Characterization of chemically modified chitosan microspheres as adsorbents using standard proteins (bovine serum albumin and lysozyme)

Chitosan microspheres with a mean size of 140 119 pm were produced by the spray and coagulation methods. The microspheres were chemically modified using the following routes: a) crosslinking with glutaraldehyde b) crosslinking with epychlorohydrin and c) acetylation. For investigation of their ability as adsorbents, the following standard proteins were chosen as adsorbates: bovine serum albumin - BSA (pl = 4.8 and MW = 66 kDa) and lysozyme (pI = II and MW = 14 kDa). The adsorption experiments were performed using a static method. The adsorption media and equilibrium concentration of adsorbates were varied in the ranges of pH 4-11 and 0.07-0.70 mg.ml(-1), respectively. The maximum adsorption capacities (q(m)) and the constant of the Langmuir model (K-s) were shown to be dependent on charge interactions and on the kind of treatment performed on chitosan rnicrospheres. The satisfactory fit of a kinetic model to the experimental data shows that the step that controls the adsorption kinetics is probably the initial adsorbate transport.