Research On The Technology And Mechanism Of Comprehensive Recovery And Harmless Disposal Of Typical High-acid Zinc Leaching Residu

Zinc leaching residue contains a large number of heavy metal ions,which is easy to cause serious environmental pollution to the surrounding soil,surface water,groundwater,etc.,has been included in the National Hazardous waste list in China.A zinc smelter in Wenshan,Yunnan province uses indium-bearing marmatite as raw material for hydrometallurgical leaching,and annually produces a large amount of high-acid leaching slag containing lead,zinc,high silver,high cadmium and very fine particle size.It was found that the leaching concentrations of copper,zinc,cadmium and beryllium in the leached residue were 127 mg/L,1305 mg/L,60.5 mg/L and0.039 mg/L,respectively,far exceeding the limit of the Hazardous Waste Identification Standard for Leaching Toxicity Identification.It is difficult to dispose the leach residue by conventional methods,which can easily cause resource loss and environmental hidden danger.Therefore,it is urgent to develop new technology to realize the resource recovery and harmless utilization of the high acid leaching residue.In this paper,the physical and chemical properties and leaching toxicity of the leached residue were studied in detail.Based on this,the comprehensive recovery effect of valuable metals from leached residue by water leaching-flotation at room temperature and pressure was systematically studied,and the effect mechanism of Zn²⁺dissolved from pulp on the flotation of the main valuable mineral argentite was also studied.The ternary system geopolymer with high compressive strength and non-toxic was made from flotation final tailings for the first time.The reaction mechanism and curing mechanism of geopolymer were constructed,which laid a theoretical foundation and provided technical support for the harmless disposal of such hazardous wastes.The useful minerals mainly include argentite,elemental silver,sphalerite,chalcopyrite,cassiterite and lead vanadium,as well as the embedded sulfates such as zinc sulfate and copper sulfate,and the content of useful minerals in the-19μm fraction is more than 50%.In particular,the residual soluble salts such as zinc sulfate in the leaching slag have a great influence on the flotation of the main useful mineral argentite,resulting in a single flotation is difficult to effectively recover;Therefore,the paper carried out a systematic study on the smelting-beneficiation and separation process.New water leaching technology was developed at room temperature and pressure.The leaching rates of zinc,copper and indium reached 63.11%,38.26%and29.27%respectively.The annual recovery of zinc,copper and indium is 708.85 t,39.94 t and 0.87 t,respectively,and the adverse effect of soluble salt on the flotation of argentite is significantly reduced.In order to study the effect of residual soluble salts such as zinc sulfate in leached slag on flotation,the mechanism of Zn²⁺on argentite flotation was systematically studied by means of single mineral flotation,adsorption capacity test,Zeta potential measurement,solution chemical calculation and XPS test.The single mineral flotation test shows that the recovery effect of argentite is best when pH value is 3-5 acid.When the concentration of Zn²⁺increased from 0 g/L to 50 g/L,the recovery rate of pyroxene decreased from 79.97%to 47.32%.The solution chemical calculation results show that Zn²⁺mainly exists in the form of Zn²⁺,Zn（OH）⁺and Zn₂（OH）³⁺at pH=3～5.Zeta potential test results show that Zn²⁺is adsorbed on the surface of argentite,and the zero-electric point on the surface of argentite moves from2.2 to 2.5.The results of adsorption capacity measurement and XPS analysis confirm that Zn2+is adsorbed on the surface of pyroxene in the form of zinc oxide,which reduces the adsorption site of the collector ammonium butanate black drug.Based on the results of single mineral test,the flotation tests of pulp concentration,pH value,regulator sodium hexametaphosphate and sodium silicate,and collector amount of ammonium butaneum black were carried out.A silver concentrate with grade of 8558.20 g/t and recovery of 82.05%was obtained by closed-circuit test.After desliming,middling tin ore with grade of 1.51%and recovery of 32.05%was obtained by flotation method.The final toxic leaching results showed that the leaching concentration of cadmium in tailings was 6.2mg/L,5.2 times higher than the limit value,and it was still a hazardous waste with obvious leaching toxicity characteristics.Based on the green concept of"treating waste with waste",a new method of preparing geopolymer from final tailings was developed.It was found that the final tailings after dehydration treatment had a gelation effect and the compressive strength of the geopolymer was improved obviously.The effects of mono-binary and ternary systems on the compressive strength of geopolymer were investigated,and a high strength and low cost preparation scheme of geopolymer based on fly ash,tailing and tailings was constructed.The effect of preparation parameters on the compressive strength of ternary geopolymer system was studied.Under the optimal curing conditions for 28 d,the compressive strength of ternary geopolympic system can reach 35.6 MPa,and the toxic leaching concentration of harmful elements is lower than the limit value,which meets the strength requirements of safe landfill or building materials.Through the characterization of geopolymers of different systems,it is found that the total pore volume and maximum pore size of fly ash-tailing-tailings base polymer are the smallest,and the microstructure is more compact.XRD,SEM-EDS,FTIR and TGA studies showed that there was A synergistic effect among the three solid waste substrates,and A large number of C-A-S-H gel and N-A-S-H gel were generated.Finally,the crystals of faujasite(Na[Al Si₅O₁₂]·4H₂O),chabasite(Ca[Al₂Si₄O₁₂]·6H₂O)and ettringite（3Ca O·Al₂O₃·3Ca SO₄·32H₂O）are generated,which can package and adsorb heavy metals,forming geological polymers with high compressive strength and environmental friendliness.It provides a new technology and new idea for green disposal of zinc leaching residue.