A facile and green route to fabricate fiber-reinforced membrane for removing oil from water and extracting water under slick oil

Highlights: • The fiber-reinforced cotton/PA6/PAN membranes were prepared. • The process was simple and reduced the organic wastewater treatment burden. • The PAN/NMP/ water ternary system and wettability model were analyzed. • The membrane owned excellent separation performance for oil-in-water emulsions. • The membrane could also extract water under slick oil. Except the good separation performance, the membranes used for oil-water mixture separation should be fabricated with as little wastewater produced as possible. Thus, we proposed a green tactic--water vapor induced phase inversion to prepare the high-strength and superhydrophilic/underwater superoleophobic nonwoven fabric-based cotton/PA6/PAN membranes which is based on the polymer/solvent/nonsolvent ternary system analysis. Differing from adding additives in polymer solution or coagulation bath, above proposed strategy has an "subtractive effect" with the advantages of constructing three-dimensional porous structure and greatly reducing the organic wastewater produced during preparation process. Moreover, the obtained cotton/PA6/PAN membranes exhibited unexpected performances for separating oil-in-water emulsions. An ultrahigh permeation flux of up to 478,000 L m⁻² h⁻¹ bar⁻¹ with a separation efficiency of > 99.9% was obtained under the driving pressure of 1.6 KPa, which was one order of magnitude higher than the conventional separation membranes with similar properties. In addition, it is surprising that the cotton/PA6/PAN membranes can also extract water from the slick oil/water immiscible mixture. Therefore, it is expected that the cotton/PA6/PAN membranes can be used in practical oily wastewater purification.