Controlled in-situ crystallization in amine-rich millicapsules for hyper-efficient copper recovery

Sustainable copper (Cu) circulation is critical for both environmental protection and industrial advancement, as Cu is an essential material in electronics, energy storage, and catalysis. However, conventional adsorbents struggle with low efficiency and poor selectivity when recovering Cu from large wastewater volumes, leading to resource loss and secondary pollution. This study introduces diethylenetriamine (Dien)-rich millicapsules (DMCs) with ion-transferring porous frameworks designed for capacitive, stable, and highly selective Cu recovery from complex liquid environments. The unique three-dimensional center-radial frameworks significantly enhance Cu²⁺ ion transport to the capsule core, ensuring efficient capture and crystallization. Simultaneously, hierarchical pores with high surface curvature increase Dien density, promoting rapid Cu nucleation and controlled crystal growth. Large internal voids provide ample space for dense Cu₂(OH)₃NO₃ crystal formation, achieving Cu²⁺ adsorption capacity of 1602.30 mg g^–1 and ensuring long-term recovery stability. Additionally, a nanoporous shell prevents crystal leakage while blocking suspended solids, maintaining structural integrity. Through a synergistic chelation–crystallization mechanism, the DMCs achieve unprecedented Cu²⁺ adsorption capacity and selectivity, with effective regeneration for seven repetitive adsorption–desorption cycles. This novel transition from conventional 2D surfaces to advanced 3D spaces not only enhances resource recovery but also contributes to sustainable metal recycling, resource security, and the circular economy.

Graphical abstract