Ion exchange on resins with temperature-responsive selectivity IV. Influence of solution and column parameters on efficiency of reagentless separation of copper and zinc using thermo-induced concentration waves technique

The effect of solution and column parameters such as pH, ratio of metal ion s and the height of resin bed on formation of the thermo-induced concentrat ion waves (TICW) in the course of the thermostripping process of Cu2+ and Z n2+ ions from iminodiacetic resin Lewatit TP-207 has been studied. The form ation of TICW is attributed by both different diffusivities of metal ions a nd the presence of the third (H+) ion in the system. This effect makes it p ossible to carry out a reagentless separation of metal ions by using either the metal depletion or metal concentration mode of operation. The efficien cy of the TICW-based separation process by using the metal depletion mode a ppears to be the higher the lower relative concentration of metal ion under removal (slower diffusing ionic species). The mathematical model proposed allows for qualitative and quantitative description of thermostripping proc esses in a wide range of pH and solution compositions. The physical model o f the TICW process proposed makes it possible to account for the influence of different process parameters and generalise the applicability of the TIC W separation technique to the binary mixtures of any metal ions with differ ent diffusivities. (C) 2000 Elsevier Science B.V. All rights reserved.