Research On Technology Of Comprehensive Recovery Of Arsenic In Black Copper Sludges

As the accompanying element of copper concentrate, arsenic always isharmful, and a large number of in-process materials containing arsenic willbe produced in each process of smelting. The existence of arsenic onlyadversely affect the smelting process, but also leads to environmentalpollution problems and is harm to humans healthy. In this paper, as rawmaterials, copper sludges which is produced in copper electrolytepurification process are used to prepare sodium arsenate、 copper arsenateand arsenic trioxide. they can be widely used in wood preservation、 glasscleaner and agricultural resource etc. In this subject, the various conditionsof preparation of sodium arsenate、copper arsenate and arsenic trioxide werestudied, and the basis of mechanism is analyzed. The following researcheshave been carried out:（1） The optimum process conditions of alkaline leaching of coppersludges are certain. The optimal process conditions of alkaline leaching areas follow： the reaction temperature is85℃, the ratio of liquid to solid is10:1, the NaOH concentration is1mol/L， the reaction time is6hours， theflowing rate of air is0.8m³/h， the stirring speed is400r/min. The resultshows that under the optimal conditions， the leaching rate of arsenic incopper sludges is about92%, while copper and antimony are less than3%.The alkaline residue is leaching for As by using sodium sulfide, theoptimum process conditions of sodium sulfide leaching of the residue aredrawn by single factor experiment. Under the conditions: the NaOHconcentration is40g/L, the Na₂S concentration is160g/L, the ratio ofliquid to solid is8:1, the stirring speed is400r/min, the reaction time is2.5hours, he reaction temperature is85℃. The result shows that under theoptimal conditions， the leaching rate of As and Sb in the alkaline residueare88%and90%, respectively. In order to separate As from Sb, the sodiumsulfide leaching liquid is oxidized by oxidizer. copper arsenate is preparedby evaporating, after mixing oxidation solution with alkaline leachingsolution. After testing, the content of sodium arsenate is38.8%in theproduct.（2） The optimum process conditions of acid leaching of copper sludges are certain by experimental research and mass of data. The optimal processconditions of acid leaching are as follow： the H₂SO₄concentration is1mol/L, the ratio of liquid to solid is10:1, the reaction temperature is80℃,the reaction time is4hours， the flowing rate of air is0.8m³/h， the stirringspeed is400r/min. The result shows that under the optimal conditions， theleaching rate of copper in copper sludges is about90%, he leaching rate ofarsenic in copper sludges is about89%. CuSO₄·5H₂O is obtained from acidleaching solution after evaporating and crystallizing, the product quality ofCuSO₄·5H₂O is up to the first grade standard of china（GB4371993）.Technological conditions of preparation of copper arsenate was drawn asfollow：the reaction temperature is60℃，the reaction time is1hour, the pHvalue is3.5, the Cu/As is1.0to1.3. Results of the analysis by XRD showthat the main structure of copper arsenate is Cu₅As₄O₁₅·9H₂O, Theproduction could basic met demands of enterprise standard. Sodiumarsenate is obtained through arsenic in acid leaching residue is leaching bysodium sulfide. After testing, the content of sodium arsenate is35.7%in theproduct.（3） The optimum process conditions of sulfur dioxide reduction arecertain. Under the conditions： the reaction time is1hours, the reactiontemperature is30℃, the pH value is from0to1. The purity of As₂O₃ismore than95%, the product quality of arsenic trioxide is up to the thirdgrade standard of nonferrous metal industry of china（YS-T99-1997）.