Mesoporous and flexible polyimide aerogel as highly active catalytic membrane for AO7 degradation by peroxymonosulfate activation

Abstract

• Mesoporous and flexible PI aerogel membrane is first selected as a PMS activator. • PI/PMS aerogel can efficiently remove AO7 without adsorption–desorption equilibrium. • PI/PMS aerogel membrane could keep high removal rate and permeation flux. • Non-radical pathway plays the dominant role for AO7 degradation. Driven by the organic contaminants in wastewater, peroxymonosulfate (PMS) as a source of reactive species has been developed, and metal-free catalysts have proven to be one kind of most promising PMS activators. In this work, mesoporous and flexible polyimide (PI) aerogel membrane with high specific surface area, expanded π-conjugated system and high strength is selected as one kind of PMS activator, and the PI/PMS aerogel system shows high organic contaminants degradation performance. Interestingly, the acid orange 7 (AO7) degradation rate constant of PI/PMS aerogel system without adsorption–desorption equilibrium stage is 2.5-fold faster than that of catalyst with adsorption–desorption equilibrium stage, because the adsorption of AO7 on PI aerogel covers the active sites of PI, and little PMS can be activated on the surface of PI aerogel. Notably, PI/PMS membrane system could remove 96.21% of AO7 with a slight decreased permeation flux for the twelfth cycle. Furthermore, the possible degradation mechanism was proposed, and radical quenching tests certified non-radical pathway played the dominant role for AO7 degradation. The successful application of PI aerogel membrane as PMS activator may shed light on designing new types of aerogel membrane for wastewater treatment.