Enhanced arsenic removal by graphene oxide chitosan composites through FeOx decoration: Influences and mechanism

Iron decoration has been recognized as one of the most important paths to enhance contaminant adsorption by carbon-based composites. In this study, varying amounts of Fe (II) are used for the modification of graphene oxide chitosan (GOCS) materials to assess the impact of iron oxide (FeOx) morphology on the composites and their efficiency in arsenic (As) removal. Results show that incorporating 0.08 mol Fe(II) into GOCS yields better As removal performance, leading to a remarkable enhancement by 5 times for As(V) and 6 times for As(III). The iron minerals in the material consist of goethite (FeO(OH)) and magnetite (Fe₃O₄), with FeO(OH) playing a predominant role in As removal through the complexation and electrostatic attraction of -OH and Fe - O groups. The adsorption capacity for As (Q_e) decreases with the increasing pH and the mass and volume ratio (m/v) but increases with the increasing initial concentration (C₀). Besides, the presence of SO₄^2- and HPO₄^2- can significantly reduce As removal by the FeOx-modified GOCS. Under the conditions of pH = 3, m/v = 1.0 g/L, and C₀ = 10 mg/L, a maximum Q_e value reaches 61.94 mg/g. The adsorption is well-fitted to a pseudo-second-order kinetic model and is an endothermic, spontaneous, and monolayer adsorption process.