Feasibility studies of discontinuous electro-regeneration processes in environmentally-friendly plating for chromate separation from a binary system

Project work was carried out for feasibility and possible design of semi-industrial electro-regeneration units for diluted waters typical for rinse water systems in electroplating industry. Firstly, one subject of interest was the removal of CrO42− ions in the concentration range between 0.06 mol m−3 and 2.3 mol m−3. Ion exchange capacity of several resins under room temperature conditions was tested. A 2-compartment cell with diaphragm was found to be a suitable construction for electrochemical resin regeneration after previous discontinuous loading. The determination of resin conductivities and transport numbers was also part of the studies. Results showed sufficient high current efficiencies up to 70%. Nevertheless, low ion mobility in the resin may limit the removal rate for continuous electrodeionization. In this case, stepwise operation mode in loading and regenerating the resin bed is the only solution. Energy consumption can be lowered by using catholytes of previous electro-regeneration steps. Specific energy consumption until 0.3 kWh per treated cubic meter is to be expected.