PERFORMANCE OF DIFFUSION DIALYSIS FOR PICKLING EFFLUENT OPERATING UNDER A HIGH FLOW RATE

Abstract

Diffusion dialysis (DD) is a membrane separation process. The major driving mechanism is an ionic concentration gradient. An anion-exchange membrane (AEM) equipped with DD is efficiently used for purifying waste acid and metal ion separation. The goal of this laboratory-scale study is to investigate the efficiency of a diffusion dialyser (model HKY-001), which was equipped with an AEM (model DF120), to purify waste acid solution (sulphuric acid). This study was conducted with actual waste acid from a pickling bath of an electroplating manufacturer in Samut Prakarn Province. In the experimental tests, the operating parameters, such as time to reach equilibrium, feed flowrate, water to feed (Qwater/Qfeed) and type of stripping water, were varied. To examine the performance of this treatment unit, the concentration of H+ (mol.L-1), acid recovery (% as H+) and metal ion rejection (%) were monitored regularly. In conclusion, increasing the feed flow rate will likely decrease the H+ recovery (%). The rejection (%) of Zn, Mn and Pb is likely to increase with increases in the feed flow rate. A higher metal ion rejection (%) can be achieved at a lower water-to-feed ratio.