Adsorption and desorption of flavonoids on activated carbon impregnated with different metal ions

Abstract

In this study, four metal ions Mg²⁺, Al³⁺, Fe³⁺, and Zn²⁺ were loaded on the surface of activated carbon by an impregnation method coupled with high-temperature calcination to prepare modified activated carbon. Scanning electron microscopy, specific surface area and pore size analysis, X-ray diffraction, and Fourier infrared spectroscopy were used to evaluate the structure and morphology of the modified activated carbon. The findings show that the modified activated carbon had a large microporous structure and high specific surface area, both of which significantly improved absorbability. This study also investigated the adsorption and desorption kinetics of the prepared activated carbon for three flavonoids with representative structures. The adsorption amounts of quercetin, luteolin, and naringenin in the blank activated carbon reached 920.24 mg g⁻¹, 837.07 mg g⁻¹, and 677.37 mg g⁻¹, while for activated carbon impregnated with Mg, the adsorption amounts reached 976.34 mg g⁻¹, 963.39 mg g⁻¹, and 817.98 mg g⁻¹, respectively; however, the desorption efficiencies of the three flavonoids varied a lot. The differences in desorption rates of naringenin as compared with quercetin and luteolin in the blank activated carbon were 40.13% and 46.22%, respectively, and the difference in desorption rates increased to 78.46% and 86.93% in the activated carbon impregnated with Al. The differences provide a basis for the application of this type of activated carbon in the selective enrichment and separation of flavonoids.