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A novel environmental-friendly nanobiocomposite synthesis by EDTA and chitosan functionalized magnetic graphene oxide for high removal of Rhodamine B: Adsorption mechanism and separation property

Nekouei Marnani, Niloufar, Shahbazi, Afsaneh
Chemosphere 2019 v.218 pp. 715-725
EDTA (chelating agent), Fourier transform infrared spectroscopy, X-ray diffraction, adsorbents, adsorption, aqueous solutions, chitosan, desorption, dyes, endothermy, experimental design, graphene oxide, kinetics, magnetism, moieties, nanosheets, pH, rhodamines, scanning electron microscopy, sorption isotherms, temperature, thermodynamics, thermogravimetry, zeta potential
The synergistic combination of two different environmentally friendly functional groups (EDTA and Chitosan) with magnetic graphene oxide (mGO) nano-sheets was used for synthesizing a promising nanobiocomposite adsorbent (CS-EDTA-mGO) for efficient removal of a cationic dye, Rhodamine B (RhB), from aqueous solutions. CS-EDTA-mGO nanobiocomposite was characterized by XRD, FTIR, VSM, TGA, and zeta potential. Further, the morphological features of the synthesized graphene oxide and mGO were examined by SEM technique. The adsorption conditions were designed and optimized by experimental design applied by faced-central composite design. CS-EDTA-mGO indicated high sorption capacity where the R% of 92% was obtained under optimal conditions (sorbent dosage = 0.14 g L−1; dye concentration = 114 mg L−1; pH = 7.5; temperature = 33 °C). The result of kinetics studies revealed that the adsorption was considerably fast and the data followed the pseudo-second-order kinetic model. The adsorption equilibrium of the cationic dye by CS-EDTA-mGO showed that the Langmuir model fitted the experimental data significantly and the maximum adsorption capacity estimated from Langmuir model was 1085.3 mg g−1, which was highly consistent with the maximum experimental adsorption capacity. The thermodynamic parameters represented that the interaction in the adsorption process was endothermic and the randomness at the solid/solution interface increased during the process. Both physical and chemical mechanisms were involved in the adsorption process, owing to the complicated structural characteristics of the nanobiocomposite. After seven cycles of adsorption/desorption, the removal efficiency of CS-EDTA-mGO nanobiocomposite was still over 80% with little loss of adsorption capacity (≈2%).