Electrochemical Cleaning of Fouled Laminar Graphene Membranes

Laminar graphene (including reduced graphene oxide (rGO)) membranes have recently received significant attention because of their potentially excellent permeability and selectivity; however, their fouling problem associated with the foulants blocked within graphene nanochannels has not been thoroughly investigated. This study confirms the blockage of molecules within the rGO membranes by investigating their rejection ratios at various membrane thicknesses and then presents an electrochemical in situ cleaning strategy (with the membrane as anode) aimed at oxidative decomposition of the foulant molecules. This method could restore the permeance (<3.0 L m–2 h–1 bar–1) after the filtration of the methyl blue solution to greater than 9.2 L m–2 h–1 bar–1 in 20 min at a voltage of 2.5 V without suspending the filtration process, resulting in a recovery ratio of greater than 94%. Such a high recovery ratio could still be achieved after six "fouling–cleaning" cycles. The process is energy efficient with only approximately 6.7 Wh consumed for 1 m2 of membrane area and a single cleaning. In addition, the electrochemical cleaning could largely avoid the damage of the membrane structure by preventing the formation of microbubbles, nanoparticles, and highly active hydroxyl radicals.