Preparation, Characterization and Dye Adsorption/Reuse of Chitosan-Vanadate Films

Chitosan used on dyes adsorption when in film form shows limitations due to its low regeneration capacity. In this work, chitosan films were modified using vanadium ions to improve its regeneration capacity on the dye adsorption. Films were characterized and analyzed by FT-IR, XRD and DSC. Adsorption assays were performed using chitosan-vanadate films (CVF) to remove the Reactive Black 5 dye in aqueous solution. The adsorption was favored by the pH decrease from 8.0 to 4.0. The equilibrium data were best fitted by Langmuir model, with qm of 522 mg g−1 at 298 K. The negative value of ΔH0 (−9.91 kJ mol−1) showed an exothermic operation and the value of ΔS0 was positive (0.0705 kJ mol−1 K−1), suggesting an increase in randomness at the solid/solution interface. The kinetics was represented by pseudo-first order model and around 80 min occurred a reduction in the adsorption rates, due to the mass transfer mechanism. The most appropriate eluent to remove the RB5 from CVF was NH4OH 0.01 kg mol L−1. The CVF used to the dye adsorption were regenerated and reutilized five times, and the adsorption capacity was around 80% of the initial value after the last cycle.