Removal performance and mechanism of nano α-Fe2O3/graphene oxide on aqueous Cr(Ⅵ)

Abstract

A nanocomposite α-Fe2O3/graphene oxide (α-Fe2O3/GO) was prepared with a simple hydrothermal method. The as obtained α-Fe2O3/GO was used in removing aqueous Cr(Ⅵ). Batch adsorptions were conducted, the adsorption isotherms, kinetics, thermodynamics and removal mechanism were analyzed. The adsorption of an aqueous solution of Cr(Ⅵ) initial concentration 100 mg L−1 onto α-Fe2O3/GO of a dosage 500 mg L−1 reached equilibrium in 7 min, and the adsorption quantity and adsorption percent were 172.63 mg L−1 and 86.31%, respectively. No obvious performance fluctuations were observed under varying environmental factors such as pH and electrolyte. The fast adsorption kinetics was owing to the morphological feature: thin morphology enabled fast pore diffusion. The high adsorption capacity was owing to the structural feature: mesopores in α-Fe2O3/GO gave high specific surface area and pore volume, where accommodate abundant oxygen containing groups as adsorption sites. The good adaptability to environmental factors (pH, electrolyte) was owing to the strong chemical interactions between α-Fe2O3/GO and Cr(Ⅵ). The removal mechanism included physical adsorption, ion exchange, surface complexation, and reduction. 62.46% of the surface adsorbed Cr(Ⅵ) was reduced to Cr(Ⅲ). The facile preparation and good adsorption performance would make α-Fe2O3/GO a promising adsorbent for Cr(Ⅵ).