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The advantages of the ion exchange treatment system are: the <br />water savings are significant; the £eedstream can be dilute as <br />is the case in rinse waters; and the energy consumption is low. <br />The disadvantages are: capital costs are high; chemical, labor <br />and maintenance costs are high; the equipment is complex; and <br />the performance of the system depends on the operator. <br />Electrolytic Recovery <br />This is a process in which there is an electrochemical <br />reduction of metal ions to elemental metal. In the <br />electrochemical cell a sufficient level of direct current <br />voltage is applied across two electrodes, overcoming the <br />reversible electromotive force of the cell, causing the metal <br />ions to plate out at the cathode. The cathode is the electrode <br />at which electrons are taken up by the metal and reduct' n <br />occurs. The other electrode is the anode. Oxidation occurs <br />here and electrons are given up to the electrode. <br />The electrolytic recovery of metals has been proven technically <br />feasible by the primary and secondary copper industry. Copper <br />is purified using these electrochemical techniques. <br />Electrolytic recovery is also used to recover tin, silver, <br />copper and other metals from plating and etching drag out <br />wastes in some electroplating plants. <br />Electrolytic recovery was chosen as the metal recovery process <br />for the copper and cadmium wastes entering the Facility. <br />Copper will be recovered using a large electrowinning tank <br />while cadmium recovery will require a smaller plating cell. <br />Zinc and nickel waste streams are believed to be contaminated <br />with copper and other metals along with other impurities. The <br />electromotive series position of nickel and zinc are higher <br />than the contaminating metals so their recovery by this <br />electrolytic process is uneconomical. <br />The important factors which determine the efficiency of <br />electrolytic recovery of metals are, water temperature, water <br />flow rate, the current density and electrode area of the cell <br />(for plating), the type of metal and metal concentration in the <br />water, and the types of contaminants and their concentration in <br />the water. <br />There is also a possibility of reusing the spent electrolytic <br />solutions as a regenerant solution for the ion exchange resins. <br />A-4 <br />