Fabrication of zirconium/chitosan functionalized magnetic carbon nanotubes for enhanced adsorption of alizarin red

Abstract

In this study, a composite adsorbent (Zr-CMCNTs) based on modification of magnetic carbon nanotubes (MCNTs) with chitosan (CS) and zirconium oxychloride octahydrate (ZrOCl 2 ⋅8H 1 2 O) was synthesized and showed excellent adsorption ability for alizarin red (AR) in aqueous solution. The maximum adsorption capacity of Zr-CMCNTs for AR could reach 889 mg⋅g at 313 K (pH = 3.4). The performance was not significantly affected by the presence of common ions, showing good salt tolerance. The adsorption equilibrium process was consistent with Langmuir, Freundlich, Koble-Corrigan, and Temkin models, suggesting that both monolayer and multilayer adsorption were involved. The adsorption kinetic process was well described by the pseudo-second-order, Elovich and Double constant kinetic models. The thermodynamic parameters calculated confirm the adsorption process to be spontaneous, endothermic and entropy-increasing. Analyses of the underlying mechanism shows that the adsorption process was mainly due to complexation, hydrogen bonding, π π stacking and electrostatic attraction. The magnetic property enables Zr-CMCNTs to be recovered easily following adsorption. After three desorption and regeneration cycles, the removal rate of AR still reached 60 %, indicating good reusability. Overall, Zr- CMCNTs composite adsorbent shows great potential in dye wastewater treatment.