A wide range of chelating ion exchangers was tested for their abilities to
remove Zn, Ni, Cu and Cd from solutions simulating waste effluents from the
metal-plating industry. The task was to reduce metal discharges to the env
ironment so that metal-plating shops could keep up with the modern, more st
ringent regulations of waste effluents. The resins were tested by batch and
mini-column experiments. Decontamination factors (DFs) as high as 700 and
capacities up to 3.3 meq/mL were measured at the 5% breakthrough (BT) point
in mini-column tests. Complexing agents, especially cyanide, considerably
reduced the performance of the resins with only a few exceptions. Ammonium
seemed to improve the ion-exchange performance of some chelating resins and
capacities higher than the theoretical values, given by the manufacturer,
were measured. Comparative experiments between chelating, strong acid and w
eak acid ion-exchange resins showed that the advantage of chelating exchang
ers over strong and weak acid exchangers is a very low metal BT level, even
as low as 2 mu g/L, which is very important, especially in the end-of-pipe
polishing. (C) 2000 Elsevier Science B.V. All rights reserved.