Superoleophobic graphene oxide/halloysite nanotube composite membranes for oil-water separation

Highlights: • The modified Hummers method and vacuum filtration method are used to prepare GO/HNTs composite membranes. • The interlayer growth structure of GO and HNTs increases the spacing of membranes and improves the surface roughness. • The water flux of the composite membrane was increased by 3 times while maintaining a high removal rate of over 99.5%. • Composite membrane has excellent acid and alkali resistance and reusability. In order to obtain separation membrane materials with high permeation flux and excellent oil/water emulsion separation performance, various strategies for inserting nano-second phases have been proposed to expand the membrane spacing and thereby improve water permeability. In this work, a series of nanocomposite membranes graphene oxide/halloysite nanotubes (GO/HNTs) composed of HNTs and GO nanosheets were successfully prepared by vacuum filtration of HNTs/GO suspensions prepared by a modified Hummers' method. The HNTs intercalate and grow around the GO nanosheets to increase the interlayer spacing of the composite membrane, which is beneficial to increase the permeation flux. In addition, thanks to the doping of hydrophilic HNTs and the uneven surface morphology due to the increase in surface roughness, the membrane permeation flux is improved. The GO/HNTs composite membrane was used for oil-water separation experiments with an endless separation device. The GO/HNTs composite membrane with underwater super-oleophobicity has a water flux of 1470 L m⁻²h⁻¹ when the GO/HNTs content ratio is 1/3, which is 3 times that of pure GO membranes, while maintaining a high rejection of over 99.5%. The composite membrane maintains high water flux and high rejection rate under different pH conditions, and has acid and alkali resistance. After 10 times of repeated use, the high water flux was maintained as expected, indicating that the composite membrane is reusable.