Polymeric membrane with nanohybrids of Cu nanocomposites and metalloporphyrin-based nanosheets for enzyme-like catalytic degradation of Congo Red

Metalloporphyrin-based nanozymes are effective peroxidase-like catalysts for dye degradation; however, their reusability is a challenge due to the nanoscale dimensions. Membrane technology has the advantages of high efficiency, low energy consumption, and easy operation. Here, we integrate poly (vinylidene fluoride) (PVDF) membrane with nanozyme for effective decolorization of Congo Red (CR). A nanozyme (Cu@Cu-FeTCPP) is prepared by growth of copper hydroxide-copper oxide (Cu(OH)2-CuO) nanocomposites onto the metal organic framework (MOF) nanosheet consisting of tetrakis-(4-carboxyphenyl)-porphyrin iron ligands and cupric ion nodes. The functional membrane is achieved by loading Cu@Cu-FeTCPP nanozyme on the PVDF membrane surface (Cu@Cu-FeTCPP/PVDF). The as-prepared membrane shows catalytic activity for the degradation of CR. Under flow through conditions, the catalytic degradation in tangential flow plays a major role in overall decolorization of CR, far exceeding the contribution of adsorption. The membrane can rapidly catalyze the dye degradation even at different operating pressures (0.1–0.7 kPa) and feed solutions with higher CR concentrations (eg. 60 mg·L-1). Compared with the static batch catalysis and the free nanozyme catalysis, the membrane exhibits higher decolorization efficiency and outstanding reusability in the continuous flow process owing to the promoted mass transfer. After 40 min of continuous flow reaction in a feed solution containing CR (40 mg·L-1) and H2O2 (50 mM), the decolorization efficiency approaches 90% and remains above 85% after five catalytic cycles. The membrane with enzyme-mimicking ability has application prospect in wastewater treatment.