A novel hydrogel composite of chitosan-phytic acid complex with PAAm: Characterization and adsorptive properties for UOand methylene blue.

The composite of a polyelectrolyte combination of chitosan and phytic acid (CsPa) and its entrapped form in polyacrylamide (PAAmCsPa) were synthesized. The composites were characterized by a number of methods including ATR-FTIR, SEM-EDX, XRD and XPS. The adsorptive properties of CsPa and PAAmCsPa were analyzed and modelled for UO and methylene blue (MB). The results showed that the composites exhibited physico-chemical properties that were both inherited from the components as well as unique to them. The isotherms of UO and MB were L-type Giles isotherms. The adsorption kinetics followed the pseudo-second-order model, in contrast to the Langmuir model, which predicts first-order kinetics for both species. According to the Weber-Morris model, the nature of the adsorption process was ion exchange and/or complex formation for both composites and ions. The thermodynamics showed that the adsorption process was endothermic (ΔH > 0), with increasing entropy (ΔS > 0) and spontaneous (ΔG < 0). The reusability tests of the composites for UO adsorption showed that the composites were substantially reusable for 6 cycles. The composites were selective for UO over MB ions, and UO adsorption increased significantly when MB adsorbed composites were used. Reproducible measurements demonstrating the storability of the composites were obtained over a period of approximately one year.