Electrochemical treatment of municipal reverse osmosis concentrates by a TiO2-BNTs/SnO2-Sb reactive electrochemical membrane

Abstract

With the wide application of reverse osmosis technology in municipal wastewater treatment, the abundance of generated reverse osmosis concentrates (ROC) has become a significant challenge for water ecosystems. In this work, a fabricated TiO2-BNTs/SnO2-Sb reactive electrochemical membrane (REM) was used to dispose of municipal ROC wastewater. The effects of the TiO2 nanotube array (TiO2-BNTs) interlayer, current density, initial pH and flow rate on the COD removal of ROC were investigated. In addition, the 3D-EEM fluorescence spectra showed that humic acid-like substances and soluble microbial byproduct-like substances could be removed effectively. GC-MS analysis indicated that most organics, including aldehydes, phenols, ethers, nitriles, ketones, silanes and alcohols, were eliminated after treatment. The REM also exhibited prominent membrane anti-fouling performance in high-salinity wastewater. After 20 cycles, the transmembrane pressure (TMP) was only slightly changed (within 3 kPa) compared to that of the first cycle. Two key parameters, i.e., service lifetime and energy consumption, were investigated in ROC treatment. The service lifetime reached 31350 h (3.5 years, 20 mA cm−2) in 0.5 M NaCl solution and 40390 h (20 mA cm−2, 4.6 years) in actual wastewater, which is highly competitive with previously reported electrodes. Energy consumption reached 10.5 kWh·kg COD−1 in actual ROC wastewater, which is more acceptable compared with current reported electrochemical technologies and exhibits great application prospects for TiO2-BNTs/SnO2-Sb REMs.