Promisingly prioritized elimination performance of europium and uranium from industrial wastewater by recyclable polydopamine functionalized hydroxyapatite/ZIF-67 hybrids

Abstract

In recent decades, the nuclear industry has undergone robust growth leading to an increasingly severe issues of radionuclide contaminants in wastewater. Consequently, the development of a novel, efficient, regenerative and environmentally friendly adsorbent has become a significant challenge. In this study, recyclable polydopamine functionalized hydroxyapatite/ZIF-67 (HAP/ZIF-67/PDA) hybrids with a mass of functional groups, were successfully synthesized using the ultrasonic-assisted method. The especially characterized techniques illustrated that the HAP/ZIF-67/PDA hybrids were outstanding stable, excellent physicochemical properties and abundant functional groups. The elimination performances of Eu(III) and U(VI) from wastewater were also explored and deliberated through macroscopic experiment under diverse wastewater chemistry environment. The optimal adsorption capacity of HAP/ZIF-67/PDA was approximately 1.33 × 10-3 mol/g for Eu(III) and 8.85 × 10-4 mol/g for U(VI), surpassing those reported materials in previous literatures. The particular adsorption isotherms of Eu(III) and U(VI) were favorably fitted by Langmuir model, illustrating that the adsorption Eu(III) and U(VI) were totally endothermic reaction. The remarkable adsorption performance of HAP/ZIF-67/PDA hybrids (within 80 min for Eu(III) and 100 min for U(VI)) was verified through dynamic model, and then the kinetics results were well simulated through pseudo-second-order kinetic model, which further illustrated outstanding performance for rapidly treating Eu(III) and U(VI) under extreme emergency conditions. The primary adsorption mechanisms HAP/ZIF-67/PDA hybrids towards Eu(III) and U(VI) were surface complexation, competitive interaction, cation change, π-π* bonds and electrostatic interaction. Based on the excellent adsorption performance and recyclability of HAP/ZIF-67/PDA, it holds significantly potential and promising prospects for the efficient elimination of lanthanide and actinium contaminants from the practical treatments and disposals fields of industrial wastewater.