Preparation Of Zero-valent Iron Composite Membrane And Catalytic Reduction Of Organic Pollutants

In this paper,modified PAN flat membranes assembled with polydiallyldimethylammonium chloride(PDADMAC)and poly acrylic acid(PAA)were successfully prepared via layer-by-layer self-assembly technology.(Fe~0-PDADMAC/PAA)n composite catalytic membranes were then prepared via coordination of carboxyl and ferrous ion.The composite membranes were applied to reduce N-nitrosodimethylamine(NDMA)and acid red B(ARB)in aqueous solution.Based on FTIR analysis,the hydrophilicity and charge property of PAN membrane were improved.The content of iron on membranes were 25.7,77.6,114,151.7,171.4 mg·g-1,while the number of layer(n)is 1,3,5,7,9.The SEM results showed that the ZVI particles with sizes of 200nm dispersed on the surface of membrane uniforamly.After reducing reaction,zero-valent iron was converted into Fe3+/Fe2+,which existed in form of Fe2O3 and Fe3O4,according to the analysis of XPS and XRD.In addition,a series of reduction experiments was conducted and the results indicated that the(Fe~0-PDADMAC/PAA)n has excellent reduction capacities towards NDMA and ARB.At a 150 ?g·g-1 initial concentration of NDMA,reaction efficiency of 65.8%was achieved.The reduction rate of ARB could be close to 100%in condition that the initial concentration is 100mg·L-1.It is confirmed that elements such as initial pH,temperature and coexisting ions had significantly influence on the reduction of pollutant.Electron released from Fe~0 was transferred to H+ and formed activated hydrogen.Reducing reaction occurred between activated hydrogen and pollutant.It is showed that,during the reduction,the leak quantities of iron from composite catalytic membrane was less than 0.1 mg g-1.On account of carboxyl groups on the surface of membranes,Fe ions could be remained on the PAN membrane.