Multifunctional amphoteric resin to remove both anionic and cationic dyes from aqueous solution

This study reports the synthesis and characterization of a new amphoteric resin, which can be used for the removal of both cationic, methylene blue (MB) and anionic dyes, reactive red-120 (RR-120). The amphoteric resin was characterized by ATR-FTIR, SEM-EDX, TGA/DTA, DLS, BET analysis and also its surface pHpzc was determined. The prepared resin has micro porous structure and its particle size was at the nano level. The prepared amphoteric resin showed high removal affinity for MB in both acidic and basic medium, while for RR-120 high removal affinity in acidic medium. Moreover, it was observed that the amphoteric resin has exhibited almost 100% dye removal up to 600 ppm for MB and up to 300 ppm for RR-120, respectively. The adsorption behavior of both dyes on the amphoteric resin is in agreement with the Langmuir isotherm and the pseudo-second order kinetic model and also electrostatic interaction is dominant in adsorption. Its capacity was slightly low for the MB than that of the commercial activated carbon, but higher for the RR-120. Furthermore, it was observed that the amphoteric resin almost did not lose its high removal efficiency in the concentrated matrix environment for both dyes. After five repeated adsorption-desorption cycles, the high removal efficiency of the resin for the MB (almost 100%) unchanged, but for the RR-120 decreased to 83%.

Automated summary

This study synthesized a new amphoteric resin for efficient removal of both cationic (methylene blue) and anionic (reactive red-120) dyes, displaying high removal affinity and stability. Adsorption behavior followed Langmuir isotherm and pseudo-second order kinetic model, with electrostatic interaction playing a dominant role. The resin maintained its high removal efficiency even in concentrated matrix environments, with minimal decrease after repeated cycles.