DEVELOPMENT OF A NANO-ADSORBENT BASED FILTER FOR REMOVAL OF HEXAVALENT CHROMIUM FROM WATER IN A CONTINUOUS FLOW REACTOR

Abstract

This work aimed at the development of a novel GO-MoS 2 composite-based adsorbent as an alternate filter medium for the removal of toxic hexavalent chromium (Cr(VI)) from an aqueous solution in an up-flow fixed-bed column. The GO-MoS 2 composites were immobilized over silane-functionalized sand. The synthesized nanocomposites were validated through FTIR, XRD, SEM, and BET. Subsequently, changes in breakthrough, saturation time, adsorption capacity, and Cr(VI) removal percentage were evaluated for various column operating conditions, such as GO-MoS 2 coating percentages, bed heights, inlet metal concentrations, and flow rates. Results revealed that a maximum uptake capacity of 556 mg·g -1 was obtained for 0.05% GO-MoS 2 -coated sand, while a maximum removal efficiency of 56% was attained for 0.1% GO-MoS 2 -coated sand. The adsorption dynamics were modeled using nonlinear Thomas, Yoon-Nelson, and Adams-Bohart models, which revealed that Thomas and Yoon-Nelson provided the best data fitting (R 2 = 0.9988). Thomas model also predicted the adsorption capacities closer to experimental ones. The Bed Depth Service Time model was also used to scale up the adsorption process for higher throughputs. Moreover, the Modified Mass Transfer Factor model suggested that mass transfer of Cr(VI) from bulk solution to the adsorption site on the surface of adsorbent is dependent on porous diffusion rate at the early breakthroughs. Furthermore, after three regeneration cycles, GO- MoS 2 -coated sand retained more than 50% regeneration efficiency and a comparatively high adsorption capacity. Current study indicates potential of novel GO-MoS 2 -coated sand as an adsorbent for treatment of heavy metals from water.

This work aimed at the development of a novel GO-MoS 2 composite-based adsorbent as an alternate filter medium for the removal of toxic hexavalent chromium (Cr(VI)) from an aqueous solution in an up-flow fixed-bed column. The GO-MoS 2 composites were immobilized over silane-functionalized sand. The synthesized nanocomposites were validated through FTIR, XRD, SEM, and BET. Subsequently, changes in breakthrough, saturation time, adsorption capacity, and Cr(VI) removal percentage were evaluated for various column operating conditions, such as GO-MoS 2 coating percentages, bed heights, inlet metal concentrations, and flow rates. Results revealed that a maximum uptake capacity of 556 mg·g -1 was obtained for 0.05% GO-MoS 2 -coated sand, while a maximum removal efficiency of 56% was attained for 0.1% GO-MoS 2 -coated sand. The adsorption dynamics were modeled using nonlinear Thomas, Yoon-Nelson, and Adams-Bohart models, which revealed that Thomas and Yoon-Nelson provided the best data fitting (R 2 = 0.9988). Thomas model also predicted the adsorption capacities closer to experimental ones. The Bed Depth Service Time model was also used to scale up the adsorption process for higher throughputs. Moreover, the Modified Mass Transfer Factor model suggested that mass transfer of Cr(VI) from bulk solution to the adsorption site on the surface of adsorbent is dependent on porous diffusion rate at the early breakthroughs. Furthermore, after three regeneration cycles, GO- MoS 2 -coated sand retained more than 50% regeneration efficiency and a comparatively high adsorption capacity. Current study indicates potential of novel GO-MoS 2 -coated sand as an adsorbent for treatment of heavy metals from water.