Ex Situ and In Situ Organic Fouling Monitoring in Laser-Induced Graphene-Based Electroconductive Membranes for Desalination and Wastewater Treatment

During operation, the inevitable fouling of ultrafiltration (UF) membranes severely affects their performance in industrial separation processes, desalination, and wastewater treatment, necessitating effective fouling monitoring. Laser-induced graphene (LIG) is a facile method for fabricating UF electroconductive membranes (ECMs) and has shown enhanced emerging contaminant removal, antibiofilm and antimicrobial properties. However, no study has investigated the use of electrical signals for monitoring of organic fouling in LIG-based ECMs. This study investigates using LIG-based ECMs as an advanced tool for fouling detection and monitoring using a neutral foulant. The effect of fouling on electrical responses like surface resistance, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS) was investigated in ex situ and in situ modes with three-electrode and two-electrode systems. Current responses showed a decreasing trend with fouling cycles, while the Nyquist plot showed both rightward and upward shifts with an increase in fouling. The normalized changes in EIS-derived resistance and impedance were found to be more sensitive than flux signals in the detection of fouling and continuous monitoring. The LIG-based ECM performs the dual role of the membrane as well as an advanced fouling monitoring tool, demonstrating early detection of fouling and a sudden increase in foulant concentration as compared to conventional methods. Such LIG-based ECMs provide better fouling monitoring strategies via both ex situ and in situ monitoring and can be used with more field-applicable two-electrode systems for industrial-scale applications. This can further help in optimizing fouling mitigation strategies for desalination and wastewater treatment.