Influence of Low Molecular Weight Organic Carboxylic Acids on Cr (VI) Photo-Reduction in Montmorillonite Suspensions

Chromium is an environmental contaminant of global concern. This study focuses on the reduction of Cr (VI) using montmorillonite in the presence of organic carboxylic acids under UV-vis irradiation. The Cr (VI) reduction rate can be greatly accelerated when low-molecular-weight organic acid is present. This process of photoreduction follows approximately zero order kinetics. The effects of pH values on the reduction efficiency are also investigated. The photoreduction efficiency of chromium is higher under acidic pH than that of in the weakly alkaline pH. The photoreduction efficiency of Cr (VI) is found to increase with concentrations of organic carboxylic acids and montmorillonite. However, the reaction is independent of Cr (VI) concentration.