Enhanced low-concentration phosphate adsorption using magnetic UiO-66@Fe3O4 composite with potential linker exchange

A magnetic FenUiO-66 adsorbent was created to achieve high phosphate adsorption capacity. The incorporation of Fe3O4 facilitated the precipitation and growth of UiO-66 during crystallization, resulting in a shift towards a multilayer heterogeneous distribution of adsorption sites. The increased Fe3O4 content notably enhanced the magnetic properties of FenUiO-66, while negligibly affecting its adsorption performance. The Fe1.5UiO-66 demonstrated exceptional phosphate adsorption capacity (136.54 mg/g), outstanding selectivity, and sustained reusability, with an 80% removal efficiency after nine cycles of treating actual water. The mechanism of phosphate adsorption by FenUiO-66 involved electrostatic attraction, ligand exchange, and linker exchange. Notably, while linker exchange significantly contributed to high adsorption capacity, it resulted in irreversible damage to the FenUiO-66 crystal. These unequivocal findings will serve as a solid foundation for further research and underline the critical role of linkers in the process of phosphate adsorption. [Display omitted] •Magnetic MOF for phosphate adsorption realized via synthesis of UiO-66 on Fe3O4.•Fe3O4 changed adsorption mode of UiO-66 with sufficient adsorption capacity.•Linker exchange created defects to improve phosphate adsorption for first use.•Linker exchange cause irreversible structural damage and decrease reusability.•High performance remained after repeatedly treating actual water.