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The advantages of the ion exchange treatment system are: the <br /> water savings are significant; the feedstream 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 /> ' I <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 reduction <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 /> • <br /> A-4 <br />