-B)sludge is an important secondary resource of rare-earth elements(REEs).However,the state-of-the-art recycling method,i.e.,HCl-preferential dissolution faces challenges such as slow leachin...Neodymium-iron-boron(Nd-Fe-B)sludge is an important secondary resource of rare-earth elements(REEs).However,the state-of-the-art recycling method,i.e.,HCl-preferential dissolution faces challenges such as slow leaching kinetics,excessive chemical consumption and wastewater generation.In this work,the in situ anodic leaching of Nd-Fe-B sludge was developed to selectively recover REEs with high efficiency.The leaching rates of the REEs are 2.4-9.0 times higher using the in situ anodic leaching at the current density from 10 to 40 mA/cm^(2)than using conventional chemical leaching under the maintained pH of 3.7.Mechanism studies reveal that the anode-generated H~+plays the key role during the in situ anodic leaching process that locally increases the H^(+)concentration at the interface of sludge particles,accele rating the leaching kinetics.By achieving a total leaching efficiency of Nd-Fe-B sludge close to 100%and the Fe deposition efficiency in the range of 70.9%-74.3%,selective leaching of REEs is successfully realized and thus largely reduces chemical consumption.Additionally,a two-step recycling route involving electrolysis-selective precipitation was proposed that enables a stable REEs recovery of 92.2%with recyclable electrolyte.This study provides a novel and environmentally-friendly strategy for the efficient recovery of REEs from secondary resources.展开更多
Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reage...Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reagents that can replace cyanide. This paper intro-duces a method for synthesizing a gold leaching reagent. Sodium cyanate is used as the main raw material, with sodium hydroxide and so-dium ferrocyanide used as additives. The gold leaching reagent can be obtained under the conditions of a mass ratio of sodium cyanate,sodium hydroxide, and sodium ferrocyanide of 15:3:1, synthesis temperature of 600℃, and synthesis time of 1 h. This reagent has a goodrecovery effect on gold concentrate and gold-containing electronic waste. The gold leaching rate of roasted desulfurized gold concentratecan reach 87.56%. For the extraction experiments of three types of gold-containing electronic waste, the gold leaching rate can reach over90% after 2 h. Furthermore, the reagent exhibits good selectivity towards gold. Component analysis indicates that the effective compon-ent in the reagent could be sodium isocyanate.展开更多
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
基金Project(2004CB619204) supported by the National Basic Research Program of ChinaProject(50374077) supported by the National Natural Science Foundation of ChinaProject(07D069) supported by the Education Department Foundation of Hunan Province, China
文摘The principle for the electro-generative leaching was applied to simultaneous leaching of sphalerite-MnO2. A galvanic system for the bio-electro-generative leaching was set up. The effects of grain size and temperature on rate of zinc extraction from sphalerite under the conditions of presence and absence of Acidithiobacillus ferrooxidans (A.ferrooxidans) were studied, respectively. The results show that with bacteria, the maximum extraction of zinc from the ores with grain size of 16.6 μm can reach 32.01% after leaching for 12 h, while to obtain the same extraction ratio in the traditional bio-leaching route (i.e. not electro-generative one) 10 d is needed to ore granules with same size. The unreacted shrinking core model was used for describing the reaction-relative and diffusion-relative phenomena presented in the process of the electro-generative leaching with and without bacteria, which is considered to be diffusion controlled. The activation energies of the anodic reaction for leaching system in the presence and absence of bacteria are 11.97 and 14.39 kJ/mol, respectively, indicating that leaching rate can be decreased by A. ferrooxidans. SEM was used to study the effect of A. ferrooxidans on the ores in the simultaneous electro-generative leaching, which indicates that the produced sulfur on the surface of the sulfides can be oxidized by A. ferrooxidans after bio-electro-generative leaching for 24 h, and the transferred charge due to the bacterial oxidation is up to 17.86%, which is an important part of the output electric quantity.
基金Supported by National Natural Science Foundation(52374279)。
文摘The efficient extraction and separation of valuable metal elements from coal gasification fine slag(CGFS)are crucial for the comprehensive high-value utilization of its constituents.This study focused on the carbon-rich components of CGFS(CGFS-H)and systematically investigates the selective leaching behavior of Fe^(3+),Al^(3+)and Ca^(2+)using three organic acid extractants,i.e.,citric acid,tartaric acid,and tetrasodium iminodisuccinate.Additionally,the stepwise leaching of iron,aluminum and calcium from CGFS-H is explored.The selective dissolution mechanisms of these metals by different organic acids are elucidated through X-ray diffraction(XRD),X-ray fluorescence(XRF),and scanning electron microscopy(SEM)analyses.The results indicate that tetrasodium iminodisuccinate exhibits the highest leaching selectivity for Fe^(3+),while tartaric acid demonstrateds a comparable affinity for both Fe^(3+)and Al^(3+).In contrast citric acid shows superior selectivity toward Ca^(2+).The leaching yield of Fe^(3+),Al^(3+)and Ca^(2+)after sequential leaching with the three organic acids were 79.8%,65.08%and 78.6%,respectively.These findings confirm that effective and selective separation of Fe^(3+),Al^(3+)and Ca^(2+)from CGFS-H can be achieved via optimized organic acid-based leaching strategies.This advancement provides a critical foundation for developing Ca/Fe/Al hydrotalcite materials using CGFS-H as a sustainable feedstock,thereby facilitating the transformation of waste residue into high-value functional materials and promoting resourceefficient utilization of coal gasification fine slag.
基金supported by the National Natural Science Foundation of China(Grant Nos.52178361,52178328,and 42377190).
文摘Phosphogypsum,an industrial solid waste,is an effective binder for partially replacing cement in stabilizing dredged sediments.Acid rain,as a worldwide ecological problem,also affects the long-term stability and sustainability of geotechnical materials and structures.However,the research on leaching effects and long-term durability of phosphogypsum-stabilized soils under acid rain conditions is limited and remains a significant challenge for practical applications.This study investigates the leaching effects and long-term durability of phosphogypsum-stabilized soils by simulating acid rain erosion through semi-dynamic leaching tests.Key parameters,including leached Ca^(2+)concentration,leachate pH,and unconfined compressive strength after leaching,were evaluated.Microscopic analyses with X-ray diffraction(XRD)and scanning electron microscopy(SEM)were also conducted to explore the underlying mechanisms.The results indicate that the presence of phosphogypsum in stabilized soil with high water content shows a significant improvement in leaching resistance subjected to acid ions,evidencing a lower Ca^(2+)concentration and pH value in the leachate,and a higher strength after leaching compared to those samples without phosphogypsum.SEM images and XRD analysis revealed that samples with higher phosphogypsum content possess denser structures due to more needle-shaped ettringite and other minerals in the soil matrix,contributing to improved strength and leaching resistance.The enhanced strength and leaching resistance of phosphogypsum-stabilized soil can be attributed to additional gel formation,a rise in swelling potential,ettringite bridging,and a denser microstructure,which reduces Ca^(2+)availability for leaching in acidic environments.
基金financially supported by the National Key Research and Development Program of China(No.2022YFC2904900)the National Natural Science Foundation of China(Nos.52204392,52274385,52204347)the Young Elite Scientists Sponsorship Program by CAST,China(No.2022QNRC001)。
文摘The leaching mechanism of gallium(Ga)and germanium(Ge)from zinc powder replacement residue(ZPRR)was investigated through ultrasonic-assisted sulfuric acid leaching.Characterization via XRD,SEM,XPS,and FT-IR revealed that ultrasonic treatment promotes the dehydration of H_(4)SiO_(4)colloids,thereby reducing their adsorption capacities for Ga and Ge complexes.Additionally,ultrasound enhances the dissolution of CaS in H_(2)SO_(4),increasing H_(2)S production,which aids in the reduction of Fe^(3+)and mitigates iron precipitate formation.Process parameters including ultrasonic power(0-450 W),temperature(100-120℃),and leaching time(30-120 min)were systematically optimized,achieving optimal leaching efficiencies of Ga and Ge at 95.7%and 94.5%,respectively.
基金supported by the National Natural Science Foundation of China(No.52122407)the National Key Research&Development Program of China(No.2022YF2906200)the Science and Technology Innovation Program of Hunan Province,China(No.2022RC3048)。
文摘The leaching process and kinetic behavior of lepidolite in hydrochloric acid were explored systematically.The influence of leaching conditions on the leaching efficiency of valuable metals in lepidolite was investigated.Under optimized conditions,the leaching efficiencies of Li,K,Rb,Cs and Al are 92.02%,93.31%,88.59%,86.75%and 81.07%,respectively.Kinetics research results show that the leaching process conforms to the shrinking core model that is under the mixed control of chemical reaction and diffusion through the solid product layer.In addition,the contribution of solid product layer diffusion to the leaching gradually expands as the temperature rises,but it is still significantly less than the contribution of chemical reaction.Cost saving in the neutralizing agent and leaching processes makes hydrochloric acid an economical leaching agent for lepidolite.Finally,the Li2CO3 product with a purity of 99.89%was synthesized from the hydrochloric acid leachate.
基金supported by the National Natural Science Foundation of China(Nos.42077067,42277329)the Projects of Talents Recruitment of GDUPT(No.XJ2005000301)。
文摘Phosphorus(P)leaching in alkaline soils,exacerbated by excessive fertilizer application,represents a significant pathway for P loss.While soil pore structure and texture critically regulate P transport,mechanisms governing P loss in texturally diverse alkaline soils remain unclear.This study investigated P leaching dynamics and transport parameters across four alkaline soil textures(silty clay,clay loam,loam,sandy loam)using a one-dimensional convective-diffusion equation(CDE)based on column experiments.Results indicated that phosphorus leaching kinetics were predominantly governed by diffusion transport,evidenced by low Peclet numbers(P_(e))(ranged from 0.02 to 0.31)across varying textures and initial P concentrations(C_(0)).Comparative analysis of transport parameters revealed significant textural effects on dispersion coefficient(D),retardation factor(R),pore water velocity(V),P_(e),and diffusion coefficient(λ)(F>523.42,p<0.001).Among these,only D,P_(e) andλexhibited substantial differences in response to variations in C_(0)(F>89.47,p<0.001).Saturated hydraulic conductivity(K_(s))(R^(2)=62.9%,p<0.01)and total pore area(A)(R^(2)=12.4%,p<0.01)emerged as primary regulators of P leaching.Enhanced clay content increased total pore area while reducing average pore diameter,concurrently decreasing pore water velocity and saturated infiltration rates.These textural modifications amplified diffusive P transport within soil matrices.The findings provide mechanistic insights into texturedependent P mobility in alkaline environments,informing targeted strategies for agricultural phosphorus management.
基金supported by the National Natural Science Foundation of China(No.42077135).
文摘Heavy metal contamination of soil is one of the major challenges to sustainable agriculture.This contamination can be transmitted through the soil food chain and poses a serious threat to human health.In this study,we found that freeze-thaw leaching(FTL)effectively complements the low removal rate of chemical leaching,and investigated the effects of different numbers of FTL on Cd contamination,soil chemical properties and microbial communities.The results showed that repeated FTL significantly reduced(P<0.05)the total Cd content in the top soil(19.02%-49.35%)and subsoil(0.41%-21.13%)and promoted the transformation of Cd to a more stable form,mainly through various removal mechanisms such as complexation,ion-exchange,and chemical precipitation.This finding was supported by reductions in several soil properties,including pH,available potassium(AK),and available phosphorus(AP).FTL treatment initially increased the bioavailability of Cd compared to chemical leaching,but bioavailability of Cd progressively decreased as the number of freeze-thaw cycles increased.Additionally,FTL reduced the richness and diversity of bacteria communities,destabilized ecological symbiotic networks,while increasing the richness and diversity of fungi in the soil.Various model analyses indicated that FTL treatment,available Cd,soil pH,AP and AK were the key drivers influencing the changes in microbial community structure.This study provides new insights and scientific bases for the effective management of heavy metal pollution in agricultural soils,the restoration of ecosystem health,and the improvement of soil sustainability.
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(2004CB619204) supported by the Major State Basic Research Development ProgramProject(50374077) supported by the National Natural Science Foundation of ChinaProject(07D069) supported by the Education Department Foundation of Hunan Province, China
文摘A dual cell system was used to study the output power, output voltage, galvanic polarization of anode and cathode, and the relationship between the electric quantity(Q) and some factors, such as the dissolved Fe2+ magnitude, the time in the electro- generative simultaneous leaching with bacteria(BEGSL) and without bacteria(EGSL). A three-electrode system was adopted to study their individual self-corrosion current, which was smaller compared with the galvanic current. The results show that the output power and voltage in BEGSL are higher than those in EGSL. The accumulated sulfur on the surface of sulfides produced in BEGSL can be oxidized by A. ferrooxidans, and the ratio of biologic electric quantity reaches 51.50% in 72 h. The first stage both in EGSL and in BEGSL is the dissolution of pyrite on the surface to ferrous ion and sulfur element, which was oxidized by A. ferrooxidans in the further procedure.
基金Project(50874119) supported by the National Natural Science Foundation of ChinaProject supported by the Post-doctoral Program of Central South University, China
文摘To clarify the role and mechanism of Acidithiobacillus ferrooxidans (A. ferrooxidans) in bio-electro-generative-leaching (BEGL), an experiment was made on the electro-generative leaching of chalcopyrite-MnO2 in the presence of the bacteria which grew respectively in Fe(Ⅱ) and S0 media. A dual cell system with chalcopyrite anode and MnO2 cathode was used to study the relationship between time and both of electric quantity and dissolved rate of the two minerals in BEGL. The results show that the dissolved rates for Cu2+ and Fe2+ under the action of the bacteria cultivated by S0 medium are almost 2 times faster than those by Fe(Ⅱ). And the leaching ratio for Mn2+ and the electric output increase by near 3 times. The oxidation residue of chalcopyrite was characterized by SEM and XRD, whose patterns are similar to those of raw ore in BEGL. The mechanism of anodic reaction for CuFeS2-MnO2 leaching in the presence of A. ferrooxidans cultivated by S0 medium is proposed as a successive reaction of two independent sub-processes. The first stage is the dissolution of chalcopyrite to produce Cu2+, Fe2+ and sulfur, and the second stage is bio-oxidation of sulfur, which is the control step of the process. However, dissolution of MnO2 lasts until the reaction of chalcopyrite stops or the ores exhaust in two types of leaching.
基金support by the National Natural Science Foundation of Inner Mongolia (2022SHZR1885)Natural Science Foundation of Hebei province (E2022402101,E2022402105)。
文摘To completely recover valuable elements and reduce the amount of waste,the impact of phosphoric acid on the decomposition of rare earth,fluorine and phosphorus during cyclic leaching was studied based on the characteristics of low-tempe rature sulfuric acid deco mposition.When a single monazite was leached using 75 wt% H_(2)SO_(4) solution with phosphoric acid,the size and number of monazite particles in the washing slag gradually decrease with the increase in phosphoric acid content in the leaching solution.The monazite phase can hardly be found in the slag when the phosphoric acid content reaches 70 g/L,which indicates that phosphoric acid is favorable for monazite decomposition.The mixed rare earth concentrate was leached by 75 wt% H_(2)SO_(4) containing 70 g/L phosphoric acid,the mineral compositions of the washing slag are only gypsum and unwashed rare earth sulfuric acid.After cyclic leaching of75 wt% H_(2)SO_(4),the mineral compositions of the primary leaching washing slag are mainly undecomposed monazite,rare earth sulfate and calcium sulfate.However,monazite is not found in the mineral phase of the second and third leaching washing slag.The leaching rates of rare earth and phosphorus gradually increase with the increase in cyclic leaching times.In addition,the phosphoric acid content in the leaching solution increases with the increase in the number of cyclic leaching time.However,the rising trend decreases when the phosphoric acid content reaches 50 g/L by adsorption and crystallization of phosphoric acid.A small amount of water can be used to clean the leaching residue before washing to recover the more soluble phosphorus acid according to the difference of dissolution between phosphoric acid and rare earth sulfuric acid.
基金supported by the Chilwee Group(No.CWDY-ZH-YJY-202101-001)the Fundamental Research Funds for the Central Universities(No.2042023kf0214)the Starting Funding from Wuhan University.
文摘The efficient recycling of spent lithium iron phosphate(LiFePO_(4),also referred to as LFP)should convert Fe(Ⅱ)to Fe(Ⅲ),which is key to the extraction of Li and separation of Fe and is not well understood.Herein,we systematically study the oxidation of LiFePO_(4)in the air and in the solution containing oxidants such as H_(2)O_(2)and the effect of oxidation on the leaching behaviors of LFP.In the air,O_(2)breaks down the LFP olivine structure at 550℃for 1 h by oxidizing Fe(Ⅱ)to Fe(Ⅲ)in terms of converting LFP to Li_(3)Fe_(2)(PO_(4))_(3)and Fe_(2)O_(3).After that,Li is leached in 0.5 M sulfuric acid solution and is further recycled as Li_(3)PO_(4)with a Li recovery efficiency of 97.48%.Meanwhile,Fe is recovered as FePO_(4)and Fe_(2)O_(3).Compared with H_(2)SO_(4)-H_(2)O_(2),the air oxidation saves H_(2)O_(2)but increases the leaching efficiency of Fe and H_(2)SO_(4)consumption.The discrepancy of Fe leaching efficiency can be attributed to the different leaching mechanisms involving the solid-to-solid and solid-to-liquid-to-solid conversions.Furthermore,the results of the Everbatt model analysis show that the air roasting-H_(2)SO_(4)leaching method has low emission and potentially high income,which is simple and safe.Overall,this work will deepen the understanding of acid leaching of LFP and favorably stimulate the maturation of the LFP recycling technique.
基金Project supported by the Thousand Talents Program of Jiangxi Province,China(JXSQ2023201003)National Natural Science Foundation of China(42107254)+4 种基金Science and Technology Major Program of Ordos City(2022EEDSKJZDZX014-2)Technological Innovation Guidance Program of Jiangxi Province(20212BDH81029)Rare Earth Industry Fund(IAGM2020DB06)Selfdeployed Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055A01)the Key Research Program of the Chinese Academy of Sciences(ZDRW-CN-2021-3-3)。
文摘The rare earth elements(REEs)extraction by chemical leaching from ion-adsorption type rare earth ores(IAREO)has led to serious ecological and environmental risks.Conversely,demand for bioleaching is on the rise with the advantage of being environmental-friendly.As one of the organic acids produced by biological metabolism,citric acid was used to leach REEs and explore the performance and process.The results demonstrate that citric acid exhibits higher leaching efficiency(96.00%)for REEs at a relatively low concentration of 0.01 mol/L compared with(NH_(4))_(2)SO_(4)(84.29%,0.1 mol/L)and MgSO_(4)(83.99%,0.1 mol/L).Citric acid shows a preference for leaching heavy rare earth elements,with 99%leaching efficiency in IAREO,which shows higher capacity than(NH_(4))_(2)SO_(4)and MgSO_(4)(as inorganic leaching agents).Kinetic analysis indicates that the leaching process of REEs with citric acid is controlled by both the internal diffusion kinetics and chemical reaction kinetics,which is different from inorganic leaching agents.Visual Minteq calculations confirm that RE-Citrate is the main constituent of the extract solution in the leaching process of the IAREO,thereby enhancing the leaching efficiency of REEs from the IAREO.It suggests that citric acid may be used as a promising organic leaching agent for the environmentalfriendly extraction of REEs from IAREO.
文摘The leaching of sulfuric acid converted product of scheelite in NH_(3)·H_(2)O−NH_(4)HCO_(3)solution was systemically studied to improve sulfuric acid conversion−ammonium salts leaching technology route for ammonium paratungstate production.The results showed that the WO_(3)leaching efficiency was about 99%under optimal conditions of 350 r/min,liquid-to-solid ratio of 3 mL/g,1 mol/L NH_(4)HCO_(3),4 mol/L NH_(3)·H_(2)O,25℃,and 15 min.During the leaching,CaSO_(4)almost had no change and was still in a banding or rod-like shape in short leaching time,while conglobate CaCO_(3)was gradually formed on the CaSO_(4)surface.A secondary reaction might occur between CaSO_(4)and WO_(4)^(2−),which could be restrained by a certain amount of CO_(3)^(2−)in the solution.There was no CaCO_(3)phase determined by XRD in leaching residue of converted product for scheelite concentrate under optimal conditions,which was different from that for synthetic scheelite.The leaching process could be explained by neutralization reaction of H_(2)WO_(4)and solid transformation of CaSO_(4)in NH_(3)·H_(2)O−NH_(4)HCO_(3)solution.
基金Project supported by the National Natural Science Foundation of China(51964009)。
文摘Co-associated rare earth elements(lanthanide and yttrium,REY)in coal and its by-products have been considered important potential nontraditional rare earth sources.In this study,a coal gangue sample collected from a coal processing plant in Jinsha County of Guizhou Province,southwest China,was used as the research object.The content,modes of occurrence,and extraction(acid leaching after pretreatment of selective grinding,tailings discarding,and alkali roasting)of REY from the sample were analyzed.The result shows that the content of REY(1038.26μg/g)in pyrite and quartz is low but mainly enriched in kaolinite.Under the following conditions of a filling ratio of 40%(grinding media steel ball)and grinding time of 8 min,selective grinding pretreatment is applied to achieve 176.95μg/g(yield 24.08%)and 1104.93μg/g(yield 75.92%)of REY in+2 mm and-2 mm fractions,respectively.Thus,the-2 mm coal gangue fraction is selected,used as the feed,and roasted and leached with HCl.When Na_(2)CO_(3)and NaCl are separately used as roasting activators,the REY leaching ratios are 91.41%and 68.88%,respectively,under the optimum conditions.The contents of REY in the final leachate are 1010.02 and 761.08μg/g when Na_(2)CO_(3)and NaCl are used,respectively.The two REY contents are relatively higher than the impurity ions in the leachate,which facilitates further REY separation.The mechanism study reveals that high-temperature roasting increases the pore size and the total pore area of the gangue,which promotes leachate penetration and improves reaction efficiency.In addition,roasting facilitates the reaction between the sodium salt activator and kaolinite and other aluminosilicate minerals in the coal gangue to generate soluble salts,thus releasing REY into the solution.The appropriate roasting temperature transforms the activator into a molten state.Thus,the reaction between coal gangue and activator is a solid-liquid reaction rather than a solid-solid reaction,which improves the efficiency of the chemical reaction.
基金Project(2022YFC2904900) supported by the National Key Research and Development Program of ChinaProject(U1902221) supported by the National Natural Science Foundation of China。
文摘Selenium distillation slag(SDS)is a high-value-added secondary resource with a high recovery value.This paper aims to investigate the leaching behavior and kinetics of selenium,tellurium,and copper in the SDS acid oxidation leaching process with H_(2)SO_(4) and H_(2)O_(2).The experimental results showed that under the optimum conditions,the contents of selenium,tellurium,and copper in the SDS were reduced from 22.13 wt%,3.58 wt%,and 6.42 wt%to 3.06 wt%,0.27 wt%,and 0.33 wt%,respectively.Correspondingly,the recovery rates are 87.08%,97.15%and 99.7%.The leaching processes of selenium and tellurium were controlled by diffusion and chemical reactions,and the leaching behavior of copper was controlled by chemical reactions.Below 45℃,the activation energies for selenium,tellurium,and copper were found to be 26.47,62.18 and 19.67 kJ/mol,respectively.In addition,the contents of lead,silver and gold in the leaching residue are increased to 46.8 wt%,8.35 wt%and 0.27 wt%,respectively.These substances can be utilized as raw materials for the recovery of these valuable metals.Importantly,the entire process does not generate toxic or harmful waste,making it a green and environmentally friendly method for resource recovery.
基金Scientific and Technological Project of Nanyang(23KJGG017)Key Specialized Research&Development and Promotion Project(Scientific and Technological Project)of Henan Province(232102221022)+1 种基金College Students and Technology Innovation Fund Project of Nanyang Institute of Technology(2023139)Project of Doctoral Scientific Research Startup Fund of Nanyang Institute of Technology(NGBJ-2023-25)。
文摘The leaching process of magnesiothermic self-propagating product generated during the multistage deep reduction process was investigated.The influence of magnesiothermic self-propagating product particle size,HCl solution concentration,and leaching solution temperature on the leaching behavior of elements Al and V was investigated.Results demonstrate that the leaching rate of Al and V is increased with the rise in leaching solution temperature,the increase in HCl solution concentration,and the enlargement of magnesiothermic self-propagating product particle size.The leaching processes of Al and V are consistent with the chemical reaction control model.When the magnesiothermic self-propagation product with D_(50) of 59.4μm is selected as the raw material,the leaching temperature is 40℃,and 1 mol/L HCl solution is employed,after leaching for 180 min,the leaching rates of Al and V are 24.8%and 12.6%,respectively.The acid-leached product exhibits a porous structure with a specific surface area of 3.5633 m^(2)/g.
基金Project supported by the Natural Science Foundation of Inner Mongolia Autonomous Region of China(2021BS02007,2022MS02014)the"Science and Technology Project of Ordos"Program(2021 CGI 17-9,2021 ZDI11-14)+2 种基金the National Natural Science Foundation of China(21971129,21961022,51903125,21661023)the"Inner Mongolia Autonomous Region 2022 Leading Talent Team of Science and Technology"Program(2022LJRC0008)China Postdoctoral Science Foundation(2018M640043,2019T120038)。
文摘Neodymium-iron-boron(Nd-Fe-B)sludge is an important secondary resource of rare-earth elements(REEs).However,the state-of-the-art recycling method,i.e.,HCl-preferential dissolution faces challenges such as slow leaching kinetics,excessive chemical consumption and wastewater generation.In this work,the in situ anodic leaching of Nd-Fe-B sludge was developed to selectively recover REEs with high efficiency.The leaching rates of the REEs are 2.4-9.0 times higher using the in situ anodic leaching at the current density from 10 to 40 mA/cm^(2)than using conventional chemical leaching under the maintained pH of 3.7.Mechanism studies reveal that the anode-generated H~+plays the key role during the in situ anodic leaching process that locally increases the H^(+)concentration at the interface of sludge particles,accele rating the leaching kinetics.By achieving a total leaching efficiency of Nd-Fe-B sludge close to 100%and the Fe deposition efficiency in the range of 70.9%-74.3%,selective leaching of REEs is successfully realized and thus largely reduces chemical consumption.Additionally,a two-step recycling route involving electrolysis-selective precipitation was proposed that enables a stable REEs recovery of 92.2%with recyclable electrolyte.This study provides a novel and environmentally-friendly strategy for the efficient recovery of REEs from secondary resources.
基金financially supported by the National Natural Science Foundation of China (No.51974016)。
文摘Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reagents that can replace cyanide. This paper intro-duces a method for synthesizing a gold leaching reagent. Sodium cyanate is used as the main raw material, with sodium hydroxide and so-dium ferrocyanide used as additives. The gold leaching reagent can be obtained under the conditions of a mass ratio of sodium cyanate,sodium hydroxide, and sodium ferrocyanide of 15:3:1, synthesis temperature of 600℃, and synthesis time of 1 h. This reagent has a goodrecovery effect on gold concentrate and gold-containing electronic waste. The gold leaching rate of roasted desulfurized gold concentratecan reach 87.56%. For the extraction experiments of three types of gold-containing electronic waste, the gold leaching rate can reach over90% after 2 h. Furthermore, the reagent exhibits good selectivity towards gold. Component analysis indicates that the effective compon-ent in the reagent could be sodium isocyanate.
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.
