Efficient removal of crystal violet by sulphonic-modified multi-walled carbon nano-tube and graphene oxide

One of the greatest worldwide problems is environmental pollution, and the elimination of contaminants, such as heavy metals, organic dyes, and aromatic compounds, is vital for human health and ecosystems. Among the various released pollutants into the environment, dyes are classified as highly toxic and hazardous materials, which can cause serious problems due to non-observance of the safety and health laws and regulations in some industries. In this research, the magnetite multi-walled carbon nano-tube (MWCNT) and modified graphene oxide (GO) were successfully modified with sulphonic acid groups as the new carbonic adsorbents. The morphology, surface properties as well as the chemical properties of functional groups of the prepared materials were characterized by scanning electronic microscope (SEM) and Fourier transform infrared spectrometer (FT-IR). The sulphonic acid-functionalized magnetite multi-walled carbon nano-tube and synthetic graphene oxide were applied as an effective adsorbent for cationic dye crystal violet (CV) removal from aqueous solutions using the batch adsorption technique. Several experimental parameters such as pH, adsorbent dosage, initial dye concentration, and contact time for adsorption of the crystal violet on the synthesized sorbents were studied and optimized. The Langmuir, Freundlich, and Temkin adsorption models were investigated to obtain adsorption isotherms. The results exhibited that the MWCNT and GO could be removed more than 80% and 90% of the above-mentioned dye at the first 15 and 20 min of contact time, respectively. The experimental adsorption kinetic was proved to be in accordance with a pseudo-second-order reaction rate. The equilibrium data showed that the adsorption behaviour of the crystal violet dye on the MWCNT and GO well fitted with the Langmuir model. On the Langmuir analysis basis, the maximum adsorption capacity of the MWCNT and GO for crystal violet dye was found to be 384 mg/g and 222 mg/g.