Chemoenzymatic Cascade Reaction for Green Cleaning of Polyamide Nanofiltration Membrane.

Chemical cleaning is indispensable for the sustainable operation of nanofiltration (NF) in wastewater treatment. However, the common chemical cleaning methods are plagued by low cleaning efficiency, high chemical consumption, and separation performance deterioration. In this work, a chemoenzymatic cascade reaction is proposed for pollutant degradation and polyamide NF membrane cleaning. Glucose oxidase (GOD) enzymatic reaction in this cascade system produces hydrogen peroxide (H 2 O 2 ) and gluconic acid to trigger the oxidation of foulants by Fe 3 O 4 -catalyzed Fenton reaction. By virtue of the microenvironment (pH and H 2 O 2 concentration) engineering and substrate enrichments, this chemoenzymatic cascade reaction (GOD-Fe 3 O 4 ) exhibits a favorable degradation efficiency for bisphenol A and methyl blue (MB). Thanks to the strong oxidizing degradation, the water flux of the NF10 membrane fouled by MB is almost completely recovered (∼95.8%) after a 3-cycle fouling/cleaning experiment. Meanwhile, the chemoenzymatic cascade reaction improves the applicability of the Fenton reaction in polyamide NF membrane cleaning because it prevents the membrane from damaging by high concentration of H 2 O 2 and inhibits the secondary fouling caused by ferric hydroxide precipitates. By immobilizing GOD on the aminated Fe 3 O 4 nanoparticles, a reusable cleaning agent is prepared for highly efficient membrane cleaning. This chemoenzymatic cascade reaction without the addition of an acid/base/oxidant provides a promising candidate for sustainable and cost-effective cleaning for the polyamide NF membrane.