# Metachrylate-Based Polymeric Sorbents for Recovery of Metals from Aqueous Solutions
## 7 Adsorption on Amino-Functionalized Glycidyl Methacrylate-Based Polymers
The sorption of Cu(II) ion on PGME-en, PGME-data, and PGME-teta were successfully modeled by quantum chemical calculations [125]. Higher maximum sorption capacities (\(Q_{max}\)) were obtained for deta- and tetra-copolymers, due to their abilities to form binuclear complexes. The study offers an explanation of the experimentally obtained trend for Cu(II) by applying theoretical techniques to predict the selectivity of ligands. A comparison of the Gibbs free energy (\(\Delta\)Ga) for mononuclear and binuclear tetraOH complex suggests that the formation of mononuclear complexes is a slightly more favorable (spontaneous) process. The results indicate that the amines with three nitrogen ligator atoms were preferable (due to the possibility of binuclear complex formation). On the other hand, the more ligator atoms it contains, the amine diffusion inside the polymer is more difficult. In addition, a higher number of ligator atoms increases the strain of chelate rings and reduces the stability of amino-functionalized complex with the sorbed ion. In a very complex and detailed study, [PERSON] et al. used quantum chemical calculation for modeling Cu(II), Cd(II), Co(II), and Ni(II) sorption by PGME-teta [124]. Cambridge Structural Database (CSD) was a source of geometries of aqua complexes of the studied metal ions and coordination modes of the teta ligand in crystal structures. Cd(II), Co(II), and Ni(II) ions form complexes with octahedral geometry, while Cu(II) ion forms complexes with the coordination number 5. The agreement of theoretical and experimental results was achieved when mononuclear tetaOH complexes of Cu(II) and Cd(II) were compared with mononuclear complexes of Ni(II) and Co(II) with monoprotonated teta OH ligand (tetaOH). It was observed that the inclusion of the solvation effect was needed since the sorption takes place in an aqueous solution. In addition, it was shown that solvation energy contributions significantly improve the stability of ions in an aqueous solution. Macroporous PGME copolymers amino-functionalized with ethylene diamine, diethylene triamine and hexamethylene diamine (PGME-en, PGME-theta, PGME-HD) were tested as potential Cr(VI) oxyanion sorbents from aqueous solutions [89; 128; 129]. [PERSON] et al. studied kinetics and temperature dependence of Cr(VI) sorption by PGME-theta in the temperature range 25\(-\)70 \({}^{\circ}\)C [129]. Pseudo-first order, pseudo-second-order, Elovich, intraparticle diffusion, and Bangham kinetic models were used for sorption behavior analysis. Equilibrium data were tested with Langmuir, Freundlich, and Tempkinadsorption isotherm models. Langmuir model was the most suitable, while thermodynamic data suggested spontaneous and endothermic Cr(VI) adsorption onto PGME-data. The best kinetic results fit was observed with the pseudo-second-order model, with a definite influence of pore diffusion. Additionally, the authors proposed electrostatic interactions Cr(VI) sorption mechanism by PGME-data at acidic media. Namely, at acidic pH, the amino groups were in the protonated cationic form (NH\({}_{3}\)+), which results in stronger attraction with negatively charged ions in the solution (HCrO\({}_{4}\)-). Consequently, electrostatic interaction between the adsorbent and anions and high chromium removal is observed. The sorption kinetics of Cr(VI), Cu(II), Co(II), Cd(II), and Ni(II) by PGME-en and PGME-eta, was studied under single-component and mixed metal salt solutions [128]. The competitive sorption was analyzed for the following mixed solutions: Cu(II) and Cr(VI); Cu(II), Co(II), Cd(II), and Ni(II); Cr(VI), Cu(II), Co(II) and Cd(II) solutions. Very rapid uptake of Cr(VI) ions under non-competitive conditions (the sorption half time \(\leq 1\) min) was observed.