Sustainable removal of Cr(VI) using graphene oxide-zinc oxide nanohybrid: Adsorption kinetics, isotherms and thermodynamics

Singh, S and Anil, AG and Khasnabis, S and Kumar, V and Nath, B and Adiga, V and Kumar Naik, TSS and Subramanian, S and Kumar, V and Singh, J and Ramamurthy, PC (2022) Sustainable removal of Cr(VI) using graphene oxide-zinc oxide nanohybrid: Adsorption kinetics, isotherms and thermodynamics. In: Environmental Research, 203 .

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Abstract

Metal-based adsorbents are limited for hexavalent chromium Cr(VI) adsorption from aqueous solutions because of their low adsorption capacities and slow adsorption kinetics. In the present study, decorated zinc oxide (ZnO) nanoparticles (NPs) on graphene oxide (GO) nanoparticles were synthesized via the solvothermal process. The deposition of ZnO NPs on graphene oxide for the nanohybrid (ZnO-GO) improves Cr(VI) mobility in the nanocomposite or nanohybrid, thereby improving the Cr(VI) adsorption kinetics and removal capacity. Surface deposition of ZnO on graphene oxide was characterized through Fourie Transform Infra-red (FTIR), UV�Visible, X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), and Brunauer�Emmett�Teller (BET) techniques. These characterizations suggest the formation of ZnO-GO nanocomposite m2/g and pore volume of 0.058 cm2/g. Batch adsorption analysis was carried to evaluate the influence of operational parameters, equilibrium isotherm, adsorption kinetics and thermodynamics. The removal efficiency of Cr(VI) increases with increasing time and adsorbent dosage. FTIR, FESEM and BET analysis before and after the adsorption studies suggest the obvious changes in the surface functionalization and morphology of the ZnO-GO nanocomposites. The removal efficiency increases from high-acidic to neutral pH and continues to decrease under alkaline conditions as well. Mathematical modeling validates that the adsorption follows Langmuir isotherm and fits well with the pseudo 2nd order kinetics (Type 5) model, indicating a homogeneous adsorption process. The thermodynamics study reveals that Cr(VI) adsorption on ZnO-GO is spontaneous, endothermic, and entropy-driven. A negative value of Gibb's Free Energy represents the thermodynamic spontaneity and feasibility of the sorption process. To the best of our knowledge, this is the first study of Cr(VI) removal from aqueous solution using this hybrid nanocomposite at near-neutral pH. The synthesized nanocomposites prove to be excellent candidates for Cr(VI) removal from water bodies and natural wastewater systems. © 2021 Elsevier Inc.

Item Type:	Journal Article
Publication:	Environmental Research
Publisher:	Academic Press Inc.
Additional Information:	The copyright for this article belongs to Academic Press Inc.
Keywords:	adsorption; alkalinity; aqueous solution; chromium; isotherm; nanoparticle; oxide group; parameterization; pollutant removal; reaction kinetics
Department/Centre:	Division of Interdisciplinary Sciences > Interdisciplinary Centre for Energy Research Division of Interdisciplinary Sciences > Interdisciplinary Centre for Water Research Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	01 Dec 2021 14:43
Last Modified:	01 Dec 2021 14:43
URI:	http://eprints.iisc.ac.in/id/eprint/70050

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