Remediation of Cr(VI) using a radiation functionalized green adsorbent: Adsorption modelling, mechanistic insights and prototype water purifier demonstration

Abstract

The work reports remediation of hexavalent Chromium (Cr(VI)) in water using a radiation functionalized cellulose based green adsorbent, fabricated via gamma radiation assisted Mutual Irradiation Grafting Process (MIGP), wherein poly(2-Trimethylammoniumethyl methacrylate chloride) (PTMAEMC) was grafted onto Woven Cotton Cellulose Fabric (WCCF). The grafted adsorbent “ChromClear” efficiently sequestered Cr(VI) from water and demonstrated a maximum adsorbent capacity of ∼55 mg.g−1, successfully curtailing Cr(VI) concentrations to <20 μg.L−1. Characterization of samples was performed using 13C NMR, XPS, SEM-EDS, FTIR, TGA, and BET analysis. The equilibrium adsorption, kinetic, and breakthrough curve data were analysed using various theoretical models to infer the adsorption mechanism and extract important process parameters. Artificial Neural Network (ANN) modelling was used to predict adsorption capacity and % Cr(VI) removal in continuous flow column mode under different operational conditions, with a high degree of agreement (R2 > 0.99) between experimental and modelled data. Density Functional Theory (DFT) calculations established the interaction between CrO42− and PTMAEMC groups of ChromClear to be occurring in a 1:2 ratio. ChromClear could be regenerated for over five recycled iterations with >88 % retention in adsorption capacity. Concept based prototype water purification systems were also developed for pump as well as gravity driven continuous flow operations, and successfully demonstrated for remediation of Cr(VI) contaminated ground water samples. The efficacy and simplicity of the process provides ample scope for further upscaling and deployment for community level water treatment applications, with a special emphasis on compliance with drinking water norms in affected areas.