Effective mitigation of single-component and mixed textile dyes from aqueous media using recyclable graphene-based nanocomposite.

The present study reported the synthesis and utilization of a graphene-based hybrid nanocomposite (MnFe ₂ O ₄ /G) to mitigate several synthetic dyes, including methylene blue, malachite green, crystal violet, and Rhodamine B. This adsorbent was structurally analyzed by several physicochemical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, N ₂ adsorption-desorption isotherm measurement, point of zero charge, and Boehm titrations. BET surface area of MnFe ₂ O ₄ /G was measured at 382.98 m ² /g, which was substantially higher than that of MnFe ₂ O ₄ . MnFe ₂ O ₄ /G possessed diverse surface chemistry properties with the presence of many functional groups such as carboxylic acid, phenolic, lactone, and basic groups. MnFe ₂ O ₄ /G was used to remove synthetic dyes in the aqueous media. The effect of many factors, e.g., concentration (5-50 mg/L), pH (4-10), dose (5-20 mg), and temperature (25-45 °C) on adsorption performance of MnFe ₂ O ₄ /G was conducted. Kinetic, isotherm, intraparticle, and thermodynamic models were adopted for investigating adsorption phenomenon of dyes on MnFe ₂ O ₄ /G. The maximum adsorption capacity of dyes over MnFe ₂ O ₄ /G was found as Rhodamine B (67.8 mg/g) < crystal violet (81.3 mg/g) < methylene blue (137.7 mg/g) < malachite green (394.5 mg/g). Some tests were performed to remove mixed dyes, and mixed dyes in the presence of antibiotics with total efficiencies of 65.8-87.9% after 120 min. Moreover, the major role of π-π stacking interaction was clarified to gain insight into the adsorption mechanism. MnFe ₂ O ₄ /G could recycle up to 4 cycles, which may be beneficial for further practical water treatment.
(© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)