Adsorption of catechol by Zr-loaded carbon nanotubes from solution

Abstract

Catechol in water seriously affects the oxygen balance in the water and endangers the human nervous system. Therefore, the removal of phenolic organic compounds from water is of vital importance. Zr-modified carboxylic multi-walled carbon nanotubes (Zr-cCNTs) were prepared by chemical precipitation method and the adsorption properties toward catechol were studied. The maximum adsorption capacity of Zr-cCNTs for catechol was 42.7 mg g–1, which greatly improved the adsorption ability for catechol on carboxylic multi-walled carbon nanotubes (cMWCNTs). The adsorption of catechol onto Zr-cCNTs was slightly affected by pH and the coexistence of Cl– 2– and SO4 in an aqueous solution. The adsorption process of catechol by Zr-cCNTs accorded with Freundlich and Koble–Corrigan models. The adsorption kinetics confirmed to the Elovich and pseudo-second-order kinetic model, which indicated that the adsorption was dominated by chemical adsorption and there was an ion exchange process. The thermodynamic study showed that the adsorption of catechol by Zr-cCNTs was a spontaneous, endothermic and entropy-increasing physical and chemical adsorption process. But after adsorbing catechol, the desorption and regeneration effect of Zr-cCNTs was poor, which also showed that Zr-cCNTs had a strong binding force to catechol. Moreover, the adsorption capacity and adsorption constant of Zr-cCNTs for catechol in single-component and mix-component systems were higher than other adsorbates. This proved that Zr-cCNTs showed selectivity for the adsorption of catechol due to the presence of o-dihydroxyl in the catechol structure. The mechanism is major complexation through X-ray photoelectron spectroscopy analysis and experimental results. The synthesized adsorbent Zr-cCNTs had excellent adsorption capacity and could be used in the adsorption treatment of related wastewater.