Highly performant nanocomposite cryogels for multicomponent oily wastewater filtration

Abstract

This paper reports the fabrication of multifunctional composite cryogels that simultaneously remove oil and dye from polluted water through gravity-driven filtration. The cryogels were prepared via cryopolymerization of a poly(sodium acrylate) (PSA) and graphitic carbon nitride nanosheets (CNNs) mixture. Although the different CNNs concentrations tested do not significantly affect the morphology of the hybrid cryogels (PSA_CNN), they do influence their optical properties, with the PSA_CNN hybrid fabricated with the lower CNNs concentration (i.e., PSA_CNN1) to demonstrate the best photoactive properties. PSA_CNN1 presents attractive wetting properties such as fast and high swelling capacity, rapid water permeability, and underwater superoleophobicity. We found that the presence of CNNs enhances the methylene blue (MB) adsorption capacity of the hybrid cryogel. When used for the gravity-driven filtration of oil–water, dye-water, and oil-dye-water mixtures, the hydrogel composite can purify efficiently and rapidly the water, and its performance is maintained after diverse filtration cycles. Its photocatalytic self-cleaning property enables it to be cleaned before the next filtration cycle when exposed to visible light irradiation. The herein presented approach is expected to be an insightful contribution to the field of multicomponent oily wastewater filtration, offering inspiration for the design of photoactive hydrogel-based 3D filters for the simultaneous removal of water pollutants through cost-effective and energy-safe processes.