title: Comparative study of carbon nanotubes and granular activated carbon: Physicochemical properties and adsorption capacities.
abstract: The overall goal was to determine an optimum pre-treatment condition for carbon nanotubes (CNTs) to facilitate air pollutant adsorption. Various combinations of heat and chemical pre-treatment were explored, and toluene was tested as an example hazardous air pollutant adsorbate. Specific objectives were (1) to characterize raw and pre-treated single-wall (SW) and multi-wall (MW) CNTs and compare their physical/chemical properties to commercially available granular activated carbon (GAC), (2) to determine the adsorption capacities for toluene onto pre-treated CNTs vs. GAC. CNTs were purified via heat-treatment at 400 °C in steam, followed by nitric acid treatment (3N, 5N, 11N, 16N) for 3-12 h to create openings to facilitate adsorption onto interior CNT sites. For SWNT, Raman spectroscopy showed that acid treatment removed impurities up to a point, but amorphous carbon reformed with 10h-6N acid treatment. Surface area of SWNTs with 3 h-3N acid treatment (1347 m(2)/g) was higher than the raw sample (1136 m(2)/g), and their toluene maximum adsorption capacity was comparable to GAC. When bed effluent reached 10% of inlet concentration (breakthrough indicating time for bed cleaning), SWNTs had adsorbed 240 mg/g of toluene, compared to 150 mg/g for GAC. Physical/chemical analyses showed no substantial difference for pre-treated vs. raw MWNTs.
authors.affiliation: Department of Civil Engineering, Box 19308, University of Texas at Arlington, Arlington, TX 76019, USA. Electronic address: rojaharitha@gmail.com.
authors.forename: Roja Haritha
authors.initials: RH
authors.lastname: Gangupomu
authors.affiliation: Department of Civil Engineering, Box 19308, University of Texas at Arlington, Arlington, TX 76019, USA. Electronic address: sattler@uta.edu.
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Sattler
authors.affiliation: Department of Environmental Engineering, Texas A&M Kingsville, MSC 213, 700 University Blvd., Kingsville, TX 78363-8202, USA. Electronic address: david.ramirez@tamuk.edu.
authors.forename: David
authors.initials: D
authors.lastname: Ramirez
keywords: Adsorption; Granular activated carbon; Hazardous air pollutant; Nanotubes; Toluene