In-situ synthesis of UiO-66-NH2 on porous carbon nanofibers for high performance defluoridation by capacitive deionization

Highly fluoridated water threatens human health. This paper reports on the in-situ synthesis of UiO-66-NH2 on a porous carbon nanofibers (PCNF) surface by a solvothermal method and its application for the selective removal of F− by capacitive deionization (CDI). The obtained UiO-66-NH2 @PCNF was highly flexible, with UiO-66-NH2 uniformly and firmly attached to the fiber surface. As an anode, it exhibited exceptional adsorption performance, with a maximal F− adsorption capacity of 213 mg g−1. This UiO-66-NH2 @PCNF electrode had high stability, and 88% of F− adsorption capacity was retained after 10 adsorption/regeneration cycles. In addition, this electrode held good F− selectivity, in the presence of Cl−, NO3−, SO42− and CO32−, attributed to pore size sieving effect of UiO-66-NH2 nanochannels and strong F-binding ability with the specific active sites in the UiO-66-NH2 nanochannels. In the simulated groundwater with high concentration of F−, the removal percentage is near 87%, and the residual content of F− was down to 0.64 mg L−1 after CDI adsorption, which is far below the acceptable limit in drinking water standards of World Health Organization (WHO). The superior F− removal performance of the UiO-66-NH2 @PCNF self-supporting electrode bestowed the corresponding CDI device great promise for the purification of F−-contaminated water.