Design of a synergistic combined electrodialysis/anodic oxidation system for simultaneous AMX membrane fouling mitigation and enhanced dye degradation

Abstract

Electrodialysis is a common process which is widely applied for water purification and desalination or/and chemical species recovery. Solving the fouling of ion-exchange membranes is the bottleneck of this technology for stable processing along with low maintenance at large scale. This work aims to design combined electrodialysis/anodic oxidation (ED–AO) using as-prepared Pb/PbO2 anode to boost the oxidation of organic dye (methyl orange, MO) and overcome the issue of AMX membrane fouling. Hybrid ED–AO process works synergistically to accumulate, by ion-exchange reaction, MO species in the anodic Pb/PbO2 oxidative compartment to be oxidized and mineralized. As compared to single ED, excellent oxidation rates and membrane anti-fouling activities were found in ED–AO process. The characterization of the AMX membrane in single ED shows that the fouling was the main issue behind the low oxidation rate, causing a significant increase in the cell's electrical resistance, unlike in hybrid ED–AO process. Most of operating parameters including applied current density, initial concentration of MO, pH, supporting electrolyte (Na2SO4) concentration were investigated. The mechanistic pathways of MO oxidation and anti-fouling activity were discussed in depth. Through ten recycling tests, hybrid ED–AO process showed excellent stability and performance.