Using an anti-fouling electro- (stainless-steel/ PVC) membrane reactor in electrocoagulation process for arsenic removal: Experimental study and mechanism development in multiphase media using CFD

Abstract

The electrocoagulation (EC) method is an effective way to remove arsenic (As) from water. However, to obtain high-quality floc-free water, it needs further purification, and membrane processes can be used to achieve this goal, but fouling is their main problem. In this study, a PVC/stainless steel electro-conductive membrane was used as a cathode electrode, and the effects of voltage, current, and time on the reduction of membrane fouling and arsenic removal were investigated. By increasing the applied voltage, due to the increase of the repulsive force between the membrane and negatively charged arsenic particles, the percentage of arsenic removal increased. While increasing the current density, more coagulant materials were produced from the anode, and the rejection rate of arsenic also became higher. The optimal conditions for removing arsenic at 22 V, 0.2 A, and 50 min were obtained according to the box-Behnken design in deionized water. After the second one-hour cycle, the concentration of arsenic in the model water decreased by 99.6% and fell below the maximum permissible level. Additionally, increasing voltage and current reduces membrane fouling due to an increase in the repulsive force and formation of bubbles on the membrane surface, respectively. Also, the process modeling results, considering the adsorption mechanism and repulsive force, showed that at 0.2 and 0.32 amperages, the model follows the Freundlich and Langmuir isotherms better, respectively, and showed an accurate prediction of experimental outcomes. Furthermore, 3D process modeling results indicated the distribution of velocity, current, voltage, and concentration inside the reactor.