Study of the adsorption of 2,4-dichlorophenoxyacetic acid from the aqueous solution onto carbon nanotubes

Abstract

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from the aqueous solution on carbon nanotubes (CNTs-TC) was investigated in the concentration range from 52.248 to 205,672 mg L⁻¹. The results indicated that carbon nanotubes exhibited the highest 2,4-D uptake capacity of 84.034 mg g⁻¹ at 283 K. Freundlich isotherm model showed a better fit with obtained adsorption data than Langmuir and Temkin isothermal models. The adsorption performance of 2,4-D onto CNTs-TC fitted the pseudo-second-orđer model and apparent equilibrium was reached within 50 minutes. The overall rate process appeared to be influenced by both extemal mass transfer and intra-particle diffusion, but mainly govemed by intra-particle diffusion. The activation energy of adsorption was determined to be 6.4514 kcal.mol⁻¹. The calculated thermodynamic parameters showed adsorption of 2,4-D onto CNTs-TC was exothermic and spontaneous.