Preparation of SCOF/UiO-66-NH2 immobilized laccase biocatalytic membrane for micropollutants removal from water

Abstract

The concentration of micropollutants (MPs) in water is low, but they are highly harmful and difficult to remove. Biocatalytic membrane combines membrane separation and enzyme catalysis thus being efficient. Herein, a sulfonated covalent organic framework (SCOF) was grown in situ on the surface of a hydrolyzed polyacrylonitrile (HPAN) membrane coated with a polydopamine (PDA) layer to provide a defect-free substrate layer for the pressure-assisted self-assembly of rigid UiO-66-NH₂ nanoparticles and organic laccase with electrostatic attraction. In the obtained multilayer loose biocatalytic membrane, UiO-66-NH₂ nanoparticles can provide trans-membrane mass transfer channels for water molecules and intercept pollutants, and laccase can degrade MPs and eliminate defects among UiO-66-NH₂ nanoparticles. By optimizing the membrane preparation conditions, the biocatalytic membrane has a bisphenol A (BPA) removal rate of 96.9 %. The removal rate of dyes can reach more than 98 % with a pure water permeance of 211.3 LMH/bar, and the generally <20 % salt removal efficiency endows the membrane with good dye/salt separation ability. At the same time, the membrane has BPA removal rate of over 80 % under pH of 4 ∼ 11 and feed BPA concentration of 4–100 mg/L, respectively. The membrane initial activity can maintain more than 90 % after 10 days of storage in aqueous solution. After 7 times of reuse, the removal rate of BPA was still more than 60 %. Overall, this study opens up a convenient avenue for the facial fabrication of multilayer biocatalytic membranes for efficient MPs removal.