Polymeric Ultrafiltration Membrane with in Situ Formed Nano-Silver on the Inner Pores for Simultaneous Separation and Catalysis

Polymeric ultrafiltration membrane with in situ formed nano-silver on the inner pores for simultaneous separation and catalysis

Xiaofeng Fang ^a,b, Dapeng Wang ^a, Jiansheng Li,^a*, Zhipeng Liao ^a, Qin Li ^a, Shunlong Pan ^a, Lianjun Wang ^a, Dionysios D. Dionysiou ^b*

^a Key Laboratory of Jiangsu Province for Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

^b Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH, 45221-0071, USA

Abstract: Novel catalytic-ultrafiltration membranes (CUMs) were designed via blending coordination complexes in UF membrane matrix to in situ form Ag nanoparticles on inner pores and surface of polymeric membrane. Specially, the natural polyphenol tannic acid (TA) and Fe^III were chosen as the organic ligand and the inorganic cross-linker and blended in the polyethersulfone (PES) UF membrane via phase inversion method. The catechol moiety in TA could reduce metal ions without adding any external reducing agent, so that metal nanoparticles could be firmly anchored adsorbed on the surface. The results indicated that the introduction of TA-Fe complex and Ag nanoparticles on the walls of internal pores endowed the composite membrane with enhanced UF performance and remarkable catalytic performance for 4-nitrophenol (4-NP). The obtained CUMs exhibited maintainable pure water flux (239.8 L/m² h), ascendant bovine serum albumin (BSA) rejection (96.1%) and excellent humic acid (HA) rejection (87.3%). The catalytic performance was conducted with three paralleled experiments, i.e, dynamic catalysis, static catalysis and membrane-free catalysis. Compare to static catalysis and membrane-free catalysis, dynamic catalysis indicated significant catalytic performance with filtering aqueous solution containing humic acid and 4-NP through CUMs. This is due to the eradication of the negative effect of HA on the reduction of 4-NP in dynamic catalysis mode. In this case, the HA can be rejected by membrane and shy away from the Ag NPs on the inner pores. The conversion rate of 4-NP was 98% for the catalysis of mixture solution (4-NP and HA) in dynamic mode. Furthermore, CUMs could be reused with high stability as they kept a high level than 95% for filtering the mixture solution over seven cycles. The results therefore demonstrate the CUMs have good potential for continuous reduction of 4-NP and as well as the macromolecular pollutants separation.