Upcycling waste polyimide foam into efficient adsorbent for deep removal of nickel complex from wastewater

We report a "treating waste with waste" strategy for the removal of high-concentration nickel tartrate (Ni-TA) complexes from electroplating wastewater. Using waste polyimide foam as the raw material, an amine-sulfhydryl dual-functionalized material (PI-ACS) was prepared through chemical modification. At the optimal molar ratio of sulfhydryl to amine groups (1.5:1), PI-ACS exhibited a maximum Ni(II) adsorption capacity of 232.7 mg/g and demonstrated excellent adsorption selectivity. Material characterization combined with Density Functional Theory (DFT) calculations confirmed that the adsorption of Ni-TA by PI-ACS is driven primarily by chelation interactions between the nitrogen atoms in amine groups and sulfur atoms in sulfhydryl groups of PI-ACS with Ni-TA molecules. Furthermore, by integrating this method with the improved Fenton-precipitation approach, the Ni(II) content in Ni-TA wastewater with an initial concentration of 300 mg/L was reduced to 0.026 mg/L, meeting direct discharge standards. This demonstrates the guiding significance of the strategy for both the recovery of metallic nickel resources and the upgraded utilization of waste polyimide materials.