Removal of arsenic from aqueous solution: A study of the effects of pH and interfering ions using iron oxide nanomaterials

Nanophase Fe3O4 and Fe2O3 were synthesized through a precipitation method and were utilized for the removal of either arsenic (III) or (V) from aqueous solution as a possible method for drinking water treatment. The synthesized nanoparticles were characterized using X-ray diffraction, which showed that the Fe3O4 and the Fe2O3 nanoparticles had crystal structures of magnetite and hematite, respectively. In addition, Secherrer's equation was used to determine that the grain size nanoparticles were 12 +/- 1.0 nm and 17 +/- 0.5 nm for the Fe2O3 and Fe3O4, respectively. Under a 1 h contact time, batch pH experiments were performed to determine the optimum pH for binding using 300 ppb of either As(III) or (V) and 10 mg of either Fe3O4 or Fe2O3. The binding was observed to be pH independent from pH 6 through pH 9 and a significant drop in the binding was observed at pH 10. Furthermore, batch isotherm studies were performed using the Fe2O3 and Fe3O4 to determine the binding capacity of As(III) and As(V) to the iron oxide nanomaterials. The binding was found to follow the Langmuir isotherm and the capacities (mg/kg) of 1250 (Fe2O3) and 8196 (Fe3O4) for As(III) as well as 20,000 (Fe2O3) and 5680 (Fe3O4) for As(III), at 1 and 24 h of contact time, respectively. The As(V) capacities were determined to be 4600 (Fe2O3), 6711(Fe3O4), 4904 (Fe2O3), and 4780 (Fe3O4) mg/kg for nanomaterials at contact times of 1 and 24 h respectively. Published by Elsevier B.V.