RGO/CNF/PANI as an effective adsorbent for the adsorption of uranium from aqueous solution

In this paper, we present a recent study in the adsorption of uranium from an aquatic environment by reduced graphene oxide - Cu0.5Ni0.5Fe2O4 ferrite – polyaniline (RGO/CNF/PANI) composite. Uranium concentration was carried out by batch techniques. The effect of pH, contact time, concentration of equilibrium state and reusability on uranium adsorption capacity have been studied.
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RGO/CNF/PANI as an effective adsorbent for the adsorption of uranium from aqueous solutionVietnam Journal of Science and Technology 56 (1A) (2018) 25-32 RGO/CNF/PANI AS AN EFFECTIVE ADSORBENT FOR THE ADSORPTION OF URANIUM FROM AQUEOUS SOLUTION Tran Quang Dat*, Nguyen Vu Tung, Pham Van Thin, Do Quoc Hung Le Quy Don Technical University, 236 Hoang Quoc Viet Street, Ha Noi * Email: dattqmta@gmail.com Received: 15 August 2017; Accepted for publication: 5 February 2018 ABSTRACT In this paper, we present a recent study in the adsorption of uranium from an aquaticenvironment by reduced graphene oxide - Cu0.5Ni0.5Fe2O4 ferrite – polyaniline(RGO/CNF/PANI) composite. Uranium concentration was carried out by batch techniques. Theeffect of pH, contact time, concentration of equilibrium state and reusability on uraniumadsorption capacity have been studied. The adsorption process was accomplished within 240min and could be well described by the pseudo-second-order model. The adsorption isothermagrees well with the Langmuir model, having a maximum adsorption capacity of 2000 mg/g, atpH = 5 and 25 oC. The RGO/CNF/PANI materials could be a promising absorbent for removingU (VI) in aqueous solution because of their high adsorption capacity and convenient magneticseparation.Keywords: Cu0.5Ni0.5Fe2O4, polyaniline, reduced graphene oxide, uranium, adsorption. 1. INTRODUCTION With fast improvement of atomic technologies, worries about wastewater treatment haveprompted an incredible number of examinations to remove uranium squander from water. Theradioactivity and toxicity of uranium present serious hazards to human beings [1]. There aredifferent techniques to treat uranium from watery solutions, for example chemical precipitation,layer dialysis, dissolvable extraction, buoyancy and adsorption [2]. In those techniques,adsorption is presumably the most well-known technique. Advancement of adsorbents with highadsorption capacity, quick adsorption and simple detachment has gotten impressive enthusiasmfor late years [3, 4]. The magnetic-based nanomaterials are superior adsorbent because it could be easilyseparated from wastewater [3]. Graphene oxide (GO) -polyaniline(PANI) composites areappealing materials with high uranium adsorption [5]. But the GO-PANI composites are hard toisolate aqueous solution from after the adsorption process, which may increase the cost ofindustrial application. Therefore, the composite material which consists of magneticnanoparticles, GO and PANI, has promised an effective adsorbent [6]. Tran QuangDat, Nguyen Vu Tung, Pham Van Thin, Do Quoc Hung In our previous reports, reduced graphene oxide - Cu0.5Ni0.5Fe2O4 ferrite – polyaniline(RGO/CNF/PANI) composite have been prepared by a three-step method [7]. The purpose ofthis work is to investigate the feasibility of adsorption of uranium (VI) by this material. Theuranium (VI) adsorption was analyzed as functions of pH, contact time, concentrations andreusability. 2. EXPERIMENTAL Analytical grade chemicals were used. Sodium hydroxide (NaOH, 99 %), nitric acid(HNO3, 65 %) and hydrochloric acid (HCl, 37 %) and uranyl nitrate hexahydrate(UO2(NO3)2.6H2O, 99 %) were supplied by Sigma-Aldrich company. A batch technique was carried out to study the adsorption of U (VI) from aqueous solutionsby RGO/CNF/PANI. All aqueous solutions using in adsorption experiments were prepared bydissolving UO2(NO3)2∙6H2O in deionized water. All the adsorption experiments were performedat 25 oC and 20 mg of adsorbent. After the adsorption reached the equilibrium, the adsorbent wasisolated by a magnet. It took a few minutes to separate this suspension from solutions. Then, thesamples were filtered and the uranium concentration of the effluent was measured by inductivelycoupled plasma mass spectrometry (ICP-MS, Agilent 7500). The effect of pH on adsorption wasstudied using a 400 mL (50 mg/L uranium) solution, a contact time of 240 min. The pH valuesranging from 2 to 10 were adjusted by adding 0.1 mol/L NaOH or 0.1 mol/L HNO3 solutions.The effect of contact time on adsorption capacity was studied at Vsolution = 400 mL, 50 mg/Luranium solution and pH = 5. The contact time was varied from 15 min to 360 min. Inadsorption equilibrium isotherm studies, the initial concentrations of uranium were varied andthe other parameters were kept constant (Vsolution = 400 mL, contact time = 240 min and pH = 5). The amount of uranium adsorbed per unit mass of the adsorbent was calculated accordingto the following equation: Co Ce Qe V (1) mwhere Qe (mg/g) is the adsorption capacity, Co and Ce (mg/L) are the concentrations of theuranium at initial and equilibrium states, respectively, m is the weight of sorbent (g), and V is thevolume of the solution (L). The regeneration–reuse studies were performed in six cycles. In each cycle, 20 mgadsorbent was mixed in 400 mL uranyl solution (50 mg/L). Adsorption of U (VI) was carried outat pH = 5, contact time = 240 min and 25 oC. After adsorption experiment, derived sample ofU(VI) laden RGO-CNF-PANI composites were mixed with 0.1 mol/L HCl for 2 h at 25 oC. Thecomposites were separated by a magnet.The recovered composite materials were washedthoroughly a few times with distilled water and dried at 50 oC. The adsorption efficiency in eachcycle was calculated from the amount of uranium adsorbed on the adsorbents and the initialamount of uranium. ...