Alkalinity of Electro-Activated Aqueous Solutions

Abstract

Electro-activated alkaline (basic) solution known as catholyte has been reported to have a number of unique properties. The changes in the pH and alkalinity of the catholyte were monitored in the current study. A full-factorial design was applied in order to examine the effects of current, time of treatment, and salt concentration on the electro-activated solutions treated in 4 types of configurations. Two configurations were constructed as three-compartment cells with chambers separated by anion exchange membrane (AEM) and cation exchange membrane (CEM) with different dispositions in the cell. The other two configurations were two-compartment cells with chambers separated by either an AEM or a CEM. For pH increase, time was the most significant factor, whereas for the alkalinity the cell configuration had a significant impact. Thus, when CEM was used to separate central and cathodic compartments in a three-cell reactor, or anodic and cathodic compartments in a two-cell reactor only current and time were found to be highly significant. On the other hand, when the AEM was used the salt concentration appeared to be an important factor too. Maximum values for pH (pH 12) and alkalinity (25.46 ± 0.31 mmol/L) were obtained after 60 min of treatment and 0.2 A current, and regardless of NaCl concentrations when CEM was used, whereas maximum values for the AEM membrane were achieved only with maximum NaCl concentration of 1 M. Despite highly alkaline medium (pH ~ 12) the strength of the solution was comparable to dilute NaOH solution (~0.03 M).