Conductive reverse osmosis membrane for electrochemical chlorine reduction and sustainable brackish water treatment

Abstract

The susceptibility of RO membrane for chlorine, which is widely used for disinfecting the feedwater, remains a biggest challenge. Herein for the first time, we report an electrochemical chlorine reduction on a conductive RO membrane interface as a sustainable solution to overcome this limitation. In this study, cyclic voltammetry was employed to investigate the potential of electrochemical chlorine reduction. Later, a conductive RO membrane with an embedded carbon nanotubes layer (CNT-RO) was fabricated, and its resistance to chlorine was tested via batch soaking into a sodium hypochlorite solution (NaOCl; 1,000 ppm; pH = 5) used as the chlorine source, followed by the flux and salt rejection monitoring.The CNT-RO membrane resulted in 3.5% and 9.3% chlorine uptake after chlorinating for 1 h and 24 h, hence faced prominent decline in the amide II and aromatic amide peak positioned at 1541 cm−1 and 1609 cm−1, respectively. In contrast, the application of 2 V on conductive CNT-RO membrane interface when used as a cathode resulted in an irreversible chlorine reduction, hence formed chloride as validated via ion chromatography. Chlorination of CNT-RO membrane under conducting mode could not cause any significant change in the membrane morphology, elemental composition, amide bonding structure, and surface wettability. Therefore, CNT-RO membrane demonstrated 88% rejection against monovalent salt even after 24 h of chlorination under conducting mode as compared to the commercial and CNT-RO (chlorinated without DC charge application) which showed 69% and 74% rejection, respectively. These findings clearly illustrated the potential of conductive RO membrane for sustainable desalination and water reuse applications.