Choline chloride–glycerol deep eutectic solvent-engineered RGO/MWCNT hybrid for methyl orange removal: Equilibrium, kinetic, and thermodynamic assessment

An RGO/MWCNT hybrid nanocomposite was synthesized by using the deep eutectic solvent (DES) choline chloride and glycerol (۱:۲ molar ratio; glyceline) as a dispersing and interfacial medium for the removal of methyl orange (MO) from water. The formation of hydrogen-bonded liquid and embedding of MWCNT domains in a textured carbon matrix were confirmed by FTIR, ¹H NMR, ¹³C NMR and FESEM. The amount of adsorbent, contact time, initial pH of the solution, addition of inorganic salts, and temperature were determined in batch experiments with ۱۰ mL of the ۳۰ mg L⁻¹ MO. The removal efficiency obtained from mass balance was found to be ranging from ۹۹.۳۶ to ۹۹.۷۶% in the range of ۰.۰۲–۰.۰۸ g adsorbent, with the highest value being ۱۴.۹۶۴ mg g−۱ for ۰.۰۲ g of adsorbent. The equilibrium was almost reached after ۹۰ min, and the pseudo-second-order model was the best kinetic model (R² = ۰.۹۹۹۹۸; qₑ,cal = ۱۴.۴۸۶ mg g⁻¹). The values of R² obtained for Langmuir, Freundlich and Temkin were ۰.۹۸۸۹۵, ۰.۹۹۸۹۵ and ۰.۹۹۹۸۰, respectively, while the values of estimated qmax, n or Bᵀ were ۱۵.۱۶ mg g⁻¹, ۲۱.۳۵ and ۴۸.۵۵ mg g⁻¹, respectively. The pH ۴ favored adsorption and it decreased slightly with increasing temperature. The apparent ΔH value was found to be exothermic and negative, and the apparent ΔG values were negative, which are thermodynamically favorable for uptake under the conditions investigated. The structural and adsorption trends are in agreement with π–π interactions, hydrogen bonding, electrostatic contributions and interfacial diffusion. The results indicate that glyceline is a potential neutral-polyol DES for the optimization of RGO/MWCNT interfaces in the dilute-dye treatment.

کلیدواژه ها:

Deep eutectic solvent ، Glycerol ، Reduced graphene Oxide ، Multi-walled carbon nanotubes ، ethyl orange