Applications of Ion Exchange in Hydrometallurgy

Abstract

A list of metals that have been recovered and purified commercially by ion exhcange is given in Table 1. In some cases, the scale of operation is relatively small, e.g. the rare earth elements, the transuranic elements, the platinum group metals, though the value of metal recovered is usually extremely high. Ion exchange is particularly suitable for high cost, low throughput purification processes. On the other hand, recovery of trace amounts of metals from waste streams accounts for many applications, e.g. chromium from spent metal plating solutions and copper and zinc from the wastes arising in the rayon and synthetic fibre industry. However, the largest single application in hydrometallurgy is the recovery and concentration of uranium from naturally-occurring orebodies. At the present time, about 30,000 tons/annum of uranium ore concentrate are processed as yellow cake (ammonium diuranate) in the Western World. Principal producers are the United States of America, Canada, South Africa and Australia. Traditionally, fixed bed ion exchange plants were installed to meet the early demand of the nuclear industry, though more recently, liquid extraction using liquid ion exchange reagents has found wide acceptance in many locations. Uranium plants are typically capable of processing 100–1000 m³/hr of pregnant solution and it is the uranium industry that has been responsible for the many innovations that have occurred in the development of ion exchange technology in recent years. These developments are now beginning to pervade into new areas of application for ion exchange in hydrometallurgy and these will be mentioned in this paper.