Superhydrophilic membrane with photo-Fenton self-cleaning property for effective microalgae anti-fouling

Abstract

Membrane filtration is one of the effective approaches to harvest microalgae for industrial biofuel production. However, during the filtration process, microalgae cells and extracellular organic matter (EOM) will deposit on the membrane surface leading to reversible membrane fouling that can be removed by physical methods. When hydrophobic EOM is adsorbed on the membrane surface or inside pores, it will build up a gel layer, causing irreversible membrane fouling. Irreversible fouling can only be removed using chemical methods that will decrease membrane lifespan and increase operational costs. Here, we introduce a versatile superhydrophilic membrane with photo-Fenton self-cleaning property, which can prevent the reversible fouling and remove the irreversible fouling. Tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) were co-deposited on the polyvinylidene fluoride (PVDF) membrane via Schiff base and Michael addition reactions, and β-FeOOH nanorods were inlaid on the membrane surface by in situ mineralization. The water contact angle of the modified membrane is reduced from 120° to 0° Under 60 min visible light, the hydroxyl radical (·OH) generated by the photo-Fenton reaction degraded the irreversible fouling that blocked membrane pores. The irreversible fouling rates of modified membrane was reduced from 39.57% to 3.26%, compared with the original membrane. Microalgae harvesting results illustrated that the membrane has a high flux recovery rate (FRR) of 98.2%, showed excellent passive antifouling and active antifouling performance. We believe this work will spark a novel platform for optimizing energy-efficient microalgae harvesting separation membrane modules. In addition, this method of anti-fouling filtration for microorganisms can be extended to the industrial production of various bioenergy sources and will have very promising practical applications.