Facile fabrication of flexible ceramic nanofibrous membranes for enzyme immobilization and transformation of emerging pollutants

Abstract

Biocatalytic nanofibrous membranes, integrating the benefits of membranes and enzymes, have drawn attention in wastewater treatment because of their efficient catalytic performance and operational catalytic stability. However, these membranes are typically polymeric membranes, and their fate as plastic waste is not considered environmentally sustainable. By contrast, ceramic-based membranes are considered more environmental-friendly due to their low-risk recycling and disposal procedures, but the brittleness of these membranes limits their implementation. Here, we report the fabrication of high flexibility SiO2 biocatalytic nanofiber membranes (NFMs) and their previously unreported application in emerging pollutant bioremediation. We used a commercial laccase (EC 1.10.3.2) as a model biocatalyst to evaluate the impact of different strategies to improve the catalytic properties of the NFMs in terms of enzyme load and apparent activity per membrane weight. Enzyme immobilization with the co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) resulted in the best immobilization yield (57.9 ± 0.5 %) and apparent activity of 6.4 ± 1.1 U g−1 membrane. Compared to the free enzyme, the fabricated bio-catalytic membranes maintained 80 % of residual activity after five cycles. In addition, the membranes exhibited > 95 % depletion of the five emerging pollutants diclofenac, mefenamic acid, benzefabrite, bicalutamide, and clarithromycin. The successful fabrication of flexible biocatalytic ceramic membranes holds promise as a new technological platform for sustainable wastewater treatment and brings novel insights into a previously less explored realm of membrane applications.