Selective Separation of Bi ³⁺ /Cu ²⁺ by Bis(2-ethylhexyl) Phosphate Functionalized Pore-Filling Membranes

The development of efficient separation technologies for Bi 3+ is highly desirable to meet the increasing demand for technology-critical bismuth. In this study, bis(2-ethylhexyl) phosphate (HDEHP)-functionalized pore-filling membranes were fabricated for the efficient separation of Bi 3+ and Cu 2+ via electrodialysis. Microstructural and chemical characterizations demonstrated the superior compatibility between HDEHP and the polymer chains. The tight arrangement of functional groups within the membrane established a continuous transport pathway for metal ions, enabling selective separation of Bi 3+ via an ion-exchange process. Under optimal conditions, the Bi 3+ flux reached 2.6 mmol m –2 h –1 with an outstanding perm-selectivity P Cu 2+ Bi 3+ of 26.3 during electrodialysis. Moreover, the separation efficiency could be further improved by increasing the number of repeating membrane units, laying a foundation for practical industrial applications. This work provides a promising candidate for the efficient and convenient selective recovery of technology-critical metals from industrial wastewater.