α-Fe2O3 nanowires deposited diatomite: highly efficient absorbents for the removal of arsenic

Abstract

α-Fe₂O₃ nanowires deposited diatomite was prepared using a precipitation–deposition method with FeCl₃ as metal source and (NH₂)₂CO aqueous solution as precipitating agent. Physicochemical properties of the samples were characterized by means of numerous techniques, and their efficiency for the removal of As(III) and As(V) was determined. It is found that the solution pH value, reaction temperature, reaction time, and FeCl₃ concentration had effects on the α-Fe₂O₃ amount loaded on the diatomite. Parameters, such as adsorbent amount, adsorption time, adsorption temperature, pH value, and initial As(III) or As(V) concentration, could influence the As(III) or As(V) removal efficiency of the α-Fe₂O₃ nanowires/diatomite sample (prepared with a 8 wt% FeCl₃ aqueous solution at pH = 4.5 and 50 °C for 35 h) for the removal of As(III) and As(V). Over the α-Fe₂O₃/diatomite sample at pH = 3.5, the maximal As(III) and As(V) adsorption capacities were 60.6 and 81.2 mg g⁻¹, and the maximal As(III) and As(V) removal efficiency was 99.98 and 100%, respectively. The Langmuir model was more suitable for the adsorption of As(V), whereas the Freundlich model was more suitable for the adsorption of As(III). The adsorption mechanism of the sample was also discussed.