Synthesis and characterization of a quaternary composite based on RGO/MWCNTs/choline chloride + malonic acid for methyl orange dye adsorption

Abstract

The objective of this study is to synthesis a quaternary composite of reduced graphene oxide (RGO), miltiwaled carbon nanotube (MWCNTs), choline chloride, and malonic acid by using discrete flame deposition technology to make multi-walled carbon nanotubes. Ascorbic acid was used to produce reduced graphene oxide through reduction and subsequently synthesize the deep eutectic solvent. The product was characterized using several techniques: such as Raman spectroscopy, X-ray difruction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM). The current study used a mixed material made of Deeb Eutictic Sol(DES) like choline chloride and Malonic acid with RGO and MWCNTs to adsorb and remove the dye methyl orange (MO). Some techniques such as: HNMR, C13 and IR tests, were used to examine the data for the eutectic solvents of malonic acid and choline chloride. Efffect of some parametrs upon adsorption of dye were investigated such as weight of adsorbent, the contact time between dye with composite, as well as the temperature, pH and ionic density. Also investigation on the adsorption kinetics, and isotherms were studied. The results showed that according to Giles classification, the adsorption curve on the surface of the prepared compound is (S3) for methyl orange dye, which follows the Freundlich model and enables adsorption. The results of the adsorption study of methyl orange dye at different temperatures showed that the amount of adsorbed dye increases with decreasing temperature, indicating that the adsorption process was thermal and exothermic. The adsorption process of methyl orange dye was studied, where it was found that the highest amount of dye adsorbed on the surface of the prepared compound was pH = 4. The results also showed the effect of ionic strength on the adsorption process of salts (NaCl, CaCO3) where it was found that CaCO3 salts with greater solubility affect the amount of adsorbed material compared to NaCl salts. The results also indicated that the adsorption temperature equation applies to Freundlich and Mecan and does not apply to Langmuir. Therefore, the adsorption is physical adsorption because the surface energy of the adsorbent materials is heterogeneous and multilayered and the enthalpy value for us was a negative value, which confirms the type of adsorption since the adsorption here is physical. The results also showed that the adsorption kinetics study of methyl orange dye is of the pseudo-second order, and its surface adsorption ability was tested by reactivating it after each use by washing it with distilled water, and it was found that it has the ability to adsorption after the activation process with the same efficiency, then a decrease occurs in its surface adsorption ability.