Polymers are considered to be among the important materials in membrane technology, given their good flexibility, toughness, and separation capacity. Among these biopolymers, chitosan has been investigated as a very promising material (1). Chitosan is primarily composed of β (1→4) linked 2-amino-2-deoxy-D-glucopyranose units. Several methods have been used to modify natural chitosan either physically of chemically in order to improve the adsorption capacity. The crosslinking with glutaraldehyde or epichlorohydrin can be cited as examples of chemical modifications promoted on chitosan (2, 3). Chitosan can be molded in several shapes, membranes, microspheres; gel beads and films, and it is able to provide a ratio: surface area/mass that maximizes the adsorption capacity and minimizes the hydrodynamic limitation effect, such as column clogging and friction loss. The required characteristic for an adsorptive membrane are large specific surface area, high density of reactive functional groups and good mechanical and chemical resistance (4).

⁹⁹Tc produced in nuclear reactors originates from the fission of ²³⁵U and ²³⁹Pu and it can be released to environment from nuclear power plants and reprocessing facilities, nuclear weapons test, nuclear accidents and underground depositories as well. One of ⁹⁹Tc species, pertechnetate ion ⁹⁹TcO₄^- under oxidizing conditions, is soluble and mobile in environment. On the other hand, the insoluble species of ⁹⁹Tc in a lower oxidation state are present under aerobic and anaerobic conditions (5, 6).

This work was aimed to study swelling and adsorptive properties of chitosan membranes. The influence of contact time on the sorption of pertechnetate anions was studied. The percentage of technetium sorption on MMWChi-TiO₂ membrane of area 1 cm² was > 15 % and the sorption for this membrane of areas 3 cm² and 5 cm² was ≈30 %. The maximum percentage of technetium sorption for MMWChi-Ag membrane of area 5 cm² and MMWChi-TEOS IPN+halloysite membrane of area 5 cm² was ≈45 % and ≈48 %, respectively.