Liquid-Phase Adsorption of an Organic Dye on Non-Modified and Nanomodified Activated Carbons: Equilibrium and Kinetic Analysis

Abstract

The present paper reports on a study of kinetic parameters of the adsorption of the Methyl Orange organic dye from aqueous solutions on nanomodified and non-modified carbon materials under static conditions. Commercially available NWC coconut shell-based activated carbon was used as a pristine adsorbent. It was modified with multi-walled carbon nanotubes to obtain a nanomodified material. These carbon nanotubes were synthesized via chemical vapor deposition over a metal-oxide catalyst prepared by a citrate sol-gel method. A spectrophotometric method was used to determine Methyl Orange concentrations (at wavelength of 400 nm). For each type of adsorbents (nanomodified and non-modified activated carbon), chemical interactions between its surface functional groups and the dye were observed. The adsorption kinetics for both types of activated carbons were analyzed by pseudofirst and pseudosecond-order models, which were well-described by the pseudosecond-order model with a correlation coefficient of about 0.99. Besides, adsorption rate constants were calculated using kinetic models. It was found that equilibrium of the Methyl Orange adsorption on the nanomodified carbon is achieved 1.5 times faster than that of the Methyl Orange adsorption on the pristine carbon, and the adsorption capacity of the former is 2.1 times higher than that of the latter one. These findings suggested that the activated carbons could be regarded as a promising adsorbent for the removal of the organic dye – Methyl Orange – from wastewaters.