Highly efficient fluoride removal from water using 2D metal-organic frameworks MIL-53(Al) with rich Al and O adsorptive centers

Lei Huang; Zhihui Yang; Sikpaam Issaka Alhassan; Zhixuan Luo; Baocheng Song; Linfeng Jin; Yixian Zhao; Haiying Wang

doi:10.1016/j.ese.2021.100123

Highly efficient fluoride removal from water using 2D metal-organic frameworks MIL-53(Al) with rich Al and O adsorptive centers

Environ Sci Ecotechnol. 2021 Sep 11:8:100123. doi: 10.1016/j.ese.2021.100123. eCollection 2021 Oct.

Authors

Lei Huang^{1

2

3}, Zhihui Yang^{1

2}, Sikpaam Issaka Alhassan¹, Zhixuan Luo³, Baocheng Song⁴, Linfeng Jin⁵, Yixian Zhao¹, Haiying Wang^{1

2}

Affiliations

¹ School of Metallurgy and Environment, Central South University, Changsha, 410083, PR China.
² Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution, Changsha, 410083, PR China.
³ School of Environmental Science and Engineering, Guangzhou University, Guangzhou, 510006, China.
⁴ Fujian Environmental Protection Design Institute Co. Ltd, Fuzhou, 350000, PR China.
⁵ School of Material Science and Engineering, Central South University, Changsha, 410083, PR China.

Abstract

In this study, metal-organic framework MIL-53(Al) was synthesized and studied to understand the different mechanisms between normal MIL-53(Al) and 2D metal-organic framework MIL-53(Al) for removing fluoride. Comparatively, the 2D MIL-53(Al) had two-dimensional linear morphology rather than block shape, indicating more expose adsorptive sites than normal MIL-53(Al). The batch adsorption experiments were applied to investigate the performance of 2D MIL-53(Al), including pH, adsorption kinetics, and thermodynamics. The 2D MIL-53(Al) (75.50 mg/g) showed better adsorption capacity than normal MIL-53(Al) (35.63 mg/g). The adsorption process of 2D MIL-53(Al) followed the pseudo-first-order model and Langmuir model. The adsorption mechanism of this material was further studied by using experimental characterization and density functional theory calculations in detail. The main adsorptive sites were Al and O in the 2D MIL-53(Al), and the relationship between fluoride binding with Al and O was HF₂ ^- > HF > F^-. The species of fluoride were HF₂ ^-, HF, F at different pH and concentrations. Hence, this study provides a significant way on the application of two-dimensional materials for removing fluoride.

Keywords: Adsorption; Fluoride; MIL-53(Al); Metal-organic frameworks; Two dimensions.