Fabrication of robust, superhydrophobic-superoleophilic PVA sponge by one-pot hydrothermal method for oil-water separation

Abstract

Superhydrophobic surfaces have promising application prospects in the field of oil-water separation. In this study, a superhydrophobic-superoleophilic polyvinyl alcohol sponge modified by stearic acid/nano-TiO2 particles (referred to as STt@PVA, where S, T and t denoted stearic acid, nano-TiO2 particles with diameters of 50 nm and 20 nm, respectively) was constructed for oil-water separation. The results showed that STt@PVA had a water contact angle (WCA) of 163°, a water sliding angle (WSA) of less than 3° and an oil contact angle (OCA) of 0°. Moreover, the oil can be completely adsorbed within 1 s, indicating that the functional PVA sponge can effectively separate and adsorb the organic solvents or oils in oil-water mixtures. The oil-water separation results showed that the modified sponge could adsorb 5 - 8 times more oil than its own mass. After being reused for 5 times, the sponge could still maintain the oil sorption capacity of 5 times of its own mass, and the separation efficiency remained above 83%. In addition, in order to demonstrate its performance in actual oil pollution treatment, the durability, robustness, acid and alkali resistance and self-cleaning ability of STt@PVA were also analyzed. The results showed that the reasonably designed superhydrophobic-superoleophilic functional PVA sponge had the advantages of easy preparation, low cost, recyclability and strong robustness, and had great practical application potential in the processing of oil-bearing wastewaters and oil spills.