Electrostatic multilayers of chitosan (CHI) with sodium alginate (SA) and poly (styrene sulfonate) sodium salt (PSS) were alternatively coated on electrospun cellulose acetate (CA) fiber mat. Morphologies of the composite membranes were characterized by scanning electron microscope (SEM). The morphology of the CHI/SA coated membrane was denser than the CHI/PSS coated membrane. Functional groups of the top layers were quite clear with carboxyl (1,596 and 1,411 cm-1) and sulfonic (1,007 and 1,035 cm-1) for SA and PSS, respectively. Amino groups of CHI were only presented in slight quantity. X-ray photoelectron spectroscopy (XPS) confirmed the deposition of amino groups from CHI on multilayer membrane surface. These membranes were characterized for its pure water permeability. It was found that the flux of water decreased with increasing the number of bilayers. The pure water flux was in the range of 60 L m¯² h¯¹ for 15 bilayers and 40 L m¯² h¯¹ for 25 bilayers. The sodium chloride (NaCl) solution flux was lower than the pure water flux due to the effect of osmotic pressure, and this flux decreased with increasing NaCl concentration. The rejection of NaCl increased substantially with the number of bilayers of the polyelectrolytes multilayers. The level of NaCl rejection from this work was in the range of 15 % for 25 bilayers and 6 % for 15 bilayers.

Thesis (M.Eng.)--Chulalongkorn University, 2007