Graphene oxide-MnO2-goethite microsphere impregnated alginate: A novel hybrid nanosorbent for As (III) and As (V) removal from groundwater

Synthesis, characterization and application of Graphene oxide-MnO2-goethite nanocomposite impregnated alginate hydrogel beads for As (III) and As (V) removal. [Display omitted] •Core-shell microspheres of GO-MnO2-Goethite (GO-MnO2-Goe) was synthesised.•GO-MnO2-Goe was impregnated into alginate polymeric matrix to form hybrid beads.•Developed hydrogel beads were used for efficient removal of both As(III) & As(V).•Sorption capacities were 27.53 and 34.17 mg g−1 respectively for As(III) & As(V).•In-situ transformation of As(III) to (V) was explained with XPS analysis. This study presents a simple method for facile synthesis of core-shell microspheres of Graphene oxide-MnO2-Goethite (GO-MnO2-Goe). Synthesised GO was used as the core material for treatment with the pre-decided molar ratio mixture of Fe and Mn to form a MnO2-Goe shell over the GO surface optimising various parameters. Subsequently the GO-MnO2-Goe nanoparticles were impregnated into alginate polymer to form GO-MnO2-Goethite impregnated alginate hydrogel beads (GO-MnO2-Goe-Ca-Alg) using displacement reaction. The product was characterized by XRD, FTIR, BET, SEM-EDS and zeta potential measurement. The GO-MnO2-Goe-Ca-Alg hybrid nanosorbent was used to efficiently remove both arsenic (III) and arsenic (V) from groundwater (80–96 % for 0.1−100 μg mL−1 concentration range) at pH 4–6. Uptake processes for both As (III) and As (V) followed Langmuir isotherm model with maximum sorption capacity evaluated as 27.53 and 34.17 mg g-1 respectively for As (III) and As (V). The reaction kinetics, thermodynamic parameters, interparticle diffusion model were studied. Mechanism of uptake was suggested based on fraction diagram of As (III) and As (V) species along with zeta potential of GO-MnO2-Goe at various pH. The in-situ transformation of As (III) to As (V) before its sorption was investigated and explained with the help of XPS analysis.