Immobilization of nano-Cu on ceramic membrane by dopamine assisted flowing synthesis for enhanced catalysis

Abstract

Catalytic membranes containing metal nano-catalysts are effective in removing organic pollutants from wastewater. The relative low catalytic activity of the non-noble metals (such as Cu nanoparticles) presents a challenge for their widespread application. Herein, Cu nanoparticles were in-situ immobilized on ceramic substrate by a dopamine assisted flowing synthesis method to strengthen its catalytic property. Firstly, a precursor solution containing dopamine and Cu2+ was cyclically permeated through the ceramic microfiltration substrate to form a polydopamine coating with chelated Cu2+. Then, Cu nanoparticles were in-situ formed with the aid of NaBH4. FESEM, EDS, XPS and XRD analyses demonstrate the successful formation of the Cu nanoparticles. The obtained membrane depicts good hydrophilicity and permeability (556.51 L m-2h−1 at 0.1 MPa). In the continuous catalytic degradation under cross-flow filtration mode, the membrane achieves 90.84 % reduction of 4-nitrophenol (4-NP) and 92.36 % degradation rate of methyl orange (MO). The large amount of Cu nanoparticles immobilized within the membrane pores (form inner-pore microreactors) enhance the catalytic activity of the membrane, resulting in an apparent reaction rate constant of 38.78 min−1 on the permeation side. The composite membrane has good antifouling and easy-cleaning properties (the flux recovery rate is 84.3 %). In long-term experiments, the catalytic degradation rate of MO remains above 96 % throughout 50 cycles, demonstrating good stability. This study provides a novel strategy for developing catalytic membrane with immobilized non-noble metal nanoparticles, which has potential applications in environmental remediation.