Page 62 - חוברת תזות הנדסה ירוקה 2023

TGA thermograms of different polysaccharides, before and after the UO22+ adsorption, showed similar typical decomposition stages, in which the curves of all the polysaccharides, after adsorption, showed higher thermal stability than those of the pure polysaccharides. Additionally, it was found that the residue obtained after adsorption was larger than before the adsorption, suggesting the presence of an inorganic substance in the residue, most likely uranyl.
Furthermore, rheological measurements showed that the presence of electrostatic repulsion, due to the adsorption of the uranyl and the altered distances between the polysaccharide chains lowered both the G’ and G’’ modules. This study also tested the adsorption yields of uranyl ions on hydrogel beads prepared from I, K, and A polysaccharides. Beads were prepared using various salts; the adsorption reached saturation after about 30 min. The highest adsorption yields were obtained from hydrogels of A prepared with CaCl2 )83.45%(. The I hydrogels had the highest adsorption yield when prepared with FeCl3 )70.59%(, while K hydrogels showed maximum adsorption when prepared with FeCl2 )50.98%(.
Analyses of the kinetic experiments found that the kinetic model suitable for hydrogel systems is a pseudo-second order model, strengthening the hypothesis that there is a reaction between the functional polysaccharide groups and the uranyl. We found that adsorption yield increased )91%( with the decrease in salt concentration to 0.2M.
Keywords: Carrageenan, UO22+, Polysaccharides, Adsorption.
Book Of Abstracts | Class 2022
62