Electrochemical Cleaning of Fouled Laminar Graphene Membranes

Abstract

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 m 2 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.

Influence of Fermi‐Level Engineering in Multi‐Interface CuO/Cu2O||rGO||h‐WO3||rGO|| Photoelectrodes on Photoelectrochemical CO2 Reduction

“…The estimated thickness of the 20-layer rGO was 10 nm, consistent with previous work. [30] The thickness difference between the graphene layers (%3.5 Å) was attributed to surface modifications of the functional groups formed during the GO reduction, and was also consistent with previous work. [31] From the present AFM observations, the single thickness was estimated as 5 Aº (Figure 1).…”

Electrochemical Opening of Impermeable Nanochannels in Laminar Graphene Membranes for Ultrafast Nanofiltration

“…The CNT dispersion (100 mg L –1 ) was prepared with a method previously reported. , GO was fabricated with a modified Hummers’ method . The hydrazine-based reduction preparation of the rGO dispersion (50 mg L –1 ) was similar to the method shown in our previous work, , except for the heating duration during the reduction process. To fabricate the rGO membranes, 10 mL of a CNT dispersion was first vacuum-filtered by a PVDF membrane to form a CNT layer, on which rGO nanosheets were then deposited by vacuum filtration of the rGO dispersion.…”

Carbon nanomaterial-based membranes for water and wastewater treatment under electrochemical assistance

“…7d-f). 172,265,[289][290][291] Besides, the movements of large cations in the CNT core (denoted as ionic pump) were considered to remove the adsorbed foulants in the membrane pores. 172 In addition, the hydroxide ions generated from water electrolysis on the membrane surface efficiently dissolved the silicate scaling developed during the MD process, negating the need for chemical cleaning.…”