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

• Published in: Chemosphere (Oxford) 2021-10, Vol.280, p.130722-130722, Article 130722
• Main Authors: Wang, Ying, Lin, Zaiwen, Liu, Qi, Zhu, Jiahui, Liu, Jingyuan, Yu, Jing, Chen, Rongrong, Liu, Peili, Wang, Jun
• Format: Article
• Language: English
• Subjects: Amidoxime groups; Ethylene-acrylic acid copolymer; Mechanical property; Multi-layer porous structure; Radioactive wastewater
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.130722

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. The amidoximation ethylene-acrylic acid copolymer balls (EAA-AO) with ultra-high mechanical property and multi-layer porous structure was revealed for the first time the modulation of hot alkali ethanol water mixed solution on the structure, and exhibited superior adsorption performance and specific selectivity for U(VI) from radioactive wastewater. [Display omitted] •The EAA-AO were successfully synthetized through two-step approach: the dehydration condensation reaction and amidoximation reaction, and the ultra-high mechanical and aciduric property didn’t be destroyed by preparation process.•The hot alkaline ethanol-water mixed solution transformed the original dense structure of EAA into a multi-layer porous structure of EAA-AO, which accelerated the mass transfer process and maximized utilization of adsorption active sites.•The EAA-AO showed superior adsorption performance for U(VI) in radioactive wastewater because -NH2 and unreacted -C≡N groups from diaminomaleonitrile adjusted the pKa of