Highly selective capture of phosphate ions from water by a water stable metal-organic framework modified with polyethyleneimine

In this work, a series of polyethyleneimine (PEI) impregnated metal-organic framework (UiO-66) with varying PEI loadings were prepared and applied as sorbents to capture phosphate ions from water. As indicated by SEM and XRD analysis, PEI was dispersed on the outer surface and the inner pores of UiO-66. At 9.45% PEI loadings (UiO-66-3), the saturated adsorption capacity of phosphate reached 73.15 mg P/g at 298 K, which is superior to most sorbents ever reported. UiO-66-3 could sequestrate phosphate over a wide pH range from 2.0 to 7.0 with high efficiency. The sorption toward phosphate reached equilibrium in 50 min. Unlike commercial anion exchanger IRA-900, UiO-66-3 still exhibited high removal toward phosphate even large amount of coexisted anions were present. Successive sorption assay demonstrated that the removal efficiency of UiO-66-3 toward phosphate remained constant after six cyclic runs. All the above results indicated the great potential of UiO-66-3 as a promising sorbent for the decontamination of water from phosphate.