Facile synthesis of Aluminium fumarate metal-organic framework and hydroxyapatite composite with improved adsorption characteristics for efficient fluoride removal from water

An aluminium fumarate (AlFu)-hydroxyapatite (HAP) composite (AlFu-HAP) with numerous functional groups for fluoride binding was synthesised by a simple solid-solid mixing process. The produced AlFu-HAP composite with numerous functional groups results in outstanding adsorption capability in the sequence AlFu-HAP > AlFu > HAP. This composite was studied under different pH, initial fluoride concentrations, temperatures, and contact times. The adsorption kinetics and isotherms were pseudo-second-order model and Freundlich adsorption isotherm, respectively. XRD, SEM, FTIR, Raman spectroscopy, and XPS analysis of the samples before and after the adsorption reaction indicate that the fluoride removal mechanism was controlled by anion exchange of the OH- group in AlFu-HAP and F- in water. At high concentrations (150-200 mg F -/L) in groundwater and industrial effluent, the AlFu-HAP showed > 90 % fluoride removal. Thus, the current study will provide an effective strategy for developing an AlFu-HAP composite adsorbent to be used for the effective elimination of fluoride from wastewater.