rGO/CNQDs/ZIF-67 composite aerogel for efficient extraction of uranium in wastewater

Radioactive pollution is extremely harmful to humans and the environment and is difficult to manage. Therefore, finding an economical and efficient adsorbent for the treatment of uranium-contaminated wastewater is urgent. A composite carbon aerogel (CNQDs/rGO) was prepared by a simple one-step hydrothermal method by using CNQDs and graphene oxide as monomers. The ZIF-67 crystal was directly deposited on the template (expressed as CNQDs/rGO/ZIF-67 carbon aerogel (CGZCA)). The combination of CNQDs and graphene can not only graft some target groups (–OH, –COOH, and –NH-) onto the surface of 3D graphene carbon aerogels to promote adsorption, but also transform the zeta potential of rGO/ZIF-67 from positive to negative, which is more conducive to the adsorption process. The material observed by SEM and TEM shows that ZIF-67 and CNQDs are distributed on the carbon aerogel. The relationship of the adsorption of CGZCA to UO22+ with contact time and initial concentration is examined. Results show that the adsorption of UO22+ follows a pseudo-second-order kinetic model (R2 = 0.999), and is consistent with the Langmuir adsorption isotherm model (R2 = 0.991). The adsorption mechanism of the prepared adsorbent to UO22+ is studied by XPS. Various parameters are studied in detail in the static adsorption experiment, and the removal of uranyl by adsorbents in different water bodies is simulated. In addition, dynamic adsorption behavior and adsorption effect of CGZCA on UO22+ are investigated, which provides an appropriate reference basis for practical applications. Results show that the prepared ternary composite carbon aerogel is expected to be used in the extraction of uranium in wastewater and large-scale industrial production applications.