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Fluoride removal efficiencies and mechanism of schwertmannite from KMnO4/MnO2–Fe(II) processes
- Zhu, Feng, Guo, Zhaobing, Hu, Xingyun
- Journal of hazardous materials 2020 v.397 pp. 122789
- adverse effects, fluorides, industrial wastewater, ion exchange, ions, iron, manganese dioxide, oxidation, pollution, potassium permanganate, sulfates
- Fluoride has an adverse effect on both the environment and industrial production. In particular, wastewater from smelting systems containing high concentrations of fluoride is a major cause of fluoride pollution. Based on the characteristics of such wastewater, a targeted and integrated method for removal fluoride using schwertmannite is proposed. The schwertmannite, prepared from the oxidation of Fe(II) by KMnO₄ (Ksw) and MnO₂(Msw), effectively removed fluoride within 30 min under certain conditions. Under most experimental conditions, the removal efficiency of F ion by Ksw was always 13 % higher than that by Msw, which is attributed to the different concentrations of OH⁻ and SO₄²⁻ for ion exchange. The calculations showed that the chemical formulas of Ksw and Msw are Fe₈O₈(OH)₅.₄₂±₀.₀₄(SO₄)₁.₂₉±₀.₀₂ and Fe₈O₈(OH)₅.₂₈±₀.₀₄(SO₄)₁.₃₆±₀.₀₂, respectively. In the Ksw system, 0.70 mol of OH⁻ and 0.30 mol of SO₄²⁻ were released per mole of F ions sorbed; those released for the Msw system were 0.69 mol and 0.31, respectively. The results showed that OH⁻ played a primary role in the ion exchange and the schwertmannite showed good practicability for actual industrial wastewater.