Biocatalytic metal–organic framework membrane towards efficient aquatic micropollutants removal

Abstract

The micropollutants in water sources are harmful to the aquatic environment and human health, and remain a significant challenge to be completely eliminated by conventional processes. Here, an original biocatalytic enzyme/metal–organic framework (MOF) composite membrane is developed to facilitate continuous and efficient removal of micropollutants from aqueous solution. In this work, an in-situ biomineralization strategy of simultaneous MOF (zeolitic imidazolate framework-8 or ZIF-8) nucleation and immobilization of horseradish peroxidase (HRP) is employed to form an enzymatic reactive HRP@ZIF-8 layer on modified ultrafiltration membrane. Such a hybrid structure design successfully integrates selective separation with stable enzymatic catalysis to prepare a reactive molecular sieve membrane, which realizes desirable decontamination performance toward micropollutants under low pressure. The as-prepared membrane sets a new record of bisphenol A (BPA) removal efficiency of 98% accompanied with high permeance (~33.32 L/m2.h.bar) at continuous mode. The removal mechanism is considered to be a combination of enhanced adsorption by MOFs enriching BPA molecules near the enzymes, catalytic oxidation by enzymes breaking the adsorption saturation limitation, and also membrane retention that reduced the enzymatic burden. In addition, the biocatalytic membrane displays enhanced stability and reusability due to the protection effect by the ZIF-8 exoskeleton, demonstrating good potential for stable and efficient removal of micropollutants for water treatment.