Swelling of chitosan and copolymers
The swelling properties of chitosan and the copolymers in waterwere determined gravimetrically. A clean, lidless, pre-weighed vialwas obtained and 40–50 ± 1 mg of adsorbent was added to thesample vial. 6.00 mL of deionized water was added to each vialand the heterogeneous solid/solution system was shaken for 48 hat 160 rpm. The materials were then removed and using a pre-weighed filter paper, the hydrated copolymers were isolated andtamped dry to remove excess water prior to obtaining final sam-ple weights. The filter paper and the vial were air dried for 12 h.Both the filter paper with the copolymer and the vial containingresidual adsorbent was weighed after constant weight (∼12 h). The difference between the mass of the hydrated copolymer and thedried copolymer is related to the degree of swelling. The relativeamount of swelling (S; %) is given by Eq. (2), where the mass of thehydrated polymer (ms) and the mass of the dry polymer (md) aredetermined directly.