Highly efficient removal of As(III) from aqueous solutions using goethite/graphene oxide/chitosan nanocomposite.

A goethite/graphene oxide/chitosan (α-FeO(OH)/GO/CS) nanocomposite adsorbent was prepared and firstly used to remove As(III) from aqueous solution. The composite was characterized by FTIR, XPS, XRD, and EDS techniques. Batch experiments were conducted to investigate the effects of several factors (initial concentration, pH, m/v, contact time, co-existing ions, and temperature) on As(III) adsorption and to evaluate adsorption kinetic, equilibrium isotherm, and thermodynamics. Results showed that As(III) adsorption increased with the increasing initial concentration, contact time, and temperature, but decreased with the increasing m/v and co-existing ions concentrations of SO42-, PO43- and Fe3+. As(III) adsorption remained high at a wide pH range of 3-10. The adsorption was well fitted to a pseudo-second-order kinetic model and was endothermic and spontaneous. The best fit of As(III) adsorption with the Freundlich and Sips models indicated that it was monolayer adsorption, and the maximum adsorption capacity was 289.42 mg/g. As(III) removal was related to -NHCO-, CO, OH, and FeO groups, but the complexation between As(III) ions and hydroxyl iron oxide was the major contributor. After the fifth desorption, the removal efficiency was still as high as 79.6%, indicating excellent reusability. Thus, this composite had great potential for removing As(III) from aqueous solutions.