Adsorption of nicotine and tar from the mainstream smoke of cigarettes by oxidized carbon nanotubes
Introduction
The pollution and health hazard caused by smoking have been an urgent problem in the world [1], [2], [3]. Tobacco smoke is a very complex mixture containing more than 3800 compounds, which are aerosol composed of volatile agents in the vapor phase and of semi- and non-volatile compounds [4], [5]. Besides nicotine, the major inducer of tobacco dependence, cigarette smoke also contains various toxic compounds and notably carcinogenic agents like polycyclic aromatic hydrocarbons, commonly called ‘tar’ [6]. Both of them constitute a serious health risk. In the past years, great efforts have been made in the development of filter tips. It is an effective and convenient way to add some additives such as active carbon [7], zeolite [5], [8] and NaClO3 [9] in the filter tips, utilizing their abilities to physisorb and/or chemisorb substances from the mainstream smoke (MS) of cigarette. However, increasingly stringent standard on the quality of cigarette has stimulated a growing effort on the improvement of removal efficiency of toxic compounds.
Carbon nanotubes (CNTs), a fascinating new material, are attracting more and more attention since their discovery [10]. Their small sizes, large surface areas, hollow and nanosized layered structures, high mechanical strength and remarkable electrical conductivities make them have a wide range of promising applications, such as field emission [11], reinforcing materials in composites [12], nanoprobes [13] and chemical sensors [14]. Studies of CNTs used as absorbents have also been reported [15], [16], [17], [18], [19]. Li et al. [16] have found that CNTs show exceptional adsorption capability and high adsorption efficiency for cadmium (II) removal from aqueous solution. It has been known that surface oxidized CNTs can be used as the prime material for adsorption of gas such as H2 [17], O2 [18] and methane [19]. Thus, it is supposed that CNTs can be used as a candidate for removal of ingredients from MS.
In this paper we compare the removal efficiencies of nicotine and tar from MS by the filter tips filled with oxidized carbon nanotubes (O-CNTs), activated carbon and zeolite (NaY). Adsorption mechanism of O-CNTs and the effect of O-CNTs mass on the removal efficiency are also investigated.
Section snippets
Experimental
CNTs were fabricated by catalytic pyrolysis of the propylene (C3H6) at about 750 °C in a ceramic tube with Fe particles as the catalysts. The as-prepared CNTs were dispersed in concentrated nitric acid and refluxed at 140 °C to remove most of the catalyst particles and obtain oxidized carbon nanotubes (O-CNTs). Adsorption and desorption of nitrogen on O-CNTs was measured at 77 K in a volumetric system in the whole relative pressure range. From the isotherms, the BET surface area and the pore size
Results and discussion
The reduction results of nicotine and tar by O-CNTs, activated carbon and zeolite are shown in Table 2. According to Table 2, the adsorption capacity of O-CNTs for nicotine (up to 0.56 mg/cigarette) and tar (up to 13.0 mg/cigarette) is higher than that of zeolite and even higher than that of activated carbon.
Zeolite, whose adsorption capacity is determined by its pore size and surface area, can physisorb some ingredients from MS. For example, zeolite (NaY) with the pore size of 7.4 Å can remove
Conclusions
In conclusion, the adsorption capability of O-CNTs for nicotine and tar from MS is much higher than that of activated carbon and zeolite (NaY). Nicotine and tar may be adsorbed in the inner hole, at the interior of the tube wall, in the inter-layers and at the exterior of the tube wall of O-CNTs. In addition, capillary condensation of some ingredients of MS in the inner hole of O-CNTs may be the primary reason for their exceptional removal efficiency. When about 20–30 mg O-CNTs per cigarette is
References (29)
- et al.
Cancer Lett.
(1995) - et al.
Microp. Mesop. Mater.
(2003) - et al.
Food Chem. Toxicol.
(2000) - et al.
Fundam. Appl. Toxicol.
(1997) - et al.
Chem. Phys. Lett.
(2001) - et al.
Fluid Phase Equilibr.
(2002) - et al.
Chem. Phys. Lett.
(2000) - et al.
Chem. Phys. Lett.
(2001) - et al.
Solid State Commun.
(2004) - The World Health Report 1995, World Health Organization, Geneva, 1995, p....