HODJAOGLU Gyunver Institute of Physical Chemistry

The copper cake under investigation is a dense red-brown color filtrate from zinc plant of KCM-Plovdiv, Bulgaria. Through its morphology and content properties, the copper cake is an interesting physicochemical system. As a product of cementation process, the waste cake consists of very small submicron particle aggregates. In this study the copper cake was regarded as a new starting material for pure copper metal recovery. The waste copper cake has a very complex chemical composition including mainly different copper, zinc and lead compounds, as well as a large variety of metal impurities. The results show that the usual leaching with mineral acid is an unsatisfactory process because of a large solid residium and low concentration of copper ions in final electrolytes. In this order more perspective is combined treatment of the copper cake with application of low current in acid medium. All experiments and results have contributed to formulation of a simple laboratory scheme for fast conversion of copper cake in form of fine suspension or dense material for anodic treatment and finally in pure cathodic copper metal. The obtained electrolytes were used as a suitable model for selective electrodeposition of copper in the presence of large amounts of zinc ions. The electroextraction experiments were carried out in galvanostatic regime at current density 1,0 A/dm2 for 1 hour in the presence of 130 g/L sulfuric acid. At this conditions the applied overpotencial is not sufficient for the reduction of more negatively charged zinc ions and only copper ions take place in the cathodic process. The copper electrodeposits from industrial waste copper cake were compared with former results on copper deposition from model electrolytes, containing copper and zinc ions. The morphology and grain size of obtained copper coatings from model and real electrodeposition experiments were comparable to a great extend only in cases of unique experimental conditions, such as similar copper and zinc ion concentrations and amount of sulfuric acid. In all other cases copper coatings from industrial waste were rough, non regular, non adherent, as a consequence of the presence impurity ions in the initial copper cake

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