Adsorption of methylene blue, crystal violet and congo red from binary ...

Journal of Environmental Chemical Engineering 5 (2017) 5921–5932

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Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece

Research Paper

Adsorption of methylene blue, crystal violet and congo red from binary and ternary systems with natural clay: Kinetic, isotherm, and thermodynamic

MARK

⁎

Safae Bentahar , Abdellah Dbik, Mohammed El Khomri, Noureddine El Messaoudi, ⁎ Abdellah Lacherai Ibn Zohr University, Faculty of Science, Department of Chemistry, Laboratory of Applied Chemistry and Environment, BP 8106, 80000,Agadir, Morocco

A R T I C L E I N F O

A B S T R A C T

Keywords: Clay Adsorption Isotherms Dye Kinetic Ternary system

The adsorption of Methylene Blue (BM), Crystal Violet (CV) and Congo Red (CR) onto natural clay from Agadir region in the binary and ternary system was carried out. All the parameters influencing the adsorption of three dyes were studied namely effect of percentage, contact times (20–120 min), initial dye concentration (100–600 mg L−1), temperature (22–50 °C), and dye solution pH (2–12). The obtained results showed that the adsorption of MB, CV, and CR is highly dependent on the initial dye concentration, the temperature, and the dye solution pH. The kinetic study was performed by applying two kinetic models, the pseudo-first-order and the pseudo second-order. According to the obtained results, the pseudo-second-order model is better described the adsorption of dyes onto natural clay. The adsorption isotherms were studied such as Langmuir, Freundlich, the obtained results indicate that the adsorption followed the Langmuir model with correlation coefficients which are very close to 1. The maximum adsorption capacities for three dyes are 202.13 mg g−1 for MB (MB + CV), 289.59 mg g−1 for MB (MB + CR), 281.31 mg g−1 for MB (MB + CV + CR), 179.28 mg g−1 for CV (CV + MB), 289 mg g−1 for CV (CV + CR), 280.61 mg g−1 for CV (CV g MB + CR), 253.53 mg g−1 for CR (CR + MB), 240.06 mg g−1 for CR (CR + CV) and 264.54 mg g−1 for CR (CR + MB + CV). The thermodynamic study showed that the adsorption of dyes in the binary and ternary system is spontaneous, physical and endothermic.

1. Introduction The presence of dyes in textile effluents can pose a serious environmental menace when they are discharged into biosphere without previous treatment or with an insufficient level of treatment [1–4]. Treatment will therefore be essential to remove these dyes which are harmful to the environment [5–7]. Several techniques have been developed to remove dyes from wastewater such as coagulation/flocculation [8,9], oxidation/ozonation [10], membrane separation [11,12], photodegradation [13] et biological process [14], but most of these conventional methods are beginning to prove insufficient for simple and effective treatment, in addition they are very expensive [15]. It is necessary to think about effective techniques and inexpensive. Adsorption onto activated carbon has been recognized as one of the best techniques for the treatment polluted water by organic and inorganic materials, because the activated carbon has a high adsorption capacity due to its large surface area [16,17], but activated carbon remains very expensive and onerous [18]. Consequently, the treatment of water by adsorption onto natural materials such as clays responds to this

constraint in an efficient and economical manner. Clays are now considered as interesting adsorbent materials, due to their low-cost, their abundance in nature, their small size (less than 2 μm), their high specific surface area, high cation exchange capacity and high chemical stability [19,20]. Consequently, these minerals are considered as natural wells to be facing to organic and inorganic pollutants. Our main objective is to apply our support as an effective adsorbent to treat textile effluents, which contains different types of dyes namely cationic, anionic, and neutral. In this context, we have tested the effectiveness of our adsorbent which has several advantages such as its availability and low cost because it requires no treatment, in the mixture of dyes in a binary and ternary system. In our work, we chose three dyes, Methylene Blue, Crystal Violet (cationic type), and Congo Red (anionic type) as model dyes (Fig. 1), because of their harmful effects on health and the environment. Methylene Blue is much used in textile, printing, dyeing wood and strainers for medicinal surgery [21–23]. Crystal Violet dye is widely used in coloring paper, cotton and silk [24], it is also employed in animal and veterinary medicine as a biological stain [25]. Congo Red is employed as colorants in textiles, printing,

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Corresponding author. E-mail addresses: [email protected] (S. Bentahar), [email protected] (A. Dbik), [email protected] (M.E. Khomri), [email protected] (N.E. Messaoudi), [email protected] (A. Lacherai). https://doi.org/10.1016/j.jece.2017.11.003 Received 6 August 2017; Received in revised form 9 October 2017; Accepted 1 November 2017 2213-3437/ © 2017 Elsevier Ltd. All rights reserved.


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Fig. 1. Chemical structures of dyes used.

2.2. Characterization

dyeing, paper, and plastic industries and also as the indicator of pH [26–28]. This dye can cause cancer, vomiting, jaundice, skin irritation, diarrhea in human beings [29–35]. For this reason, we have carried out the adsorption of MB, CV, and CR onto the clay to evaluate the behavior of these three dyes in binary and ternary mixtures. We studied all the parameters influencing the adsorption of these dyes in the mixtures such as the percentage effect, the contact time, the initial dye concentration, the temperature and the initial dye solution pH. The adsorption isotherms, kinetic models and thermodynamic study were performed to describe the mechanism involved in the adsorption process.

According to our previous study [36,37], the results of the analyzes are: The X-ray diffractogram shows that the natural clay is characterized by the presence of the dolomite phase which is the majority. This phase is confirmed by the existence of intense peaks at 21.6°, 24.01°, 30.89°, 33,46°, 37.3°, 41.11°, 43.77°, 44.85°, 49 0.21°, 50.5°, 51.06°, 58.92° (in 2θ) which may be attributable to the Miller indices:(101) (012) (104) (006) (110) (113) (021) (202) (024) (018) (116) (211), by comparison with the standard JCPDS No. 36-0426 (corresponding to the dolomite). In addition, this diffractogram also shows the existence of a minority phase corresponding to silica, whose peaks 26.64°, 35.98°, 50.13°, 56.80° (in 2θ) attributable to the Miller indices (101) (110) (112) (103) which is in accordance with standards JCPDS No. 33–1161(Fig. 2) [36]. The FTIR spectrum shows some characteristic bands of the silica in the zone 1250–700 cm−1. Indeed, the bands appear at 1250 and 1000 cm −1 are due to the stretching mode of Si-O and Si-O-Si respectively. Silica is also justified by an intense peak at 1099 cm−1 due to Si-O-Si stretching vibration. In addition, the bands appear at 791 and 728 cm−1 and at 474 cm−1 are attributed to the Si-O stretching vibration. It remains to be noted that the absorption spectra located at 3423 cm−1 (medium intensity) and 1638 cm−1 correspond to the hydroxyl group OH and the deformation of the H2O molecules respectively (Fig. 2) [36]. SEM analysis shows that this sample is characterized by the presence of particles having different sizes and uniform morphology. The

2. Materials and methods 2.1. Materials The natural clay was collected from Agadir region and was crushed to obtain clay with a diameter less than 50 μm [36]. Methylene Blue (MB) is a cationic dye, the molecular formula C16H18ClN3S·3H2O, a molar mass of 373.90 g mol −1 and a maximum absorbance is equal 661 nm. Crystal Violet (CV) is a cationic dye, the chemical formula C25H30ClN3, a molar mass 407.979 g mol−1, and a maximum absorbance is 589.5 nm. Congo Red (CR) is an anionic diazo dye, the chemical formula C32H22N6Na2O6S2, a molar mass 696.66 g mol−1 and a maximum absorbance is 498 nm. These three dyes were purchased from Sigma-Aldrich and used without purification. 5922


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Fig. 2. Characterization of natural clay, (a): the XRD patterns, (b): FTIR, and (c): SEM micrographs image [36,37]. maxCV = 589.5 nm and λ maxCR = 498 nm) by UV–vis spectrophotometer (Techcomp UV2300). Dye concentrations were calculated as follows: For a binary mixture of components A and B, the optical densities d1 and d2 were measured at λ1 and λ2 [38]:

shape of the sample is dispersed and characterized by grains whose size is between 2 and 5 μm. These grains are characterized by the presence of different cavities and pores which are very important for adsorbing dyes [37]. The local analysis carried out by EDXS is in relatively good agreement with those of X-ray diffraction (Fig. 2) [37]. The specific surface area was determined by application of the BET method which is equal to which is equal to 76.971 m2 g−1, and the pore diameter was calculated by Dubinin Radushkevich equation amounts to 1.69 nm. In addition, the N2 adsorption/desorption isotherms of the natural clay were of type IV according to the International Union of Pure and Applied Chemistry (IUPAC) [36].

CA =

kB2 d1 − kB1 d2 kA1 kB2 − kA2 kB1

(1)

CB =

kA1 d2 − kA2 d1 kA1 kB2 − kA2 kB1

(2)

For a ternary mixture of components A, B and C, the optical densities d1, d2 and d3 were measured at λ1, λ2 and λ3 respectively [39,40]: 2.3. Batch studies

Cei =

The adsorption of Methylene Blue (MB), Cristal Violet (CV) and Congo Red (CR) onto local clay in binary (BM + CV), (BM + RC) and (CV + RC), and ternary mixture (BM + CV + RC) was carried out in a batch system. The adsorption of three dyes was carried out in a thermostatic bath, by adding 0.1 g of our support into flask containing 50 mL of the mixture of two dyes (BM + CV), (BM + RC) and (CV + RC) or three dyes (BM + CV + RC), by varying the concentration from 100 to 600 mg L−1 at different temperatures 22, 30, 40 and 50° C in the pH range 2–12 for a time varying from 20 to 120 min. After a suitable time, the dye solution was separated from the adsorbent by centrifugation for 15 min at 4000 rpm. The concentration of MB, CV, and CR in binary and ternary mixtures was determined by measuring the absorbance at maximum wavelengths (λ maxMB = 661 nm, λ

d1 X + d2 Y + d3 Z k i1 X + k i 2 Y + k i 3 Z

(3)

Where i = A, B or C For i = A, X = kB3kC2–kB2kC3; Y = kB1kC3–kB3kC1; Z = kB2kC1–kB1kC2 For i = B, X = kA2kC3–kA3kC2; Y = kA3kC1–kA1kC3; Z = kA1kC2–kA2kC1 For i = C, X = kA2kB3–kA3kB2; Y = kA3kB1–kA1kB3; Z = kA1kB2–kA2kB1 The adsorbed amounts of MB, CV, and CR were calculated by this equation: 5923


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Fig. 3. Effect of percentage of dye on adsorption of MB, CV and CR in single (a), binary (b, c and d) and ternary system (e) systems onto natural clay (adsorbent dose = 2 gL−1, C0 (MB) = C0 (CV) = C0 (CR) = 100 mg L−1, t = 60 min, T=22 °C, pH (MB + CV)=4.24, pH (MB + CR)=5.61, pH (CV + CR)=5.55, pH (MB+CV+ CR) = 5.5, pH (MB) = 3.48, pH (CV) = 4.28 and pH (CR) = 6.51).

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Fig. 4. Effect of contact time on adsorption of MB, CV and CR onto natural clay in binary and ternary mixture (C0 (MB) = (adsorbent dose = 2 g L−1, C0 (MB) = C0 (CV) = C0 (CR) = 100 mgL−1, T = 22 °C, pH (MB + CV)=4.24, pH (MB + CR)=5.61, pH (CV + CR)=5.55, pH (MB+CV+ CR) = 5.5, pH (MB) = 3.48, pH (CV) = 4.28 and pH (CR) = 6.51).

qe =

(C0 − Ceq) m

*V

This increase can be explained by the interactions of the CR with MB and CV. In the case of mixing two cationic dyes, we observed that the adsorbed amount of MB and CV is decreased comparing with MB and CV in the single system, this is due to the competition between MB and CV to occupy the reaction sites on the clay surface. In general, the two cationic dyes MB and CV are much adsorbed on our support in the single system contrary to CR (Fig. 3a). When MB and CV are mixed, they come in competition with a slight favor for the minority, which is normal since the latter in low concentration, is in front of an important free support surface. In the case of a binary system consisting of a cationic dye (MB or CV) and an anionic dye (CR), we observed that adsorption is selective. Thus adsorption saturation is achieved for the dye cationic (MB or CV) for the different compositions, which leads to an increase in the adsorbed amount of the dye anionic by decreasing its percentage. This can be explained by the interactions between the CR molecules which are accentuated by increasing the concentration of CR, by disadvantaging its adsorption.

(4)

where qe (mg g−1), C0 (mg L−1), Ce (mg L−1), V (L) et m (g) are the adsorbed amount of dye on the absorbent, the initial dye concentration, the concentration of dye at equilibrium, volume of dye solution used and mass of absorbent respectively. 3. Results and discussion 3.1. Effect of composition dyes on adsorption Effect of percentage on the adsorption of MB, CV and CR dye onto natural clay in binary (CV + MB, CV + CR and MB + CR) and ternary mixture (CV + MB + CR) comparing with the same dyes Taken individually has been investigated by varying the percentage of MB, CV and CR in the binary and ternary mixture with the adsorbent dose, the initial dye concentration and the contact time have been fixed at 2 g L −1 , 100 mg L−1 and 60 min respectively, at the room temperature and at the initial dye solution pH. The obtained results are illustrated in Fig. 3. These results show that in the case of a single system MB (qe = 98.06 mg g−1) and CV (qe = 82.13 mg g−1) are better adsorbed than CR (qe = 23.52 mg g−1). Whereas in the binary (MB + CR) and the ternary system (MB + CV + CR), the adsorbed amount of CR increased from 32.62 to 49.79 mg g−1 and from 32.25 to 49.7 mg g−1 respectively with increase in the percentage of MB and CV in the mixture of two dyes CR + MB and CR + CV respectively, and from 47.35 to 48.57 mg g −1 in the mixture of three dyes CV + MB + CR.

3.2. Effect of contact time on adsorption Effect of the contact time on the adsorption of MB, CV and CR dye onto clay in binary (MB + CV, CV + CR and CR + MB) and ternary mixture (CV + MB + CR) has been studied by varying the contact time between 20 and 120 min with 2 g L−1 at initial dye concentration of 100 mg L−1, at room temperature, at the initial dye solution pH and with percentages 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR (Fig. 4). As shown in Fig. 4, the adsorbed amount of all dyes 5925


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Fig. 5. Effect of initial concentration on adsorption of MB, CV and CR onto natural clay in binary and ternary mixture (adsorbent dose = 2 g L−1, T = 22 °C, t = 60 min, pH (MB + CV) =4.24, pH (MB + CR)=5.61, pH (CV + CR)=5.55, pH (MB + CV + CR) = 5.5, pH (MB) = 3.48, pH (CV) = 4.28 and pH (CR) = 6.51).

mixing two cationic dyes MB (MB + CV) and CV (CV + MB), we noticed that the adsorbed amount increased from 49.97 to 193.13 mgg−1 and from 49.96 to 171.77 mg g−1 for MB and CV respectively. However, these adsorbed quantities are lower than those in the binary mixture MB (MB + CR), CV (CV + CR) and ternary MB (MB + CV + CR) and CV (MB + CV + CR). This probably is due to the competition between CV and MB to occupy the vacant surface sites. In the case of binary system of CR (MB + CR) and CR (CV + CR), we also observed that the adsorbed amount of CR increases from 45.2 to 213.88 mg g−1 and from 43.61 to 207. 59 mg g−1 for (MB + CR) and (CV + CR) respectively, saturation is reached after 500 mg L−1. Whereas in the mixture of three dyes CR + MB + CV we found a strong increase in the adsorbed amounts of CR from 48.84 to 256.71 mg g−1 comparing with the binary mixture of CR (MB + CR) and CR (CV + CR). This can be explained by the strong interaction of CR with CV and MB in the ternary mixture. The increase in the adsorbed amount of all dyes in binary and ternary system with increased the concentration can be attributed to an increase in motive force in the driving force to transfer dye molecules between the aqueous and solid phases [47–49].

in a binary and ternary mixture increases rapidly with the contact time between the adsorbate and the adsorbent in the first stage, then it has slowed down in the second stage until equilibrium was reached after 60 min with adsorbed amounts which are equal to 49.97 mg g−1, 49.98 mg g−1,49 0.64 mg g−1, 49.05 mg g−1, −1 −1 −1 49.43 mg g , 49.02 mg g , 45.2 mg g , 42,99 mg g−1, and 48.22 mg g−1 respectively for MB (MB + CV), MB (MB + CR), MB (MB + CV + CR), CV (CV + MB), CV (CV + CR), CV (CV + MB + CR), CR (CR + MB), CR (CR + CV) and CR (CR + MB + CV). The increase in the amount adsorbed in the first stage is due to the availability of the reaction sites on the clay surface [41,42]. After a lapse of some time, all the reaction sites progressively become occupied by the dyes and consequently, the surface of the clay has become saturated, which implies that the adsorption becomes less efficient during this second stage [43,44]. 3.3. Effect of initial dye concentration on adsorption Effect of initial dye concentration on the adsorption of MB, CV and CR dye onto natural clay in binary and ternary mixture was studied in the concentration range 100–600 mg L−1, adsorbent dose 2 g L−1 at 22 °C and at initial dye solution pH for 60 min. The percentages used are 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR (Fig. 5). According to Fig. 5, we have found the amount of dye adsorbed increased as the initial dye concentration increased [45,46]. Indeed, at binary mixtures of MB (MB + CR) and CV (CV + CR), we observed a strong increase in the adsorbed amount from 49 0.97 to 289.59 mg g−1 and from 49.81 to 282.25 mg g−1 for MB and CV respectively with increasing initial dye concentration from 100 to 600 mg L−1. The same results were observed at ternary mixture of MB (MB + CV + CR) and CV (MB + CV + CR). While in the case of

3.4. Effect of temperature on adsorption The temperature effect on the adsorption of MB, CV and CR dye in binary and ternary mixture was studied at different temperature 22, 30, 40 et 50 °C, with 2 g L −1, a constant initial dye concentration of 500 mg L−1 at initial dye solution pH for 60 min. The percentages used are 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR (Fig. 6). The obtained results indicate that the temperature has a remarkable effect on the adsorption of MB and CV in the mixture (CV + MB) and CR in the mixture of (CR + MB), 5926


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Fig. 6. Effect of temperature on adsorption of MB, CV and CR onto natural clay in binary and ternary mixture (adsorbent dose = 2 g L−1, C0 (MB) = C0 (CV) = C0 (CR) = 500 mg L−1, t = 60 min, pH (MB + CV)=4.24, pH (MB + CR)=5.61, pH (CV + CR)=5.55, pH (MB + CV + CR) = 5.5, pH (MB) = 3.48, pH (CV) = 4.28 and pH (CR) = 6.51).

case of binary mixture of MB (MB + CR) and CV (CV + CR), and at the ternary mixture MB (MB + CV + CR) and CV (MB + CV + CR), we observed a slight increase in the adsorbed amount. The increase of adsorbed amount with the rise in temperature [50] is due to the increase of the mobility of the dye molecules with temperature which ensures a better connection of the dye molecules with the active sites on the surface of clay [32,51]. 3.5. Effect of pH on adsorption The effect of pH on the adsorption behavior of MB, CV and CR dye in binary and ternary systems was studied with 2 gL−1 of the adsorbent dose at the initial dye concentration of 100 mgL−1 at 22 °C for 60 min. The pH of all binary and ternary mixtures was adjusted to values between 2 and 12. The percentages used are 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR (Fig. 7). The obtained results indicate that the adsorbed amount of MB and CV increases with the rise in pH [50,52] in the case of binary mixtures of MB (MB + CV), MB (MB + CR), CV (MB + CV) and CV (CV + CR), and ternary mixtures of MB (MB + CV + CR) and CV (CV + MB + CR). The maximum adsorption occurs at pH 12 with an adsorbed amount which is equal to 53.79 mgg−1 for MB (MB + CV), 56.19 mgg−1 for MB (MB + CR), 55.99 mgg−1 for MB (MB + CV + CR), 49.54 mgg−1 for CV (CV + MB), 54.61 mgg−1 for CV (CV + CR) and 54.19 mgg−1 for CV (CV + MB + CR). The increase in the amount adsorbed at basic pH is due to the increase of negatively charged sites on the surface of the clay and consequently the increase in

Fig. 7. Effect of initial pH on adsorption of MB, CV and CR onto natural clay in binary and ternary mixture (adsorbent dose = 2 g L−1, C0 (MB) = C0 (CV) = C0 (CR) = 100 mg L−1, t = 60 min).

(CR + CV) and (CR + MB + CV). Indeed, the adsorbed amount increased from 177.44 to 199.44 mg g−1, from 159.99 to 183.99 mg g−1, from 206.05 to 225.52 mgg−1, from 203.44 to 224.83 mg g−1 and from 217.42 to 229.84 mg g−1 for MB (MB + CV), CV (MB + CV), CR (CR + MB), CR (CR + CV) and CR (CR + MB + CV) respectively. In the 5927


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Fig. 8. (a) Pseudo- first-order model (b) Pseudo-second-order model for adsorption of MB, CV and CR onto natural clay in binary and ternary mixture.

Table 1 Characteristic parameters of kinetic models. Pseudo first-order kinetic model

MB (with CV) MB (with CR) MB (with CV + CR) CV (with MB) CV (with CR) CV (with MB + CR) CR (with MB) CR (with CV) CR (with MB + CV)

Pseudo second-order kinetic model

qe (mg g−1)

K1

R2

qe (mg g−1)

K2

R2

0,062 0,277 0,224 0,285 1532 0,982 14,35 15,62 13,17

0,005 0,065 0,023 0,026 0,029 0,052 0,0409 0,067 0,057

0.152 0.844 0.511 0.712 0.515 0.805 0.916 0.697 0.722

50 50 49,751 49,261 49,504 49,261 48,309 45,045 49,751

4 0,571 0,288 0,171 1,0201 0,082 0,004 0,004 0,006

1 1 1 1 1 1 0.999 0.998 0.999

temperature with 2 gL−1, at initial dyes concentration of 100 mgL−1 and initial dye solution pH for 60 min. The percentages used are 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR (Fig. 8). A linear form of the pseudo-first-order kinetic model is represented by the following equation:

Table 2 isotherms parameters for the adsorption of MB, CV and CR in single system. dye

MB CV CR

Langmuir

Freundlich 2

KL

Qm

R

0.01498 0.01475 0.05671

279.95 231.74 61.12

0.9787 0.9774 0.9921

KF

nF

R2

32.8996 26.313 17.3099

2.5483 2.7193 4.6042

0.9482 0.9662 0.8878

log (qe − qt ) = logqe −

K1 t 2.303

(5)

A linear form of the pseudo-second-order kinetic model is represented by the following equation:

electrostatic attractions between the negatively charged surface site on the clay and positively charged cationic dye molecules (CV and MB) [18]. While at acid pH we observed a decrease in the adsorbed amounts of MB and CV in binary and ternary mixtures, this can be explained by the competition between H+ protons and positively charged dye CV and MB to occupy the reaction sites [30,53]. In the case of binary mixture of CR with MB and CR with CV, and ternary mixture of CR with MB and CV, we observed that the best adsorption of CR occurs at acidic pH. This results in the increase in a number of positively charged sites on the clay surface at acidic pH, and consequently the increase in electrostatic attractions between positively charged sites and negatively charged of CR [49].

1 1 t = + t qt K2 qe2 qe −1

(6) −1

Where qt (mg g ) and qe (mg g ) represent the amount of dye adsorbed at time t and equilibrium time, respectively, k1 and k2 are the rate constants for pseudo-first and pseudo-second-order kinetic rates respectively. The obtained results are summarized in Table 1. The obtained results indicate that the pseudo-second-order kinetic model is better described the adsorption of the three dyes in all the binary and ternary mixtures onto natural clay with coefficients which are close to or equal to 1 [39,50,56,57]. In addition, the theoretical (qe,the) values calculated by the pseudo-second-order model are very close to the experimental adsorption values (qe,exp) for all mixtures.

3.6. Adsorption kinetics in binary and ternary systems To understand the mechanism of adsorption of MB, CV and CR dye in binary and ternary mixtures, two kinetic models were used pseudofirst-order [54] and pseudo-second-order kinetic models [55], at room

3.7. Adsorption isotherms in binary and ternary systems The adsorption isotherms were used to describe the adsorption 5928


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Fig. 9. Equilibrium adsorption of MB, CV and CR in single, binary and ternary systems onto natural clay.

obtained at 40° C), which implies that adsorption of MB, CV, and CR on the natural clay in single system were well-fit to the Langmuir isotherm model and does not follow the Freundlich isotherms. And therefore the adsorption of three dyes occurs in monolayer coverage. In addition, the maximum adsorption capacity calculated by the Langmuir isotherm is much closer to the experimental value of adsorption. According to Fig. 9, we noticed that the amount adsorbed increases with increasing concentration from 100 to 600 mg g−1 at 40 °C: For the binary mixture of MB and CV: the adsorbed amount increased from 49.97 to 202.13 mg g−1 and from 49.98 to 179.28 mg g−1 for MB and CV respectively. For the binary mixture of MB and CR: the adsorbed amount increased from 49.78 to 289.59 mg g−1 and from 48.09 to 253.53 mg g−1 for MB and CR respectively. For the binary mixture of CV and CR: the adsorbed amount increases from 49.85 to 289 mg g−1 and from 48.1 to 240.06 mg g−1 for CV and CR respectively. For the ternary mixture of MB, CV, and CR: the adsorbed amount increased from 49.97 to 281.31 mg g−1, from 48.69 to 280.61 mg g−1 and from 49.22 to 264.54 mg g−1 for MB, CV and CR respectively. Interactions between the three dyes in the binary and ternary mixture were evaluated by the ratio Qm.mix/QS [61,62] (Qmmix is the maximum adsorption capacity in binary and ternary mixtures and QS is the maximum adsorbed amount in the single system). If Qm.mix/QS < 1, the presence of other dyes has an inhibitory effect on the adsorption, if Qm.mix/QS = 1 there are no interactions between the dyes and if Qm.mix/QS > 1 the presence of other dyes has a positive effect on the adsorption. The maximum adsorption capacities of MB, CV and CR are

mechanism of MB, CV and CR dye onto natural clay in binary and ternary mixture [58]. Three models including the Langmuir [59] and Freundlich [60] models were studied by varying the concentration in a range of 100–600 mg L−1, at different temperatures 22, 30, 40 and 50 °C, with 2 g L−1 at initial dye solution pH for 60 min at pH (MB + CV)=4.24, pH (MB + CR)=5.61, pH (CV + CR)=5.55, pH (MB + CV + CR) = 5.5, pH (MB) = 3.48, pH (CV) = 4.28 and pH (CR) = 6.51). The percentages used are 50% MB + 50% CV, 50% MB + 50% CR, 50% CV + 50% CR, 33% MB + 33% CV + 34% CR. The Langmuir isotherm is represented as:

qe =

qm KL Ce 1 + KL Ce

(7) −1

−1

−1

−1

Where Ce (mg L ), qe (mg g ), qmax (mg g ) and KL (L mg ) are the concentration of dyes at equilibrium, the amount adsorbed at equilibrium, maximum adsorption capacity, and Langmuir constant respectively. The Freundlich isotherm is represented as: 1/ nf

qe = KF Ce

(8)

Where qe (mg g−1), Ce (mg L−1), 1/n and KF are the amount adsorbed at equilibrium, the equilibrium dye concentration in solution, the adsorption intensity and the Freundlich constant respectively. The obtained results are listed in Table 2. The non-linear Langmuir and Freundlich isotherm models for MB, CV [36] and CR [37] dyes in the single system are shown in Fig. 9. According to the obtained results, we found that the Langmuir correlation coefficients are higher than those of Freundlich (the best fit was 5929


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Fig. 10. The comparison between the experimental and calculated qeq values for MB, CV and CR in binary and ternary mixtures.

Table 3 Thermodynamic parameters of adsorption. Dye

MB (MB + CV) MB (MB + CR) MB (MB + CV + CR) CV (CV + MB) CV (CV + CR) CV (CV+MB + CR) CR (CR + MB) CR (CR + CV) CR (CR + MB + CV)

ΔH° (kJ mol−1)

14.422 91.833 39.577 26.779 40.97 33.721 49.301 38.861 34.577

ΔS° (J mol−1 K−1)

ΔG° (kJ mol−1)

116.579 431.225 291.599 172.714 304.744 262.146 257.786 225.621 252.395

279.95 mg g−1, 231.74 mg g−1 [36] and 61.12 mg g−1 [37].In this work, when mixed two cationic dye, the ratio Qm.mix/QS is less than 1, which shows a great competition between the two dyes to occupy the active sites (antagonism effect). Whereas in the case of mixing a cationic dye with an anionic dye or two cationic dye with an anionic dye, the ratio Qm.mix/QS was greater than 1, this is due to the presence of strong interactions between the cationic and anionic dyes (synergism effect). The modified Langmuir model [63] has been applied to analyze interference and competition phenomena between the MB, CV and CR dyes in the binary and ternary mixture onto the natural clay. The modified Langmuir isotherm model is given as:

295,15 K

303,15 K

313,15 K

323,15 K

−19.985 −35.442 −46.488 −24.197 −48.975 −43.65 −26.783 −27.731 −39.917

−20.918 −38.892 −48.82 −25.578 −51.413 −45.747 −28.846 −29.536 −41.936

−22.084 −43.204 −51.736 −27.306 −54.46 −48.369 −31.424 −31.792 −44.46

−23.25 −47.516 −54.652 −29.033 −57.508 −50.99 −34.002 −34.048 −46.984

qeq, i =

qi, max K a, i Ceq, i 1+

N

∑j = 1

K a, j Ceq, j

(9)

where qmax,i, and KL,i are physical parameters of single dyes. The comparison between the experimental equilibrium data and calculated values (qeq,exp; qeq,calc) for binary and ternary mixtures are shown in Fig. 10. The analysis of the obtained results shows that the extended-Langmuir model represents the experimental adsorption data of MB, CV, and CR in the binary and ternary mixture. 3.8. Adsorption thermodynamic The thermodynamic study was carried out to reveal the nature of 5930


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endothermic. Based on the obtained results in this work, we can conclude that the natural clay from Agadir region can be considered as a good material for the removal of MB, CV and CR dyes in binary and ternary mixtures, due to their availability, their efficiency and also low cost. All the results obtained are encouraging to use our support on an industrial scale.

the adsorption of MB, CV and CR dye onto natural clay in binary and ternary mixtures. The thermodynamic parameters, such as the Gibbs energy change (ΔG °) (J mol−1), the enthalpy change (ΔH °) (J mol−1) and the entropy change (ΔS °) (J.K−1 mol−1) were determined by these equations [56]: ΔG° = ΔH° − TΔS°

(10)

ΔG° = RTlnKa

(11)

Conflict of interest

Where Ka, T (K) et R(J.mol−1 K−1) are the thermodynamic equilibrium constant without units, the absolute temperature and the universal gas constant (8.314 J mol−1 K−1) respectively. Liu [64] has demonstrated the relationship between the Langmuir equilibrium constant KL and the thermodynamic equilibrium constant Ka, can be represented by this equation:

ka =

KL γe

None declared. References [1] G. Bayramoglu, M.Y. Arica, Kinetics of mercury ions removal from synthetic aqueous solutions using by novel magnetic p(GMA-MMA-EGDMA) beads, J. Hazard. Mater. 144 (2007) 449–457. [2] A. Shajahan, S. Shankar, A. Sathiyaseelan, S.K. Narayan, V. Narayanan, V. Kaviyarasan, S. Ignacimuthu, Comparative studies of chitosan and its nanoparticles for the adsorption efficiency of various dyes, Int. J. Biol. Macromol. 104 (2017) 1449–1458. [3] A. Adak, M. Bandyopadhyay, Fixed bed column study for the remov al of crystal violet (C. I. Basic Violet 3) dye from aquatic environment by surfactant-modified alumina, Dyes Pigm. 69 (2006) 245–251. [4] J. Qiu, Y. Feng, X. Zhang, M. Jia, J. Yao, Acid-promoted synthesis of UiO-66 for highly selective adsorption of anionic dyes: adsorption performance and mechanisms, J.Colloid Interface Sci. 499 (2017) 151–158. [5] Y. Cheng, H.Y. Lin, Z. Chen, M. Megharaj, R. Naidu, Biodegrada tion of crystal viole t using Burkholderia vietnamiensis C09 V immobilized on PVA–sodium alginate–kaolin gel beads, Ecotoxicol. Environ. Saf. 83 (2012) 108–114. [6] M. Ramakrishnan, S. Nagarajan, Utilization of waste biomass for the removal of basic dye from water, World Appl. Sci. J. 5 (2009) 114–121. [7] V. Tangaraj, J.-M. Janot, M. Jaberb, M. Bechelany, S. Balme, Adsorption and photophysical properties of fluorescent dyes over montmorillonite and saponite modified by surfactant, Chemosphere 184 (2017) 1355–1361. [8] J. Panswed, S. Wongchaisuwan, Mechanism of dye wastewater color removal by magnesium carbonate-hydrated basic, Water Sci. Technol. 18 (1986) 139–144. [9] Fengfei Zhou, Ying Cheng, Li Gan, Zuliang Chen, Mallavarapu Megharaj, Ravendra Naidu, Burkholderia vietnamiensis C09 V as the functional biomaterial used to remove crystal violet and Cu(II), Ecotox. Environ. Saf. 105 (2014) 1–6. [10] P.K. Malik, S.K. Saha, Oxidation of direct dyes with hydrogen peroxide using ferrous ion as catalyst, Sep. Purif. Technol. 31 (2003) 241–250. [11] G. Ciardelli, L. Corsi, M. Marucci, Membrane separation for wastewater reuse in the textile industry, Resour. Conserv. Recycl. 31 (2000) 189–197. [12] K.B. Tan, M. Vakili, B.A. Horri, P.E. Poh, A.Z. Abdullah, Sep. Purif. Technol. 150 (2015) 229–242. [13] D.K. Gardiner, B.J. Borne, Textile waste waters: treatment and environmental effects, J. Soc. Dyers Colour 94 (1978) 339–348. [14] S. Ledakowicz, M. Solecka, R. Zylla, Biodegradation, decolourisation and detoxification of textile wastewater enhanced by advanced oxidation processes, J. Biotechnol. 89 (2001) 175–184. [15] Z. Chen, T. Wang, X. Jin, Z. Chen, M. Megharaj, R. Naidu, Multifunctional kaolinite16supported nanoscale zero-valent iron used for the adsorption and degradation of crystal violet in aqueous solution, J.Colloid Interface Sci. 398 (2013) 59–66. [16] M.A. Ahmad, R. Alrozi, Removal of malachite green dye from aqueous solution using rambutan peel-based activated carbon: equilibrium, kinetic and thermodynamic studies, Chem. Eng. J. 171 (2011) 510–516. [17] T. Depci, A.R. Kul, Y. Önal, Competitive adsorption of lead and zinc from aqueous solution on activated carbon prepared from Van apple pulp: study in single- and multi-solute systems, Chem. Eng. J. 200-202 (2012) 224–236. [18] G.O. El-Sayed, Removal of methylene blue and crystal violet from aqueous solutions by palm kernel fiber, Desalination 272 (2011) 225–232. [19] V. Vimonses, S. Lei, B. Jin, C.W.K. Chow, C. Saint, Kinetic study and equilibrium isotherm analysis of Congo Re d adsorption by clay materials, Chem. Eng. J. 148 (2009) 354–364. [20] A.A. Oladipo, M. Gazi, Enhanced removal of crystal violet by low cost alginate/acid activated bentonite composite beads: optimization and modelling using non-linear regression technique, J.Water Process Eng. 2 (2014) 43–52. [21] M.A. Levin, G.F. Degrange, C.D.D. Bruno, D.J. Mazo, J.J. Taborda, Methylene blue reduces mortality and morbidity in vasoplegic patients after cardiac surgery, Ann. Thorac. Surg. 77 (2004) 496–499. [22] P.N. Patel, Methylene blue for management of Ifosfamide-induced encephalopathy, Ann. Pharmacother. 40 (2006) 299–303. [23] Y.J. Wu, L.J. Zhang, C.L. Gao, J.Y. Ma, R.P. Ma, Adsorption of copper ions and methylene blue in a single and binary system on wheat straw, J. Chem. Eng. Data 54 (2009) 3229–3234. [24] S. Li, Removal of crystal violet from aqueous solution by sorption into semi-interpenetrated networks hydrogels constituted of poly(acrylic acid-acrylamide-methacrylate) and amylose, Bioresour. Technol. 101 (2010) 2197–2202. [25] S. Chakraborty, S. Chowdhury, P.D. Saha, Adsorption of Crystal Violet from aqueous solution onto NaOH-modified rice husk, Carbohydr. Polym. 86 (2011) 1533–1541. [26] M.K. Purkait, A. Maiti, S. Das Gupta, S. De, Removal of congo red using activated.

(1 mol L−1) (12)

where γe is the activity coefficient at the adsorption equilibrium. According to the Debye-Huckel, γe is a function of the ionic strength (Ie) of the solute at adsorption equilibrium and the charge carried by solute (z) (log γe = −Az 2Ie1/2 ). According to Liu [64], for neutral adsorbates or adsorbates with weak charges, eq 12 turns to: ΔG° ≈ − RTln[KL (1 mol L−1)] = − RTlnKL

(13)

The obtained results are illustrated in Table 3. According to these results, we have found that the value of ΔG° at different temperatures are negative for all three dyes in the binary and ternary mixtures, indicating that adsorption of MB, CV, and CR onto natural clay in all mixtures is spontaneous [39]. The values of ΔH ° are found to be positive for all the dyes, which confirm that the adsorption is endothermic for the three dyes [65]. In addition, the magnitude of ΔH° may give an idea about the type of sorption. The heat evolved during physical adsorption is of the same order of magnitude as the heats of condensation, i.e., 2.1–20.9 kJ mol−1, while the heats of chemisorption generally falls into a range of 80–200 kJ mol−1 [66]. In this study the values of ΔH ° are between 14.422 and 91.833 kJ mol−1 which implies that the adsorption of three dyes should be considered as between physical adsorption and chemisorption [67]. Moreover, the positive values of ΔS ° show increased randomness at the solid/liquid interface during the adsorption of the MB, CV and CR dyes onto natural clay [68–70]. 4. Conclusion In this manuscript, the removal of MB, CV, and CR onto natural clay in binary and ternary mixtures were performed. The obtained results show that the effect of concentration and temperature has a positive effect on the adsorption of three dyes in the binary and ternary mixture, we found that optimal contact time and temperature are 60 min and 40 °C respectively with adsorbent dosage 2 gL−1. Thus the adsorption is better at basic pH for these mixtures MB (MB + CV), MB (MB + CR), MB (MB + CV + CR), CV (CV + MB), CV (CV + CR) and CV (CV + MB + CR), and at acidic pH for CR (CR + MB), CR (CR + CV) and CR (CR + MB + CV). The kinetic study shows that the pseudo-secondorder kinetic is better described the adsorption of MB, CV, and CR with correlation coefficients which are close to 1. The adsorption isotherms for single system is best fitted by Langmuir isotherm with R2 = 0.9787 for MB, R2 = 0.9774 for CV and R2 = 0.9921 for CR. The maximum adsorption capacity of MB, CV and CR are 202.13 mg g−1 for MB (MB + CV), 289.59 mg g−1 for MB (MB + CR), 281.31 mg g−1 for MB (MB + CV + CR), 179.28 mg g−1 for CV (CV + MB), 289 mg g−1 for CV (CV + CR), 280.61 mg g−1 for CV (CV + MB + CR), 253.53 mg g−1 for CR (CR + MB), 240.06 mg g−1 for CR (CR + CV) and 264.54 mg g−1 for CR (CR + MB + CV). The thermodynamic study indicates that the adsorption is spontaneous, physical and 5931


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