Adsorption Characteristics of a Novel Carbon-Nanotube-Based Composite Adsorbent toward Organic Pollutants

Carbon nanotubes (CNTs) are limited in practical water treatment application for their difficulties involved in dispersion and separation, despite their superior adsorption potential toward organic pollutants. To overcome these limitations, a novel CNT-based composite adsorbent was constructed by self-assembling CNTs onto solid microparticles. The CNT-based composites were in the shell-core structure, with CNTs entirely enwrapping the template particles. The adsorption characteristics of CNT-based composite adsorbents toward organic pollutants from aqueous systems were also explored in this paper. The Freundlich model was found to fit well to the adsorption isotherms of composite adsorbents toward 2-naphthol. The adsorption coefficient (Kf) increased with increasing CNT loading on the composite adsorbents, while the CNT normalized adsorption coefficient (Kf,CNT) decreased with increasing CNT loading. Surface adsorption was proposed to be the dominant adsorption mechanism of the CNT-based composite adsorbents, and the external surfaces of CNTs were efficient adsorption sites. For a given CNT-based adsorbent, the adsorption affinity decreased in the following order: 2-naphthol, naphthalene, and 4-chlorophenol. Competitive adsorption on CNT-based composite adsorbents was observed in multiple-adsorbate systems, and the inhibition adsorption of 2-naphthol by naphthalene was higher than that by 4-chlorophenol.