Functional graphene-based magnetic nanocomposites as magnetic flocculant for efficient harvesting of oleaginous microalgae

Abstract Magnetic graphene oxide (GO) nanocomposite was assigned to decorate with cationic polymer PDDA (diallyldimethylammonium chloride) to a sponge like nanocomposite GO-Fe 3 O 4 /PDDA, and employed in magnetic harvesting of oleaginous Chlorella sp. HQ. The results showed that huge surface area, light weight and stable dispersion of GO make contribution to the high harvesting efficiency of GO-Fe 3 O 4 (80.14%), compared to Fe 3 O 4 NPs (62.65%) with 70 mg of nanomaterials / L of algal cells dose. In addition, graphene base provides more active sites to further decorate with PDDA, which imparts a positive zeta potential charge (21.94 mV) to nanoflocculants, thereby achieving 95.35% harvesting efficiency within 5 min. The adsorption followed Langmuir isotherm and pseudo-second-order kinetic model, with the maximum adsorption capacity of 14.06 g dry-biomass / g. Moreover, the harvesting efficiency decreased dramatically when pH increased for Fe 3 O 4 NPs, while GO-Fe 3 O 4 and GO-Fe 3 O 4 /PDDA could maintain in a wide pH range. Besides,GO-Fe 3 O 4 /PDDA can be effectively reactivated (88.68% harvesting efficiency after 5 times reactivation) with 70 mg L − 1 dose (add 30 mg L − 1 after every time). It can be expected that this novel graphene-based magnetic nanocomposite has great potential to be a promising magnetic flocculant applied to efficient harvesting of oleaginous microalgae.