Efficient desalination and synergistic toxic organics removal in RO concentrates with electrochemical advanced oxidation processes

Abstract

A novel Ce-doped Ti4O7 (Ti/Ti4O7-Ce) electrode was fabricated and investigated in treatment of reverse osmosis (RO) concentrates with Electrochemical advanced oxidation processes (EAOPs). Characterization results showed that Ce was successfully incorporated into the Ti4O7, leading to an increase on the hydroxyl radical (•OH) generation and electrochemical stability compared with Ti/Ti4O7. Ti/Ti4O7-Ce electrodes achieved efficient desalination and oxidation of toxic organics, which was mainly attributed to the indirect oxidation induced by electro-generated •OH and change of electrochemical properties. The action of electric field had great effect on desalination process, and the anions in reverse osmosis concentrates (ROC) deposited on the cathode through this action by characterization and analysis. In the treatment, about 10.8–11.2 % of desalination efficiencies can be obtained, and the removal efficiency of toxic organics enhanced with the increase of Ce addition and current density. In the experiments, TOC removal efficiencies were 57 %, 66 % and 69 % under 10, 20 and 30 mA/cm2 in the 180 min treatment. Toxic chemicals, such as alkanes, haloalkanes, etc., were the main components in treatment, and the organic pollutants with medium molecular weight (MMW) (1400 g/mol) and low molecular weight (LMW) (40–230 g/mol) in ROC were removed. Although slight decreased durability was observed due to Ce leaching, Ti/Ti4O7-Ce electrode maintained stable desalination performance and total organic carbon (TOC) removal efficiency within 60 cycles. This study indicated that Ti/Ti4O7-Ce was a promising electrode for synergistic toxic organics removal and desalination in EAOPs.