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Preparation and characterization of wheat straw biochar loaded with aluminium/lanthanum hydroxides: a novel adsorbent for removing fluoride from drinking water

ABSTRACT In this work, a novel adsorbent of aluminium/lanthanum loaded wheat straw biochar (Al-La-WSB), was prepared by using a facile approach and used for fluoride removal. The Al-La-WSB and its pristine wheat straw biochar (WSB) were characterized by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray powder diffraction (XRD) methods. Batch adsorption experiments were carried out to investigate adsorbent performance, the highest removal rate was observed at pH 9, contact time of 7 h and Al-La-WSB dose of 1 g L−1. Lagergren pseudo-second-order kinetics and Langmuir isotherm model fitted the experimental data well. The maximum fluoride adsorption capacity of Al-La-WSB at different experiment temperature of 298, 308 and 318 K, was 51.28 mg g–1, 46.73 mg g–1 and 50.25 mg g–1, respectively, which was better than most reported adsorbents. The Al-La-WSB performed well over a considerable wide pH range of 3–10 and carried positive charge at pH < 4.8. The presence co-existing ions of SO4 2−, HCO3 −, Cl− and NO3 − had a minor impact on fluoride adsorption besides PO4 3−. Regeneration experiment results showed that the Al-La-WSB had an excellent reusability. According to the adsorbent characterization and batch adsorption experiment, the adsorption of fluoride on the Al-La-WSB was primarily a chemisorption, involving electrostatic interactions and ion exchange, which nitrate ion and hydroxyl played a major role. The results suggested that the Al-La-WSB could be a great adsorbent for removing fluoride from drinking water. GRAPHICAL ABSTRACT