Simultaneously enhancing purification, catalysis and in situ separation in a continuous cross-flow catalytic degradation process of multi-component organic pollutants by a double-layer PVDF composite membrane

Abstract

Organic pollutant degradation of waterbody by membrane catalysis is widely reported due to the low operation cost and high catalytic degradation efficiency. However, it still faces a great challenge to effectively treat the complicated wastewater with coexisting multi-component organic pollutants. Herein, we design and then fabricate a novel double-layer composite membrane to realize the separation of multi-component organic pollutants, selectively catalytic degradation and in situ product separation in a one-step. This double-layer membrane systematically characterized by FTIR, XPS, SEM, AFM and the other techniques, comprises a top semi- interpenetrating polymer network(semi-IPN) layer and a bottom poly(vinylidene fluoride)-Pd catalytic layer. In a continuous cross-flow filtration process, some pollutants such as congo red, direct black 38, direct red 23 and BSA are directly separated by the membrane, while the pollutant p-nitrophenol controllably penetrates through the top semi-IPN layer and then reacts in the catalytic layer; subsequently, the product p-aminophenol is in situ separated and collected. In this process, the pollutant p-nitrophenol is purified by filtration in advance; further, the product is isolated by the top layer and timely dischared out by penetrative flow. Therefore, this process prevents the undesired pollutants and products from interfering the catalytic degradation of the catalytic layer. Thus, degradation reaction can continuously and conveniently proceed, companying with products in situ separation and collection.