Analysis of the Relationship between Available Chlorine Concentrations and pH in Slightly Acidic Electrolyzed Water Based on Dissociation Equilibrium

Abstract

Slightly acidic electrolyzed water, prepared by electrolyzing dilute hydrochloric acid, has a strong anti-microbial effect, and is widely used for various washing and disinfecting purposes. To obtain the desired effect, it is important to understand quantitatively how operating parameters affect available chlorine concentrations and pH in slightly acidic electrolyzed water. In this paper, a model was developed for prediction of available chlorine concentrations and pH in slightly acidic electrolyzed water by considering dissociation equilibrium for calcium carbonate and hypochlorous acid as well as electrochemical reactions in the electrolytic cell. Calculated results were generally in agreement with experimental results, which showed a decrease in pH with an increase in either available chlorine concentrations or water flow rates for dilution. The pH of the electrolytic solution in the cell was estimated to be less than 0.5. This finding supported our assumption that gaseous chlorine generated by electrolysis did not dissolve in the strongly acidic electrolytic solution. The model also predicted available chlorine concentrations and pH of the slightly acidic electrolyzed water prepared using source water with a different hardness reasonably well.