Effect of sorption conditions on the state of copper(II) ions in the phase of AN-31 ion exchange resin, according to data from ESR and UV–vis diffuse reflectance spectroscopy

Abstract

It is found that the sorption recovery of copper ions from water solutions in the phase of AN-31 low basicity anion exchanger has a mixed character. It is established via diffuse reflectance spectroscopy that ions are stabilized through complexation with the participation of the functional groups of the sorbent with the formation of structures [Cu(NR₃)₂(OH)₂(H₂O)₂], [Cu(NR₃)₃(OH)(H₂O)₂], and as a result of the physical adsorption of oxide dimers and planar-squared copper clusters. It is shown that increasing the ionic strength of a solution by introducing sodium chloride into the system greatly improves the capacity of the sorbent and leads to the uniform distribution of copper ions in the resin matrix. The similarity between the ESR spectrum parameters of copper-containing samples of the ion exchanger, obtained in a wider range of pH, is determined via ESR and testifies to the homogeneity of the stabilization positions of Cu²⁺ ions. The crystalline field of tetragonal-elongated octahedron is typical of all Cu²⁺ ions. All of the complexes have Cu(NO₃)₂ coordination nodes with the covalent bonding of Cu²⁺ ions and the amine groups of the sorbent.