Design of adjustable hypercrosslinked poly(ionic liquid)s for highly efficient oil-water separation

Abstract

Considering the environmental problems caused by oily wastewater, how to realize oil-water separation has attracted extensive attention from researchers. Herein, a series of hypercrosslinked poly(ionic liquid)s (HCPILs) were fabricated by using dimethoxymethane as an external crosslinking agent combined with different auxiliary crosslinking agents to “weave” the ionic liquid of 1,3-dibenzylimidazolium chloride for oil-water separation. The hydrophilicity and hydrophobicity of HCPL can be adjusted by changing different auxiliary crosslinking agents. When using aniline as an auxiliary crosslinking agent, the resulting HCPIL-A2 with approximately 5500 L/m2·h of water flux exhibits super hydrophilicity-oleophobicity, its static water contact angle and underwater oil contact angle are close to 0° and 132°, respectively. When using benzyl alcohol instead of aniline, the obtained HCPIL-B2 exhibits good lipophilicity and hydrophobicity. Its static water contact angle and underwater oil contact angle are close to 126° and 0°, respectively. And its oil fluxes of chloroform and carbon tetrachloride are approximately 7645 and 7241 L/m2·h, respectively. However, when using toluene instead of aniline, the obtained HCPIL-C2 exhibits hydrophilicity-lipophilicity and can’t separate the oil-water mixtures. Moreover, HCPILs show permanent pore structure, good stability, and environmental friendliness due to their high degree of crosslinking are constructed. Their loose surface roughness can realize the separation of the oil-water mixture by gravity. Therefore, the designed new materials can selectively remove water or oil mixture. Efficient separation of crude oil and seawater mixture will provide new ideas for future environmental problems such as offshore oil spills.