Magnetic iron oxide nanoparticles functionalized multi-walled carbon nanotubes for toluene, ethylbenzene and xylene removal from aqueous solution.

An effectively and functionally magnetic multi-walled carbon nanotube (MWCNTs) nano-composite (APCNT-KOH) was synthesized by a one-pot and facile method. The residual Fe catalyst particles of the as-prepared MWCNTs were utilized as magnetic materials through KOH activation. The resulting APCNT-KOH exhibited very high adsorption capacities for toluene (T), ethylbenzene (E), and xylene (X) (TEX) pollutants than many other adsorbents, because of their large specific surface area and high degree of surface activity. The adsorption process was found to be pH, ionic strength, and temperature dependent, and the maximum adsorption capacity was observed at pH 6 for TEX pollutants. The adsorption isotherm data were analyzed by applying the Langmuir, Freundlich, and Dubinin-Radushkevich isothermal models. The Langmuir model showed the best fit to the experimental isotherm data with a maximum adsorption capacity(qm,toluene = 63.34 mg/g, qm, ethylbenzene = 249.44 mg/g, qm,m-xylene = 227.05 mg/g, qm,o-xylene = 138.04 mg/g, qm,p-xylene = 105.59 mg/g). Adsorption kinetics of TEX on APCNT-KOH was appropriately described by the pseudo-second-order rate model. The desorption experiments revealed the typical adsorption-desorption hysteresis, indicating that the adsorption and desorption processes of TEX undergo different pathways due to porous structure changes before and after adsorption and desorption. Collective results demonstrate that the functionalized magnetic APCNT-KOH composites are highly-effective adsorbents for TEX removal, which provides a promising and green route for MWCNTs in wastewater treatment.