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Journal of Hazardous Materials 169 (2009) 1034–1039

Contents lists available at ScienceDirect

Journal of Hazardous Materials

journa l homepage: www.e lsev ier .com/ locate / jhazmat

liminating carcinogenic pollutants in environment: Reducing the tobaccopecific nitrosamines level of smoke by zeolite-like calcosilicate

ing Gaoa, Yi Caoa, Shi Lu Zhoub,c, Ting Ting Zhuanga, Ying Wangb, Jian Hua Zhua,∗

Key Laboratory of Mesoscopic Chemistry of MOE, College of Chemistry & Chemical Engineering, Nanjing University, 22 Hankou Road, Gu-lou, Nanjing, Jiangsu 210093, ChinaDepartment of Chemistry, College of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210093, ChinaTechnology Centre of Etsong Tobacco Group, Qingdao 266021, China

r t i c l e i n f o

rticle history:eceived 22 January 2009eceived in revised form 10 April 2009ccepted 14 April 2009vailable online 19 April 2009

a b s t r a c t

Trapping carcinogens such as tobacco-specific nitrosamines (TSNA) in environmental tobacco smoke(ETS) is a challenge for the application of zeolite in environment protection because most TSNA existin the particles whose size exceed the micropores of zeolites. In this paper, a new strategy to interceptthe particles and to trap the TSNA in smoke by use of the porous calcosilicate material with fiber-likemorphology plus two-dimensional eight-ring channel system is depicted and assessed. Owing to the

eywords:AS-1 calcosilicateeolite-like porous materialsorphology

obacco specific nitrosaminesigarette smoke

specific fiber-like morphology and chemical composition, zeolite-like calcosilicate CAS-1 can effectivelyintercept the particles and thus reduces the TSNA level of mainstream smoke in the range of 30–60% once itis added into the cigarette filter, which is superior to zeolite NaA additive with the same amount. Moreover,the importance of morphology of zeolite-like porous materials on the adsorption of nitrosamines in smokeis reported for the first time.

© 2009 Elsevier B.V. All rights reserved.

nvironment protection

. Introduction

Environment protection is the new application realm of zeolitesnd one of the extensive efforts is to control the pollution causedy smoking that has been a global problem. Cigarette smoke con-ains thousands of compounds and among them nitrosamines arearcinogenic to cause serious health risk even in trace amounts1,2]. Most of the nitrosamines are characterized with functionalroup of N–NO, and tobacco-specific nitrosamines (TSNA) arehe most abundant carcinogens identified in tobacco and tobaccomoke [3]. TSNA play an important role as causative agents in can-er of the esophagus, pancreas, and oral cavity associated withmoking. N′-Nitrosonornicotine (NNN), N′-nitrosoanatabine (NAT),′-nitrosoanabasine (NAB) and 4-methylnitrosarnino-1-3-pyridyl--butanone (NNK) are the main components of TSNA, NNK and NNNre the most carcinogenic TSNA in laboratory animals. In order torotect environment and public health, it is necessary to reduce the

evel of nitrosamines in environmental tobacco smoke (ETS), spe-

ially decreasing the content of TSNA [4]. Zeolites are the porousrystalline materials with the regular pore size similar to the molec-lar dimensions. As the pores preferentially adsorb molecules thatt snugly inside the pore and exclude molecules that are too large,

∗ Corresponding author. Tel.: +86 25 83595848; fax: +86 25 83317761.E-mail address: jhzhu@nju.edu.cn (J.H. Zhu).

304-3894/$ – see front matter © 2009 Elsevier B.V. All rights reserved.oi:10.1016/j.jhazmat.2009.04.042

they act as sieves on a molecular scale [5]. Consulting the pore sizeof zeolite and the molecular diameter of nitrosamines, it seems pos-sible to capture the nitrosamines in environment by use of zeoliteadsorbents, and this notion has been confirmed by many experi-ments done in laboratory [6–8]. However, new problem arises oncezeolite is applied to purify the tobacco smoke. Cigarette smoke is acomplex system consisting of many great suspended particles anda surrounding gas phase [9], and most TSNA exist in the particleswhose size exceeds the micropores of zeolites.

The clue to trap the TSNA in environmental tobacco smokecomes from cigarette filter itself. The cellulose acetate on filter cancapture the TSNA in smoke because of its special silk-like morphol-ogy. Thus, utilizing the zeolite-like candidate with the morphologyclose to fiber seems to be the key to trap the TSNA in the environ-mental tobacco smoke. Accordingly, CAS-1 is selected because of itsspecific morphology. CAS-1 sample is the porous calcosilicate mate-rial with long stick-like crystal [10], possessing two-dimensionalpore structure but the pore size is smaller than that of zeoliteNaA. Rigorously, CAS-1 is a layer silicate, and its structure can bedescribed as a series of silicate double layers connected via chainsof edge-sharing CaO5(H2O) octahedra. There is a two-dimensional

eight-ring channel system within the silicate layer, and K+ ions,which balance the charge, are located in the eight rings [11]. Toquickly evaluate the actual performance of porous materials intrapping the TSNA in tobacco smoke, we directly put the mate-rial into the cigarette filter to examine the variation of the TSNA

ous Materials 169 (2009) 1034–1039 1035

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evel in the mainstream smoke, because the main stream smokef cigarette has a complex composition similar to that of environ-ental tobacco smoke. Another objective of this study is to compare

he efficiency of common zeolite and the zeolite-like material withifferent morphology in adsorbing nitrosamines under both labo-atory and cigarette smoking conditions, in order to examine thempact of morphology of the porous adsorbent in environmentrotection that is rarely studied [12]. For these purpose two zeo-

ites, NaA and KA are chosen in the present investigation becausehey have the small pore size similar to that of CAS-1 and theargest number of cation among the commercial zeolites [7]. Both ofhese zeolites have particle appearance. Besides, two nitrosamines,-nitrosopyrrolidine (NPYR) and N′-nitrosonornicotine (NNN), areelected to perform adsorption or temperature programmed sur-ace reaction (TPSR) tests in laboratory in order to assess thedsorptive and catalytic properties of CAS-1 and zeolites. NPYRas a structure of five-member ring with a molecular diameter of.42 nm × 0.54 nm [7], the structure of NNN looks like the H atom

n the five-membered ring of NPYR to be replaced by a pyridine, sots molecular size can reach 0.75 nm × 0.80 nm [13]. Both of theseitrosamines are carcinogenic compounds, but they can be catalyt-

cally degraded by zeolite, starting from the rupture of N–NO bondo form less harmful fragments such as NOx and amines [8].

. Experimental

.1. Materials preparation

Zeolite NaA and KA were the commercially available pow-er samples supplied by Shanghai zeolite factory. CAS-1 is

porous material with the pore size close to that of zeo-ite KA, and it was synthesized according to the literature10]. Typically, the rough materials were mixed as a recipe of.2TEAOH:0.3K2O:0.15CaO:SiO2:30H2O and stirred at 298 K for.5 h. The resulting sol was sealed in a Teflon-lined stainless auto-lave and held at 493 K for 10 days. The solid product was separatedy centrifuge, washed with distilled water and dried at 373 K.able 1 lists the relevant parameters of these porous materials.PYR and NNN were purchased from Sigma and dissolved inichloromethane at volume ratio of 1:19 and stored at 273 K respec-ively. The purity of N2 and H2 carrier gases was 99.99%, and all othergents used here were of AR grade. The Virginia type cigarette with4 mg tar and 1.3 mg nicotine was purchased from market. Thesear and nicotine yields were determined by machine-smoking theigarettes under a standard (ISO) smoking method [14].

.2. Measurements

Scanning electron microscopy (SEM) images were taken by usingEO-1530 VP microscope operated at 5 kV. The sample discs wererepared by sputtering a thin layer of gold–palladium (90–10%)nto their outer surface.

Instantaneous adsorption of volatile nitrosamines in the gastream was performed in a fixed-bed micro-reactor filled withmg samples, in 20–40 meshes [7], and the samples were directlyeated at 338 K without activation in the flow of H2 with a ratef 30 mL min−1. Nitrosamine solution was pulse injected onto theample with 2 �L each time, and the gaseous effluent was analyzedy a gas chromatography.

TPSR experiments were performed in the manner reported pre-

iously [8]. 40 mg sample (20–40 mesh) was first activated initrogen at 773 K for 2 h, and then cooled down to 338 K to contacthe dichloromethane solution of NPYR (0.1 mL). After the sampleas purged by the nitrogen carrier gas for 0.5 h or more, the tem-erature rose from 338 to 773 K at the rate of 10 K min−1, and the

Scheme 1. Schematic representation of filter modification in sample cigarette.

nitrosamines adsorbed were catalytically degraded through therupture of N–NO bond to form NOx and amines [8]. Since onemolecule of NPYR produces only one NOx, the liberated NOx wasdetected by spectrophotometric method to represent the amountof nitrosamines decomposed [8]. Same procedure was applied forthe TPSR experiment of NNN.

To evaluate the effect of porous materials in reducing the TSNAlevel of mainstream smoke, the sample with a given amount, in20–40 meshes, was carefully added into the filter of cigarette toreplace part of cellulose matrix with a same volume. Two cigarettesamples were also used for comparison, one was the originalcigarette named as Blank and another was denoted as Controlwhose cellulose filter was cut to be three parts (Scheme 1). 20test cigarettes were conditioned at 295 K and 60% relative humid-ity for 48 h and then smoked using a Borgwaldt Smoking MachineRM20/CS under the standard ISO machine-smoking regime (35 cm3

puff, 2-s duration every 60 s [14]). Each Cambridge filter pad withtrapped smoke particulate was extracted, purified and finally ana-lyzed by LC–MS/MS method as described below.

2.3. Sample collection and extraction

After the smoking procedure, the Cambridge pad filter wastransferred to 50-mL ammonium acetate solution for ultrasonic of0.5 h. The obtained extractive solution was further cleaned-up usingthe GX-274 ASPEC autosolid-phase extraction machine. Finally, theeluant was diluted to 5-mL by ammonia–methanol solution andanalyzed by Agilent 6410 Triple Quad LC–MS/MS.

2.4. Liquid chromatography–tandem mass spectrometry(LC–MS/MS) analyses

An Agilent 1200 LC system was used for chromatographicseparation. The system was fitted with a SB-C18 MS columnand equilibrated with 68% solvent A (water) and 32% solvent B(methanol). 2 �L of sample or calibration standard was injected.An Applied Biosystems API 5000 mass spectrometer was used forthe MS/MS analysis. The instrument was operated in positive ESImode and mass spectral data on precursor and product ions werecollected in multiple reaction-monitoring (MRM) mode. Peak area

determinations for all samples, blanks, and standards were pro-cessed using the Analyst software version 1.2. Each ion of interestin the chromatogram was automatically selected and integrated.The peak integrations were manually inspected for errors and re-integrated if necessary.

1036 L. Gao et al. / Journal of Hazardous Materials 169 (2009) 1034–1039

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the TPSR procedure was about one-third of that on NaA (Table 1).The amount of NOx detected on CAS-1 was smaller than that onNaA but exceeded KA zeolite (Table 1, Fig. 3a), signifying a catalyticactivity higher than KA but inferior to NaA zeolite in the TPSR test;and a majority of NOx desorbed at a temperature higher than 673 K

Fig. 1. SEM images of (a) NaA, (b) K

. Results

.1. Instantaneous adsorption and catalytic degradation ofitrosamines in laboratory

Fig. 1 presents the morphologies of zeolites NaA, KA and CAS-1amples observed with SEM. Zeolite NaA possesses a typical cubicrystal with the size of about 4 �m, while zeolite KA has a similarorphology and crystal size. Nonetheless, CAS-1 sample possesses

ong stick-like crystals that interlace each other. The length of theseong stick-like crystals varies from 40 to 240 �m, much larger andonger than the crystal of zeolite NaA or KA. Close inspection revealshat the width of CAS-1 crystal can achieve 2–3 �m (image d inig. 1). So, CAS-1 sample looks very much like the fibers of cotton inacroscopy while two zeolites seem to be white powder. The inim-

table morphology of CAS-1 originates from its special syntheticrocedure consisting of long crystalline time, say, 493 K for 10 days,long with its special components in which a lot of calcium existednd the ratio of Si/Ca/K reached 4:1:1 [11].

Fig. 2 reveals the impact of pore structure and morphology ofeolite-like porous materials on the instantaneous adsorption ofPYR. With a five-membered ring in its molecular structure, NPYRossesses a diameter of about 0.54 nm × 0.42 nm, slightly largerhan the pore size of zeolite NaA (0.40 nm). As the amount ofPYR passed through the adsorbent accumulated to 1.2 mmol g−1,bout 12% of the carcinogen was trapped by NaA. Since the poreize of zeolite KA decreased to 0.3 nm, the adsorption of NPYRas suppressed and only 1.6% of NPYR was captured under the

ame conditions. No obvious adsorption of NPYR was observedn CAS-1 sample as demonstrated in Fig. 1. This result was notnexpected because CAS-1 had a two-dimensional eight-ring chan-

el system and actually it could hardly adsorb either nitrogen orthanol [10,11].

Fig. 3a illustrates the TPSR of NPYR on zeolite NaA and KaAs well as CAS-1. The volatile nitrosamines were adsorbed by theorous material at 338 K and then catalytically decomposed at ele-

lite, and (c) and (d) CAS-1 samples.

vated temperature as the adsorbent was heated. The amount ofNOx detected during the procedure represents the decomposednitrosamines [8,15], indicating the catalytic activity of the sample(Table 1). Zeolite NaA has small pore but plenty of cation hence itsadsorption capability toward NPYR is low (Fig. 2) but the adsorptivestrength is high due to the strong electrostatic interaction betweencation and nitrosamine [7], which makes the adsorbed NPYR and itsdegraded products difficult to desorb therefore only a trace amountof NOx desorbed at 523 K and most of them emerged at 773 K(Fig. 3a). As the pore size reduced to 0.3 nm, KA zeolite was hardto adsorb or decompose NPYR, and the amount of NOx detected in

Fig. 2. Instantaneous adsorption of NPYR on zeolite NaA and KA as well as CAS-1samples at 338 K.

L. Gao et al. / Journal of Hazardous M

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ig. 3. The profile of NOx detected in the temperature programmed surface reactionTPSR) of NPYR on zeolite NaA and KA as well as CAS-1 sample.

nstead of 773 K, mirroring the weaker adsorption than that of NaAeolite. Based on these results, it is clear that the pore size of zeoliteimits the degradation of volatile nitrosamines such as NPYR, andhere is no obvious impact of morphology on the experiment.

Fig. 3b depicts the TPSR test of NNN, one of the tobacco specificitrosamines with a molecular size of 0.80 nm [13], over the mate-ial with small pores. Neither NaA nor KA zeolite could adsorb NNN13] so that both of them showed a very weak activity in this exper-ment and the amount of degraded NNN on NaA and KA was about.0 �mol g−1. CAS-1 exhibited a slightly higher activity, and about.8 �mol g−1 of NNN was decomposed to form the NOx desorb-ng at a temperature above 673 K. Also, the morphology of porous

aterials has no obvious effect on the experiment.

.2. Reducing the TSNA level of the mainstream smoke

Table 2 lists the actual reduction of TSNA level in the mainstreammoke by using zeolite NaA and CAS-1. To avoid the influence of

able 1elevant parameter of zeolites and other porous adsorbents.

ample Si/Al Surface area m2 g−1) Pore volume (cm3 g−1) P

aA 1 800 0.28 0A 1 740 0.24 0AS-1 –b –c –c 0

a The accumulated amount of nitrosamines passed through the adsorbent bed is 1.2 mmb Aluminum is absent in this adsorbent.c It is impossible to be measured by common nitrogen adsorption method.

aterials 169 (2009) 1034–1039 1037

dividing cellulous filter to three parts (Scheme 1) on the meanamount of TSNA in smoke, we use the control cigarette insteadof the original cigarette (Blank) to compare with the test sam-ple containing the porous additive in cigarette filter. Addition ofzeolite NaA in the filter of test cigarette did not obviously affectthe pressure drop and the total particular materials (TPM) so thatthe amount of CO kept almost unchangeable within the experi-ment error. At the same time, the absolute amount of TSNA in thesmoke decreased about 11% when the NaA additive of 30 mg cig−1

was used. Among the main components of TSNA, more NNN wereremoved than NNK by the zeolite additive but the reduction of NATand NAB was irregular because of the extraordinarily low amountof NAT + NAB in the smoke that caused uncertainty in quantitativemeasurement.

CAS-1 exhibited a higher activity than zeolite NaA to reduce theTSNA level of mainstream smoke. Once 10 mg CAS-1 was addedinto the filter, the amount of TSNA in the smoke decreased about30%, superior to the function of 30 mg zeolite NaA (Table 2). Atthe same time, the pressure drop of the test cigarette containing10 mg CAS-1 was unchangeable while the amount of TPM loweredslightly, mirroring the function of the CAS-1 to intercept the par-ticles in the smoke. As the amount of CAS-1 increased to 20 and30 mg per cigarette, reduction of the particles in the smoke becameclear since the corresponding TPM value was lowered 21% and 32%respectively. However, the decrease of TSNA was more obvious,achieving 55% and 58% respectively. For an overall analysis of therelation between the reduction of TSNA and the decrease of TPM, weestablished the parameter of TSNA/TPM and found that this valuedeclined from 0.13 to 0.10 as the amount of CAS-1 additive increasedfrom 10 to 30 mg per cigarette. That means, in our opinion, moreTSNA than particles in the mainstream smoke seem to be trappedby the CAS-1 in the filter. Similar phenomenon was observed in thecase of using zeolite NaA additive as demonstrated in Table 2 inwhich NaA lowered the value of TSNA more distinctly than that ofTPM.

4. Discussion

Most of the TSNA exist in the particulate phase of tobacco smoke,and the average size of these particles achieve micrometer grade[16], close to that of the zeolite crystal so that the zeolite in filter failsto trap these particles because of its pore size of nanometer grade.Another factor to make zeolite NaA hardly intercept the movingparticle in the gas stream is its morphology of cubic crystal (Fig. 1);in case the crystal of zeolite contacts with the particle in smoke, arigid collision will happen because the flow rate of the gas flow thatpasses through the filter can reach 36 cm s−1 under the standardcigarette-smoking test conditions [14]. Such rigid collision occurredbetween them enables the particle to rebound, which, of course, is

unbeneficial for zeolite to intercept the particle. Consequently, thenew candidate with different morphology such as CAS-1 is adoptedto overcome the drawback of zeolite, through which we want torealize the soft-collision with the particles in smoke and then tocapture the TSNA adhered on the particle.

ore size (nm) Adsorbed NPYR at Degraded NPYR in TPSR test338 K (mmol g−1)a NPYR (�mol g−1) Tmax (K)

.40 0.14 14.3 773

.30 0.02 5.0 623

.30 <0.01 10.9 773

ol g−1.

1038 L. Gao et al. / Journal of Hazardous Materials 169 (2009) 1034–1039

Table 2Reduction of TSNA content in the mainstream smoke of Virginia type cigarette by use of zeolite-like materials.

Sample Blank Control CaS-1 NaA

Amount of additive (mg cig−1) 0 0 10 20 30 30Pressure drop (mmH2O) 1180 940 943 1014 1120 912TPM (mg cig−1) 17.9 17.8 16.6 14.0 12.0 17.1CO (mg cig−1) 14.9 15.1 14.8 14.3 14.5 14.2NNN (ng cig−1) 1.99 1.58 1.00 0.65 0.42 1.28NNK (ng cig−1) 2.34 1.21 0.91 0.66 0.76 1.16NAT + NAB (ng cig−1) 0.31 0.18 0.18 0.02 0.05 0.21TSNA (ng cig−1) 4.64 2.97 2.09 1.33 1.23 2.65TSNA/TPM 0.26 0.17 0.13 0.10 0.10 0.15

Reduction (%)NNN – – 36.7 58.7 73.4 19.0NNK – – 24.8 45.5 16.5 4.1

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NAT + NAB – –TSNA – –TPM – –

Although CAS-1 sample has a pore size smaller than zeoliteaA, it could trap nitrosamines if the adsorption time was longnough as reported previously. For example, 19 mg g−1 of bulk N-itrosodiphenylamine (NDPA) in solution was adsorbed by CAS-1t 277 K within 24 h [17], which may result from the interaction ofation in CAS-1 with nitrosamines to induce the adsorbate insert-ng its N–NO group into the channel of adsorbent. CAS-1 couldlso adsorb the volatile nitrosamines in the smoke passing throughith slow speed, reducing the level of nitrosamines from 1.93

o 1.15 nmol cig−1 [15]. However, when the contact time betweendsorbent and adsorbate deceased to less than 0.1 s in the instan-aneous adsorption at 338 K, CAS-1 failed to trap NPYR (Fig. 2).he molecular diameter of NPYR is about 0.54 nm × 0.42 nm, obvi-usly larger than the pore size of CAS-1; rather, the very shortontact time hinders the adsorbate to insert into the pore of thedsorbent therefore almost no adsorption of NPYR was detected.onsequently, CAS-1 only shows a weak activity similar to thatf NaA or KA zeolites in the TPSR of NPYR or NNN (Fig. 3). How-ver, CAS-1 additive in filter exhibited a higher activity to lower theSNA level of mainstream smoke than zeolite NaA (Table 2), whichay originate from two factors. One is the morphological impact of

eolite-like materials, and another is the orientation-change of theas stream caused by the additive.

As aforementioned, CAS-1 cannot directly adsorb TSNA due tohe limitation of its small micropores. Thanks to its special mor-hology, CAS-1 can intercept the bulky particle similar to that theobweb captures the flying inspects. The long stick-like crystalsith length of 40–240 �m interlaced each other enable CAS-1 to

orm a kind of net in the gas flow. It is not difficult to image thathen the particles in smoke collide with this net, the toughness of

he net will lighten the rigidity of collision and avoid the rebound ofarticles, which is beneficial for intercepting the particles. Another

actor should be taken into account for the excellent performancef CAS-1 additive in filter is the possible orientation-change of gastream. Dividing the cellulose filter into three segments changes therientation of smoke passing through, because whirling and swerv-ng of flow will occur in the seam to prolong the contact time of themoke with the cellulose acetate. Also, the speed of the smoke islowed down more or less in the seam of the filter, which is ben-ficial for enhancing the efficiency of filtration such as selectiveltration and elution [18]. This enhancement has been proven byhe comparison between the control and blank cigarettes demon-trated in Table 2, since the TSNA level in the smoke of the former

s reduced 36% in comparison with that of the latter. Replacementf the middle cellulose segment by CAS-1 no doubt enlarges thisffect because the net formed by the long-stick crystals consistlot of seams where the orientation of smoke is changed more

r less therefore the contact frequency of particles in the smoke

0 88.9 72.2 −16.729.6 55.2 58.6 10.8

6.7 21.3 32.6 3.9

with the porous additive increases, which is helpful to elevate theefficiency of filtration. To confirm this inference, 15 mg novel meso-porous silica additive with 3D net-like morphology is also used infilter and as expected it reduces 33% of TSNA in the mainstreamsmoke of Virginia type cigarette, which will be reported elsewherein future. On the other hand, it is necessary to point out that CAS-1is not simply the physical filter. In CAS-1, Ca2+ ion is present andit is coordinated to five terminal oxygens and one water molecule[11]. The existence of Ca2+ in framework along with the potassiumcation in its structure provide a strong affinity to attract the N–NOgroup of nitrosamines that has negative charge, similar to that ofcopper oxide in zeolite [6], resulting in preferential retention ofTSNA superior to cellulose acetate. This, in our opinion, may be thereason why the reduction of TSNA is larger than that of particlesin smoke by use of CAS-1 additive in filter (Table 2), though theavailable data do not allow a discussion of the possible mechanisminvolved. In general it is quite apparent that the obvious reduc-tion of TSNA level in smoke by using CAS-1 additive in filter relieson the particular morphology and the specific chemical composi-tion of the zeolite-like material: the fiber-like morphology of CAS-1realizes the effective interception of particles in smoke, better thancommon zeolite, while the plenty of cations plus zeolite-like micro-porous structure in CAS-1 enables the TSNA adhered on particle tobe trapped, superior to the cellulose acetate on which only physicalinterception occurs. The success in the preliminary study of CAS-1 may provide an available clue not only for reducing the healthhazard caused by smoking, but also for preparing novel functionalmaterials to protect environment.

5. Conclusion

Some conclusive remarks can be tentatively drawn from theseprimary investigations:

(1) Zeolite-like calcosilicate CAS-1 can efficiently reduce the TSNAlevel of mainstream smoke in the range of 30–60% once theporous material is added in the filter of Virginia type cigarette,providing a serviceable candidate for the protection of environ-ment.

(2) The morphology of porous adsorbents seriously affects theiractual performance to reduce the TSNA level of tobacco smokein the smoking experiment. The CAS-1 with fiber morphologyexhibits a higher activity than zeolite NaA with the cubic crystal,

because its specific morphology is beneficial to intercept theparticles in smoke where TSNA adhered.

(3) No obvious impact of morphology is observed in the instan-taneous adsorption of volatile nitrosamines over CAS-1 andzeolites, in which CAS-1 shows a weak ability similar to that

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L. Gao et al. / Journal of Hazard

of KA zeolite owing to its two-dimensional eight-ring channelsystem.

This study is our first preliminary approach to demonstrate theerformance characteristics of calcosilicate CAS-1 for the reductionf TSNA concentration in environmental tobacco smoke. Furtheromprehensive investigations are required to clearly identify detailharacteristics of the process.

cknowledgements

Financial support from the National Natural Science Founda-ion of China (20773601, 20873059 and 20871067), National Basicesearch Program of China (2007CB613301), 863 projects of Chi-ese Science Committee (2008AA06Z327), and Analysis Center ofanjing University is gratefully acknowledged. The authors arerateful to Professor J.X. Dong and Dr. L. Liu of Taiyuan Universityf Technology for their beneficial discussions and technical assis-ances.

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