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Thermodynamic Study Of System ZnO-ZnSO4-H2O

Posted on:2012-08-19Degree:MasterType:Thesis
Country:ChinaCandidate:Y S WuFull Text:PDF
GTID:2231330374996373Subject:Inorganic Chemistry
Abstract/Summary:PDF Full Text Request
The technology of zinc hydrometallurgy play an important role in the zinc smelt industry,whose yield account for about80%of zinc production. The hydrometallurgical process ofzinc can be divided into four stages, including: roasting, leaching, purification and electrowinning process. But the crystallization of basic zinc sulfate in the purification stage blockedthe pipes and filter cloth, impeded the smooth progress of production. The zinc smeltingenterprises have taken appropriate measures, but with little success. However, there is lessresearch about basic zinc sulfate, current data does not meet the requirements of solving thisproblem. So, it is of great significance to carry on systematic researches on the solubility ofbasic zinc sulfate, and find out the influence of temperature, concentration and pH value onthe generation of basic zinc sulfate. In this paper, the solubility and the pH value of basic zincsulfate system were determined at the different temperature, and the proper thermodynamicmodel was combined with experimental data in order to obtain the pH value range of basiczinc sulfate exists when zinc ion concentration or temperature changed, which can be thetheoretical direction for eliminating the generation of basic zinc sulfate in the process of zinchydrometallurgy. To this end, we carried out a series of experimental and theoretical researchas follows:(1) Five widely used typical thermodynamic models were selected to describe andpredict the thermodynamic properties of a variety of binary salt-water systems, and theoriginal Pitzer model was investigated systematically about its predictive ability used for lowconcentration electrolyte solution. The results show that the original Pitzer model can beapplied to calculate the phase diagram of ZnO-ZnSO4-H2O ternary system.(2) The solubility of the ZnSO4-H2O binary system at T=(298.15,309.15) K and thesolubility and pH value of the ZnO-ZnSO4-H2O ternary system at T=(291.15,298.15,308.15,323.15) K were elaborately determined by the isothermal method. The measured solubilityof the ZnSO4-H2O binary system was in good agreement with literature data.(3) Based on the reasonable assumption about ionization equilibrium of theZnO-ZnSO4-H2O ternary system, we calculated the solubility phase diagram of the ternarysystem by using the original Pitzer model combined with limited experimental data.
Keywords/Search Tags:zinc hydrometallurgy, basic zinc sulfate, thermodynamic model, solubility, pH value
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