The potential of SAPO-44 zeolite filler in fouling mitigation of polysulfone ultrafiltration membrane

Durable polysulfone (PSI) membrane is less suitable for wastewater treatment as it is susceptible to severe fouling by the natural organic matter. In this work, SAPO-44 zeolite was blended into PSf membranes to mitigate fouling by humic acid. The casting solutions were prepared by blending 5-20 wt.% of SAPO-44 zeolite (average particle size of 138 nm) into a mixture of PSf, 1-methyl-2-pyrrolidinone and 1 wt.% of PVA at 75 degrees C with a stirring speed of 400 rpm. The weight ratio of polymer to solvent was maintained at 1:4.84. Mixed matrix membranes were then prepared using phase inversion method. SAPO-44 zeolite was weakly adhered to the macroporous layer in asymmetric membranes. Growth of the finger-like macrovoid was promoted by blending SAPO-44 zeolite into PSf/PVA membrane. Larger pore size was also induced in P-1 and P-2 samples, causing lower water contact angle on these mixed matrix membranes. Further adding of zeolite filler resulted in smaller finger-like pores as the exchange between solvent and nonsolvent had been delayed in the viscous solution. Membrane pore size and surface energy were slightly enlarged by blending 15 wt.% or 20 wt.% of zeolite. P-3 membrane with 15 wt.% of SAPO-44 exhibited the highest water flux, with nearly 164 % of increment compared to the control membrane. Fouling mitigation could be achieved without much modification of surface energy depending on the fouling mechanisms. Embedded zeolite may reduce the fouling by humic acid initiated from pore blocking. About 80% permeate flux of P-3 membrane was maintained during the filtration of humic acid solution. However, agglomerated filler in P-4 sample with 20 wt.% of SAPO-44 caused slightly lower water permeability and relative flux of fouling test compared to P-3 membrane. (C) 2012 Elsevier B.V. All rights reserved.