Study On Technology Of The Comprehensive Recycling Of Copper Sludges

As the accompanying element of copper concentrate, arsenic is harmful, and a large number of in-process materials containing arsenic will be produced in each process of smelting. The existence of arsenic ont only adversely affect the smelting process, but also leads to environmental pollution problems. In this paper, as raw materials, copper sludges which is produced in copper electrolyte purification process were used to prepare copper arsenic. Copper arsenate can be widely used in wood preservation. In this subject, the process conditions of alkaline leaching and acid leaching of copper sludges were studied, and the kinetics mechanism of alkaline leaching was analyzed. The following researches have been carried out:The optimum process conditions of alkaline leaching of coper sludges were drawn by single factor experiment. The optimal process conditions of alkaline leaching are as follow:the reaction temperature is 85℃,the ratio of liquid to solid is 10:1,the NaOH concentration is 1mol/L,the reaction time is 6 hours,the flowing rate of air is 0.8 Nm³/h,the stirring speed is 400r/min. The result shows that under the optimal conditions,the leaching rate of arsenic in copper sludges is more than 92% ,while copper and bismuth are less than 2%,antimony is around 3%. After the copper sludges were alkaline leached, the content of copper,arsenic and antimony respectively are 68%～73%,4%～9% and 3%～5%. The experimental results show that: copper and arsenic achieve the separation, copper is beneficated in the leaching residue, antimony and bismuth also have different degrees of enrichment.The alkaline leaching process of copper sludges are heterogeneous reaction with gas,liquid and solid. The alkaline leaching process can be described by the shrinking core model which is controlled by the diffusion in the boundary layer,product layer diffusion and chemical reaction.The optimum process conditions of acid leaching of coper sludges were drawn by single factor experiment. The optimal process conditions of acid leaching are as follow:the reaction temperature is 80℃,the ratio of liquid to solid is 10:1,the H₂SO₄ concentration is 1mol/L,the reaction time is 6 hours,the flowing rate of air is 0.8 Nm³/h,the stirring speed is 400r/min. The result shows that under the optimal conditions,the leaching rates of copper and arsenic in copper sludges are more than 88%, the slag rate is around 20%. In the leaching solution, the concentration of copper is about 45 g/L, while arsenic is approximately 16 g/L.Reference to previous experimental results, technological conditions of preparation of copper arsenate was drawn as follow: the Cu/As is equal to 1.1 after mixing acid leaching solution with alkaline leaching solution, the pH value is 3.5, the reaction temperature is 60℃, the reaction time is 1 hour. Copper arsenate which is obtained by precipitating should be mixing washed at least 3 times. Results of the analysis by XRD show that the main structure of copper arsenate is Cu₅As₄O₁₅·9H₂O. Contents of copper,total arsenic,trivalentarsenic,Ferrum,sodium,moisture and acid-insoluble matter respectively are 31.22%,29.86%,0.14%,0.0073%,2.91%,0.32% and 3.26%. The production could basicly met demands of New Zealand copper srsenate quality standard, only the content of sodium is exceeds the standard. It should be caused by that the washing times of copper arsenate are not enough. The content of sodium can be reduced by increasing the number of washing.