Hydrothermal synthesis of hydrocalumite assisted biopolymeric hybrid composites for efficient Cr(vi) removal from water
This study focused on the hydrothermal synthesis of hydrocalumite (HC) incorporated biopolymer (alginate and chitosan) based hybrid composite materials for the selective removal of chromium. The synthesized hydrocalumite/alginate (HCAlg) and hydrocalumite/chitosan (HCCS) composites were characterized by FTIR, XRD, SEM, EDAX with mapping images and BET analysis. The synthesized HCCS composite possesses enhanced chromium sorption capacity (SC) compared to HCAlg composite, but both the hybrid composites showed a quick chromium sorption rate at 40 min. The depending adsorption parameters, namely equilibrium time, solution pH, competing co-ions, dosage, initial chromium concentration and temperature, were optimized for the maximum Cr(VI) sorption. The obtained equilibrium data was explained using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherms. The thermodynamic result shows that the nature of the Cr(VI) adsorption attributed to the biopolymeric composites is spontaneous and endothermic. The possible Cr(VI) uptake mechanism of the synthesized biocomposites was occurred by electrostatic attraction and ion-exchange. The reusability of the synthesized adsorbents was carried out using NaOH and they can be used upto five cycles. Both the prepared biocomposites showed promising results against chromium contaminated ground water by reducing the chromium concentration below the tolerance limit.