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 SO₄²⁻, HCO₃⁻, Cl⁻ and NO₃⁻ had a minor impact on fluoride adsorption besides PO₄³⁻. 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

KEYWORDS:

• Adsorption
• fluoride
• La(OH)₃
• Al(OH)₃
• wheat straw biochar

Disclosure statement

No potential conflict of interest was reported by the author(s).

Acknowledgements

This work was supported by 2019 Overseas Research Projects of Excellent Young and Middle-aged Teachers and Presidents in Colleges and Universities of Jiangsu Province, National Natural Science Foundation of China (Youth Fund:21107054), Nantong Science and Technology Project (MS 12020076) and Innovation Training Plan for College Students in Jiangsu Province (201910304035Z).

Additional information

Funding

This work was supported by National Natural Science Foundation of China [grant number 21107054]; Nantong Science and Technology Project [grant number MS 12020076]; Innovation Training Plan for College Students in Jiangsu Province [grant number 201910304035Z]; Large Instruments Open Foundation of Nantong University [grant number KFJN2053].