Drinking and wastewater are to be treated for safe human consumption and for keeping surface waters clean. There are multiple water purification procedures, but the use of ion-exchange resins significantly enhances water purification efficiency. This review was targeted on highlighting the concept and classification of polymeric ion-exchange resins as well as pointing out their real-world applications. Their successful use for purification purposes has been linked to their chemical structure, simplicity of operation, accessibility, and reusability. Therefore, polymeric ion-exchange resins have been used for the removal of a wide range of organic and inorganic pollutants such as pharmaceutical compounds, dyes, organic matter, metals, and many others. Ion-exchange resins are obtained directly by synthesis methods or grafting ionizable groups on polymer matrix in order to ensure continuous improvement. Furthermore, the newly designed ion-exchange resins take into consideration biodegradability potential towards obtaining ecofriendly compounds.

Despite Acid Blue 113 (AB 113)’s extensive use and negative environmental impact, very few studies have focused on its efficient and environmentally friendly removal. This research aims the removal of AB 113 from environmental aqueous media and its consequent enzymatic biodegradation. A strongly basic anion exchange resin in Cl⁻ form, Amberlite IRA 402 (IRA 402(Cl⁻)) was used for AB 113 adsorption and a laccase was used to further biodegrade it. For the first time, two novel, efficient and environmentally friendly physical–chemical and biological assays for AB 113 wastewater removal and subsequent biodegradation were combined. The adsorption of AB 113 onto IRA 402(Cl⁻) was tested in batch and continuous flux modes. Influence of contact time, concentration and desorption in acidic media were evaluated. The kinetic data were best modulated by the Lagergren model with R² = 0.9275. The Langmuir isotherm model best fitted the experimental data, and the maximum adsorption capacity was 130 mg/g. Dye, resin and AB113 loaded resin were characterized by thermogravimetry and FTIR to evaluate their physical chemical properties modification. Based on the performed studies, a consecutive methodology is proposed, incorporating the ion exchange process in the first stage and the biodegradation process in the second. Thus, in the second stage the residual concentration of AB 113 is reduced by an efficient bio-degradation process produced by the laccase at pH = 4.

In this paper, two chelate resins prepared by a simple procedure were used for the removal of Cd²⁺, Ni²⁺, Cu²⁺, and Pb²⁺ (M²⁺) from aqueous solutions. Amberlite IRA 402 strongly basic anion exchange resin in Cl⁻ form (IRA 402 (Cl⁻) together with Amberlite XAD7HP acrylic ester co-polymer (XAD7HP) were functionalized with chelating agent Direct red 23 (DR 23). The chelate resins (IRA 402-DR 23 and XAD7HP-DR 23) were obtained in batch mode. The influence of interaction time, pH and the initial concentration of DR 23 solution was investigated using UV-Vis spectrometry. The time necessary to reach equilibrium was 90 min for both resins. A negligible effect of adsorption capacity (Q_e) was obtained when the DR 23 solution was adjusted at a pH of 2 and 7.9. The Q_e of the XAD7HP resin (27 mg DR 23/g) is greater than for IRA 402 (Cl⁻) (21 mg DR 23/g). The efficiency of chelating resins was checked via M²⁺ removal determined by the atomic adsorption spectrometry method (AAS). The M²⁺ removal by the IRA 402-DR 23 and XAD7HP-DR 23 showed that the latter is more efficient for this propose. As a consequence, for divalent ions, the chelated resins followed the selectivity sequence: Cd²⁺ > Cu²⁺ > Ni²⁺ > Pb²⁺. Additionally, Cd²⁺, Cu²⁺ and Ni²⁺ removal was fitted very well with the Freundlich model in terms of height correlation coefficient (R²), while Pb²⁺ was best fitted with Langmuir model for IRA 402-DR 23, the Cu²⁺ removal is described by the Langmuir model, and Cd²⁺, Ni²⁺ and Pb²⁺ removal was found to be in concordance with the Freundlich model for XAD7HP-DR 23. The M²⁺ elution from the chelate resins was carried out using 2 M HCl. The greater M²⁺ recovery from chelating resins mass confirmed their sustainability. The chelate resins used before and after M²⁺ removal by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were evaluated.