Removal of xylene (a toxic compound) from aqueous solution by modified multi wall carbon nano tubes
(MWCNT) via silica as sheeted carbon nanotube (SCNT) was evaluated. The physicochemical properties of
MWCNT such as structure and availability surface were improved due to convert tubes into sheets that
cause significantly increase in xylene adsorption. The equilibrium amount (qe (mg/g)) in nano material's
dose of 1g/l, xylene concentration of 10mg/l, contact time of 10min, and pH 7, for SCNT (qe 9.8 mg/g) was
higher than single wall carbon nano tubes (SWCNT) (qe 9.2 mg/g) and MWCNT (qe 8.9 mg/g). It is concluded
that sheeted carbon nanotube due to their large surface area improve performance of xylene adsorption.
Also carbon nano tube (CNT) recycling by heating, showed better adsorption performance for recycled
SCNT. A comparison study on xylene adsorption revealed that sheeted carbon nanotube has better xylene
adsorption performance as compared to CNT, carbon and silica adsorbents. This suggests that the SCNT is
an efficient adsorbent for xylene removal in environmental pollutions cleanup.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3508

Amin, M.M.

Bina, B.

Pourzamani, H.

Rashidi, A.

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 2, 02PCN01(4pp) (2013)   2304-1862/2013/2(2)02PCN01(4) 02PCN01-1  2013 Sumy State University Using of a New Carbon Nano Tube Version in Sheet Shape for Water  and Wastewater Treatment  Mohammad Mehdi Amin1, Bijan Bina1, Alimorad Rashidi2, Hamidreza Pourzamani1,*  1 Environment Research Center, Isfahan University of Medical Sciences, Isfahan, Iran 2 Gas Division, Research Institute of Petroleum Industry (RIPI), Tehran, Iran  (Received 16 December 2012; published online 29 August 2013)  Removal of xylene (a toxic compound) from aqueous solution by modified multi wall carbon nano tubes (MWCNT) via silica as sheeted carbon nanotube (SCNT) was evaluated. The physicochemical properties of MWCNT such as structure and availability surface were improved due to convert tubes into sheets that cause significantly increase in xylene adsorption. The equilibrium amount (qe (mg/g)) in nano material's dose of 1g/l, xylene concentration of 10mg/l, contact time of 10min, and pH 7, for SCNT (qe  9.8 mg/g) was higher than single wall carbon nano tubes (SWCNT) (qe  9.2 mg/g) and MWCNT (qe  8.9 mg/g). It is con-cluded that sheeted carbon nanotube due to their large surface area improve performance of xylene adsorp-tion. Also carbon nano tube (CNT) recycling by heating, showed better adsorption performance for recycled SCNT. A comparison study on xylene adsorption revealed that sheeted carbon nanotube has better xylene adsorption performance as compared to CNT, carbon and silica adsorbents. This suggests that the SCNT is an efficient adsorbent for xylene removal in environmental pollutions cleanup.   Keywords: Sheeted carbon nanotube, Regeneration, Xylene, Wastewater pollution.    PACS number: 61.48.De                                                             * Pourzamani@hlth.mui.ac.ir  1. . INTRODUCTION  Xylene is an aromatic compound that is found in air, surface and ground water due to introducing petroleum product or wastewater polluted by its products in envi-ronment [1, 2]. Every year, large amounts of xylene dis-charge into the aqueous environment via manufacturing, transportation and disposal sites wastewater [3]. Such contamination in water sources making them unsuitable for many uses (spatially for drinking) due to their toxic properties [4]. Environmental protection agency (EPA) has classified the xylene as a priority compound due to its toxic effect on human health and environmental [5]. Previous studies show that various kinds of technologies used for xylene removal. Physicochemical process was preferred because of easy to use and cost-effectiveness [6-9]. These studies show that CNT have more potential-ly for removal of organic pollutant in environmental filed. The nanomaterials have been used for removing many kinds of organic pollutants such as BTEX from aqueous solutions [3, 4, 7]. The modified carbon nano-tubes as the tube opening to achieve higher levels of ad-sorption surface area, can improve the performance of their absorption. So in this study, multi wall carbon nanotubes was converted to sheets by silica and em-ployed as adsorbent for xylene removal from aqueous solution. The main objective of this paper is to investi-gate the performance of sheeted multi wall carbon nano-tube in xylene removal from aqueous solution.   2. MATERIALS AND METHODS  2.1 Materials  Xylene (purity 99%) purged from Merck and three different nano materials were tested: (1) SWCNT with 1-2nm diameters (figure 1). (2) MWCNT with 10nm diameter (figure 2). (3) sheeted carbon nanotube (SCNT) that made by MWCNT in hybrid with silica. SWCNT and MWCNT were purchased form Iranian Research Institute of Petroleum Industry and SCNT was made in this industry. The morphology of adsor-bents was analyzed by transmission electron microsco-py (TEM) Philips CM10-100KV.    Fig. 1 – TEM image of SWCNT Fig. 2 – TEM image of MWCNT  The surface area, pore volume and pore size distri-bution were measured by nitrogen adsorption at 77K using an ASAP-2010 porosimeter from the Micromerit-ics Corporation GA. The pore size distribution (PSD) was evaluated from the adsorption isotherms using the Barrett, Joyner and Halenda (BJH) algorithm (ASAP-2010) available as a built-in software from Micromerit-ics. The surface area, average pore size diameter, and pore volume of the SWCNT and MWCNT are presented in table 1.  Table 1 – N2 adsorption data of SWCNT and MWNT  Adsorbents BET surface area (m2/g) Average pore diameter-by BET (nm) BJH ad-sorption cumulative surface area of pores (m2/g) BJH adsorption average pore diameter (nm) BJH ad-sorption cumulative pore vol-ume of pores (cm3/g) SWCNT 198.93 11.87 253.12 12.02 0.62 MWCNT 132.42 13.21 175.74 13.57 0.58  MOHAMMAD MEHDI AMIN, BIJAN BINA ET AL. PROC. NAP 2, 02PCN01 (2013)   02PCN01-2 2.2 Experimental   Batch adsorption experiments were conducted using 110ml glass bottles with addition of 100mg of adsor-bents and 100ml of xylene solution with concentrations (C0) 10mg/l. The glass bottles were sealed with 20mm stopper. Headspace within each beaker was minimized to exclude any contaminant volatilization phenomena. The glass bottles of the batch experiments were placed on a shaker (Orbital Shaker Model OS625), and were stirred at 240rpm for 10min in room temperature. The solution samples were then settled for 2min. The su-pernatant was used to determining xylene in the liquid phase using GC/MS chromatography. All the experi-ments were repeated three times and only the mean values were reported.  The reversibility of sorbents that used for xylene removal from aqueous solution was evaluated via 2 adsorptions followed by 2 desorption. Recycling was also conducted at 105±2ºC in 24h by oven (Memmert D-91126, Schwabach FRG). All samples were performed at least in triplicate. Xylene concentrations were analyzed by Agilent Technologies system consisting of a 5975C Inert MSD with Triple Axis Detector equipped with a 7890A gas chromatograph with a split/splitless injector. A HP-5 ms column (30m×0.25mm Id, 0.25μm), was employed with helium (purity 99.995%) as carrier gas at flow rate of 1ml/min. Static headspace analysis was performed using a CTC PAL- Combi PAL headspace sampler.  In order to compare adsorption performance of em-ployed carbon nanotubes in this study, design of exper-iments (DOE) software (design expert 6) was used.  Isotherm study was evaluated for xylene adsorption by SCNT with initial concentration of zero to 100mg/l (interval 10mg/l), CNT dose 2g/l, contact time 14min, and pH  7. Water solubility (Sw) of xylene was esti-mated 50mg/l at pH 7 [2].   3. RESULTS   Figure 3 shows TEM image of carbon tubes that sheeted in contact with silica. The results obtained for SCNT include surface area, average pore size diameter, adsorption cumulative surface area of pores, adsorption average pore diameter and adsorption cumulative pore volume of pores was 273.6m2/g, 12.9nm, 258.6m2/g, 12.1nm, 0.78cm3/g respectively.     Fig. 3 – TEM image of SCNT   Table 2 shows the xylene removal percent by SCNT, SWCNT, and MWCNT under initial xylene concentra-tion, 10mg/l; adsorbent concentration of nano material, 1000mg/l; contact time, 10min; and shaking in 240rpm. A different way for comparison of CNTs performance in xylene removal is in terms of surface area instead of the unit weight that adsorbed by CNT.  Table 2 – Xylene removal by CNT at C0  10mg/l   Adsorbent Xylene concentra-tion Removal percent (%) Xylene adsorption capacity by CNT (mg/m2) C0 (mg/l) Ct (mg/l) MWCNT 10±0.2 1±0.05 89.5 0.07 SWCNT 10±0.1 0.8±0.08 91.6 0.05 SCNT 10±0.2 0.2±0.05 98 0.04  Figure 4 shows the xylene removal by SCNT, SWCNT, and MWCNT and that comparison of them. It reveals that SCNT is better than SWCNT and MWCNT to remove the xylene.    Fig. 4 – Comparison of SCNT, MWCNT, and SWCNT in xy-lene removal with a C0  10mg/l  Figure 5 indicates the equilibrium amounts of xy-lene adsorbed on SCNT, MWCNT, and SWCNT (qe (mg/g)) with a C0 of 10mg/l and contact time, 10min.    Fig. 5 – Equilibrium amount of xylene adsorbed on CNTs with a C0 of 10mg/l  Table 3 shows the xylene removal percent by SCNT, MWCNT, and SWCNT that was recycled in the first cycle (SCNTrec1, MWCNTrec1, and SWCNTrec1) and the second cycle (SCNTrec2, MWCNTrec2, and SWCN-Trec2) under initial xylene concentration of 10mg/l, car-bon nanotubes concentration of 1000mg/l, contact time of 10min and shaking in 240rpm. Figure 6 compares raw SCNT, SWCNT, and MWCNT with their recycling in cycles of 1 and 2.   USING OF A NEW CARBON NANO TUBE VERSION IN SHEET SHAPE … PROC. NAP 2, 02PCN01 (2013)   02PCN01-3 Table 3 – Xylene removal by raw and recycled SCNT, MWCNT, and SWCNT at C0  10mg/l and contact time of 10min  Adsorbent  Xylene  C0 (mg/l) Ct (mg/l) Removal percent (%) SCNTrec1  10±0.2 1.1±0.04 98.8 MWCNTrec1  10±0.1 0.6±0.1 89.3 SWCNTrec1  10±0.2 0.1±0.01 93.6 SCNTrec2  10±0.1 1.3±0.08 96.8 MWCNTrec2  10±0.2 0.95±0.1 87.3 SWCNTrec2  10±0.1 0.32±0.06 90.5      Fig. 6 – Comparison of raw and recycled: (a) SCNT, (b) SWCNT and (c) MWCNT in xylene removal with a C0  10mg/l  Table 4 summarizes some of the diagnostic statis-tics computed by ISOFIT and reported in the output file for xylene removal.  Figure 7 contain plot of the fitted isotherms for xy-lene adsorption by SCNT, along with the observed data points.  Table 4 – Summary of selected diagnostics for xylene ad-sorbed by SCNT  Isotherms Multi model ranking (AICc) Correlation between measured and simu-lated observation ( 2yR ) Correlation between residual and nor-mality (2NR ) linssen measure of non-linearity (M2) Linearity assessment GLF 20.6 0.996 0.916 7.6×101 non-linear P-P 24.4 0.920 0.781 2.6×10-1 uncertain Polanyi 24.5 - 0.936 4×10-15 linear Langmuir 49.3 0.983 0.923 8×10-10 linear Toth 49.4 0.953 0.931 8×10-10 linear F-P 49.4 0.953 0.913 8×10-10 linear Linear 49.4 0.953 0.913 8×10-10 linear L-P 52.6 0.903 0903 1×105 non-linear Freundlich 52.7 0.953 0.905 3.8 non-linear BET 74 0.305 0.923 9.4×10-2 uncertain    Fig. 7 – Plot of GLF isotherm and observed data for xylene adsorption  4. DISCUSSION  As can be concluded, the use of silica in MWCNT producing process causes important changes in MWCNT properties. This change in surface area and pore volume of pores are more specific. It caused an increase in surface area of about 52% as well as could increase cumulative pore volume of pores about 20%. This is attributed to modify MWCNT shape from tube to sheet due to silica operation. Silica cause destruction of tube wall and a corresponding increase in surface area and volume of pores but decrease the average pore diameter. It is evident that SCNT has greater surface area and pore volume but smaller average pore diame-ter than MWCNT. On the other hand, the mesopore of MWCNT have smaller pore volume than SCNT, which could be attributed to the open of tubes that produce sheet carbon nanotubes. When tubes of MWCNT were opened and converted to sheet via contact with silica, high surface area was created for xylene adsorption. Based on DOE analysis there is a significant difference between SCNT, MWCNT, and SWCNT in xylene re-moval (values of "Prob>|t|" less than 0.05). So that SCNT has better performance in xylene removal than SWCNT and MWCNT in this study. This is due to in-creasing in surface area that was 132.4 and 198.9m2/g for MWCNT and SWCNT respectively and was 273.6m2/g for SCNT. The order of xylene removal effi-ciency (SCNT > SWCNT > MWCNT) is consistent with the order of surface area and pore volume but is not in agreement with the pore diameter of CNTs. This indi-cates that the adsorption of xylene to the CNTs is de-pendent on the surface characteristics. Similar findings  MOHAMMAD MEHDI AMIN, BIJAN BINA ET AL. PROC. NAP 2, 02PCN01 (2013)   02PCN01-4 have been reported in the literature for adsorption of xylene on activated carbon and modified MWCNT [7, 8]. Also SCNT has the greatest qe=9.8mg/g, so that is higher than SWCNT and MWCNT. Moreover, it is evi-dent that the mass of xylene adsorbed on MWCNT was increased when used of silica in MWCNT production process. This phenomenon can be attributed to the fact that silica causes structure changing, so it effect on MWCNT surface area and increases it. This speculates the presence of chemically inherited groups that lead to such direction of affinity to xylene removal, irrespective of the texture characteristics. The results also show that sheeted MWCNT improve performance of MWCNT base on increasing adsorption site and avail-able surface. So that it was better than SWCNT in xy-lene removal. It can be expected that the adsorption of xylene to the SCNT is dependent on the surface chemi-cal nature and the porosity characteristics. Because there were not pH variation during experiments, π-π electron-donor–acceptor is main mechanism for xylene adsorption to SCNT. Carboxylic oxygen-atom of CNT surface performs as the electron-donor and the aro-matic ring of xylene as the electron-acceptor. So in-creasing adsorption surface is due to sheet form of CNT, cause more available carboxylic oxygen atoms for electron donor and better xylene removal [7]. Further-more, the electrostatic interaction between the xylene molecules and the CNT surface may also explain the observation of high xylene adsorption via the sheeted carbon nanotube. Since the xylene molecules are posi-tively charged [7], adsorption of xylene is thus favored for adsorbents with a negative CNT surface charge. This results in more electrostatic attraction and thus leads to a higher xylene adsorption. It is apparent from recycling results that SCNT, SWCNT, and MWCNT used in xylene removal can be reused through a large number of water and wastewater treatments for several regeneration cycles.  After CNTs oxidization by heating process, a large amount of metal catalysts and amorphous carbons that were used for CNT making, was removed and both ends of the nanotubes were be opened. Also the struc-ture and nature of carbon surface were changed after thermal treatment including the increasing in graphi-tized structure, surface functional groups, and negative charges [1]. This is caused that SCNT and SWCNT could be adsorbed more xylene after first recycling. As regards the possibility of CNT recycling by heat pro-cessing, it is expected that the unit cost of CNTs can be further reduced.  Isotherm expressions are important for describing the partitioning of contaminants in environmental sys-tems. The AICc values indicate that the GLF isotherm expression provides the best fit of the sorption data for xylene adsorption.  ISOFIT used by Shawn Matott for zinc adsorption by ferrihydrite, indicate that ISOFIT produced equiva-lent or better fits, in terms of minimum and median RMSE values. In particular, ISOFIT provided superior fits for the GLF, Toth, Polanyi and Polanyi-Partition isotherms [11]. The adsorption process of atrazine on CNTs study by Yan et al. shows the adsorption equilib-rium isotherms were nonlinear and were fitted by Freundlich, Langmuir, and Polanyi–Manes models. They were found that the Polanyi–Manes model de-scribed the adsorption process better than other two isotherm models [10]. Wibowo et al. studied the adsorp-tion of benzene and toluene from aqueous solutions onto activated carbon, there study show that the Langmuir equation can describe the experimental data fairly well than Freundlich [12].   5. CONCLUSION  The main goal of this study was CNT comparison to xylene adsorption (a certain common petroleum pollu-tant). Therefore SWCNT, MWCNT and a new type of CNT (SCNT) were tested for xylene removal from aqueous solution. It is concluded that SCNT shows the greatest enhancement in xylene adsorption. The sheet shape of CNT as SCNT by silica can change the availa-ble area surface for adsorption. The results appear that xylene isomers are the components with the high ad-sorption tendency onto CNT. The equilibrium amount (qe) sequence is SCNT > SWCNT > MWCNT. After re-cycling of carbon nanotubes via 2 cycles, SCNT, SWCNT, and MWCNT are efficient xylene sorbents and can be regenerated and reused in water and wastewater treatment works. Furthermore, heating could be upgraded adsorption of recycled SCNT and SWCNT. The removal of metal catalysts by thermal treatment in raw CNTs can change the structure and nature of carbon surface and cause increasing in sur-face functional groups and negative   AKNOWLEDGEMENTS  This article is the result of PhD thesis approved in the Isfahan University of Medical Sciences (IUMS). The authors wish to acknowledge to Vice Chancellery of Research of IUMS for the financial support Research Project, # 389065.    REFERENCES  1. B. Bina, H. Pourzamani, A. Rashidi, M. M. Amin, JEPH (2012). 2. B. Bina, M. M. Amin, A. Rashidi, H. Pourzamani, Arch. Environ. Prot. 38, 3 (2012). 3. F. Su, C. Lu, S. Hu, Coll. Surf. A 353, 83 (2010). 4. M. Aivalioti, I. Vamvasakis, and E. Gidarakos, J. Hazard. Mater. 178, 136 (2010). 5. J. M. M. d. Mello, H. de Lima Brandão, A. A. U. de Souza, A. da Silva, S. M. d. A. G. U. de Souza, J. Petrol Sci. Eng. 70, 131 (2010). 6. H. Shim, E. Shin, S.-T. Yang, Adv. Env. Res. 7 203, (2002). 7. C. Lu, F. Su, S. Hu, Appl. Surf Sci. 254, 7035 (2008). 8. R. G. Zytner, J. Hazard. Mater. 38, 113 (1994). 9. S. H. Lin, C. Y. Huang, J. Hazard. Mater. 70, 21 (1999). 10. X. M. Yan, B. Y. Shi, J. J. Lu, C. H. Feng, D. S. Wang, H. X. Tang, J. Coll. Interf. Sci. 321, 30 (2008). 11. L. S. Matott, A. J. Rabideau, Environ. Modell. Softw. 23, 670 (2008). 12. N. Wibowo, L. Setyadhi, D. Wibowo, J. Setiawan,  S. Ismadji, J. Hazard. Mater. 146, 237 (2007). 

Using of a New Carbon Nano Tube Version in Sheet Shape for Water and Wastewater Treatment

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 2, 02PCN01(4pp) (2013) 
 
 
2304-1862/2013/2(2)02PCN01(4) 02PCN01-1  2013 Sumy State University 
Using of a New Carbon Nano Tube Version in Sheet Shape for Water  
and Wastewater Treatment 
 
Mohammad Mehdi Amin1, Bijan Bina1, Alimorad Rashidi2, Hamidreza Pourzamani1,* 
 
1 Environment Research Center, Isfahan University of Medical Sciences, Isfahan, Iran 
2 Gas Division, Research Institute of Petroleum Industry (RIPI), Tehran, Iran 
 
(Received 16 December 2012; published online 29 August 2013) 
 
Removal of xylene (a toxic compound) from aqueous solution by modified multi wall carbon nano tubes 
(MWCNT) via silica as sheeted carbon nanotube (SCNT) was evaluated. The physicochemical properties of 
MWCNT such as structure and availability surface were improved due to convert tubes into sheets that 
cause significantly increase in xylene adsorption. The equilibrium amount (qe (mg/g)) in nano material's 
dose of 1g/l, xylene concentration of 10mg/l, contact time of 10min, and pH 7, for SCNT (qe  9.8 mg/g) was 
higher than single wall carbon nano tubes (SWCNT) (qe  9.2 mg/g) and MWCNT (qe  8.9 mg/g). It is con-
cluded that sheeted carbon nanotube due to their large surface area improve performance of xylene adsorp-
tion. Also carbon nano tube (CNT) recycling by heating, showed better adsorption performance for recycled 
SCNT. A comparison study on xylene adsorption revealed that sheeted carbon nanotube has better xylene 
adsorption performance as compared to CNT, carbon and silica adsorbents. This suggests that the SCNT is 
an efficient adsorbent for xylene removal in environmental pollutions cleanup.  
 
Keywords: Sheeted carbon nanotube, Regeneration, Xylene, Wastewater pollution. 
 
  PACS number: 61.48.De 
 
 
                                                          
*
 Pourzamani@hlth.mui.ac.ir  
1. . INTRODUCTION 
 
Xylene is an aromatic compound that is found in air, 
surface and ground water due to introducing petroleum 
product or wastewater polluted by its products in envi-
ronment [1, 2]. Every year, large amounts of xylene dis-
charge into the aqueous environment via manufacturing, 
transportation and disposal sites wastewater [3]. Such 
contamination in water sources making them unsuitable 
for many uses (spatially for drinking) due to their toxic 
properties [4]. Environmental protection agency (EPA) 
has classified the xylene as a priority compound due to 
its toxic effect on human health and environmental [5]. 
Previous studies show that various kinds of technologies 
used for xylene removal. Physicochemical process was 
preferred because of easy to use and cost-effectiveness 
[6-9]. These studies show that CNT have more potential-
ly for removal of organic pollutant in environmental 
filed. The nanomaterials have been used for removing 
many kinds of organic pollutants such as BTEX from 
aqueous solutions [3, 4, 7]. The modified carbon nano-
tubes as the tube opening to achieve higher levels of ad-
sorption surface area, can improve the performance of 
their absorption. So in this study, multi wall carbon 
nanotubes was converted to sheets by silica and em-
ployed as adsorbent for xylene removal from aqueous 
solution. The main objective of this paper is to investi-
gate the performance of sheeted multi wall carbon nano-
tube in xylene removal from aqueous solution.  
 
2. MATERIALS AND METHODS 
 
2.1 Materials 
 
Xylene (purity 99%) purged from Merck and three 
different nano materials were tested: (1) SWCNT with 
1-2nm diameters (figure 1). (2) MWCNT with 10nm 
diameter (figure 2). (3) sheeted carbon nanotube 
(SCNT) that made by MWCNT in hybrid with silica. 
SWCNT and MWCNT were purchased form Iranian 
Research Institute of Petroleum Industry and SCNT 
was made in this industry. The morphology of adsor-
bents was analyzed by transmission electron microsco-
py (TEM) Philips CM10-100KV. 
 
  
Fig. 1 – TEM image of SWCNT Fig. 2 – TEM image of MWCNT 
 
The surface area, pore volume and pore size distri-
bution were measured by nitrogen adsorption at 77K 
using an ASAP-2010 porosimeter from the Micromerit-
ics Corporation GA. The pore size distribution (PSD) 
was evaluated from the adsorption isotherms using the 
Barrett, Joyner and Halenda (BJH) algorithm (ASAP-
2010) available as a built-in software from Micromerit-
ics. The surface area, average pore size diameter, and 
pore volume of the SWCNT and MWCNT are presented 
in table 1. 
 
Table 1 – N2 adsorption data of SWCNT and MWNT 
 
Adsorbents 
BET 
surface 
area 
(m2/g) 
Average 
pore 
diameter-
by BET 
(nm) 
BJH ad-
sorption 
cumulative 
surface 
area of 
pores (m2/g) 
BJH 
adsorption 
average 
pore 
diameter 
(nm) 
BJH ad-
sorption 
cumulative 
pore vol-
ume of 
pores 
(cm3/g) 
SWCNT 198.93 11.87 253.12 12.02 0.62 
MWCNT 132.42 13.21 175.74 13.57 0.58 
 MOHAMMAD MEHDI AMIN, BIJAN BINA ET AL. PROC. NAP 2, 02PCN01 (2013) 
 
 
02PCN01-2 
2.2 Experimental  
 
Batch adsorption experiments were conducted using 
110ml glass bottles with addition of 100mg of adsor-
bents and 100ml of xylene solution with concentrations 
(C0) 10mg/l. The glass bottles were sealed with 20mm 
stopper. Headspace within each beaker was minimized 
to exclude any contaminant volatilization phenomena. 
The glass bottles of the batch experiments were placed 
on a shaker (Orbital Shaker Model OS625), and were 
stirred at 240rpm for 10min in room temperature. The 
solution samples were then settled for 2min. The su-
pernatant was used to determining xylene in the liquid 
phase using GC/MS chromatography. All the experi-
ments were repeated three times and only the mean 
values were reported.  
The reversibility of sorbents that used for xylene 
removal from aqueous solution was evaluated via 2 
adsorptions followed by 2 desorption. Recycling was 
also conducted at 105±2ºC in 24h by oven (Memmert D-
91126, Schwabach FRG). All samples were performed 
at least in triplicate. 
Xylene concentrations were analyzed by Agilent 
Technologies system consisting of a 5975C Inert MSD 
with Triple Axis Detector equipped with a 7890A gas 
chromatograph with a split/splitless injector. A HP-5 
ms column (30m×0.25mm Id, 0.25μm), was employed 
with helium (purity 99.995%) as carrier gas at flow rate 
of 1ml/min. Static headspace analysis was performed 
using a CTC PAL- Combi PAL headspace sampler.  
In order to compare adsorption performance of em-
ployed carbon nanotubes in this study, design of exper-
iments (DOE) software (design expert 6) was used.  
Isotherm study was evaluated for xylene adsorption 
by SCNT with initial concentration of zero to 100mg/l 
(interval 10mg/l), CNT dose 2g/l, contact time 14min, 
and pH  7. Water solubility (Sw) of xylene was esti-
mated 50mg/l at pH 7 [2].  
 
3. RESULTS  
 
Figure 3 shows TEM image of carbon tubes that 
sheeted in contact with silica. The results obtained for 
SCNT include surface area, average pore size diameter, 
adsorption cumulative surface area of pores, adsorption 
average pore diameter and adsorption cumulative pore 
volume of pores was 273.6m2/g, 12.9nm, 258.6m2/g, 
12.1nm, 0.78cm3/g respectively.  
 
 
 
Fig. 3 – TEM image of SCNT 
 
 
Table 2 shows the xylene removal percent by SCNT, 
SWCNT, and MWCNT under initial xylene concentra-
tion, 10mg/l; adsorbent concentration of nano material, 
1000mg/l; contact time, 10min; and shaking in 240rpm. 
A different way for comparison of CNTs performance in 
xylene removal is in terms of surface area instead of 
the unit weight that adsorbed by CNT. 
 
Table 2 – Xylene removal by CNT at C0  10mg/l  
 
Adsorbent 
Xylene concentra-
tion Removal 
percent (%) 
Xylene adsorption 
capacity by CNT 
(mg/m2) 
C0 
(mg/l) 
Ct 
(mg/l) 
MWCNT 10±0.2 1±0.05 89.5 0.07 
SWCNT 10±0.1 0.8±0.08 91.6 0.05 
SCNT 10±0.2 0.2±0.05 98 0.04 
 
Figure 4 shows the xylene removal by SCNT, 
SWCNT, and MWCNT and that comparison of them. It 
reveals that SCNT is better than SWCNT and MWCNT 
to remove the xylene. 
 
 
 
Fig. 4 – Comparison of SCNT, MWCNT, and SWCNT in xy-
lene removal with a C0  10mg/l 
 
Figure 5 indicates the equilibrium amounts of xy-
lene adsorbed on SCNT, MWCNT, and SWCNT (qe 
(mg/g)) with a C0 of 10mg/l and contact time, 10min. 
 
 
 
Fig. 5 – Equilibrium amount of xylene adsorbed on CNTs with 
a C0 of 10mg/l 
 
Table 3 shows the xylene removal percent by SCNT, 
MWCNT, and SWCNT that was recycled in the first 
cycle (SCNTrec1, MWCNTrec1, and SWCNTrec1) and 
the second cycle (SCNTrec2, MWCNTrec2, and SWCN-
Trec2) under initial xylene concentration of 10mg/l, car-
bon nanotubes concentration of 1000mg/l, contact time of 
10min and shaking in 240rpm. Figure 6 compares raw 
SCNT, SWCNT, and MWCNT with their recycling in 
cycles of 1 and 2. 
 
 USING OF A NEW CARBON NANO TUBE VERSION IN SHEET SHAPE … PROC. NAP 2, 02PCN01 (2013) 
 
 
02PCN01-3 
Table 3 – Xylene removal by raw and recycled SCNT, 
MWCNT, and SWCNT at C0  10mg/l and contact time of 
10min 
 
Adsorbent 
 Xylene 
 C0 (mg/l) Ct (mg/l) Removal percent (%) 
SCNTrec1  10±0.2 1.1±0.04 98.8 
MWCNTrec1  10±0.1 0.6±0.1 89.3 
SWCNTrec1  10±0.2 0.1±0.01 93.6 
SCNTrec2  10±0.1 1.3±0.08 96.8 
MWCNTrec2  10±0.2 0.95±0.1 87.3 
SWCNTrec2  10±0.1 0.32±0.06 90.5 
 
 
 
 
 
Fig. 6 – Comparison of raw and recycled: (a) SCNT, (b) 
SWCNT and (c) MWCNT in xylene removal with a C0  10mg/l 
 
Table 4 summarizes some of the diagnostic statis-
tics computed by ISOFIT and reported in the output 
file for xylene removal.  
Figure 7 contain plot of the fitted isotherms for xy-
lene adsorption by SCNT, along with the observed data 
points. 
 
Table 4 – Summary of selected diagnostics for xylene ad-
sorbed by SCNT 
 
Isotherms 
Multi 
model 
ranking 
(AICc) 
Correlation 
between 
measured 
and simu-
lated 
observation 
( 2yR ) 
Correlation 
between 
residual 
and nor-
mality 
(
2
NR ) 
linssen 
measure 
of non-
linearity 
(M2) 
Linearity 
assessment 
GLF 20.6 0.996 0.916 7.6×101 non-linear 
P-P 24.4 0.920 0.781 2.6×10-1 uncertain 
Polanyi 24.5 - 0.936 4×10-15 linear 
Langmuir 49.3 0.983 0.923 8×10-10 linear 
Toth 49.4 0.953 0.931 8×10-10 linear 
F-P 49.4 0.953 0.913 8×10-10 linear 
Linear 49.4 0.953 0.913 8×10-10 linear 
L-P 52.6 0.903 0903 1×105 non-linear 
Freundlich 52.7 0.953 0.905 3.8 non-linear 
BET 74 0.305 0.923 9.4×10-2 uncertain 
 
 
 
Fig. 7 – Plot of GLF isotherm and observed data for xylene 
adsorption 
 
4. DISCUSSION 
 
As can be concluded, the use of silica in MWCNT 
producing process causes important changes in 
MWCNT properties. This change in surface area and 
pore volume of pores are more specific. It caused an 
increase in surface area of about 52% as well as could 
increase cumulative pore volume of pores about 20%. 
This is attributed to modify MWCNT shape from tube 
to sheet due to silica operation. Silica cause destruction 
of tube wall and a corresponding increase in surface 
area and volume of pores but decrease the average pore 
diameter. It is evident that SCNT has greater surface 
area and pore volume but smaller average pore diame-
ter than MWCNT. On the other hand, the mesopore of 
MWCNT have smaller pore volume than SCNT, which 
could be attributed to the open of tubes that produce 
sheet carbon nanotubes. When tubes of MWCNT were 
opened and converted to sheet via contact with silica, 
high surface area was created for xylene adsorption. 
Based on DOE analysis there is a significant difference 
between SCNT, MWCNT, and SWCNT in xylene re-
moval (values of "Prob>|t|" less than 0.05). So that 
SCNT has better performance in xylene removal than 
SWCNT and MWCNT in this study. This is due to in-
creasing in surface area that was 132.4 and 198.9m2/g 
for MWCNT and SWCNT respectively and was 
273.6m2/g for SCNT. The order of xylene removal effi-
ciency (SCNT > SWCNT > MWCNT) is consistent with 
the order of surface area and pore volume but is not in 
agreement with the pore diameter of CNTs. This indi-
cates that the adsorption of xylene to the CNTs is de-
pendent on the surface characteristics. Similar findings 
 MOHAMMAD MEHDI AMIN, BIJAN BINA ET AL. PROC. NAP 2, 02PCN01 (2013) 
 
 
02PCN01-4 
have been reported in the literature for adsorption of 
xylene on activated carbon and modified MWCNT [7, 
8]. Also SCNT has the greatest qe=9.8mg/g, so that is 
higher than SWCNT and MWCNT. Moreover, it is evi-
dent that the mass of xylene adsorbed on MWCNT was 
increased when used of silica in MWCNT production 
process. This phenomenon can be attributed to the fact 
that silica causes structure changing, so it effect on 
MWCNT surface area and increases it. This speculates 
the presence of chemically inherited groups that lead to 
such direction of affinity to xylene removal, irrespective 
of the texture characteristics. The results also show 
that sheeted MWCNT improve performance of 
MWCNT base on increasing adsorption site and avail-
able surface. So that it was better than SWCNT in xy-
lene removal. It can be expected that the adsorption of 
xylene to the SCNT is dependent on the surface chemi-
cal nature and the porosity characteristics. Because 
there were not pH variation during experiments, π-π 
electron-donor–acceptor is main mechanism for xylene 
adsorption to SCNT. Carboxylic oxygen-atom of CNT 
surface performs as the electron-donor and the aro-
matic ring of xylene as the electron-acceptor. So in-
creasing adsorption surface is due to sheet form of 
CNT, cause more available carboxylic oxygen atoms for 
electron donor and better xylene removal [7]. Further-
more, the electrostatic interaction between the xylene 
molecules and the CNT surface may also explain the 
observation of high xylene adsorption via the sheeted 
carbon nanotube. Since the xylene molecules are posi-
tively charged [7], adsorption of xylene is thus favored 
for adsorbents with a negative CNT surface charge. 
This results in more electrostatic attraction and thus 
leads to a higher xylene adsorption. 
It is apparent from recycling results that SCNT, 
SWCNT, and MWCNT used in xylene removal can be 
reused through a large number of water and 
wastewater treatments for several regeneration cycles.  
After CNTs oxidization by heating process, a large 
amount of metal catalysts and amorphous carbons that 
were used for CNT making, was removed and both 
ends of the nanotubes were be opened. Also the struc-
ture and nature of carbon surface were changed after 
thermal treatment including the increasing in graphi-
tized structure, surface functional groups, and negative 
charges [1]. This is caused that SCNT and SWCNT 
could be adsorbed more xylene after first recycling. As 
regards the possibility of CNT recycling by heat pro-
cessing, it is expected that the unit cost of CNTs can be 
further reduced.  
Isotherm expressions are important for describing 
the partitioning of contaminants in environmental sys-
tems. The AICc values indicate that the GLF isotherm 
expression provides the best fit of the sorption data for 
xylene adsorption.  
ISOFIT used by Shawn Matott for zinc adsorption 
by ferrihydrite, indicate that ISOFIT produced equiva-
lent or better fits, in terms of minimum and median 
RMSE values. In particular, ISOFIT provided superior 
fits for the GLF, Toth, Polanyi and Polanyi-Partition 
isotherms [11]. The adsorption process of atrazine on 
CNTs study by Yan et al. shows the adsorption equilib-
rium isotherms were nonlinear and were fitted by 
Freundlich, Langmuir, and Polanyi–Manes models. 
They were found that the Polanyi–Manes model de-
scribed the adsorption process better than other two 
isotherm models [10]. Wibowo et al. studied the adsorp-
tion of benzene and toluene from aqueous solutions 
onto activated carbon, there study show that the 
Langmuir equation can describe the experimental data 
fairly well than Freundlich [12].  
 
5. CONCLUSION 
 
The main goal of this study was CNT comparison to 
xylene adsorption (a certain common petroleum pollu-
tant). Therefore SWCNT, MWCNT and a new type of 
CNT (SCNT) were tested for xylene removal from 
aqueous solution. It is concluded that SCNT shows the 
greatest enhancement in xylene adsorption. The sheet 
shape of CNT as SCNT by silica can change the availa-
ble area surface for adsorption. The results appear that 
xylene isomers are the components with the high ad-
sorption tendency onto CNT. The equilibrium amount 
(qe) sequence is SCNT > SWCNT > MWCNT. After re-
cycling of carbon nanotubes via 2 cycles, SCNT, 
SWCNT, and MWCNT are efficient xylene sorbents 
and can be regenerated and reused in water and 
wastewater treatment works. Furthermore, heating 
could be upgraded adsorption of recycled SCNT and 
SWCNT. The removal of metal catalysts by thermal 
treatment in raw CNTs can change the structure and 
nature of carbon surface and cause increasing in sur-
face functional groups and negative  
 
AKNOWLEDGEMENTS 
 
This article is the result of PhD thesis approved in 
the Isfahan University of Medical Sciences (IUMS). 
The authors wish to acknowledge to Vice Chancellery 
of Research of IUMS for the financial support Research 
Project, # 389065. 
 
 
 
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Using of a New Carbon Nano Tube Version in Sheet Shape for Water and Wastewater Treatment

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