Simultaneous alkali recovery, coagulant recycling and organics removal from textile wastewater via membrane electrochemical system

The membrane electrochemical reactor (MER) achieved synergistic textile wastewater treatment, alkaline solution recovery and magnesium coagulant recycling by the one-time addition of magnesium salt to the anode, solving the problems of reagent wastage and increased wastewater salinity caused by the continuous addition of chemicals in traditional treatments. In this study, the rapid adsorption and precipitation (within 3 min) of DB-86 in the cathode chamber by the magnesium coagulant were stimulated by the hydrophobicity of DB-86, resulting from the relatively dispersed localization of negative charges on the H atoms on the molecule's surface. The precipitated solids in the cathode effluent were recovered through an ultra-filtration process and recycled to the anode for dissolution. Effective mineralization of dyes was achieved by anode electrolysis, generating large amounts of active chlorine on its surface as an indirect oxidant, resulting in 80.15 % TOC removal after 30 min. Operational stability tests were conducted using both simulated dye wastewater and actual textile wastewater. The decolorization efficiency of the system remained at 99.9 % for simulated dye wastewater and 99.5 % for actual textile wastewater after six cycles of long-term operation. Magnesium hydroxide is re-dissolved at the anode, then passes through the ion exchange membrane into the cathode for recycling. Loss of magnesium ions occurs only at the ultra-filtration surface, achieving recovery efficiencies exceeding 95 % for simulated dye wastewater and 80 % for actual textile wastewater. The MER/Mg system in this study achieved rapid coagulation and mineralization of DB-86, along with efficient recycling of Mg²⁺ ions, thus avoiding wastage of chemical sludge and reagents, and reducing chemical consumption and treatment costs.