Facile fabrication of expanded graphite/polydimethylsiloxane foams for oil–water separation

Abstract

3D porous foams for oil–water separation via selective adsorption were obtained by incorporating expanded graphite (EG) granules into polydimethylsiloxane (PDMS) foams. The EG@PDMS6-t foam prepared with a PDMS:EG and NaCl:PDMS mass ratio of 6:1 and 8:1, respectively, possesses a high porosity of 80.3%, a water contact angle of 127.7°, and an oil contact angle close to 0°. The foam exhibits an impressive adsorption capacity towards light oil (hexane,6.28 g/g), heavy oil (trichloromethane, 13.33 g/g), and kitchen waste oil (4.51 g/g), being able to separate 100% of oils from an immiscible oil–water mixture and 39.0% of camellia oil and 45.3% of kitchen waste oil from oil-in-water emulsions via selective adsorption. The foams possess excellent elasticity and desirable reusability in oil–water separation and exhibit outstanding resistance to acidic and alkaline environments. EG accounts for 96.5% of the EG@PDMS6-t foam’s volume. SiO2@PDMS hydrophobic layer was constructed on the top of EG@PDMS6-t foams by a spraying technique to tailor-make 3D filters for oil–water gravity-driven separation. The P20s-S0.2-EG@PDMS6-t filter shows an excellent immiscible trichloromethane-water gravity-driven separation, with a trichloromethane permeate flux of 11,024 L/m2h, a water rejection time of 60 s, and a separation efficiency of 99.7%. The filters are highly robust to chemical corrosion and tape-peeling.