| As the development of non-ferrous metallurgical industry, the amount of arsenic wastewater increased rapidly. Its permissible discharge has become the major environmental problem to be solved in Chinese non-ferrous metallurgical processes, and it is of great social, economic and environmental significance to research and develop efficient and economical wastewater treatment technology. In this research, the treatment of arsenic wastewater from the copper smeltery of Daya non-ferrous metal company has been investigated. The new technology includes steps of neutralization by CaO and NaOH, precipitation by CUSO4, Reduction by SO2 and further removal of arsenic by flocculant. As2O3 was produced and is up to the industrial standard. The metals are reclaimed such as Cu, Pb and Zn. The whole process from the treatment of arsenic wastewater to the reclaiming and recycling of intermediates was studied, and successfully applied to industry.The arsenic wastewater was neutralized by CaO and NaOH. The removal rates of Pb2+, Cu2+, Bi3+, Fe2+, Mg2+ are all 90% above when pH value of the wastewater is adjusted to 2.0 by CaO, then pH value to 6.0 by NaOH. The lost of arsenic is 7.1%. The neutralized sediment by CaO contains CaSO4·1/2H2O and CaSO4·H2O. The neutralized sediment by NaOH contains nonferrous metals which can be reclaimed. The suitable factors of copper arsenite preparation are that the reaction time is 1h, the pH value is 8, the molar ratio of CUSO4 to As is 2:1, the reaction temperature is about 20℃. The yield rate of copper arsenite is up to87.77%.SO2 reduces copper arsenite to produce arsenious acid and red sediment. X-rays diffraction tests tesitify that thered sediment is Cu3(SO3)2·2H2O called the red salt. The suitable reduction factors are that the ratio of liquid volume to solid mass of copper arsenite is 4:1, the reactin time is 1h and the reaction temperature is 60℃. White As2O3 powder was obtained from arsenious acid solution after evaporating and crystallizing. The conditions of evaporation and crystallization are that pH value of the solution is 0, crystallized temperature is 20-30℃and As concentratin is 90g·L-1.The product quality of arsenic trioxide is up to the third grade standard of nonferrous metal industry of China(YS-T 99-1997).Sulphuric acid leached red salt under the action of air to recover copper sulfhate. The leaching rate of Copper is up to 99% when the reaction time is 1.5h, the molar ratio of H2SO4 to Cu is 1.70, the mass concentration of sulphuric acid is 24%, the reaction temperature is about 80℃. CuSO4·5H2O of the pruduct is 94.29% after evaporating the leached solution,then cooling and crystallizing.The direct yield of copper sulphate is 76.20%. The arsenious acid and the mother liquor could be used for circulatory leaching of dregs, and the leaching efficiences of As and Cu are almost invariant.The research on further removal of asenic by flocculant PFFS has been employed. As decreases from 89mg·L-1 to 0.29mg·L-1 after treating by polyphosphoric ferric sulfate when pH value is 7.2, nFe:nAS is 3.5 and the wastewater is aerated. Compared to copperas and polyferric sulphate, Polyphosphoric ferric sulfate has better effect, lower dose and less dreg than copperas and polyferric sulphate.Copper arsenite prepared from the arsenic wastewater was applied to purify copper electrolyte. Sb decreased from 0.95g·L-1 to 0.31g·L-1, Bi from 0.25g·L-1 to 0.07g·L-1 and the removal rates of Sb and Bi were 64.42% and 68.57% respectively when As increased from 4.10g·L-1 to 12 g·L-1 after adding copper arsenite in the electrolyte. The removal rates of Sb and Bi were 71.93% and 61.03%% respectively in the industry experiment. The results of cyclic voltammetry curve tests show that As(Ⅲ) in a electrolyte decreases the polarization of the cathode and As(Ⅴ) increases the polarization of the cathode.In the industry test the precipitation rates of Cu, Zn, Ni, As in the wastewater are 90.87%,30.41%,64.28%,7.92% and the Cu, Zn, Ni components of NaOH neutralization dreg are respectively 7.92%,1.10% and 1.03%. The direct recovery rates of As and Cu are respectively 75.67% and 94.26% after pH value of the wastewater is adjusted to 2 by CaO, then pH value to 6 by NaOH. As content of the treated wastewater is 0.09mg·L-3 which is less the standard of of China (GB8978-1996) after polyphosphoric ferric sulfate treats the watsewater precipitated by copper sulphate.The project fesibility of arsenic trioxide preparation was estimated.The outputs of As2O3, Cu, Ni and Zn are respectively 2047t, 197t,32.85t,68.43t when the treatment capability is 750t/d and As is 6.6g·L-1 in the wastewater. This process shows a comprehensive recovery effect and economic, environmental and social benefits significantly.
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