Preparation and characterization of organo-montmorillonites. Application in adsorption of the 2,4,5-trichlorophenol from aqueous solution

Advanced Powder Technology 22 (2011) 735–740

Contents lists available at ScienceDirect

Advanced Powder Technology journal homepage: www.elsevier.com/locate/apt

Original Research Paper

Preparation and characterization of organo-montmorillonites. Application in adsorption of the 2,4,5-trichlorophenol from aqueous solution H. Zaghouane-Boudiaf ⇑, Mokhtar Boutahala Laboratoire de Génie des Procédés Chimiques, Faculté de Technologie, Université Ferhat Abbas, Sétif 19000, Algeria

a r t i c l e

i n f o

Article history: Received 28 May 2010 Received in revised form 13 October 2010 Accepted 16 October 2010 Available online 1 November 2010 Keywords: Organo-clay X-ray diffraction FTIR analysis Thermogravimetric analysis BET measurement 2,4,5-Trichlorophenol

a b s t r a c t X-ray diffraction has been used to study the changes in the surface properties of montmorillonitic clay through the changes in the basal spacings of sodium-montmorillonite (NaMt), acid-activated montmorillonite (AMt), pillared-montmorillonite (AlMt) and surfactant-intercalated organoclays. The basal spacing value of the NaMt increased from 12.01 to 18.1 Å by pillaring with Keggin ions ((hydroxyaluminum polycation) and until 21 Å by intercalation of the cationic surfactant in the interlayer space of the clay. Confirmations of the intercalated cationic surfactant have been characterized using Fourier transform infrared spectroscopy (FTIR). Thermogravimetric analysis shows that the thermal decomposition of montmorillonites modified with the cationic surfactant hexadecyltrimethylammonium (HDTMA) takes place in four steps. The surface areas of organo-montmorillonites were found to be much lower than that of raw montmorillonite. Surface areas of pillared and acid-activated montmorillonite are very high. This was explained by the emergence of the micropores and mesopores in the structure of the sample resulting from treatment. Adsorption of the 2,4,5-trichlorophenol (2,4,5-TCP) onto samples was studied. The greatest value of adsorption capacity of samples is attributed to the organo-montmorillonite (MtC16). Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

1. Introduction Montmorillonite is widely used in a range of applications because of its high cation exchange capacity (CEC), swelling capacity, high surface area, and consequential strong adsorption and absorption capacities [1–3]. The montmorillonite is a 2:1 layered silicate. The inner layer is composed of an octahedral sheet of general form M2–3(OH)6 (M is typically Al), which is located between two SiO4 tetrahedral sheets [4,5]. Replacement of Al3+ for Si4+ in the tetrahedral layer and Mg2+ for Al3+ in the octahedral layer results in a net negative charge on the clay surfaces. The charge imbalance is offset by the exchangeable cation Na+ or Ca2+ in the interlayer. In aqueous phase, water molecules are intercalated into the interlamellar space of montmorillonite, leading to an expansion of the clays. The hydration of inorganic cations on the exchange sites causes the clay mineral surface to be hydrophilic. The clay properties can be enhanced by converting the montmorillonite to an organo-montmorillonite by ion exchange of the cation with a surfactant molecule. Modification of the montmorillonite with surfactant molecules changes the properties of the montmorillonite from

⇑ Corresponding author. E-mail address: [email protected] (H. Zaghouane-Boudiaf).

hydrophilic to hydrophobic and organophilic. It also increases the basal spacing of the layers; such surface property changes will affect the applications of the organo-montmorillonite [6,7]. These solids show interesting properties toward adsorption for organic micropollutants such as phenol, phenolic compounds and other benzene compounds [8–10], pesticides [11–13], and dyes [14,3]. They have also confirmed their high affinity towards organic compounds. The synthesis of a second class of organo-clays has focused on intercalation of long-chain quaternary ammonium cations in the interlayer space of pillared and acid-activated clay [15–17]. Water purification is of extreme importance in many parts of the world. Many of the world’s water ways and water sources are polluted or contaminated with a phenols, chlorophenols. pesticides and herbicides. The objective of this study is to determine the feasibility of removal organic pollutants from water by the modified Algerian bentonite. Because the adsorption of the 2,4,5-TCP has not been reported, in this research it is used as a test molecule in the adsorption study. It well-known that bentonite is a low cost adsorbent compared to activated carbon. X-ray powder diffraction, thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, and surface area measurement (BET) techniques were used to study the changes in the structure and surface properties of prepared clay.

0921-8831/$ - see front matter Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. doi:10.1016/j.apt.2010.10.014

736

H. Zaghouane-Boudiaf, M. Boutahala / Advanced Powder Technology 22 (2011) 735–740

2. Experimental 2.1. Materials The bentonite used in this study was obtained from Hammam Boughrara (West Algeria). Its chemical composition was found to be: 69.4% SiO2, 1.1% MgO, 14.7% Al2O3, 0.8% K2O, 0,3% CaO, 1.2% F2O3, 0.5% Na2O, 0.2% TiO2, 0.05% As and 11% loss of ignition [18]. This bentonite is not a single phase but contains 97.1% of montmorillonite with presence of cristobalite and quartz [19]. Its cation exchange capacity (CEC) is 97 meq/g [20]. Sodium chloride (analytical grade); sulfuric acid (H2SO4, 98 wt.%), aluminium-chloride (AlCl3, 6H2O), sodium hydroxide (NaOH), HDTMA (C19H42NCl, 99%) and 2,4,5-trichlorophenol (2,4,5-TCP) (purity of >99%) were purchased from Sigma–Aldrich Chemicals. 2.2. Sample preparation The bentonite was converted to a sodium montmorillonite (NaMt) using the following procedure: 30 g of crude bentonite were mixed with 1 M NaCl solution and stirred for 24 h. After three successive treatments, the homoionic bentonite was dialyzed in deionized water until it was free of chloride. Then it was separated by centrifugation to eliminate all other solid phases (quartz, cristoballite). The Na+-montmorillonite noted NaMt (fraction <2 lm) was recovered by decantation and dried at 80 °C. The pillared clays were prepared with a procedure similar to that of reported by Khalaf et al. [18]. The pillaring oligocation was prepared from 0.2 M of AlCl36H2O solution and 0.5 M of NaOH solution, with a basicity relationship OH/Al = 2,5. The sodium hydroxide solution was incorporated drop by drop into the aluminium chloride solution, which was maintained under vigorous stirring. The resultant solution was aged during 24 h. The polymeric solution was incorporated drop by drop into a suspension made with 10 g of NaMt. The amount of the incorporated oligocation has a ratio of 25 meq of Al per gram of clay to ensure complete saturation of exchange sites. The sample was washed in a dialysis membrane, dried at 80 °C and heated at 450 °C for 4 h 30 min. The resulting material was called pillared-montmorillonite noted AlMt. The NaMt was treated under mechanical stirring with 1 M H2SO4 solution at 90 °C for 4 h. The mass ratio of the bentonite to the acid solution was 1:1. After activation, the solid was washed by distilled water until SO2 4 free and dried at 80 °C. The derivate is an acid-activated montmorillonite noted AMt. The NaMt, AlMt and AMt were treated with the cationic surfactant HDTMA+ with the molecular formula C19H42N+ for the purpose of sorption enhancement. Surfactant-modified montmorillonite was prepared by adding amounts of the cationic surfactant equivalent to 100% of the value CEC of montmorillonite. The surfactant was dissolved in 1 L of distilled water at 80 °C and stirred for 3 h. A total of 10 g of sample (NaMt, AlMt, AMt) was added separately to the 1 L surfactant solution. The dispersions were stirred for 3 h at 80 °C. The separated organo-montmorillonites were washed with distilled water. Washing was repeated until the supernatant solution was free of chloride ions, as indicated by the AgNO3 test. The organo-montmorillonites were oven-dried at 80 °C until the water was completely evaporated. The derivates are MtC16 (organo-montmorillonite), AlMtC16 (organo-pillared-montmorillonite) and AMtC16 (organo-acid-activated montmorillonite), respectively. 2.3. Characterization of prepared samples The distance between the layers of the modified clays, the basal spacing d001, was determined by X-ray diffraction analysis using a

Bruker D8 advance diffractometer operating at 40 kV and 30 mA with CuKa radiation (k = 0.15406 nm). Radial scans were recorded in the reflection scanning mode from 2h = 1–80°. Bragg’s law, defined as nk = 2d sin h, was used to compute the crystallographic (d) for the examined clay samples. Thermal characterization of the materials was carried out by thermogravimetric analysis (TGA) on 30 mg sample by heating from 50 to 1000 °C at 5 °C/ min, under nitrogen using a TA Instruments thermobalance TGA Q500. Nitrogen gas adsorption–desorption isotherms were measured using a Quanta Chrome Autosorb-1 instrument at 77 K. The measurements were made after degassing under vacuum at 180 °C for 6 h. The specific surface area (S.B.E.T) was calculated by the B.E.T method [21] and the pore size was calculated by the B.J.H method [22] using the adsorption and desorption isotherms, respectively. The total pore volume was calculated from the maximum amount of nitrogen gas adsorption at partial pressure (P/ P0) = 0.999. FT-IR study was carried out using FTIR 8400S Shimadzu having a standard mid-IR DTGS detector. FT-IR spectra were recorded, in the range of 400–4000 cm1 with KBr pellets technique. 2.4. Adsorption isotherms A constant volume of 2,4,5-TCP solution (50 mL) with varying initial concentrations (10–200 mg/L) was mixed with a constant amount of prepared samples (20 mg). The dispersions were shaken at a temperature of 20 ± 1 °C, under an agitation speed of 100 rpm. The dispersions were maintained at a constant pH of 4.0 over 120 min. The 2,4,5-TCP qe loading (in mg per unit weight of sample) was obtained using the following equation:

qe ¼

ðC 0  C e Þ  V m

ð1Þ

where C0 and Ce in (mg/L) are initial and equilibrium TCP concentration, respectively. V (L) is the volume of the 2,4,5-TCP solution and m (g) is the adsorbent weight. The initial concentration C0 and the equilibrium concentration Ce of TCP in solution were determined using ShimadzuUV-1700 UV–visible spectrophotomer at the wavelength of 290 nm. 3. Results and discussion 3.1. XRD study The XRD pattern of NaMt (Fig. 1A) showed the reflection 2h equals to 7.24° which corresponds to d001 spacing of NaMt and its value is 12.2 Å. This value indicates that some molecules of water were adsorbed in the layer space. The d001 for anhydrous montmorillonite heated over 400 °C is 9.60 Å [6,7]. After modification of montmorillonite with an amount of cationic surfactant (about CEC value), the d001 value shifts to 21 Å in MtC16 (see Fig. 1B). This indicated that the surfactant ions were entered in the interlayer space of the montmorillonite. Fig. 1B showed also two new d001 spacing. These new peaks are attributed to the sample AlMt and AlMtC16 with d001 of 18.1 Å. The increase in d001 spacing from 12.2 to 18.1 Å indicated the presence of Al13 like polymers in the interlamelar region. This polymer has structural formula, [AlO4Al12(OH)24(H2O)12]7+. After intercalation of surfactant ions in AlMt sample no change in d001 spacing was observed. It can be concluded that insertion of the surfactant ions after the formation of stable pillars caused by heating of AlMt sample does not destabilise the porous network. Fig. 1C showed that activation has affected mainly the d001 reflection. Acid activation of montmorillonite yielded two new peaks at 25 Å (2h = 3.46°) and 14.71 Å (2h = 6°). These were absent in the untreated montmorillonite. Appearance of new peaks

737

H. Zaghouane-Boudiaf, M. Boutahala / Advanced Powder Technology 22 (2011) 735–740

B

A 1,49Å

3,02Å

M t C16 Counts/sec.

150

21Å

1,69Å

200

12,2Å

Counts/sec

250

3,42Å

4,45Å

300

18,1Å

AlM t C16

100

AlM t

18,1Å 50

0 20

40

60

80

20

0

40

Deg. Two Theta

C

60

80

600

800

Deg. Two Theta

25 Å

59 Å

Counts/sec.

14.71 Å

AM t 19.4 Å

AM t C16 0

20

40

60

80

Deg. Two Theta Fig. 1. XRD of (A) montmorillonite NaMt, (B) MtC16, AlMt and AlMtC16, (C) AMt and AMtC16.

3.2. Thermogravimetric analysis The curve related to the NaMt exhibited mass loses in temperature ranges 30–200 and 200–855 °C (Fig. 2). The large mass loss in NaMt in the range of 30–200 °C denote the release of different water species coordinated to the interlayer cations and surface humidity. It represents stronger hydrogen bonding between water molecules and exchangeable cation water. Half of the coordinated water is lost in the second dehydration process between 200 and 380 °C. The last part is lost at higher temperatures between 400 and 700 °C. At 800 °C another degradation step starts due to the dehydroxylation of NaMt anhydride that loses its structure. This

0 -4 -8

Mass loss %

indicated the formation of expansible phases and interlamellar expansion. Activation has also affected the d060 reflection (partial dissolution of Fe3+). The intensity of the d060 reflection has been reduced. The same result was found by Erena [23]. In addition, as shown in Fig. 1C, the new peaks in AMt shift to 59 Å (2h = 1.49°) and 19.4 Å (2h = 4.55°) in sample AMtC16. This indicates that the surfactant ions take place in interlayer space of the acid-activated montmorillonite by the exchanged cations (H+ and Na+) process. The value of W.H.P. (width high peak) of the XRD peak for NaMt is lower than the W.H.P. of the XRD peak for AMt. The increase in value W.H.P. of the d001 XRD peak showed that the crystallinity of NaMt decreases by acid treatment, so the NaMt clay is better organized than the acid-treated clay.

-12

NaMt -16

AMt -20

AlMt

-24

AlMtC16

-28

AMtC16 MtC16

-32 0

200

400

1000

Temperature (°C) Fig. 2. TG curves for all samples.

step, which results in the formation of enstatite and silica, is completed over 900 °C. Fig. 2 presents TG curves for all prepared samples. The great mass loss in the range of 30–200 °C corresponds to the removal of free and interlayer water. The mass loss is proportional to the

H. Zaghouane-Boudiaf, M. Boutahala / Advanced Powder Technology 22 (2011) 735–740

water comprised in the samples. NaMt and AMt contain the largest quantity of water because of the hydrated sodium cations intercalated within the clay layers. This quantity was successively reduced with the intercalation of the cationic surfactant. The temperature required for the complete volatilization of this water was also reduced. Alkylammonium presence lowers the surface energy of the inorganic material. It converts the hydrophilic silicate surface to an organophilic and hydrophobic one. On the other hand, organically modified montmorillonite follows a four-step decomposition process. The vaporization of free water takes place at temperatures below 200 °C. The cationic surfactant’s decomposition happens in the temperature range 150–520 °C. The mass loss between 150 and 280 °C is attributed to the decomposition of the cationic surfactant adsorbed on the external surface. The mass loss between 280 and 520 °C is attributed to the decomposition of the cationic surfactant intercalated within the clay layers. Dehydroxylation of the aluminosilicates occurs between 520 and 800 °C [24]. Decomposition associated with the reaction between organic carbon and inorganic oxygen takes place at temperatures between 800 and 1000 °C. 3.3. Surface area The BET specific surface area, pore volume and pore diameter data for the samples are summarized in Table 1. The specific surface area of the montmorillonite (NaMt) increased by attack acid from 82 to 298.5 m2/g. Table 1 shows an increase in the porous volume from 0.085 to 0.434. The increase in porosity is due to the partial dissolution of the exchangeable cations Na+, and also structural cations such as Al3+, Fe3+, and Mg2+ from 2:1 layers of the smectite mineral. Octahedron and tetrahedron spaces remaining from Mg2+, Fe3+ and Al3+ ions have left the layers of montmorillonite. The pores and empty spaces are accessible to the nitrogen molecules. We notice also a decrease in BET specific surface area by modifying the montmorillonite with a cationic surfactant. It was reported in a literature [25] that when a montmorillonite was modified with smaller sized surfactant such as tetramethylammonium, the surface area of prepared organoclay increased. But in this study, the results showed that the surface area of clay decreased. The decrease of surface area may be attributed to exchange sites which were satisfied by HDTMA with large molecular size resulting in inaccessibility of the internal surface to nitrogen gas and the blocking of the micropores in the organo-clays. It was in accordance with the conclusion drawn in literature [26]. Pillared clay (AlMt) has a higher surface than that of purified clay (NaMt); this is due the intercalation of the polycation between the layers which maintains a structure opens accessible to nitrogen. 3.4. FTIR analysis In order to obtain complementary evidence for the intercalation of quaternary alkylammonium cations into the silicate lattice, FTIR spectra were recorded in the region 400–4000 cm1. A pair of strong bands (Fig. 3) 2856 and 2929 cm1, were observed only on organo-montmorillonite; they can be assigned to the symmetric

Table 1 Structural parameters of samples. Samples

Surface area (m2/g)

Pore volume (cm3 N2 g/g)

Pore diameter (Å)

NaMt AMt AlMt AlMtC16 AMtC16 MtC16

82.0 298.5 266.5 44 23 12

0.085 0.434 0.335 0.072 0.042 0.004

41.6 58.5 43.8 55.2 34.4 13.3

200

150

Transmittance

738

1639 100

50

NaMt AlMtC16 AMtC16 MtC16

2929

0

2856

4000

3500

3000

2500

2000

1486 1500

1000

500

Wavenumber (cm-1) Fig. 3. FTIR spectra of the raw and organo-montmorillonites.

and antisymmetric stretching vibrations of the methylene group (mCH2), and their bending vibrations between 1396 and 1486 cm1 [27]. The band at 1639 cm1 is assigned to water bending modes within the clay interlayer [28]. The intensity of this band decreases with intercalation of surfactant molecules between the silica layers. The 3230 cm1 band intensity decreases also when compared with the original montmorillonite showing that water of hydration is lost as the cations (Na+) is replaced by the cationic surfactant. 3.5. Adsorption isotherm studies Adsorption isotherm can be used to describe how solute interacts with adsorbent. Therefore, it is critical in optimizing the use of adsorbent. The adsorption data obtained were analyzed with the Langmuir and Freundlich isotherm equations. The best fitting isotherm was tested by determination of the non linear regression, and the parameters of the isotherms have been obtained. 3.5.1. Langmuir isotherm The well-known expression of the Langmuir model is

qe ¼

qm K L C e 1 þ qm K L

ð2Þ

where qe is the equilibrium TCP concentration on adsorbent (mg/g), Ce is the equilibrium TCP concentration in solution (mg/L), qm is the monolayer capacity of the adsorbent (mg/g) and KL is the Langmuir adsorption constant (L/mg). The Langmuir equation is applicable to homogeneous sorption, where the sorption of each sorbate molecule onto the surface has equal sorption activation energy [29]. 3.5.2. Freundlich isotherm The Freundlich isotherm is an empirical equation which can be used for non ideal sorption that involves heterogeneous sorption [30]. The Freundlich isotherm can be derived assuming a logarithmic decrease in the enthalpy of sorption with the increase in the fraction of occupied sites and is commonly given by the following equation

qe ¼ K F C 1=n e

ð3Þ

where qe is the equilibrium TCP concentration on adsorbent (mg/g), Ce is the equilibrium TCP concentration in solution (mg/L), KF (mg/g) and 1/n are the Freundlich constants characteristic of the system,

739

H. Zaghouane-Boudiaf, M. Boutahala / Advanced Powder Technology 22 (2011) 735–740

indicators of adsorption capacity and adsorption intensity, respectively. The experimental isotherms with the fitted curves are depicted in Fig. 4. The values of qm, KL, KF, and 1/n and the correlation coefficients R2 are given in Table 2. It can be seen from Table 2 that the values of the correlation coefficients demonstrate good agreement of the experimental data with the Langmuir and Freundlich model for all samples except for AlMtC16 sample where Langmuir isotherm is not applicable. Freundlich constant (1/n) is also a measure of the deviation of the adsorption from linearity. If 1/n is equal to unity the adsorption is linear. This means that the adsorption sites are homogeneous (as in the Langmuir model) in energy and no interaction take place between the adsorbed species. If the value of 1/n is smaller than 1, adsorption is favourable, then the sorption capacity increases and new adsorption sites occur. When the value of 1/n is larger than 1 (1/n  1), the adsorption bond becomes weak; unfavourable adsorption take place, as a result of the adsorption capacity decreases. The values of 1/n for AlMtC16 is greater than 1, so the adsorption for this sample is not favourable. There is no affinity between adsorbent and adsorbate. The values of the Freundlich constant, KF decreased from 28.1 to 0.01 mg/g indicating that adsorption is more favourable onto MtC16 and AMtC16. The high levels of adsorption indicate that the 2,4,5-TCP attracted sufficiently to the hydrophobic surfaces of samples. It must have penetrated into interlayer surfaces. In water solvent, as the number of chlorines on the phenol structure was increased, phenolic compounds were not interacted with water (hydrogen bonding)

A

Table 2 Parameters obtained in Langmuir and Freundlich model in adsorption of 2,4,5-TCP onto samples. Samples

AlMt AMt AlMtC16 AMtC16 MtC16

200

R2

62.6 96.4 – 306.5 374.9

0.009 0.005 – 0.033 0.013

0.966 0.987 – 0.992 0.997

0.93 1.59 0.01 12.0 28.1

0.77 0.64 1.93 0.63 0.48

0.981 0.941 0.992 0.988 0.994

150

100

50

0 0

-5 -20

0

20

40

60

80

100

120

0

140

20

40

60

80

100

Ce (mg/L)

Ce (mg/L)

C

Mt C16 (exp. data) AMt C16 (exp. data) AlMt C16 (exp. data) Freundlich model

250

200

qe (mg/g)

qe (mg/g)

qe (mg/g) AlMt (exp. data) AMt (exp. data) Langmuir model

5

1/n

Mt C16 (exp. data) AMt C16 (exp. data) AlMt C16 (exp. data) Langmuir model

25

10

KF

The synthesis and characterization of organoclays has a great importance. These types of materials may be used as bed filters for the removal of organic molecules such as pesticides, chlorophenols and herbicides from potentially potable water. In this work

30

15

R2

4. Conclusion

250

20

Freundlich model

KL (L/mg)

and the greater was the adsorption on the hydrophobic samples. On the other hand, most phenols are weak acids in aqueous solution [31]. The molecules species POH are the predominant in solution when pH < pKa, whereas the ionic species PO predominate in solution when pH > pKa [31] (pKa of 2,4,5-TCP is 6.9). At pH 4, more protons will be available, thereby increasing electrostatic attractions between the molecular species of 2,4,5-TCP and the positively charged adsorption sites and causing an increase in the 2,4,5-TCP adsorption.

B

35

Langmuir model qm (mg/g)

150

100

50

0

0

20

40

60

80

100

120

Ce (mg/L) Fig. 4. Equilibrium isotherms of 2,4,5-TCP adsorption onto samples: (A) and (B) Langmuir model, (C) Freundlich model.

120

740

H. Zaghouane-Boudiaf, M. Boutahala / Advanced Powder Technology 22 (2011) 735–740

FT-IR study, XRD study, thermogravimetric analysis and surface area measurement were investigated. FT-IR study clearly shows that the surfactant molecules entered into the interlayer space of the montmorillonite. The surface area is greatly affected from acid activation and pillaring. It increased from 82 m2/g for NaMt to 298.5 m2/g and 266.5 m2/g for AMt and AlMt respectively. Acid attack and pillaring create a great porosity in montmorillonite. On the other hand organo-montmorillonites are able to adsorb 2,4,5TCP at a very high extent of 374.9 mg/g at 293 K and pH 4. Materials obtained are natural, no pollutant and low cost adsorbents. We can conclude that it can be used for water purification and it can preserved environment. References [1] Fu-Chuang Huang, Jiunn-Fwu Lee, Chung-Kung Lee, Huang-Ping Chao, Effects of cation exchange on the pore and surface structure and adsorption characteristics of montmorillonite, Colloids Surf. A: Physicochem. Eng. Aspects 239 (2004) 41–47. [2] Vipasiri Vimonses, Shaomin Lei, Bo Jin, Chris W.K. Chow, Chris Saint, Kinetic Study, Equilibrium isotherm analysis of congo red adsorption by clay materials, Chem. Eng. J. 158 (2010) 535–541. [3] A. Safa Özcan, Bilge Erdem, Adnan Özcan, Adsorption of acid blue 193 from aqueous solutions onto Na–bentonite and DTMA–bentonite, J. Colloid Interface Sci. 280 (2004) 44–54. [4] G. Brown, G.W. Brindley, X-ray diffraction procedures for clay mineral identification, in: G. Brindley, G. Brown (Eds.), Crystal Structures of Clay Minerals and their X-ray Identification, Miner. Society, London, 1980, pp. 305– 356. [5] A.C.D. Newman, Chemistry of Clays and Clay Minerals, Longman Scientific & Technical, Mineralogical Society, 1987. p. 480. [6] S. Caillere, S. Henin, M. Rautureau, Minéralogie des argiles, second ed., Structure et propriétés physico-chimiques, Masson, 1982. [7] S.Y. Lee, S.J. Kim, Expansion of smectite by hexadecyltrimethylammonium, Clay Clay Miner. 50 (2002) 435–445. [8] M. Barhoumi, I. Beurroies, R. Denoyel, H. Said, K. Hanna, Coadsorption of phenol and nonionic surfactants onto clays, Colloids Surf. A: Physicochem. Eng. Aspects 223 (2003) 63–72. [9] S.M. Koh, J.B. Dixon, Preparation and application of organo-minerals as sorbents of phenol, benzene and toluene, Appl. Clay Sci. 18 (2001) 111–122. [10] Megan Fuller, James A. Smith, Susan E. Burns, Sorption of nonionic organic solutes from water to tetraalkylammonium bentonites: mechanistic considerations and application of the Polanyi–Manes potential theory, J. Colloid Interface Sci. 313 (2007) 405–413. [11] O. Bouras, M. Houari, H. Khalaf, Using of surfactant modified Fe-pillared bentonite for the removal of pentachlorophenol from aqueous stream, Environ. Technol. 22 (2001) 69–74. [12] Y.H. Hsu, M.K. Wang, C.W. Pai, Y.S. Wang, Sorption of 2,4-dichlorophenoxy propionic acid by organo-clay complexes, Appl. Clay Sci. 16 (2000) 147–159.

[13] Y. EL-Nahhal, T. Undabeytia, T. Polubesova, Y.G. Mishael, S. Nir, B. Rubin, Organo-clay formulations of pesticides: reduced leaching and photodegradation, Appl. Clay Sci. 18 (2001) 309–326. [14] S.H. Lee, D.I. Song, Y.W. Jeon, An investigation of the adsorption of organic dyes onto organo-montmorilllonite, Environ. Technol. 22 (2001) 247–254. [15] Abdellah Elmchaouri, Rabii Mahboub, Effects of preadsorption of organic amine on Al-PILCs structures, Colloids Surf. A: Physicochem. Eng. Aspects 259 (2005) 135–141. [16] Lizhong Zhu, Senlin Tian, Jianxi Zhu, Yao Shi, Silylated pillared clay (SPILC): a novel bentonite-based inorgano–organo composite sorbent synthesized by integration of pillaring and silylation, J. Colloid Interface Sci. 315 (2007) 191– 199. [17] Denis Lima Guerra, Vanda Porpino Lemos, Claudio Airoldi, Rômulo Simoes Angelica, Influence of the acid activation of pillared smectites from Amazon (Brazil) in adsorption process with butylamine, Polyhedron 25 (2006) 2880– 2890. [18] H. Khalaf, O. Bouras, V. Perrichon, Synthesis and characterization of Al-pillared and cationic surfactant modified Algerian bentonite, Micropor. Mater. 8 (1997) 141–150. [19] M. Boutahala, F. Tedjar, Application of exchanged montmorillonite as protonic solid electrolyte, Solid States Ionics 61 (1993) 257–263. [20] N. Aliouane, A. Hammouche, R.W. De Doncker, L. Telli, M. Boutahala, B. Brahimi, Investigation of hydratation and protonic conductivity of Hmontmorillonite, Solid States Ionics 148 (2002) 103–110. [21] S. Brunauer, P.H. Emmet, E. Teller, Adsorption of gases in multimolecular layers, J. Am. Chem. Soc. 60 (1938) 309–319. [22] E.P. Barrett, L.G. Joyner, P.H. Halenda, The determination of pore volume and area distributions in porous substance. I. Computations from nitrogen isotherms, J. Am. Chem. Soc. 73 (1951) 373–380. [23] E. Erena, B. Afsin, Y. Onal, Removal of lead ions by acid activated and manganese oxide-coated bentonite, J. Hazard. Mater. 161 (2008) 677–685. [24] Yunfei Xi, Zhe Ding, Hongping He, Ray L. Frost, Structure of organoclays—an Xray diffraction and thermogravimetric analysis study, J. Colloid Interface Sci. 277 (2004) 116–120. [25] R.K. Kukkadapu, S.A. Boyd, Tretramethylphosphonium and tetramethylammonium-smectites as adsorbents of aromatic and chlorinated hydrocarbons: effect of water on adsorption efficiency, Clay Clay Miner. 43 (1995) 318–323. [26] Y. Seki, K. Yurdakoç, Paraquat adsorption onto clays and organoclays from aqueous solution, J. Colloid Interface Sci. 287 (2005) 1–5. [27] Q. Zhou, R.L. Frost, H. He, Y. Xi, H. Liu, Adsorbed paranitrophenol on HDTMAB– A TEM and Infrared spectroscopic study, J. Colloid Interface Sci. 307 (2007) 357–363. [28] M. Boufatit, H. Ait-Amar, W.R. McWhinnie, Development of an Algerian material montmorillonite clay. Adsorption of phenol, 2-dichlorophenol and 2,4,6-trichlorophenol from aqueous solutions onto montmorillonite exchanged with transition metal complexes, Desalination 206 (2007) 394– 406. [29] I. Langmuir, The constitution and fundamental properties of solids and liquids, J. Am. Chem. Soc. 38 (1916) 2221–2295. [30] H.M.F. Freundlich, Über die adsorption in lösungen, Z. Phys. Chem. 57 (1906) 385–470. [31] Y. Ku, K.C. Lee, Removal of phenols from aqueous solution by XAD-4 resin, J. Hazard. Mater. 80 (2000) 59–68.