Efficient preparation of red mud-based geopolymer microspheres (RM@GMs) and adsorption of fluoride ions in wastewater
2023
Yi, Min | Wang, Kaituo | Wei, Hongyang | Wei, Deshuai | Wei, Xuefei | Wei, Binghu | Shao, Lin | Fujita, Toyohisa | Cui, Xuemin
In this paper, red mud-based geopolymer microspheres (RM@GMs: 75–150 µm) was prepared by dispersion-suspension-solidification method to remove fluoride ions (F⁻). It was found that RM@GMs still had good mechanical properties and better F⁻ removal effect at RM content reached 80 % of the total solid mass. The batch adsorption experiment results showed that the F⁻ concentration (< 1.5 mg/L) reached the drinking water standard in 45 min at pH = 2 and RM@GMs dosage was 1 g/L. RM@GMs showed maximum adsorption capacity of 76.57 mg/g for F⁻, and the adsorption kinetics and isotherm fitted the pseudo-second-order kinetic and Langmuir isotherm model, respectively. RM@GMs exhibited excellent dynamic separation effect at the flow rate of 4 mL/min and column height of 1 cm. In addition, RM@GMs had good selectivity for F⁻ in the competitive adsorption experiments and followed an order of: PO₄³⁻ > > SO₄²⁻ ≈ NO₃⁻ ≈ Cl⁻. In real seawater, natural surface water and tap water, RM@GMs still had excellent F⁻ removal effect. The adsorption mechanism revealed that RM@GMs removed F⁻ mainly through the synergistic effect of adsorption and ion exchange. Therefore, this paper provides the potential value for the large-scale utilization of RM in the application of F⁻-containing wastewater.
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