Development of a novel electrocoagulation membrane reactor with electrically conductive membranes as cathode to mitigate membrane fouling

Abstract

This study developed a novel electrocoagulation membrane reactor (ECR-ECM), an integrated system embracing electrocoagulation and membrane filtration in one individual reactor, by applying electric field to the electrically conducting membranes. Some key operational conditions (e.g. current density, pH and applied voltage) were systematically investigated to determine the synergistic influence of coagulation and electric field on the reactor performance. It was found that ECR-ECM showed the lowest flux decline (20.8%) in comparison with EC-UF (27.6%) and UF alone (41.3%) after filtration, suggesting that ECR-ECM exhibited the optimal antifouling behaviour. The increase of pH from 4 to 10 played a positive effect on the fouling mitigation by improving the electrostatic repulsive force between negatively charged pollutants and membranes. Improvement of current density from 5 to 10 A/m2 facilitated the generation of aluminum coagulant as well as bubbles, and therefore promoted the aggregation of foulants and reduced membrane fouling. Increasing applied voltage from 0 to 2.5 V led to a stronger repulsion force which have an ability to prevent the negatively charged foulants from accumulating on the membrane surface. This generated a much looser fouling layer, leading to a decreased flux decline. Importantly, the increased porosity and reduced resistance of membrane fouling layer under applied voltage was further confirmed through the calculation using Kozeny-Carman equation. This study provides a simple and feasible strategy for the fabrication of a novel electrocoagulation membrane reactor which has potential in solving membrane fouling problems with a more compact design.