Kinetic model for better understanding of the humic acid adsorption behavior onto different carbon/CNT adsorbents

Abstract The aims of the current study is to investigate the effectiveness of adsorption of carbon graphite/carbon nanotube composites (KS44/CNT) in removing humic substances from aqueous solutions. Carbon nanotubes (CNTs) were synthesized within the porous carbon material through an in-situ growth process. The results showed that the adsorption capacity of humic acid (HA) was significantly affected by the presence of CNTs. Furthermore, Chemical oxidation of KS44/CNT has a more pronounced effect on the adsorption behavior of humic acid compared to the graphite carbon composite (KS44/0). The most sensitive sites to interacting with the acidic functionalities of Humic Acid are favored by carbon nanotubes due to their greater tendency to oxidize than graphite structure. The kinetic study, including the pseudo-first order, pseudo-second order and Elovich equations, was carried out to better understand the adsorption mechanism of HA on the elaborated supports. The pseudo-second order kinetic model provided the best match to the equilibrium data derived from the adsorption tests. Based on this model, it can be postulated that the adsorption rate is limited by the rate of adsorbate transport occurring at the pore surface of the adsorbents.