Comparative study of adsorption of Cu(II) ions from aqueous solutions by industrial ion exchangers and ion exchange systems based on them

Abstract

The sorption of Cu(II) ions from aqueous solutions on the sulfocation exchanger KU-2-8, the anion exchanger AN-31 and the ion exchange system with long-range interaction based on the industrial ion exchangers KU-2-8 and AN-31 was studied. A study was conducted to ascertain the influence of various parameters on the process. It was demonstrated that under optimal conditions of an adsorption duration of 12 hours, a pH value of 4.6 and a temperature of 293K, the maximum adsorption of copper ions by the cation exchanger KU-2-8 (H⁺ form) is 112.4 mg/g, by the anion exchanger AN-31 (Cl^- form) 114.2 mg/g, and for the ion exchange system composed of the sulfonic cation exchanger KU-2-8 and the anion exchanger AN-31 296.7 mg/g. It is evident that the static exchange capacity of the ion exchange system at this temperature is higher than the sum of the individual capacities of the ion exchangers (226.6 mg/g). The results obtained demonstrate that the ion exchange system with long-range interaction absorbs Cu(II) ions more effectively than individual sorbents. In order to elucidate the activation mechanism, the conductivity of individual ion exchangers and the ion exchange system in aqueous solutions was measured by the conductometric method. Accordingly, the conductivity of AN-31 (OH^- form) was 20.5 µs/cm, and KU-2-8 (H⁺ form) – 2.48 µs/cm, and the conductivity of the KU-2-8-AN-31 system was 27.9 µs/cm. The presence of H⁺ and OH^- ions in the system, capable of forming water molecules, resulted in an increase in the ionization of sulfogroups in the KU-2-8 cation ion exchanger, thereby enhancing their capacity to sorb Cu(II) ions. In the ion exchange system KU-2-8-AN-31 (1:1), compared to other systems, a deeper cross-activation of the functional groups of polymers can occur due to their transition to a highly ionized state, leading to a significant increase in the sorption capacity of the studied system. The adsorption isotherms of Cu(II) ions by ion exchangers and ion exchange systems were analysed using various models. The findings indicated that the Langmuir model provides a superior fit to the experimental results. Moreover, kinetic studies demonstrated that the adsorption process of Cu(II) ions is more accurately described by the pseudo-second order kinetic model.