ABSTRACT

Many of the benefits claimed for moving-bed ion exchange need to be treated with caution, since the improvement in performance is often due to countercurrent operation, rather than to moving-bed operation per se. Moving-bed ion exchange has been slow to gain acceptance outside the uranium industry, partly because the goal of engineering simplicity has rarely been attained, and partly because of improvements in fixed-bed technology. In the uranium industry, moving-bed ion exchange is used for treatment of uranium-containing mine water as well as the more concentrated leach liquors. Treatment of industrial wastewater by ion exchange has been relatively rare, but is becoming widespread. Traditional wastewater treatment processes such as precipitation generate residues whose ultimate disposal may simply result in the pollution problem being moved elsewhere. As with fixed-bed ion exchange, countercurrent operation means that incoming feed meets resin which is already partly loaded, while freshly regenerated resin contacts outgoing, nearly depleted, product water.