Selective adsorption mechanism of copper from nickel electrolytes by tert-butyl 2-(N-octyl-2-picolyamino) acetate functionalized chelating resin: A DFT study

Exploring the selective adsorption of Cu(II) from nickel electrolytes by tert-butyl 2-(N-octyl-2-picolyamino) acetate (AMPA) functionalized chelating resin is of great implication for accurately regulating the interface interaction. In this study, based on the first-principles density functional theory (DFT), the pK a values of functional group AMPA were calculated, the H 2 O and Cl − were considered as ligands, and the valence bond properties were elucidated by electron localization function (ELF) and ligand field theory. AMPA is protonated to AMPAH 1 H 2 under acidic conditions, and Cu(II) could replace protons of AMPAH 1 H 2 and be chelated to form AMPA-Cu(II) substrate while Ni(II) cannot. An irregular octahedral configuration is formed with the coordination of H 2 O and Cl − based on the AMPA-Cu(II) substrate. Cl − promotes Ni(II) to replace protons of AMPAH 1 H 2 to form [AMPA-NiCl n ] 2−n (n ≤ 2), while Ni(II) in [AMPA-NiCl n ] 2−n (n = 2, 3) presents poor stability and will be further replaced by Cu(II). In addition, the interaction between Cl − and Ni(II) is stronger than that with Cu(II), and [NiCl n ] 2−n (n > 2) clusters are not conducive to being adsorbed, while the Cu(II) with weak binding ability to Cl − is selectively adsorbed. Finally, an interface interaction model of selective adsorption of Cu(II) by AMPA-based chelating resin was proposed.