Selective Adsorption of Fluorine Contaminants from Spiked Wastewater via a Novel FeIII–CeIV-Based Layered Hydroxide Composite and Mechanism Analysis of Colloids and Surfaces

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Excessive intake of fluorine (F) over time can lead to acute or chronic fluorosis. In this study, a novel FeIII–CeIV-based layered hydroxide composite (DD-LHC) was synthesized and applied in both batch and column modes to develop new adsorbent materials and to obtain efficient removal of fluorine (F) anions from wastewater. DD-LHC achieved better adsorption results and material stability compared to green rusts (GR, FeII–FeIII hydroxide). The maximum adsorption capacity of DD-LHC for F− was 44.68 mmol·g−1, obtained at an initial pH of 5 and initial concentration of 80 mM. The substitution of CeIV for FeII in the intercalated layered structure of GR potentially changed the reaction pathways for F− removal, which are typically dominant in the layered double hydroxides (LDHs) of FeII–FeIII. The molecular structure of layered hydroxides combined with the three-dimensional (3D) metal frame of Fe-O-Ce was integrated into DD-LHC, resulting in nanoscale particle morphologies distinct from those of GR. The pseudo-first-order kinetic model effectively described the whole adsorption process of DD-LHC for F−. DD-LHC exhibited notable selectivity for F− across a wide pH range. The removal process of F− by DD-LHC was dominated by Ce–F coordination bonds, with additional influences from auxiliary pathways to different extents.