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

Abstract

Excessive intake of fluorine (F) over time can lead to acute or chronic fluorosis. In this study, a novel Fe^III-Ce^IV-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, Fe^II-Fe^III 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 Ce^IV for Fe^II 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 Fe^II-Fe^III. 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.