Removal of Paraquat from Aqueous Solutions Using Multi-Walled Carbon Nanotubes: Kinetic, Isotherm and Thermodynamic Studies

Abstract

Multi-walled carbon nanotubes (MWCNT) were used as an efficient adsorbent to remove Paraquat (PQ) molecules from its aqueous solutions. The initial PQ concentration, adsorption time and temperature had considerable effect on the removal of PQ onto MWCNT. The adsorption of PQ onto MWCNT followed the pseudo second-order kinetic model involving the particle-diffusion mechanism. The adsorption isotherms were fitted by the Langmuir isotherm, with the maximum adsorption capacity based on the former of 79.365 mg·g-1. Thermodynamic parameters, including Gibbs free energy changes (ΔG0), as well as changes in enthalpy (ΔH0) and entropy (ΔS0), were also calculated. The results demonstrated that PQ was adsorbed onto MWCNT spontaneously and endothermically in nature.