Cationic/Anionic Poly(p-Phenylene Oxide) Membranes: Preparation and Electrodialysis Performance for Nickel Recovery from Industrial Effluents

Electrodialysis (ED) has already been applied to recover nickel in galvanizing processes, allowing nickel recovery and the production of a treated effluent with demineralized water quality. However, the growth in ED use is still limited by the production and commercialization of ion-selective membranes, currently limited to a few large companies. Therefore, this paper presents the development of homogeneous cationic and anionic membranes made from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) for ED use. Cationic membranes were prepared by the sulfonation reaction of PPO under different experimental conditions (PPO:H₂SO₄ molar ratio and reaction time). Anionic membranes were prepared by the bromination reaction of PPO, followed by the amination reaction. The membranes were characterized for their chemical and electrochemical properties, including ion exchange capacity, conductivity, thermal stability, and surface morphology. The optimal conditions for cationic membrane sulfonation were achieved with a 1:4.4 PPO:H₂SO₄ molar ratio, and a reaction time of 0.5 h. For anionic membranes, the best results were obtained with bromination, with a PPO:NBS (N-Bromosuccinimide) molar ratio of 1:0.5, followed by 14 days of amination. Overall, 91.8% chloride, 90.9% sulfate, and 85.5% nickel ion extraction was achieved, highlighting PPO as a promising polymer for the development of anionic and cationic ion-selective membranes for ED.