Adsorption behavior of methylene blue dye on nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) as new adsorbent

Adsorption behavior of methylene blue dye on nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) as new adsorbent

Journal of Molecular Liquids 216 (2016) 830–835 Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevie...

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Journal of Molecular Liquids 216 (2016) 830–835

Contents lists available at ScienceDirect

Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq

Adsorption behavior of methylene blue dye on nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) as new adsorbent D. Robati a,⁎, B. Mirza b, R. Ghazisaeidi c, M. Rajabi d, O. Moradi e,⁎, I. Tyagi f, Shilpi Agarwal g, Vinod Kumar Gupta f,g,⁎⁎ a

Department of Chemistry, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran Department of Chemistry, Faculty of Sciences, Tehran South Branch, Islamic Azad University, Tehran, Iran c Department of Textile Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran d Young Researchers and Elite Club, East Tehran Branch, Islamic Azad University, Tehran, Iran e Department of Chemistry, Shahre-Qods, Islamic Azad University, Tehran, Shahre-Qods, Iran f Department of Chemistry, Indian Institute of Technology, Roorkee 247667, India g Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa b

a r t i c l e

i n f o

Article history: Received 23 October 2015 Accepted 2 February 2016 Available online xxxx Keywords: Multi-walled carbon nanotubes Thiol functionalization Cysteamine Cationic dye Adsorption isotherm

a b s t r a c t Efficient MWCNT-SH was used as adsorbent for the rapid removal and fast adsorption of hazardous cationic dye methylene blue from the liquid phase. The surface textural and morphological properties of the developed adsorbent were characterized using Scanning electron microscopy which reveals the porous nature of the developed adsorbent. The effect of influential parameters which posses embarking affect on the adsorption process such as contact time, temperature and initial concentration of methylene blue (MB) dye in solution were well investigated and elucidated. After optimizing the influential parameters it was observed that after 60 min there is no visible change noticed in the removal of methylene blue (MB) dye using MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents, hence 60 min is the optimized contact time for the process additionally it was found that the adsorption capacity of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces increased with increasing the temperature. The adsorption capacity also increases with increase in the initial concentrations of MB dye from 10 to 40 mg L−1. The adsorption equilibrium data for MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNTS-SH5 was found to be well fitted and in good agreement with the type (III) of the Langmuir isotherm model, Freundlich isotherm model and type (II) model of the Langmuir isotherm model respectively. © 2016 Elsevier B.V. All rights reserved.

1. Introduction One of the most important environmental concerns now a day is the presence of noxious dyes in the aqueous streams of nearby industries. Today in industries a large amount of dyes were used for the production of food, leather, paper, cosmetics and textiles. Several noxious dyes and their derivatives are not readily biodegradable and have a carcinogenic, toxic, or mutagenic efficacy on mankind and animals. So, a significant

⁎ Corresponding authors. ⁎⁎ Correspondence to: V.K. Gupta, Department of Chemistry, Indian Institute of Technology, Roorkee 247667, India. E-mail addresses: [email protected], [email protected] (D. Robati), [email protected], [email protected] (O. Moradi), [email protected], [email protected] (V.K. Gupta).

http://dx.doi.org/10.1016/j.molliq.2016.02.004 0167-7322/© 2016 Elsevier B.V. All rights reserved.

area of applied and basic research is the removal dyes pollution from wastewater of industries [1]. Methylene blue (MB) is one of the cationic dyes, which is used as the material for dyeing wood, cotton, and silk. However MB dye is not classified to be a highly venomous dye, the eradication and elimination of MB dye from the aqueous solution is necessary because it possess several detrimental effects such as diarrhea, cyanosis, tissue necrosis, vomiting, jaundice, quadriplegia, shock and increased heart rate in human beings [2]. Some methods have been used for the removal of toxic dyes from the wastewater of industries, for example flocculation, ozonation, membrane separation, aerobic or anaerobic treatment, coagulation and adsorption [3–11]. Nevertheless, adsorption is one of the methods, which is most widely used because of its specific properties like it is inexpensive, easy to handle and impressive for removal of toxic dyes from wastewater of industries. Various adsorbents such as activated carbon [2], graphene nanosheets [12], multi-walled carbon

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walled carbon nanotubes functionalized carboxyl are provided from the (Nano Amor Nanostructured & Amorphous Materials), Inc. (USA) with a purity of over 95%. Average diameter 1–2 nm; length 5–30 nm and SSA ~400 m2/g). 2.2. Preparation of MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces

Fig. 1. Structure of methylene blue dye (MB).

nanotubes [13], cedar sawdust and crushed brick [14], magnetic chitosan/graphene oxide composite [15], rice husk [16–17] and several other low cost adsorbents [18–43] had been used previously for the removal and fast adsorption of the noxious impurities. Nowadays one of the materials which have attracted the attention of the several researchers is carbon nanotubes (CNTs) because it can be used in multidisciplinary areas and possess several applications due to their unique hollow tube structure and their many optical properties, electronic and outstanding mechanical [44]. In the present work, we functionalized the surface of Multi-walled carbon nanotubes using the thiol group with the different percentage of cysteamine mass and amount i.e. 0, 1, 3 and 5, after that the adsorption capacity of methylene blue (MB) dye on to the developed adsorbent i.e. MWCNT, MWCNT-SH1, MWCNT-SH3, and MWCNT-SH5 surfaces at 298 K, and pH 6 was well investigated and elucidated. The effects of influential parameters such as contact time, temperature, and initial dye concentration, on the MB dye adsorption were well studied and optimized.

According to the method [45] we dissolved 80 mg of cysteamine hydrochloride in ethanol and added 80 mg of dry powder of multi-walled carbon nanotube functionalized carboxyl then placed the sample in the shaker until the solution becomes evenly. Then 50 mg of 1-ethyl (3, 3 die-amino-propel acetate) Carobo amide (EDC) (with purity ≥99% provided by Aldrich Company) that was used for better reaction between the multi-walled carbon nanotube functionalized carboxyl and cysteamine hydrochloride, which was later followed with the addition of 30 mg of (NHS) or N-hydroxy Svsynamyd (with purity ≥99% provided by Aldrich Company). The synthesis reaction between multi-walled carbon nanotube functionalized carboxyl and cysteamine hydrochloride was shown in Fig. 2. After the completion of the synthesis reaction, the multiwalled nanocomposite carbon nanotube functionalized thiol (MWCNT-SH) separated with the help of micro filter and washed several times with deionized water and ethanol. So after several rinses, pH of output water will be neutralized. Then the resulting mixture placed in the oven at 80 °C for 48 h until its moisture removed completely. 2.3. Characterization methods The surface textural and morphological properties of the developed adsorbent were characterized using Scanning electron microscopy. The SEM image of multi-walled carbon nanotube functionalized carboxyl and nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) are shown in Fig. 3.

2. Materials and methods 2.4. Methylene blue dye adsorption study 2.1. Materials Methylene blue was provided from the Sigma-Aldrich Co (Germany) with Empirical Formula: C16H18ClN3S, Molecular Weight: 319.85 g/mol and CAS number: 7220-79-3. As shown in Fig. 1. Cysteamine is provided from the Sigma-Aldrich Co (Germany) with a purity of over 98% for synthesis the following specifications were used in this study. Cysteamine hydrochloride, CAS number: 156-57-0, Linear formula: (HSCH2CH2NH2)·HCl and molecular weight: 113.61 g/mol. Multi-

The adsorption experiment was conducted into 100 mL glass flasks on the shaker with a shaking speed of 200 rpm. In the 100 mL glass flask 20 mg of MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents is added to 20 mL of MB dye solution with known concentration of methylene blue dye (3 mg L−1) at 298 K and at fixed pH 6. It was observed that the removal of the MB dye did not change after 60 min, hence the optimum time for adsorption of MB dye by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents was selected

Fig. 2. Preparation of nanocomposite of reaction between multi-walled carbon nanotube functionalized carboxyl with cysteamine hydrochloride.

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Fig. 3. SEM of multi-walled carbon nanotube functionalized carboxyl (MWCNT-COOH) (A), SEM of nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) (B).

as 60 min. The remaining concentration of MB dye in samples was specified by using the UV–Vis spectrophotometer furnished by Varian (Cary 100 Bio) (London-England) at maximum wavelength of MB dye 660 nm. The adsorption rate and adsorption amount of methylene blue concentration in the samples before and after adsorption process was calculated using the following equation [46,47]:

qe ¼

  C0 −Ce V W

ð1Þ

where C0, in mg/L, was initial concentrations of methylene blue, Ce, in mg/L was equilibrium concentrations of methylene blue, and W in grams, was the weight of the MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 used and V, in liters, was the volume of methylene blue solution. To evaluate the fitness of isotherm and thermodynamic equations to the experimental data, the chi-square statistic (X2) was used to measure the isotherm and thermodynamic constants [46]. X2 can be defined as:

2

X ¼

 XN qe; i

exp −qe; cal

qe;

2 :

ð2Þ

cal

The subscripts “exp” and “cal” show the experimental and calculated values and N is the number of observations in the experimental data. If data from the model are similar to the experimental data, X2 will be a small number; if they are different, X2 will be a large number.

Fig. 4. Effect of contact time on the removal of the MB dye using MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces, initial concentration: 10 mg/L; adsorbent dosage: 20 mg, T: 298 (K) and pH: 6.

3. Result and discussion 3.1. Characterizations of adsorbents The surface textural and morphological properties of the developed adsorbent were characterized using SEM image. The Scanning electron microscope (SEM) of multi-walled carbon nanotube functionalized carboxyl and nanocomposite multi-walled carbon nanotube functionalized thiol (MWCNT-SH) was shown in Fig. 3, it reveals that the surface of multi-walled carbon nanotube functionalized carboxyl was dispersed in the form of active particles and nanocomposites. Absorbents used in this research, already synthesized and characterized [45]. 3.2. Contact time at removal of methylene blue dye The adsorption experiments were conducted to optimize the contact time, for the adsorption of methylene blue dye on MWCNT, MWCNTSH1, MWCNT-SH3 and MWCNT-SH5 surfaces. These experiments occurred out at various time 10, 20, 30, 40, 50, 60, 70 and 80 min. From Fig. 4, it is clear that after 60 min no great changes was observed in the removal percentage of MB dye by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents. So, 60 min was determined for adsorption of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces as optimum time at 298 K and pH = 6. 3.3. Effect of temperature on the adsorption Temperature is one of the important factors which alter the adsorption capacity of adsorbent and the adsorption process. Effect of temperature was carried out at several temperatures ranging from 283 to 303 K

Fig. 5. Effect of temperature on the removal of the MB dye using MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents, initial concentration: 10 mg/L; adsorbent dosage: 20 mg; time: 60 min and pH: 6.

D. Robati et al. / Journal of Molecular Liquids 216 (2016) 830–835

Fig. 6. Effect of initial MB dye concentration on the adsorption by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents. Initial concentration 10–40 mg/L; adsorbent dosage: 20 mg; time: 60 min and pH: 6.

contact time 60 min and pH 6. In Fig. 5, the curve displayed the effect of temperature on the adsorption capacity of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces at temperature ranging from 283 to 303 K. It was found that the adsorption capacity of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces increased with increasing the temperature.

Fig. 8. Type 2 of Langmuir isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

3.5.1. Langmuir isotherm model In the equilibrium study, one of the most extensive isotherm models is the Langmuir isotherm model that is widely used. It is observed that four different types of the Langmuir isotherm can be linearized. The four types of Langmuir isotherm model can be expressed as [48]: TypeðIÞ :

Ce 1 Ce ¼ þ qe KQ m Q m

ð3Þ

TypeðIIÞ :

1 1 1 ¼ þ qe Q m KQ m Ce

ð4Þ

TypeðIIIÞ :

qe ¼ Q m −

TypeðIVÞ :

qe ¼ KQ m −Kqe Ce

3.4. Effect of initial methylene blue dye concentration The adsorption capacity of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces were performed in various initial concentrations from 10, 15, 20, 25, 30, 35 and 40 mg L−1 at temperature 298 K, pH 6 and 60 min. As shown in Fig. 6, the adsorption capacity increases with increase in the initial concentration of MB dye from 10 to 40 mg L−1.

3.5. Isotherm of adsorption As shown at Fig. 6 adsorption of MB dye by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces increasing significantly with an increase in methylene blue dye initial concentration. In this work, for removal of methylene blue from aqueous solution by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents used the four types of Langmuir [48], the Freundlich [49], and the Halsey [50] isotherm models. These models were evaluated by the adjusted determination factor (R2) and chi-square statistic (X2).

833

qe KCe

ð5Þ

ð6Þ

where K (L/mg) and Qm (mg g−1) are Langmuir constants corresponds to energy of adsorption and removal capacity. Curve of four types of Langmuir isotherm models shown in Figs. 7, 8, 9, and 10, the value of the obtained parameters was shown in Table 1. In addition, the dimensionless separation factor (RL) pertaining the adsorption of MB dye by MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces was calculated using Eq. (7) [51]: RL ¼

1 : ð1 þ KC0 Þ

ð7Þ

If RL N 1, unfavorable; RL = 1, linear; 0 b RL b 1, favorable; RL = 0, irreversible (Table 1) [51].

Fig. 7. Type 1 of Langmuir isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

Fig. 9. Type 3 of Langmuir isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

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Fig. 10. Type 4 of Langmuir isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

Fig. 11. Freundlich adsorption isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNTSH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

3.5.2. Freundlich isotherm model The Freundlich [49] isotherm is derived by assuming a heterogeneous surface with a non uniform distribution of the heat of sorption over the surface. It can be linearly expressed as follows:

Versus ln1/Ce Halsey adsorption isotherm are presented in Table 2 and the curves are shown in Fig. 12.

qe ¼ K F C1=n e

4. Conclusion

ð8Þ

where, n and KF are the Freundlich parameters related to adsorption intensity and adsorption capacity, respectively. If the value of 1/n is lower than 1, it indicates a normal Langmuir isotherm; otherwise, it is indicative of cooperative adsorption. The Freundlich constants can be obtained from the plot of ln qe versus ln Ce (Fig. 11, Table 2). 3.5.3. The Halsey isotherm The Halsey [52,53] adsorption isotherm can be given as:  lnqe ¼

 1 1 ln K − lnCe : n n

ð9Þ

For multilayer adsorption, this equation is suitable. Especially, the fitting of this equation can be best used for heterotopous solids. lnqe

In the present work, the adsorption capacity of MB dye on developed adsorbents i.e. MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces were well studied and investigated at pH 6 and temperature 298 K. 60 min was selected as optimum time because the effect of influential parameters which posses embarking affect on the adsorption process such as contact time, temperature and initial concentration of MB dye in solution were well investigated and elucidated. After optimizing the influential parameters it was observed that after 60 min there is no visible change noticed in the removal of MB dye using MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 adsorbents, hence 60 min is the optimized contact time for the process. Results shown that for adsorption of MB dye on MWCNT surface type (III) of the Langmuir isotherm model was high fit with equilibrium data and for adsorption MB dye on MWCNT-SH1, MWCNT-SH3 surfaces. Freundlich isotherm model was high fit with equilibrium data and for adsorption of MB dye on

Table 1 Langmuir isotherm parameters and for adsorption of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6. Isotherm

Equation

Langmuir 1

Ce qe

¼

Langmuir 2

1 qe

¼ Q1m þ KQ1m Ce

Langmuir 3

qe qe ¼ Q m − KC e

Langmuir 4

qe Ce

1 KQ m

þ

Parameters

qe Qm

¼ KQ m −Kqe

−1

Qm (mg g ) K1 (L mg−1) RL1 R2 X2 Qm (mg g−1) K2 (L mg−1)

Qm (mg g−1) K3 (L mg−1) RL3 R2 X2 Qm (mg g−1) K4 (L mg−1) RL4 R2 X2

Adsorbent MWCNT

MWCNT-SH1

MWCNT-SH3

MWCNT-SH5

166.7 0.0121 0.67–0.89 0.991 5.21 100 4.930 0.02–0.05 0.998 4.49 2.373 33.33 0.02–0.07 0.999 4.17 2.991 22.94 0.01–0.04 0.946 6.28

166.7 0.0128 0.66–0.88 0.980 5.87 100 4.810 0.02–0.05 0.998 4.49 2.029 33.36 0.02–0.07 0.973 6.25 2.986 21.63 0.01–0.04 0.960 6.70

200.0 0.0129 0.65–0.89 0.979 5.91 100 4.740 0.02–0.05 0.994 4.48 2.097 34.25 0.02–0.07 0.984 5.20 2.987 19.50 0.01–0.04 0.933 7.21

142.8 0.0181 0.58–0.65 0.949 6.23 100 4.550 0.02–0.05 0.999 4.12 1.790 34.08 0.02–0.07 0.982 5.32 2.999 19.30 0.01–0.04 0.942 6.98

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Table 2 The Freundlich parameters and for adsorption of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6. Isotherm

Equation

Freundlich

qe = KFC1/n e

Halsey

lnqe ¼ ½n1 lnK− n1 lnCe

Parameters

KF 1/n R2 X2 N K R2 X2

Adsorbent MWCNT

MWCNT-SH1

MWCNT-SH3

MWCNT-SH5

0.348 0.989 0.998 4.25 1.008 4.207 0.998 4.89

0.321 0.995 0.999 4.11 1.002 4.049 0.998 4.76

0.319 1.010 0.999 4.19 0.988 4.026 0.994 5.12

0.239 0.991 0.996 4.75 1.006 3.622 0.995 5.01

Fig. 12. Halsey adsorption isotherm of MB dye on MWCNT, MWCNT-SH1, MWCNT-SH3 and MWCNT-SH5 surfaces. Initial concentration 10–40 mg/L; adsorbents dosage: 20 mg; time: 60 min and pH: 6.

MWCNT-SH5 type (II) of the Langmuir isotherm model was high fit with equilibrium data. Acknowledgements The authors would like to thank the Islamic Azad, Islamshahr Branch for their financial support. References [1] G.K. Ramesha, A. Vijaya Kumara, H.B. Muralidhara, S. Sampath, J. Colloid Interface Sci. 361 (2011) 270–277. [2] Y. Li, Q. Du, T. Liu, X. Peng, J. Wang, J. Sun, Y. Wang, S. Wu, Z. Wang, Y. Xia, L. Xia, Chem. Eng. Res. Des. 91 (2013) 361–368. [3] Y. Li, Q. Du, T. Liu, J. Sun, Y. Wang, S. Wu, Z. Wang, Y. Xia, L. Xia, Carbohydr. Polym. 95 (2013) 501–507. [4] M. Rajabi, O. Moradi, A. Mazlomifar, Int. J. Nano Dimens. 6 (3) (2015) 227–240 (Summer). [5] V.K. Gupta, T.A. Saleh, Environ. Sci. Pollut. Res. 20 (2013) 2828–2843. [6] V.K. Gupta, R. Kumar, Adv. Colloid Interf. Sci. 194 (2013) 24–34. [7] O.G. Apul, Q. Wang, Y. Zhou, T. Karanfil, Water Res. 47 (2013) 1648–1654. [8] V.K. Gupta, A.K. Jain, S. Agarwal, G. Maheshwari, Talanta 71 (2007) 1964–1968. [9] R. Jain, V.K. Gupta, N. Jadon, K. Radhapyari, Anal. Biochem. 407 (2010) 79–88. [10] V.K. Gupta, A.K. Singh, S. Mehtab, B. Gupta, Anal. Chim. Acta 566 (2006) 5–10. [11] R.N. Goyal, V.K. Gupta, S. Chatterjee, Electrochim. Acta 53 (2008) 5354–5360. [12] F.M. Machado, C.P. Bergmann, T.H.M. Fernandes, E.C. Lima, B. Royer, T. Calveteb, S.B. Faganc, J. Hazard. Mater. 192 (2011) 1122–1131. [13] L. Fan, C. Luo, M. Sun, H. Qiu, X. Li, Colloids Surf. B: Biointerfaces 103 (2013) 601–607. [14] L. Fan, C. Luo, M. Sun, X. Li, F. Lu, H. Qiu, Bioresour. Technol. 114 (2012) 703–706. [15] D. Georgiou, P.D. Petrolekas, S. Hatzixanthis, A. Aivasidis, J. Hazard. Mater. 144 (2007) 369–376. [16] Y. Onal, J. Hazard. Mater. 137 (3) (2006) 1719–1728. [17] T.A. Saleh, V.K. Gupta, Colloid Interface Sci. 371 (2012) 101–106. [18] B.J. Sanghavi, W. Varhue, A. Rohani, K.-Tang Liao, L.A.L. Bazydlo, C.-Fu Chou, N.S. Swami, Lab Chip 15 (2015) 4563–4570.

[19] B.J. Sanghavi, W. Varhue, J.L. Chavez, C.-Fu Chou, N.S. Swami, Anal. Chem. 86 (2014) 4120–4125. [20] B.J. Sanghavi, S. Sitaula, M.H. Griep, S.P. Karna, M.F. Ali, N.S. Swami, Anal. Chem. 85 (2013) 8158–8165. [21] B.J. Sanghavi, S.M. Mobin, P. Mathur, G.K. Lahiri, A.K. Srivastava, Biosens. Bioelectron. 39 (2013) 124–132. [22] B.J. Sanghavi, A.K. Srivastava, Analyst 138 (5), 1395–1404. [23] V.K. Gupta, I. Ali, Water Res. 35 (2001) 33–40. [24] V.K. Gupta, S. Sharma, I.S. Yadav, D. Mohan, J. Chem. Technol. Biotechnol. 71 (1998) 180–186. [25] T.A. Saleh, S. Agarwal, V.K. Gupta, Appl. Catal. B Environ. 106 (2011) 46–53. [26] H. Khani, M.K. Rofouei, P. Arab, V.K. Gupta, Z. Vafaei, J. Hazardous, Materials 183 (2010) 402–409. [27] V.K. Gupta, R. Kumar, A. Nayak, T.A. Saleh, M.A. Barakat, Adv. Colloid Interf. Sci. 193194 (2013) 24–34. [28] M.H. Dehghani, M.M. Taher, A.K. Bajpai, B. Heibati, I. Tyagi, M. Asif, S. Agarwal, V.K. Gupta, Chem. Eng. J. 279 (2015) 344–352. [29] H. Sadegh, R. Shahryari-ghoshekandi, S. Agarwal, I. Tyagi, M. Asif, V.K. Gupta, J. Mol. Liq. 206 (2015) 151–158. [30] V.K. Gupta, S.K. Srivastava, D. Mohan, S. Sharma, Waste Manag. 17 (1998) 517–522. [31] V.K. Gupta, P. Singh, N. Rahman, J. Colloid Interface Sci. 275 (2004) 398–402. [32] S. Karthikeyan, V.K. Gupta, R. Boopathy, A. Titus, G. Sekaran, J. Mol. Liq. 173 (2012) 153–163. [33] V.K. Gupta, R. Jain, A. Mittal, T.A. Saleh, A. Nayak, S. Agarwal, S. Sikarwar, Mater. Sci. Eng. C 31 (2011) 1062–1067. [34] V.K. Gupta, A. Nayak, Chem. Eng. J. 180 (2012) 81–90. [35] A. Asfaram, M. Ghaedi, S. Agarwal, I. Tyagi, V.K. Gupta, RSC Adv. 5 (2015) 18438–18450. [36] V.K. Gupta, B. Gupta, A. Rastogi, S. Agarwal, A. Nayak, Water Res. 45 (2011) 4047–4055. [37] V.K. Gupta, A. Nayak, S. Agarwal, I. Tyagi, J. Colloid Interface Sci. 417 (2014) 420–430. [38] V.K. Gupta, A. Nayak, S. Agarwal, M. Chaudhary, I. Tyagi, J. Mol. Liq. 190 (2014) 215–222. [39] F. Zare, M. Ghaedi, A. Daneshfar, S. Agarwal, I. Tyagi, T.A. Saleh, V.K. Gupta, Chem. Eng. J. 273 (2015) 296–306. [40] M. Ghaedi, M. reza Rahimi, A.M. Ghaedi, I. Tyagi, S. Agarwal, V.K. Gupta, J. Colloid Interface Sci. 461 (2016) 425–434. [41] V.K. Gupta, I. Tyagi, S. Agarwal, H. Sadegh, R. Shahryari-ghoshekandi, M. Yari, O. Yousefi-nejat, J. Mol. Liq. 206 (2015) 129–136. [42] M. Ghaedi, S. Hajjati, Z. Mahmudi, I. Tyagi, S. Agarwal, A. Maity, V.K. Gupta, Chem. Eng. J. 268 (2015) 28–37. [43] F. Nekouei, S. Nekouei, I. Tyagi, V.K. Gupta, J. Mol. Liq. 201 (2015) 124–133. [44] H. Li, D. Xiao, H. He, R. Lin, P. Zuo, Trans. Nonferrous Metals Soc. China 23 (2013) 2657–2665. [45] D. Robati, S. Bagheriyan, M. Rajabi, Int. Nano. Lett. (doi 10.1007/s40089–015-01529). [46] D. Robati, A. Fakhri, Phys. Theor. Chem. IAU Iran 9 (2) (summer 2012) 125–133. [47] P. Sharma, N. Hussain, D.J. Borah, M.R. Das, J. Chem. Eng. Data 58 (2013) 3477–3488. [48] X. Ren, D. Shao, S. Yang, J. Hu, G. Sheng, X. Tan, X. Wang, Chem. Eng. J. 170 (2011) 170–177. [49] V.K.K. Upadhyayula, S. Deng, M.C. Mitchell, G.B. Smith, Sci. Total Environ. 408 (2009) 1–13. [50] F. Najafi, O. Moradi, M. Rajabi, M. Asif, I. Tyagi, S. Agarwal, V.K. Gupta, J. Mol. Liq. 208 (2015) 106–113. [51] D. Robati, B. Mirza, M. Rajabi, O. Moradi, I. Tyagi, S. Agarwal, V.K. Gupta, Chem. Eng. J. 284 (2016) 687–697. [52] M. Yari, M. Norouzi, A.H. Mahvi, M. Rajabi, A. Yari, O. Moradi, I. Tyagi, V.K. Gupta, Desalin. Water Treat. 54 (2015) 1–16. [53] L. Zhuannian, Z. Anning, W. Guirong, Z. Xiaoguang, Chin. J. Chem. Eng. 17 (6) (2009) 942–948.