Composite membranes based on a selective chitosan-poly(ethylene glycol) hybrid layer: synthesis, characterization, and performance in oil-water purification

A series of poly(ethylene glycol) diglycidyl ether-cross-linked chitosan (chi-PEG hybrid) films were prepared to elucidate their potential as fouling-resistant ultrafiltration (UF) membrane coating layers. Water permeability increased as the poly(ethylene glycol) diglycidyl ether to chitosan ratio in the prepolymerization mixture increased due to increased porosity in the polymer matrix resulting from phase separation during polymerization. Composite membranes for oil-water emulsion filtration were prepared by coating an optimized member of the chi-PEG hybrid family onto a commercial polysulfone ultrafiltration membrane. Scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), and pure water permeance measurements indicated that, depending on the concentration of chitosan in the coating solution, the coating layer thickness could be controlled, so water permeance could be optimized. These composite membranes exhibited water flux values more than 5 times higher than that of uncoated membranes after 1 day of oily water crossflow filtration, indicating that the hydrophilic polymer coating significantly enhanced the fouling resistance of the underlying polysulfone membrane. The organic rejection of the coated membranes was also slightly higher than that of the uncoated polysulfone membranes.