Recovery of valuable metals from zinc leaching residue by sulfate roasting and water leaching

Zinc leaching residue(ZLR),produced from traditional zinc hydrometallurgy process,is not only a hazardous waste but also a potential valuable solid.The combination of sulfate roasting and water leaching was employed to recover the valuable metals from ZLR.The ZLR was initially roasted with ferric sulfate at640°C for1h with ferric sulfate/zinc ferrite mole ratio of1.2.In this process,the valuable metals were efficiently transformed into water soluble sulfate,while iron remains as ferric oxide.Thereafter,water leaching was conducted to extract the valuable metals sulfate for recovery.The recovery rates of zinc,manganese,copper,cadmium and iron were92.4%,93.3%,99.3%,91.4%and1.1%,respectively.A leaching toxicity test for ZLR was performed after water leaching.The results indicated that the final residue was effectively detoxified and all of the heavy metal leaching concentrations were under the allowable limit.

Physicochemical and environmental characteristics of alkali leaching residue of wolframite and process for valuable metals recovery

Physicochemical and mineralogical characteristics of an alkali leaching residue of wolframite were studied by XRD,SEM−EDS,chemical phase analysis,mineral liberation analyzer(MLA),and TG−DSC methods.Batch leaching tests,toxicity characteristic leaching procedure(TCLP)tests and Chinese standard leaching tests(CSLT)were conducted to determine the environmental mobility of toxic elements.The results show that,due to the high contents of W,Fe,Mn,Sn,and Nb,the residue is with high resource value,but the content of a toxic element,As,is also high.The existing minerals of the investigated elements mainly occur as monomer particles,but it is difficult to extract these valuable metals by conventional acid leaching due to their mineral properties.The release of As increases over time in acidic environment.The leaching concentration of all investigated harmful elements through TCLP is within the limiting value,while the leaching concentration of As through CSLT exceeds the limiting value by more than 4 times,so the residue is classified as hazardous solid waste based on the Chinese standard.A process for valuable metals recovery from this residue was proposed.Preliminary experimental results indicated that the main valuable metals could be extracted effectively.

Comprehensive recovery of lead, zinc, and iron from hazardous jarosite residues using direct reduction followed by magnetic separation

Lead, zinc, and iron were recovered from jarosite residues using direct reduction followed by magnetic separation. The influence of the coal dosage, reduction temperature, and reduction time on the volatilization rates of lead and zinc and the metallization rate of iron were investigated. The results show that the volatilization rates of lead and zinc were 96.97% and 99.89%, respectively, and the iron metallization rate was 91.97% under the optimal reduction roasting conditions of a coal dosage of 25.0 wt% and reduction roasting at 1250°C for 60 min. The magnetic concentrate with an iron content of 90.59 wt% and an iron recovery rate of 50.87% was obtained under the optimum conditions in which 96.56% of the reduction product particles were smaller than 37 μm and the magnetic field strength was 24 k A/m. Therefore, the results of this study demonstrate that recovering valuable metals such as lead, zinc, and iron from jarosite residues is feasible using the developed approach.

Coextraction of vanadium and manganese from highmanganese containing vanadium wastewater by a solvent extraction-precipitation process

High-manganese containing vanadium waste-water(HMVW)is commonly produced during the vanadium extraction process from vanadium titano-magnetite.HMVW cannot be reused and discharged directly,and is harmful to the environment and affect product quality due to heavy metals in the wastewater.The wastewater is usually treated by lime neutralization,but valuable metals(especially V and Mn)cannot be recovered.In this study,an efficient and environmentally friendly method was developed to recover valuable metals by using a solvent extraction-precipitation process.In the solvent extraction process,98.15%of vanadium was recovered,and the V2Os product,with a purity of 98.60%,was obtained under optimal conditions.For the precipitation process,91.05%of manganese was recovered as MnCO3 which meets the III grade standard of HG/T 2836-2011.Thermodynamic simulation analysis indicated that MnCO3 was selectively precipitated at pH 6.5 while Mg and Ca could hardly be precipitated.The results of X-ray diffraction and scanning electron microscopy demonstrated that the obtained V2Os and MnCO3 displayed a good degree of crystallinity.The treated wastewater can be returned for leaching,and resources(V and Mn)in the wastewater were utilized efficiently in an environmentally friendly way.Therefore,this study provides a novel method for the coextraction of V and Mn from HMVW.

Rotating hydrothermal route to red mud derived uniform hierarchical porous flowerlike boehmite(γ-AlOOH)microspheres:Force analysis on formation mechanism and superior adsorption performances for anionic dyes removal

Towards increasingly severe worldwide pollution of industrial solid waste red mud(RM)released from aluminum industry,constitutional valuable element Al has been successfully separated for a novel mild rotating hydrothermal synthesis(150℃,12 h,5 Hz)of the uniform hierarchical porous flowerlike boehmite(γ-AlOOH)microspheres in the presence of appropriate urea,which exhibit distinctly small average diameter(1.52μm)and narrow particle size distribution(PSD:1.12–1.97μm),as well as high specific surface area(129.37 m2 g^(−1)).On the one hand,the rotating hydrothermal synthesis promotes the mass and heat transfer,enablingγ-AlOOH microspheres at a lower temperature within a shorter time.On the other hand,moderate rotation provides predominant shear force,rendering the uniformγ-AlOOH microspheres with small average diameter and narrow PSD.The optimal AlOOH–U2M-R5Hz microspheres demonstrate satisfactory adsorption performance for Congo Red(CR)and Methyl Blue(MB),with the maximum adsorption capacities of 602.4 and 1208.7 mg g^(−1),respectively.Various isotherm models of Langmuir,Freundlich,Temkin and Dubinin-Radushkevich are utilized,adsorption kinetics are analyzed,adsorption mechanism is uncovered based on hydrogen bonding and electrostatic attraction.The increase in the temperature or the presence of coexisting cations facilitates the adsorption of CR,whereas coexisting anions weaken the adsorption of CR on the AlOOH–U2M-R5Hz microspheres.Furthermore,the excellent recycling performances and especially dynamic adsorption(retainment of removal efficiency of approx.99.0%within 1000 min)as well as authentic water bodies(e.g.tap water and river water)simulated wastewater treatment undoubtedly indicate great practical applications of the AlOOH–U2M-R5Hz microspheres,towards cleaner aluminum production and cost-effective sustainable solution to anionic dye-bearing wastewater.