Study on Hexavalent Chromium Reduction Using Zero-Valent Magnesium in Aqueous Solution

Chromium is an extremely important heavy metal which is used in different industries. It can be found in water resources due to insufficient treatment of industrial wastewater. The goal of this study was to survey the feasibility of application of hexavalent chromium reduction using granular magnesium as reducing agent and to investigate the affects of various operational parameters. In this experimental study, zero-valent magnesium was used for the removal of hexavalent chromium from aqueous solution. Synthetic solution of chromium was prepared from dionized water. Several experimental steps was done in 250 ml glass beakers in a shaker incubator device and different operational parameters such as pH of solution, initial concentration of chromium, temperature, contact times, magnesium dose and intercurrent factors were investigated. Concentration changes of chromium were determined with spectrophotometer at an absorbance wavelength of 540 nm. The results indicated that chromium removal efficiency, using zero-valent magnesium, increases with contact times, magnesium dose, initial concentration of chromium and temperature. However, chromium removal efficiency decreased with increasing pH of solution. The highest removal efficiency was achieved in pH 3, initial concentration of chromium at 150 mg/L and magnesium at dose of 0.7 g/L, respectively. In addition, the presence of humic acid, hardness and alkalinity in solution extensively decreased the chromium removal efficiency. The results showed that zero-valent magnesium, due to high oxidation and reduction potential, can be extensively effective for removing hexavalent chromium in aqueous solution.