Ultra-high mechanical property and multi-layer porous structure of amidoximation ethylene-acrylic acid copolymer balls for efficient and selective uranium adsorption from radioactive wastewater

Abstract

Adsorption uranium [U(VI)] from U-containing radioactive wastewater (URW) is a critical strategy for solving the resource shortage and environmental pollution in pace with the sustainable development of nuclear energy. However, the URW universally exhibits acidity and contains co-existing metal ions with high concentration. Herein, the amidoximation ethylene-acrylic acid copolymer balls (EAA-AO) with aciduric and super-high mechanical property were successfully synthesized through grafting diaminomaleonitrile and further treatment of amidoximation. Significantly, the mechanical properties of EAA-AO were not affected by the grafting process and maintained super-high mechanical properties. Furthermore, the –NH2 and unreacted –CN groups in diaminomaleonitrile adjusted the pKa to make the optimal pH be 4. In addition, the microstructure of EAA-AO was transformed from the original dense to multi-layer porous structure, which promoted the mass transfer process and the contact between uranyl ions (UO22+) and internal adsorption active sites. The adsorption capacity of EAA-AO was about 1.78 times that of EAA at pH = 4, and the adsorption capacity for U(VI) was about 8.17 times that of Ba2+ with the second highest adsorption capacity. Therefore, the EAA-AO exhibited ultra-high adsorption performance (qe = 3.196 mg g−1) in the artificial radioactive wastewater, laying a good foundation for subsequent large-scale industrial adsorption of U(VI) in nuclear industrial wastewater.