A superhydrophilic and high demulsification aramid nanofibers membrane with novel poly-pseudorotaxane structure for oil-in-water separation

Abstract

Oily wastewater caused by the traditional oil spills and the increment of emerging lipid (such as biodiesel) pollution endangers human and nature seriously. Herein, we conceive a novel β-cyclodextrin-threated interface demulsification structural strategy to assemble superhydrophilic aramid nanofibers (ANFs) membranes for surfactant-stabilized oil-in-water emulsion separation. Aim to modify the monomers, p-Phenylenediamine (PPD) molecules were covered by β-cyclodextrin (β-CD) to form inclusion compounds. Different poly (p-phthaloyl-p-phenylenediamine) with poly-pseudorotaxane structure (β-CD@PPTA) was obtained by low-temperature solution polycondensation by adjusting the proportion of modified monomers. The corresponding β-CD@ANFs membrane was successfully fabricated by non-solvent induced phase separation. The effect of β-CD@PPD monomers on the structure, element content, surface wettability, separation performances and durability of the modified membrane were investigated systematically. The modified membranes had the superhydrophilicity and underwater superoleophobicity characteristics. The flux and oil rejection of membrane both raised with the increased added proportion of β-CD@PPD monomers. The well-designed membrane exhibited tween 60 stabilized N-hexadecane-in-water emulsion permeances over 126.59 ± 5.35 L/m2h with separation efficiency above 99.73%. More significantly, the membrane had long-term demulsification performance and ideal purification effect on the separation of biodiesel wastewater, showing forceful prospect in removing lipid oil pollutants from the oil-in-water emulsions. The membrane prepared by poly-pseudorotaxane modification could better serve the development of oil-in-water separation field.