Construction of novel quaternary ammonium nitroxy-hybrid rhenium adsorbent system with dual mechanisms and separation research from rhenium (VII)/copper (II)

Rhenium (Re) is vital in the medicinal and energy sectors. However, its scarcity and the co-occurrence with copper (Cu) present ongoing challenges in developing adsorbents with high adsorption capacity and selectivity. Herein, a quaternary ammonium nitroxy-hybrid/polystyrene microsphere separation system (Tetra-DE-CMPS, Tetra-N-ACE-CMPS, Tetra-2N-ACE-CMPS) was designed for selective Re(VII)/Cu(II) separation. The results indicated that in an acidic pH range (2–6), Tetra-DE-CMPS exhibited a Re(VII) adsorption capacity of up to 734.82 mg·g⁻¹, which could be reused at least 3 times. For selective separation of Re(VII)/Cu(II) mixtures, the separation factor Sel_Re/Cu could exceed 3.77; for Tetra-2N-ACE-CMPS, the Sel_Re/Cu value was 4.72. The adsorption mechanism between the adsorbents and Re(VII) was mainly electrostatic interaction and oxidation-reduction reaction. This novel adsorption system provided a brand-new perspective (nitrogen oxide hybridization and spatial effects) to explain outstanding Re adsorption capacity, excellent Re(VII)/Cu(II) selective separation ability, and a new reactivity mechanism for the design of Re(VII) adsorbents.