Resumen
It has been widely accepted worldwide that water security is by far the greatest threat in the new millennium. Dyes are the main pollutant for water and adsorption is the most common technology used to remove dyes. Magnetic multi-walled carbon nanotubes (MMWCNTs) have recently been hailed as novel adsorbent for dyes removal. MMWCNTs which can be easily separated by magnetic field can overcome the limitations encountered by conventional adsorption process that required additional processing steps to remove the adsorbents from the discharged water. The objectives in this study include the synthesis of MMWCNTs and the evaluation of the separation efficiency and adsorption behaviour of MMWCNTs. MMWCNTs were synthesized via facile and solvent free direct doping of iron oxide nanoparticles (Fe3O4) onto CNTs. This method utilizes the concept of opposite electrostatic attraction between the positively charged Fe3O4 and negatively charged CNTs by dispersing both Fe3O4 and CNTs in distilled water under specific pH condition and rotated overnight. Characterization results (SEM-EDX, FTIR and zeta potential analysis) confirmed the successful deposition of Fe3O4 onto CNTs synthesized under this solvent free direct doping method. The MMWCNTs were subjected in the removal of methylene blue (MB) from wastewater. When the pH of the adsorption medium was increased from 3 to 11, the adsorption capacity of MMWCNTs exhibited a remarkable increment of 87.9 % from 11.69 mg/g to 21.96 mg/g. Furthermore, the removal efficiency of MB by MMWCNTs also increased from 41.5 % at pH 3 to 89.8% at pH 9. This is due to the increase in the electrostatic attraction between MB and n-MMWCNTs. The adsorption of MB on n-MMWCNTs was found to obey the Langmuir isotherm (indicating a monolayer adsorption) with a maximum adsorption capacity of 20.4 mg/g. In short, the used of MMWCNTs as adsorbent could represent a breakthrough technology for water remediation, which warrants further study.