Graphene oxide on laser-induced graphene filters for antifouling, electrically conductive ultrafiltration membranes

Laser-induced graphene (LIG) is a three-dimensional porous carbon material prepared by direct laser writing with a CO2 laser on various polymers in an ambient atmosphere, leading to electrically conducive, low fouling coatings. Recently, LIG has been synthesized on porous supports, which led to highly permeable and porous separation filters and LIG composites have greatly improved the stability. On the other hand, graphene oxide (GO) has emerged as a promising 2D nanomaterial to coat porous or non-porous polymer membrane supports resulting in separation membranes with enhanced separation and surface properties. Here, we report a robust, hybrid LIG-GO membrane fabricated by filtration and crosslinking of GO onto the LIG membrane support, generating ultrafiltration membranes with tailored performance. Increasing the amount of crosslinked GO on the LIG surface resulted in increased rejection of bovine serum albumin (BSA) up to 69%, and bacterial rejection was increased from 20 to 99.9%, which agreed with the measured molecular weight cut-off determination that approached similar to 90 kDa as the GO content increased. Higher flux recovery ratios and lower BSA adsorption were seen with LIG-GO membranes, and the hybrid membranes showed comparatively good antifouling. These composite membranes showed 83% less biofilm growth compared to a typical polymer ultrafiltration membrane under non-filtration condition. Noteworthy is that the LIG supporting layer maintained its electrical conductivity and the LIG-GO membrane used as electrodes showed complete elimination of bacterial viability with potent antimicrobial killing effects when treated with mixed bacterial culture. In cross-flow filtration, LIG-GO membranes with 3V anodic electric field showed 11% improvement of flux as compared to typical polymer ultrafiltration membrane. The LIG-GO membranes expand possibilities for the use of LIG in membrane separation applications, especially ultrafiltration.