Facile preparation of polyurethane sponge decorated with polydopamine/BiVO4 for dye photocatalytic degradation under visible light and oil–water separation

The composite materials with photocatalytic and oil–water separation properties are of great significance in purifying oily and dye wastewater. Herein, we used polydopamine and BiVO 4 to modify polyurethane sponge to obtain a sponge (B-PU) with photocatalytic dye degradation performance, and then utilized dodecyltrimethoxysilane (DTMS) to coat B-PU to obtain highly hydrophobic H-B-PU for oil–water separation. The degradation efficiency of methylene blue solution by B-PU reached 93.3% within 2 h under visible light irradiation. The prepared H-B-PU has good selectivity and cyclic adsorption performance for various oil–water mixtures. The adsorption capacity was 31.4–60.3 times the weight of the sponge itself. In addition, H-B-PU is competent for gravity-driven and pump-driven oil–water separation, and can maintain stable high hydrophobicity under various conditions. It is worth noting that after the recovery of H-B-PU, H-B-PU floats on the surface of MB solution in the form of hydrophobic debris to photocatalytically degrade MB, which provides an important idea for the reuse of oil–water separation sponge for photocatalytic degradation of dyes. The prepared materials do not need to use harmful reagents and are simple in synthesis, and have good potential in the treatment of oily and dye wastewater.