Preparation Of Zinc Sulfate From Copper Smelting Dust

Since the metallurgical activity was developed by human,not only the main metal but also by-products could be produced.Effective and reasonable route for the utilization these by-products is particularly important with more and more prominent environmental problems.As a common by-product in the smelting process,smelting flue ash contains a variety of valuable elements,and the comprehensive utilization will bring benefits both the environment and economy.In this paper a copper smelting dust has been researched.Firstly,the thermodynamics of ash leaching and solution purifying were studied,and the feasibility of experiment on thermodynamic was investigated in detail.The selective leaching of the zinc contained ash under acid condition was studied,The results showed that the optimal leaching technique of zinc from the flue dust was determined as follows: the liquid to solid ratio at 2 mL/g,pH=4,leaching for 90 min under 25℃.Under these conditions,zinc was selectively extracted at a leaching rates of 93.92% with only 4.12% arsenic leached.The arsenic and iron contained in the leaching solution was processed by arsenic removal with ferric method.The results showed that the removal efficiency of arsenic and iron can reach 99.5% and 97.4% after oxidation by hydrogen peroxide and further reacting for 90 min under 70℃ with the iron to arsenic ratio at 1.2,pH=5.0.But the residual arsenic and iron containing in the solution still reached 7.9 mg/L 42 mg/L.In order to further remove the arsenic and iron from the solution,a secondary impurity removal was conducted under the same condition.Only 0.5 mg/L iron and 1.5 mg/L arsenic were contained in solution after the secondary impurity removal.After the removal of iron and arsenic from the solution,a replacement of copper and cadmium by zinc was conducted.The results showed that under the actual molar ration of zinc to copper and cadmium at 1.4 and reacting for 30 min for 30℃,more than 99% of copper and cadmium in the solution were replaced to the leaching slag with only 0.8 mg/L copper and 1.2 mg/L cadmium residue.After the purification,zinc sulfate was obtained by further evaporation,recrystallization.Test results indicated that the final sample is accord with the top-grade product standard of industrial zinc sulfate.