Chemical Modification of Natural Magnetite and Its Application in Arsenic Removal from a Water Environment

Iron oxides and their complex oxides such as siderite and ferrihydrite have high surface charge and specific surface area, which have strong binding capacity and affinity for arsenite and arsenate under specific conditions. Natural magnetite, mainly consisting of Fe₃O₄, has low activity itself, and is not efficient for direct treatment of high arsenic water. Reported in this paper, natural magnetite is modified by acidification, alkalization, and calcined at different temperatures for different periods, in order to enhance arsenic removal from water. Experimental results show that the modified magnetite acidified in 0.5 mol/L hydrochloric acid and calcined at 150℃ for 10 min, has high removal efficiencies for both As (Ⅲ) and As (Ⅴ). Removal efficiency was 98% for As (Ⅴ), whereas the removal efficiency was 75% for As (Ⅲ) with concentration decreases from 1000 μg/L to 250 μg/L (in Fig.2). The modified natural magnetite has stronger adsorption capacity for As than natural magnetite, and is identical to other modified iron minerals. In addition, the modification method is simple and convenient. Therefore, the modified natural magnetite would be a potential adsorbent for controlling arsenic content in high arsenic water.