Fabrication of Uio-66-NH2 with 4,6-Diamino-2-mercaptopyrimidine facilitate the removal of Pb2+ in aqueous medium: Nitrogen and sulfur act as the main adsorption sites

In this work, the Zr-based MOF was successfully fabricated with 4,6-Diamino-2-mercaptopyrimidine (DMP) and a novel adsorbent (Uio-DMP) was synthesized for the immobilization of Pb 2+ in aqueous medium . The morphological and structural characteristics of Uio-DMP were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR), Field emission scanning electron microscopy (FE-SEM), Brunner Emmet Teller (BET), and X-ray photoelectron spectroscopy (XPS). The characterization results showed that the Uio-DMP maintained a pristine crystal structure and the sulfhydryl group was introduced to Zr-based MOF after chemical functionalization. The adsorption behavior of Uio-DMP for Pb 2+ was investigated in different conditions (solution pH, sorbent dose, Pb 2+ concentration, adsorption time, and co-existing ions). The experimental results indicated that the optimal pH was 6, the maximum adsorption capacity was 296.5 mg/g, and the Langmuir model well fitted the Pb 2+ removal process based on adsorption isotherm studies. The adsorption kinetic experiments revealed that the adsorption equilibrium could be achieved at 30 min and the adsorption process was consistent with the Pseudo-second-order model. The co-existing ions had a limited impact on Pb 2+ removal and the removal rate of 71.0% was maintained after five consecutive adsorption-desorption experiments. Furthermore, zeta potential and XPS analysis proved that the removal process of Pb 2+ over Uio-DMP was affected by electrostatic interaction , and nitrogen/sulfur atoms acting as the main adsorption sites. This study provides an insight into the removal of Pb 2+ in aqueous medium and the functionalization of adsorbents.