Improving cotton fiber quality can increase the economic income of cotton farmers, but achieving high fiber quality without decreasing cotton fiber yield remains a major challenge in saline-alkaline cotton fields. A f...Improving cotton fiber quality can increase the economic income of cotton farmers, but achieving high fiber quality without decreasing cotton fiber yield remains a major challenge in saline-alkaline cotton fields. A field experiment was conducted in 2020 and 2021 on saline-alkaline soil with cotton under drip irrigation to examine how amount and timing of leaching affected soils salinity, cotton fiber yield and quality. There were five leaching amounts(CK: 0 mm, W1: 75 mm, W2: 150 mm, W3: 225 mm and W4: 300 mm) and three leaching timings(T1: once at the seedling stage, T2: twice at the seedling and budding stages, and T3: thrice at the seedling, budding and pollen-setting stages). Soil salinity, soil nitrate nitrogen(NO_(3)-N), cotton nitrogen(N) uptake, irrigation water productivity(IWP), cotton fiber yield, fiber length, fiber uniformity, fiber strength, fiber elongation, micronaire and fiber quality index(FQI) were investigated. The results indicated that soil salinity and NO_(3)-N reduced with increasing leaching amount. The N uptake of cotton bolls was greater than in cotton leaves, stems and roots, and total N accumulation increased with increasing leaching amount. The optimal cotton fiber yield and IWP occurred in treatment W3T2, and were 3,199 and 2,771 kg ha^(-1), and 0.5482 and 0.4912 kg m-3in 2020 and 2021, respectively. Fiber length, strength, elongation, and uniformity increased with increasing leaching amount, while there was a negative relationship between fiber micronaire and leaching amount. Soil salinity, NO_(3)-N and fiber micronaire were negatively correlated with fiber quality(i.e., length, strength, elongation and uniformity) and yield, nitrogen uptake of various organs(i.e., root, stems and leaves) and whole plant nitrogen uptake. Pearson correlation analysis revealed that fiber elongation was most sensitive to soil salinity. The method of Entropy–Order Preference by Similarity to Ideal Solution(EM–TOPSIS) indicated that leaching of 300 mm of water applied equally at the seedling and budding periods was the optimal treatment to maintain soil salinity and nutrient levels and achieve high cotton fiber yield and quality. In conclusion, the optimal level of leaching treatment decreased soil salinity and improved nitrogen uptake and was beneficial to achieve high fiber yield and quality. Our results will be significant for guiding drip irrigation practice of leaching on saline-alkaline soils for sustainable cotton fiber production.展开更多
Cotton,as one of important economic crops,is widely planted in the saline-alkaline soil of southern Xinjiang,China.Moreover,in order to control the saline-alkaline content for seed germination and seedlings survive of...Cotton,as one of important economic crops,is widely planted in the saline-alkaline soil of southern Xinjiang,China.Moreover,in order to control the saline-alkaline content for seed germination and seedlings survive of cotton,farmers always adopt salt leaching during winter and spring seasons.However,excessive amount of salt leaching might result in the waste of water resources and unsuitable irrigation seasons might further increase soil salinization.In this study,a field experiment was conducted in the saline-alkaline soil in 2020 and 2021 to determine the effects of leaching amount and period on water-salinity dynamics and cotton yield.Five leaching amounts(0.0(W0),75.0(W1),150.0(W2),225.0(W3),and 300.0(W4)mm)and three leaching periods(seedling stage(P1),seedling and squaring stages(P2),and seedling,squaring,flowering,and boll setting stages(P3))were used.In addition,a control treatment(CK)with a leaching amount of 300.0 mm in spring was performed.The soil water-salt dynamics,cotton growth,seed cotton yield,water productivity(WP),and irrigation water productivity(WPI)were analyzed.Results showed that leaching significantly decreased soil electrical conductivity(EC),and W3P2 treatment reduced EC by 11.79%in the 0-100 cm soil depth compared with CK.Plant height,stem diameter,leaf area index,and yield under W3 and W4 treatments were greater than those under W1 and W2 treatments.Compared with W3P1 and W3P3 treatments,seed cotton yield under W3P2 treatment significantly enhanced and reached 6621 kg/hm^(2)in 2020 and 5340 kg/hm^(2)in 2021.Meanwhile,WP and WPI under W3P2 treatment were significantly higher than those under other leaching treatments.In conclusion,the treatment of 225.0 mm leaching amount and seedling and squaring stages-based leaching period was beneficial for the salt control,efficient water utilization,and yield improvement of cotton in southern Xinjiang,China.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
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
This study investigated the effect of C/N ratio,placement of plant residues,and leaching amounts on soil respiration,microbial biomass,and nutrient availability within four weeks after amendment.Young faba bean shoots...This study investigated the effect of C/N ratio,placement of plant residues,and leaching amounts on soil respiration,microbial biomass,and nutrient availability within four weeks after amendment.Young faba bean shoots(FB,C/N 7)and mature wheat straw(WH,C/N 80)were used as low and high C/N residue,respectively.Soil was unamended,mulched with FB or WH only,or mulched with one residue and mixed with the other residue.Leaching with 5 or 25 mL water was carried out on days 4,12,and 20.Cumulative respiration and microbial biomass N were higher with 25 than 5 mL only in treatments with two residues.WH under FB mulch reduced N availability compared to FB mulch alone,whereas FB under WH increased N availability compared toWHmulch alone.When soils were leached with 25 mL water,available N in FB mulch over WH was lower on day 12,but higher later,compared to WH mulch over FB.In contrast,in WH mulch over FB microbial biomass N increased over time whereas available N decreased.In conclusion,the effect of C/N ratio of the mulch on soil available and microbial biomass N was greater with the higher leaching amount.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 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
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
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
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
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
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
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
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
As the main component of electronic products,plastics contain complex and diverse metal additives.Recycling process is not conducive to stable existence of metal additives in electronic plastics.Once the e-waste plast...As the main component of electronic products,plastics contain complex and diverse metal additives.Recycling process is not conducive to stable existence of metal additives in electronic plastics.Once the e-waste plastics enter the environment,they will continue to release harmful metals into environment after aging,causing serious hazards.This study delved into the analysis and comparison of metal content of e-waste plastics,elucidating aging process and metal leaching behavior over a 112-day natural light exposure period.The findings underscored that metal content in recycled plastics surpassed that in their new counterparts.Specifically,Ti content in new plastics remained below 100 mg/kg,while recycled plastics exhibited Ti content surpassing 100 mg/kg threshold.Throughout prolonged natural light exposure,metals such as Zn,Ba and Sb demonstrated a heightened likelihood of release from electronic plastics in comparison to other metals.The aging process during light exposure led to fragmentation of electronic plastics,accompanied by a reduction in particle size.Notably,the particle size reduction was more pronounced in poly acrylonitrile butadiene styrene(ABS)and recycled ABS,experiencing reductions of 40µm and 85µm,respectively.This phenomenon was attributed to the presence of polybutadiene structural units,which proved more susceptible to aging.Along with the breaking of plastics,the ABS plastics released metal species such as Pb,Cd,Ni,Al that had not been detected in other plastics solutions.The collective evidence from this study suggested that ABS and recycled ABS electronic plastics might pose a heightened potential environmental risk compared to other electronic plastics.展开更多
A clean and efficient process for the direct extraction of valuable metals from low-grade nickel sulfide ore through oxidative leaching with(NH_(4))_(2)S_(2)O_(8)under atmosphere pressure was proposed to address the g...A clean and efficient process for the direct extraction of valuable metals from low-grade nickel sulfide ore through oxidative leaching with(NH_(4))_(2)S_(2)O_(8)under atmosphere pressure was proposed to address the growing demand for nickel and cobalt in the new energy industry.The effects of four key parameters on the metal leaching rates were systematically investigated.Characterization techniques,including XRD,SEM and EDS,were employed to analyze phase transformations during the leaching process.Under optimized conditions,approximately 96.5%of nickel,95.5%of cobalt and 65.2%of copper were successfully extracted.The kinetics of the leaching process was explored to identify the controlling mechanisms of nickel,cobalt and copper dissolution,establishing activation energies and kinetic equations for each metal.The cleanliness and efficiency of this method were confirmed through comparisons with other extraction processes for nickel sulfide ore.展开更多
基金financially supported by the National Key Research and Development Program of China (2022YFD1900401)the Science and Technology Project of Agriculture, Xinjiang Production and Construction Corps, China (2021AB037)。
文摘Improving cotton fiber quality can increase the economic income of cotton farmers, but achieving high fiber quality without decreasing cotton fiber yield remains a major challenge in saline-alkaline cotton fields. A field experiment was conducted in 2020 and 2021 on saline-alkaline soil with cotton under drip irrigation to examine how amount and timing of leaching affected soils salinity, cotton fiber yield and quality. There were five leaching amounts(CK: 0 mm, W1: 75 mm, W2: 150 mm, W3: 225 mm and W4: 300 mm) and three leaching timings(T1: once at the seedling stage, T2: twice at the seedling and budding stages, and T3: thrice at the seedling, budding and pollen-setting stages). Soil salinity, soil nitrate nitrogen(NO_(3)-N), cotton nitrogen(N) uptake, irrigation water productivity(IWP), cotton fiber yield, fiber length, fiber uniformity, fiber strength, fiber elongation, micronaire and fiber quality index(FQI) were investigated. The results indicated that soil salinity and NO_(3)-N reduced with increasing leaching amount. The N uptake of cotton bolls was greater than in cotton leaves, stems and roots, and total N accumulation increased with increasing leaching amount. The optimal cotton fiber yield and IWP occurred in treatment W3T2, and were 3,199 and 2,771 kg ha^(-1), and 0.5482 and 0.4912 kg m-3in 2020 and 2021, respectively. Fiber length, strength, elongation, and uniformity increased with increasing leaching amount, while there was a negative relationship between fiber micronaire and leaching amount. Soil salinity, NO_(3)-N and fiber micronaire were negatively correlated with fiber quality(i.e., length, strength, elongation and uniformity) and yield, nitrogen uptake of various organs(i.e., root, stems and leaves) and whole plant nitrogen uptake. Pearson correlation analysis revealed that fiber elongation was most sensitive to soil salinity. The method of Entropy–Order Preference by Similarity to Ideal Solution(EM–TOPSIS) indicated that leaching of 300 mm of water applied equally at the seedling and budding periods was the optimal treatment to maintain soil salinity and nutrient levels and achieve high cotton fiber yield and quality. In conclusion, the optimal level of leaching treatment decreased soil salinity and improved nitrogen uptake and was beneficial to achieve high fiber yield and quality. Our results will be significant for guiding drip irrigation practice of leaching on saline-alkaline soils for sustainable cotton fiber production.
基金supported by the National Key Research and Development Program of China(2021YFD1900805,2022YFD1900401)the Science and Technology Project,Xinjiang Production and Construction Corps,China(2021AB009,2024AB030).
文摘Cotton,as one of important economic crops,is widely planted in the saline-alkaline soil of southern Xinjiang,China.Moreover,in order to control the saline-alkaline content for seed germination and seedlings survive of cotton,farmers always adopt salt leaching during winter and spring seasons.However,excessive amount of salt leaching might result in the waste of water resources and unsuitable irrigation seasons might further increase soil salinization.In this study,a field experiment was conducted in the saline-alkaline soil in 2020 and 2021 to determine the effects of leaching amount and period on water-salinity dynamics and cotton yield.Five leaching amounts(0.0(W0),75.0(W1),150.0(W2),225.0(W3),and 300.0(W4)mm)and three leaching periods(seedling stage(P1),seedling and squaring stages(P2),and seedling,squaring,flowering,and boll setting stages(P3))were used.In addition,a control treatment(CK)with a leaching amount of 300.0 mm in spring was performed.The soil water-salt dynamics,cotton growth,seed cotton yield,water productivity(WP),and irrigation water productivity(WPI)were analyzed.Results showed that leaching significantly decreased soil electrical conductivity(EC),and W3P2 treatment reduced EC by 11.79%in the 0-100 cm soil depth compared with CK.Plant height,stem diameter,leaf area index,and yield under W3 and W4 treatments were greater than those under W1 and W2 treatments.Compared with W3P1 and W3P3 treatments,seed cotton yield under W3P2 treatment significantly enhanced and reached 6621 kg/hm^(2)in 2020 and 5340 kg/hm^(2)in 2021.Meanwhile,WP and WPI under W3P2 treatment were significantly higher than those under other leaching treatments.In conclusion,the treatment of 225.0 mm leaching amount and seedling and squaring stages-based leaching period was beneficial for the salt control,efficient water utilization,and yield improvement of cotton in southern Xinjiang,China.
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.
文摘This study investigated the effect of C/N ratio,placement of plant residues,and leaching amounts on soil respiration,microbial biomass,and nutrient availability within four weeks after amendment.Young faba bean shoots(FB,C/N 7)and mature wheat straw(WH,C/N 80)were used as low and high C/N residue,respectively.Soil was unamended,mulched with FB or WH only,or mulched with one residue and mixed with the other residue.Leaching with 5 or 25 mL water was carried out on days 4,12,and 20.Cumulative respiration and microbial biomass N were higher with 25 than 5 mL only in treatments with two residues.WH under FB mulch reduced N availability compared to FB mulch alone,whereas FB under WH increased N availability compared toWHmulch alone.When soils were leached with 25 mL water,available N in FB mulch over WH was lower on day 12,but higher later,compared to WH mulch over FB.In contrast,in WH mulch over FB microbial biomass N increased over time whereas available N decreased.In conclusion,the effect of C/N ratio of the mulch on soil available and microbial biomass N was greater with the higher leaching amount.
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.
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.
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.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the Natural Science Foundation of Guangdong Province(No.2021B1515020041)the National Natural Science Foundation of China(No.42277403)+4 种基金the Projects of International Cooperation and Exchange of the National Natural Science Foundation of China(NSFC-UNEP)(No:32261143459)the Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control(No.2023B1212060002)the Guangdong Major Project of Basic and Applied Basic Research(No.2023B0303000024)the High-level University Special Fund(No.G03050K001)the Research Projects of the General Administration of Customs(No.2022HK060)for financial support.
文摘As the main component of electronic products,plastics contain complex and diverse metal additives.Recycling process is not conducive to stable existence of metal additives in electronic plastics.Once the e-waste plastics enter the environment,they will continue to release harmful metals into environment after aging,causing serious hazards.This study delved into the analysis and comparison of metal content of e-waste plastics,elucidating aging process and metal leaching behavior over a 112-day natural light exposure period.The findings underscored that metal content in recycled plastics surpassed that in their new counterparts.Specifically,Ti content in new plastics remained below 100 mg/kg,while recycled plastics exhibited Ti content surpassing 100 mg/kg threshold.Throughout prolonged natural light exposure,metals such as Zn,Ba and Sb demonstrated a heightened likelihood of release from electronic plastics in comparison to other metals.The aging process during light exposure led to fragmentation of electronic plastics,accompanied by a reduction in particle size.Notably,the particle size reduction was more pronounced in poly acrylonitrile butadiene styrene(ABS)and recycled ABS,experiencing reductions of 40µm and 85µm,respectively.This phenomenon was attributed to the presence of polybutadiene structural units,which proved more susceptible to aging.Along with the breaking of plastics,the ABS plastics released metal species such as Pb,Cd,Ni,Al that had not been detected in other plastics solutions.The collective evidence from this study suggested that ABS and recycled ABS electronic plastics might pose a heightened potential environmental risk compared to other electronic plastics.
基金supported by the National Natural Science Foundation of China(No.52074069)the Natural Science Foundation of Hebei Province,China(No.E2020501029)+1 种基金the Natural Science Foundation−Steel,the Iron Foundation of Hebei Province,China(No.E2022501030)Performance Subsidy Fund for Key Laboratory of Dielectric and Electrolyte Functional Material Hebei Province,China(No.22567627H).
文摘A clean and efficient process for the direct extraction of valuable metals from low-grade nickel sulfide ore through oxidative leaching with(NH_(4))_(2)S_(2)O_(8)under atmosphere pressure was proposed to address the growing demand for nickel and cobalt in the new energy industry.The effects of four key parameters on the metal leaching rates were systematically investigated.Characterization techniques,including XRD,SEM and EDS,were employed to analyze phase transformations during the leaching process.Under optimized conditions,approximately 96.5%of nickel,95.5%of cobalt and 65.2%of copper were successfully extracted.The kinetics of the leaching process was explored to identify the controlling mechanisms of nickel,cobalt and copper dissolution,establishing activation energies and kinetic equations for each metal.The cleanliness and efficiency of this method were confirmed through comparisons with other extraction processes for nickel sulfide ore.
