Effects of pH and Anion Species on Cr(VI) Removal by Magnetite

Magnetite was prepared to remove poisonous hexavalent chromium [Cr(VI)] from aqueous solution. Batch experiments were conducted to measure the effects on removal of Cr(VI) of different parameters such as ionic strength, pH, and initial concentration. Results demonstrated that the removal of Cr(VI) on magnetite was decreased with the increase of pH in the range of 3.4-5.0, but independent of ionic strength. The removal percentage of Cr(VI) also decreased with the increase of Cr(VI) concentration in the range of 50-200 mg/L. At pH 3.5 and 5.0, the presence of SO42- retarded the removal of Cr(VI) via electrostatic interactions and/or competition for surfaces sites on magnetite. The pH of the medium and presence of anion species were critical factors in the removal of Cr(VI) from aqueous solution.