Cellulose and Chitosan Composite Membranes for Protein and Salt Filtration

Cellulose membrane (SE) was prepared by culturing Acetobacter xylinum in a media with sucrose as a carbon source and was used as a supporting membrane in this study. Pore size of the supporting membrane was studied by means of molecular weight cut off (MWCO) and SEM micrographs. For making cellulose/chitosan composite membrane SE/CH, chitosan solution was used as a coating polymer and applied by a casting method. This resulted in a smaller hydraulic permeability coefficient (Lp) from 6.7 x 10-11 m3 N-1 s-1 in membrane SE to 1.94 x 10-12 m3 N-1 s_1 in the composite membrane SE/CH. Using PEG of several molecular weights as feed solution, the MWCO of the SE membrane was 200 kDa while that of the SE/CH membrane was 6 kDa. The former rejected 1 g L_1 BSA by 80%. With pH between 3 and 8, the composite membrane SE/CH rejected NaCl and NaHC03 by 50%, independent of the pH level. However, when using a divalent salt solution of MgS04 the rejection was increased up to 85%, with an optimum at pH 6-7 and a permeate flux of 5.0 L m-2 h-1 at pressures of 0.5 MPa.