Removal of Cr(VI) from aqueous media using magnetic Co-reduced graphene oxide
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pISSN: 0256-1115 eISSN: 1975-7220
INVITED REVIEW PAPER
INVITED REVIEW PAPER
Removal of Cr(VI) from aqueous media using magnetic Co-reduced graphene oxide Nduduzo Nkanyiso Malinga† and Alan Lawrence Leigh Jarvis Discipline of Electrical, Electronic and Computer Engineering, University of KwaZulu-Natal, Howard College Campus, South Africa (Received 21 January 2020 • Revised 26 May 2020 • Accepted 14 June 2020) AbstractThe adsorption of Cr(VI) from an aqueous medium using magnetically functionalized cobalt nanoparticles-reduced graphene oxide (Co-rGO) was studied. Co-rGO was synthesized using the co-precipitation method. Graphene oxide and cobalt acetylacetonate were reduced together in water using sodium borohydride as a reducing agent. CorGO was used as the adsorbent material for the removal of dichromate ions in water. The prepared Co-rGO was characterized using powder X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Brunauer-EmmettTeller (BET) surface area analysis. Selected area electron diffraction was used to determine that the cobalt nanoparticles were on the surface of the reduced graphene oxide. The effect of the mass of the adsorbent material (Co-rGO), the concentration and pH of the Cr(VI) containing solution and the time of contact between the adsorbent and the Cr(VI) on the adsorption efficiency were investigated. It was found that the optimum adsorbent mass for the efficient removal of Cr(VI) from a fixed concentration of Cr(VI) of 100 mg L1 was 0.015 g, the optimum pH of the solution was 8, and the optimum contact time was 90 minutes. The experimental data obtained were fitted to the Langmuir, Freundlich, and Lui isotherms to obtain the characteristic parameters of each model. The experimental data fitted well to the Freundlich isotherm. The thermodynamic data was used to evaluate the nature of the adsorption. It was determined that the sorption process was physisorption. The kinetics of the adsorption process followed pseudo-second-order kinetic model. Keywords: Magnetic Properties, Adsorption, Magnetic Nanoparticles, Cr(VI), Cobalt Nanoparticles
ority toxin. Thus, there is a need for an economical method of remediation to remove Cr(VI) from fresh water. Most reported methods of remediation of Cr(VI) include ion exchange, coagulation, precipitation, adsorption and membrane filtration [7-13]. Adsorption has been categorized as an economical method when compared to the other methods. One of the contenders for adsorption is activated carbon, which has some problems such as fouling. The discovery of carbon nanotubes and graphene has allowed the expansion of the adsorption of Cr(VI) technology. These materials have been reported to have high surface area, which in turn has a large number active for the adsorption of Cr(VI). Graphene is obtained from the reduction of graphene oxide, which is a single graphite oxide sheet [14]. Graphene oxide contains oxygenated functional groups such as hydroxyl, epoxide, carbonyl and carboxyl groups. Graphene has generally slow adsorption kinetics
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