Environmentally Safe and Porous MS@TiO₂@PPy Monoliths with Superior Visible-Light Photocatalytic Properties for Rapid Oil–Water Separation and Water Purification

Frequent oil spill accidents and industrial wastewater discharge result in severe health and ecological problems. Advanced materials with superwettability have been extensively applied for oil–water separation; however, most of them lack the capacity of removing water-soluble pollutants. Therefore, developing multifunctional materials for oil–water separation including water-soluble organic contaminant removal simultaneously is extremely important and still a challenge. Herein, multifunctional porous MS@TiO2@PPy monoliths were fabricated via in situ grown TiO2 nanocrystals and vapor deposited PPy. The vapor deposition method at room temperature is environmentally friendly. The prepared MS@TiO2@PPy monolith exhibits superhydrophilicity and underwater superoleophobicity, which can separate insoluble oil–water mixtures continuously with a high flux (9549 L·m–2·h–1). Importantly, the uniform PPy layer covered on the surface of TiO2 not only enhances the stability of MS@TiO2 but also improves the photocatalytic activity by decreasing the band gap. Moreover, the porous structure of the monolith can enhance the adsorption and transportation of reactants; the strong absorption of light inside a black interior structure can improve the utilization efficiency of light. Thus, the MS@TiO2@PPy monolith presents superior photodegradation activity toward water-soluble organic pollutants under simulated sunlight irradiation. The chemical rate constant of MS@TiO2@PPy is up to 5.2 times as much as the P25 toward RhB. More importantly, compared with most powder catalysts suffering from limited dye absorption capacity, second pollution, and complicated recovery processes, the MS@TiO2@PPy monolith exhibits excellent mechanical and chemical stability, which allows its usage in complex oil–water systems and superior recyclability. Hence, we believe that the environmentally friendly and multifunctional MS@TiO2@PPy monolith with superior photocatalytic activity and deep oil–water separation not only allows natural light to be used rationally but also effectively solves the problems of water pollution at low cost and energy consumption.