| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 96 === 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 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 equilibrium amount of BTEX adsorbed on CNTs(NaOCl)(qe) increased with agitation speed, contact time, initial BTEX concentration and solution ionic strength but appeared no remarkable change with solution pH.The maximum adsorbed amounts of BTEX onto heated CNT(NaOCl) calculated by the Langmuir model at 25oC were (B:118.49mg/g, T:40.73mg/g, E:357.28mg/g, X:515.51mg/g) respectively,which were much higher than that onto commercially available granular activated carbon.
The thermodynamic analysis, the adsorption of BTEX onto CNTs(NaOCl) is an exothermic and spontaneous process. A comparative study on the adsorption of BTEX among CNTs, CNT(NaOCl) and GAC showed that under the same conditions the CNT(NaOCl) possess superior adsorption capacities for of BTEX than the CNTs and GAC. The adsorption/desorption study indicated that the CNT(NaOCl) have better reversible adsorption performance than the commercially available CNT(NaOCl) and GAC. This suggests that the as-prepared oxidized CNTs are promising BTEX adsorbents and have good potential for BTEX removal in wastewater treatment.
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