Electrochemical impedance spectroscopy study of membrane fouling and electrochemical regeneration at a sub-stoichiometric TiO2 reactive electrochemical membrane

Abstract

In this study, a novel sub-stoichiometric TiO2 ultrafiltration reactive electrochemical membrane (REM) was synthesized and used for electrochemical regeneration of membranes fouled by humic acid (HA) and polystyrene beads (PS). A non-invasive and non-destructive electrochemical impedance spectroscopy (EIS) characterization technique was used to spatially characterize fouling at the REM and data were successfully interpreted by a transmission line model. Based on these analyses, a chemical free electrochemical regeneration (CFER) scheme in backwash mode was developed. The CFER in anodic treatment mode recovered the flux of a HA fouled REM from 3.0% to between 76% and 99% of the initial flux over 5 continuous fouling/regeneration cycles. Full flux recovery of a PS fouled REM (fouling 31% to 38%) was achieved when using either cathodic or anodic CFER. By contrast, regeneration without an applied potential showed only partial flux recovery of 66% and 62% on HA fouled and PS fouled membranes, respectively. The operating cost of CFER was $0.04 m−2 to $0.06 m−2 per regeneration cycle, which is only 1.3% the cost of NaOH cleaning. Results suggest that the REM can provide an efficient and cost effective regeneration scheme that allows it to function in a diverse set of water treatment applications.