Study On Zinc Leaching Technology In Mechanically Activated Zinc Calcine

Zinc ferrite（ZnFe₂O₄）contained in zinc calcine is a kind of compound oxide with a spinel structure,which is stable and insoluble in dilute acid and alkali,and difficult to leach under conventional leaching conditions.The industry generally adopts hot and high acid to decompose zinc ferrite to improve the zinc leaching rate,but iron will be transferred to the leachate,the subsequent removal of iron will produce hazardous waste jarosite.Mechanical activation is an effective method for mineral-enhanced leaching,and in combination with a reducing agent,it can control the reduction of Zn Fe₂O₄ in zinc calcine sand to acid-soluble Zn O and acid-insoluble Fe₃O₄,which also has a spinel structure,thus realizing zinc extraction and iron separation,and solving the problem of jarosite while increasing the zinc leaching efficiency.Therefore,the thesis investigated the effect of mechanical activation time,ball-to-material ratio,sulfuric acid concentration,liquid-to-solid ratio and temperature on the zinc leaching rate and the concentration of other impurity ions by using both reduced dry grinding and reduced wet grinding with sulfuric acid as leaching agent,in order to provide theoretical and data support for the source management of jarosite.The main conclusions are as follows.1.A study on the effect of reduced dry grinding of zinc calcine is carried out and the results are as follows:Mechanical activation significantly reduces particle size and increases the specific surface area of zinc calcine.However,the crushing effect of mechanical activation has certain stages.With the enhancement of mechanical activation intensity,all phases are first released and then wrapped up.By the mechanical force,the chemical bond symmetry of Zn₂Si O₄ and Zn Fe₂O₄ crystal lattice is destroyed,and the crystal lattice of spinel Zn Fe₂O₄ is distorted and disordered,which reduces its crystallinity and amorphous degree.After mechanical activation for 10 min,the crystallinity of Zn Fe₂O₄ decreases from 47.90%to34.50%,and the disorder degree increases from 52.10%to 65.50%.2.A study on reduced wet grinding leaching process of zinc calcine is carried out and the results of single factor experiment are as follows:Reduced dry grinding is composed of mechanical activation and leaching.When the mass percentage of H₂C₂O₄·2H₂O and zinc calcine is 3.60wt%,ball-material ratio is 2:1,mechanical activation time is 10 min,H₂SO₄concentration is 70 g/L,and liquid-to-solid ratio is 10:1 m L/g,zinc leaching rate is 87.61%,5percentage points higher than that without mechanical activation（82.59%）.This is mainly caused by the reduced dry grinding reduced the particle size of zinc calcine,resulting in lattice distortion and local destruction,and enhanced reactivity.3.A study on reduced wet grinding leaching process of zinc calcine was carried out and the results of single factor experiment are as follows:When the mass ratio of H₂C₂O₄·2H₂O to zinc calcine is 3.60 wt%,ball-to-material ratio is 2:1,sulfuric acid concentration is 70 g/L,liquid-to-solid ratio is 10:1 m L/g,reduced wet grinding time is 60 min and frequency is40 Hz,zinc leaching rate could reach 90.78%.This is 3,8,and 10 percentage points higher than that of reduced dry grinding,H2C2O4·2H2O reduction leaching and leaching（without H2C2O4·2H2O and mechanical activation）.Reduced wet grinding facilitates the conversion of Zn Fe₂O₄ to Zn O and Fe₃O₄,leaching Zn from zinc calcine while leaving Fe in the leaching residue,with a conversion rate of about 42%.Wet grinding reduction can also significantly improve the leaching rate of Zn₂SiO₄,which is usually difficult to leach,at 92.53%.