In situ synthesis of MIL-53-type eco-MOF from high-alumina fly ash for efficiently removing fluoride from water.

Facing ubiquitous fluoride pollution in aquatic environments and ever-increasing discharge of coal fly ashes, this study aims to in situ synthesize a kind of Al-based metal–organic framework eco-material (eco-MOF) using high-alumina fly ash as metal raw material, and apply the obtained adsorbent to efficiently adsorb fluoride in water. The synthesized eco-MIL-53(Al) exhibits excellent thermal stability, showcasing a consistent morphology of fine columnar crystals and possessing a high specific surface area (353 ​m2·g−1). Moreover, the adsorption isotherm demonstrates a strong agreement with the Langmuir isotherm model, indicative of a maximum uptake quantity of 160 ​mg·g−1 ​at 318 ​K. In addition, fluoride adsorption experiments demonstrate that an increased dosage enhances the adsorption efficiency, the higher water pH value diminishes the removal efficiency, and the impact of coexisting anions is minimal. Also, the adsorption capacity is augmented with increasing temperature at high initial fluoride concentrations, but shows negligible variation at low initial fluoride concentrations. It is worth noting that the desiliconization filtrate can be applied to synthesize ZSM-5 zeolite, realizing the total utilization of fly ash. The present work provides a novel platform that would serve as a mutually beneficial reference for managing the environmental risks of fluoride and waste resource utilization. [Display omitted] [ABSTRACT FROM AUTHOR]