Arsenic removal from aqueous solutions by adsorption on magnetite nanoparticles

Magnetite nanoparticles were used to treat arsenic‐contaminated water. Because of their large surface area, these particles have an affinity for heavy metals by adsorbing them from a liquid phase. The results of the study showed that the maximum arsenic adsorption occurred at pH 2, with a value of approximately 3.70 mg/g for both As(III) and As(V) when the initial concentration of both arsenic species was maintained at 2 mg/L. The study showed that, apart from pH, the removal of arsenic from contaminated water also depends on the contact time, the initial concentration of arsenic, the phosphate concentration in the water and the adsorbent concentration. The results suggest that arsenic adsorption involved the formation of weak arsenic–iron oxide complexes at the magnetite surface. At a fixed adsorbent (magnetite nanoparticles) concentration of 0.4 g/L, percent arsenic removal decreased with increasing phosphate concentration. Magnetite nanoparticles removed <50% of arsenic from water containing >6 mg/L phosphate. In this case, an optimum design for achieving high arsenic removal by magnetite nanoparticles may be required.