A novel UIO-66-NH2@TA adsorbent for effective solid-phase extraction of Pb (II) from environmental water and juices

In this study, a new metal-organic framework adsorbent (UIO-66-NH2@TA) which can efficiently and selectively capture lead ions was developed by functionalizing UIO-66-NH2 with tannic acid (TA) by Michael addition reaction. The structural and morphological properties of the produced adsorbent, as well as its adsorption mechanism for Pb (II) were discussed. The maximum adsorption capacity of Pb (II) was 475.78 mg/g at pH 5.0, which was significantly higher than the adsorption capacity of many adsorbents reported in the literature. In addition, the adsorption isotherms and kinetics conformed to the Langmuir model and pseudo-second-order kinetic model, respectively. The results indicated that the adsorptive behavior of the adsorbent mainly depended on the active sites on the surface of the adsorbents. The UIO-66-NH2@TA showed favorable selectivity toward Pb (II) against the interference of coexisting metal ions. It was found that the excellent Pb (II) removal performance of UIO-66-NH2@TA was mainly attributed to the synergistic effect of physical adsorption and chemisorption. Moreover, the UIO-66-NH2@TA showed extraction efficiencies of 88.01%, 82.44%, 80.20% and 74.99% for Pb (II) with initial concentration of 100 mg/L in river water, sea water, peach juice drink, and grape juice, respectively. This work proved that the UIO-66-NH2@TA had a wide application prospect in the field of Pb (II) treatment.