Outstanding fluoride removal from aqueous solution by a La-based adsorbent

Abstract

A La-based adsorbent was prepared with La(NO3)3·6H2O, 2-methylimidazole and DMF via amide-hydrolysis and used for fluoride decontamination from aqueous water. The obtained adsorbent was lanthanum methanoate (La(COOH)3). The effects of pH value, initial F− concentration and interfering ions on defluoridation properties of as-prepared La(COOH)3 were assessed through batch adsorption tests. The adsorption kinetics, isotherm models and thermodynamics were employed to verify the order, nature and feasibility of La(COOH)3 towards fluoride removal. The results imply that La(COOH)3 is preferable for defluoridation over a wide pH range of 2 to 9 without interference. Simultaneously, the defluoridation process of La(HCOO)3 accords to the pseudo-second order model and Langmuir isotherm, revealing chemical adsorption is the main control step. The maximum fluoride capture capacities of La(COOH)3 at 30, 40 and 50 °C are 245.02, 260.40 and 268.99 mg g−1, respectively. The mechanism for defluoridation by La(COOH)3 was revealed by PXRD and XPS. To summarize, the as-synthesized La based adsorbent could serve as a promising adsorbent for defluoridation from complex fluoride-rich water.