A Novel Fluoride Removal Adsorbent of a Zr⁴⁺-Doped Mg–Al-Layered Double Hydroxide: Synthesis and Fluoride Removal Performance

In this study, a novel fluoride removal adsorbent of the Zr4+-doped Mg–Al-layered double hydroxide (MgAlZr-LDH) was synthesized by a facile hydrothermal method, and the adsorbents before and after adsorption were characterized by SEM, XRD, FTIR, and XPS. The results of the adsorption experiments showed that adsorption reached equilibrium within 10 min. The adsorption kinetics and thermodynamics fitting indicated that the adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model. Its capacity for fluoride could reach up to 51.92 mg·g–1 at room temperature. Additionally, the adsorbent is effective across a wide pH range and exhibits good selectivity for fluoride. Its adsorption capacity still remained above 75% after 5 reusability cycles. Additionally, the defluorination mechanism is proposed, including electrostatic attraction, ion exchange, and ligand exchange. MgAlZr-LDH can be used as an effective adsorbent for removing fluoride from wastewater and has promising application prospects.