The use of electrodialysis for recovery of sodium hydroxide from the high alkaline solution as a model of mercerization wastewater

The possibility of alkali recovery from a high alkaline solution as a model for mercerization wastewater by electrodialysis (ED) was examined. ED with feed and bleed configuration was used in which the diluate chamber conductivity was kept at a given value by dosing an alkaline solution. The effect of the diluate chamber's concentration on the efficiency of the ED was investigated. It was found out that the efficiency of the ED was just slightly affected by changing the concentration of the solution in diluate chamber. The calculated values of current efficiency in ED process were about 60%. Since the ion exchange membranes, particularly the anion exchange ones are suspected to be damaged in high alkaline media, their properties including electrochemical resistivity, apparent permselectivity, FT-IR spectrum, and the current-voltage characteristics were investigated. The results confirmed that the membranes possess a promising chemical stability since their properties were not affected by the alkaline media. Hence, the obtained results show that the electrodialysis is an appropriate method for alkaline recovery.