Removal of vanadium (IV) from water solution by sulfated Katira gum-cl-poly (acrylic acid) hydrogel

Abstract A novel, highly anionic hydrogel, sulfated katira gum- crosslinked -poly(acrylic acid) (SKG- cl -PAA) was prepared by sulfation of katira gum- crosslinked -poly(acrylic acid) (KG- cl -PAA) hydrogel using chlorosulfonic acid (ClSO 3 H) in presence of anhydrous pyridine and formamide. Both the hydrogels KG- cl -PAA and SKG- cl -PAA were characterized by FTIR, XRD, and SEM studies. Swelling characteristics the hydrogels were studied and maximum equilibrium swelling ratio (ESR) was found to be 2376 for the SKG- cl -PAA and 2241 for KG- cl -PAA at pH 8.5 and at 70 °C. The hydrogels were used for the adsorption of V (IV) ions from aqueous solution. Adsorption dynamics, kinetics and isotherms for adsorption were also evaluated. Selectivity of the adsorption of V(IV) ion with other competitive metal ions are evaluated. Equilibrium adsorption data were well fitted with the Langmuir isotherm model and maximum monolayer adsorption capacity was found to be 500 mg g −1 for SKG- cl -PAA and 454 mg g −1 for KG- cl -PAA. Kinetic data were well explained by pseudo second order kinetic model. The negative value of ΔG 0 confirmed that adsorption of V (IV) ions onto the SKG- cl -PAA was spontaneous and favourable. The positive value of ΔH 0 indicated that the adsorption of V (IV) ion onto SKG- cl -PAA is endothermic in nature. Electrostatic attractions are mainly responsible for the adsorption.