Surface modification of carbon nanotubes for enhancing BTEX adsorption from aqueous solutions

Carbon nanotubes (CNTs) were fabricated by the catalytic chemical vapor deposition method and oxidized by HCl, H₂SO₄, HNO₃ and NaOCl solutions for enhancing benzene, toluene, ethylbenzene and p-xylene (BTEX) adsorption in an aqueous solution. The surface nature of CNTs was changed after the H₂SO₄, HNO₃ and NaOCl oxidation, which makes CNTs that adsorb more BTEX. The NaOCl-oxidized CNTs show the greatest enhancement in BTEX adsorption, followed by the HNO₃-oxidized CNTs, and then the H₂SO₄-oxidized CNTs. The adsorption mechanism of BTEX via CNTs is mainly attributed to the π-π electron-donor-acceptor interaction between the aromatic ring of BTEX and the surface carboxylic groups of CNTs. The NaOCl-oxidized CNTs have superior adsorption performance of BTEX as compared to many types of carbon and silica adsorbents reported in the literature. This suggests that the NaOCl-oxidized CNTs are efficient BTEX adsorbents and that they possess good potential applications for BTEX removal in wastewater treatment.