| The work has high economic benefit extracting tellurium from CdZnTe which is a comprehensive utilization project of recycling waste materials. According to the composition of the raw material and existence form of tellurium, the tellurium of CdZnTe is recycled by the method of hydrothermal oxidation, acid leaching and reduction.The preliminary indicated that the experiment process produce harmful gas when NaClO3 and HNO3 are used as oxidizer. During hydrogen peroxide oxidation and heat-treatment oxidation, the recovery rate of tellurium is not high. Meanwhile, the purity of tellurium is not very high when oxidizer is KMnO4. On the other hand, a total tellurium extraction rate of 58.80%, tellurium powder with purity 99.21% is obtained from hydrothermal oxidation. And the experiment process does not produce harmful gas. Therefore, CdZnTe is oxidized by hydrothermal oxidation method.In this paper, the hydrothermal oxidation of CdZnTe is first studied. The effects of the amount of H2O2, hydrothermal temperature, hydrothermal time, solvent concentration on recovery of tellurium have been investigated. The results show that the optimum experimental conditions include H2O2 amount 10.0 mL, hydrothermal temperature 180 ?, hydrothermal time 6 h, H2SO4 concentration 2 mol/L.The acid leaching and sodium sulfite reduction is studied after hydrothermal oxidation of CdZnTe. The first plan is consist of sulfuric acid leaching and reduction of Te by sodium sulfite. The effects of concentration of H2SO4, liquid to solid ration, leaching temperature, leaching time, particle size of CdZnTe, mass ratio Na2SO3/Te and NaCl/Te, reduction temperature, reduction time on extraction rate of tellurium have been investigated. The optimum process parameters of sulfuric acid leaching and sodium sulfite reduction are as follows:H2SO4 concentration 8 mol/L, liquid to solid ration 12:1, leaching temperature 85 ?, leaching time 4 h, particle size of CdZnTe 120-300 mesh, mass ratio Na2SO3/Te= 10 and NaCl/Te= 6, reduction temperature 80 ?, reduction time 80 min. Under this condition, the extraction rate of tellurium is 81.27%.The second plan is studied on the basis of the first plan. The second plan is consist of sulfuric acid and sodium chloride leaching and reduction of Te by sodium sulfite. The factors of the amount of NaCl in leaching, leaching time, concentration of H2SO4, liquid to solid ration, mass ratio NaCl/Te and Na2SO3/Te on extraction rate of tellurium have been investigated. The results show that the optimum condition is NaCl amount 8.00 g, leaching time 15 min, H2SO4 concentration 4 mol/L, liquid to solid ration 10:1, mass ratio NaCl/Te= 6 and Na2SO3/Te= 10 when the others conditions is identical with the first plan. Under this condition, the extraction rate of tellurium is 91.39%. The second plan reduces leaching time, the concentration of sulfuric acid and raises the extraction rate of tellurium than the first plan.To sum up, the tellurium of CdZnTe is extracted by using this method of hydrothermal oxidation, sulfuric acid and sodium chloride acid leaching, reduction of Te by sodium sulfite. |
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