Investigation on Removal Performance of Multi-Element Using Layered Double Hydroxide Produced from Magnesium Oxide and Ferrous Iron

High levels of selenium(Se), boron(B), and fluorine(F) are found in wastewaters from coal-fired power plants and glass manufacture, and their efficient removal by simple and inexpensive methods is required. Magnesium oxide (MgO) and ferrous (Fe(II)) hydroxide are used for B and Se(VI), respectively, but their simultaneous removal is difficult because the pH requirements differ. In this study, we examined a wastewater treatment process that can simultaneously remove these elements. MgO and Fe(II) were added to simulated wastewater containing Se(VI), B, F, and SO₄²⁻, and the removal of the toxic elements was evaluated. When 3 g dm⁻³ of MgO and 0.415 g dm⁻³ of Fe(II) were added, concentra-tions of 1 mg dm⁻³ of Se(VI), 300 mg dm⁻³ of B, and 10 mg dm⁻³ of F could be reduced to below the effluent standard values. Solid analysis of the precipitates showed that the toxic elements were removed in association with hydroxides and layered double hydroxides (LDH) containing Fe(II), Fe(III), and Mg. These hydroxides and LDH were formed around MgO particles, resulting in a large particle size of about 300 µm and a high sedimentation property in suspen-sion. Therefore, this process using MgO and Fe(II) is efficient for removal of Se(VI), B, and F simultaneously and in terms of the sludge treatment.