Physicochemical Characterization of Moroccan Natural Clays and the Study of their Adsorption Capacity for the Methyl Orange and Methylene Blue Removal from Aqueous Solution

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 4, Pages: 1258-1267

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/8(3)1267

Physicochemical Characterization of Moroccan

Natural Clays and the Study of their Adsorption

Capacity for the Methyl Orange and Methylene Blue

Removal from Aqueous Solution

Meryem Assimeddine , Mohamed Abdennouri , Noureddine Barka , Elhossein Rifi , M’hamed

Sadiq¹

Sultan Moulay Slimane University of Beni Mellal, Research Group in Environmental Sciences and Applied Materials (SEMA),

FP Khouribga, B.P. 145, 25000 Khouribga, Morocco

Ibn Tofail University of Kenitra, Research Group in Organic Synthesis and Extraction Process, Faculty of Sciences,

University Campus, BP 133, Kenitra, Morocco

Received: 04/05/2020

Accepted: 24/8/2020

Published: 20/12/2020

Abstract

The objective of this work was the physicochemical characterization of a Moroccan natural clay from the Jorf Arfoud region (Lampert

Coodinates: x = 595610, y = 101578) and its valorization in the elimination of organic pollutants (methyl orange MO and methylene blue

MB) from aqueous solutions, with the adsorption technique on raw and calcined clay at 500°C. The clay was characterized by chemical

analysis such as X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning electron

microscopy (SEM). Crude and purified clays, consisting essentially of silica and alumina, are a characteristic property of phyllosilicates and

also contain amounts of quartz, kaolinite and calcite as associated minerals. The experiments were performed after optimization of the

parameters influencing the system, such as pH, adsorbent mass, initial dye concentration and temperature. The clays used absorb better the

MB than MO, for an initial concentration of 10 mg/L and 20 mg/L respectively. Langmuir and Freundlich models of adsorption isotherms

were applied to fit experimental equilibrium data. Results have showed that the adsorption of MB and MO followed very well the second

order kinetic model on raw clay. The adsorption process was found to be exothermic in the case of MB. However, the adsorption of MO was

endothermic.

Keywords: Natural Clay; Adsorption; isotherm and kinetic studies; Dye removal

Introduction¹

refractory organics and emerging contaminants from industrial

effluents using the microbial electrochemical technologies is a

sustainable proposition as discussed in review paper [9]. The

adsorption technique is one of the more favorable method for the

removal of dyes. It has become an analytical method of choice,

very effective and easy to use [10].

This work focuses on the use of a locally available natural

clay as adsorbent, low cost, biodegradable and made from natural

sources [11]. The clays play an important role in some areas, such

as the manufacture of therapeutic and cosmetic products [12-14]

and treatment of wastewater, for example in adsorption of toxic

organic compounds. It is a no polluting material that can be used

as a depleting agent for wastewater and heavy metal laden water,

due to its lofty adsorption capacity [15]. The adsorption and

desorption process of organic dyes by clays are principally

controlled by the surface property of the clay and the chemical

properties of the molecules [16]. goethite blended natural

Water is the most important natural resource made available

to the future of humanity. It is essential for existence of life and

maintaining ecological balance of planet. Amongst the growing

impact caused directly or indirectly by humans, science and

technology development are made the environmental mess with a

big pollution problem. Dyes industrials are one of the main

pollutants. From recent years, the textile industry emissions are

heavily loaded with most organic dyes. These are often used in

excess to improve dyeing; hence discharge water is highly

concentrated dyes whose low biodegradability makes their

treatments difficult, which is

degradation [1, 2].

Several authors used physical, chemical and biological

methods to treat and discolor polluted effluents, such as

coagulation and flocculation [3], biodegradation [4], membrane

filtration [5], photodegradation and adsorption [6-8]. Removal of

a source of environmental

Corresponding author: M’hamed Sadiq, Sultan Moulay Slimane University of Beni Mellal, Research Group in Environmental Sciences

and Applied Materials (SEMA), FP Khouribga, B.P. 145, 25000 Khouribga, Morocco. Tel: +212 666 24 81 96; Fax: +212 523 49 03 54 and

E-mail: m.sadiq@usms.ma ; sadiqmhamed@hotmail.com

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2020, Volume 8, Issue 4, Pages: 1258-1267

clayware-based membranes have been previously reported as a

low-cost alternative proton exchange membrane in microbial fuel

cell application [17]. They showed that Natural clay-based

membranes have significantly lower proton conductivity than

Nafion 117 membrane. Microbial Fuel Cell–Membrane

Bioreactor developed system by Bhowmick et al. [18]

demonstrated the best treatment of medium-strength organic

wastewater; Overall chemical oxygen demand (COD) and total

Kjeldahl nitrogen (TKN) removal efficiency of around 98% and

sampled, air-dried, and then crushed, calcined at 500°C, in a

tubular furnace for 4 hours.

2.3 Characterization techniques

Adsorbent diffractograms were recorded at room temperature

using a D2 PHASER powder diffractometer, equipped with a

copper anticathode (CuK line, λ=1,5406 Å) operated at 30 kV

and 10 mA. Bragg-geometry-Brentano has been employed. The

samples were irradiated in a 2θ angular range from 5° to 80°, with

a 0.01° measurement pitch and a 0.5 sec/step count time. Infrared

spectroscopy measurements were obtained using a Fourier

transform spectrometer, type Perkin Elmer (FTIR-2000). The

samples are packaged as pellets, consisting of 1mg of the test

substance, diluted in 100 mg KBr. The results are presented in

2% were achieved from the combined process, respectively. In

one other work of Bhowmick et al. [19], Conductive ink printed

Co and Fe were used as cathode catalyst, which

3 4

demonstrated an improved electrical performance and wastewater

treatment efficacy of microbial fuel cell.

The purpose of this study was to test the capacity of

Moroccan natural clay as a low-cost adsorbent for the removal of

methyl orange and methylene blue from aqueous solution to

replace the current expensive methods of waste water. The effect

of deferent parameter such as the adsorbent dose, pH, initial

concentration of dye and temperature were studied.

absorbance for wavenumbers between 4000 and 400 cm . We

used a scanning electron microscope JEOL JSM 6400. This

device has an acceleration voltage of up to 40 kV, the images are

usually made at 20 kV. Chemical analysis by X-ray fluorescence

makes it possible to determine precisely the overall chemical

composition of a solid sample. The device used is a wavelength

dispersion spectrometer–Type Axios and the method of

preparation is pastille (PROT -ELE03-v01).

Materials and methods

.1 Materials

.4 Adsorption kinetics

.4.1 Pseudo-first-order model

All the reagents chemicals used in the study were of analytical

grade. Methylene blue and methyl orange ware provided by the

Sigma-Aldrich chemicals and used without further puriﬁcation.

The chemical formula and some physicochemical properties of

these dyes are summarized in table 1. Methylene blue is a cationic

dye. It causes in man, in case of ingestion, an increase in heart

rate, vomiting, quadriplegia, and tissue necrosis [20]. Methyl

range is an anionic dye soluble in water, widely used in the

chemical, textile and paper industries. It is an anionic dye that

poses a serious risk to the environment [21-23].

This model assumes that the sorption rate at the moment ‘t’ is

proportional to the difference between the amount adsorbed at

equilibrium (q ), and the amount adsorbed at the moment ‘t’ (q ),

and that the adsorption is reversible [24]. The equation of the law

of speed is written:

푑푞

푘 (ꢀ − ꢀ )

(1)

푒

푡

푑푡

where; q

and q

are the adsorption capacities at time t and

is the pseudo-first order

.2 Sampling

equilibrium respectively, in (mg/g), k

velocity constant (min ) and t is the contact time (min).

The integration of equation (1) gives:

The clay samples used in this study were mineralogical

mixtures dominated by Silica and Alumina. The chemical

composition of the clay sample was determined by X-ray

fluorescence. The results are given in table 2. The clay was

= ꢀ (ꢁ − ꢂ^ꢃ^ꢄ^ꢅ^푡)

ꢀ

(2)

푒

Table 1: Physicochemical characteristics of used dyes

Name

Molecular structure

Nature

(g/mol)

max (nm)

661

Methylene blue

Basic blue 9)

Cationic

319,85

327,33

(

Methyl orange

Anionic

461

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2020, Volume 8, Issue 4, Pages: 1258-1267

.4.2 Pseudo-second-order model

The adsorption kinetics can be described by the pseudo-

isotherms into four types: Linear type C (1/n = 1), Convex type S

(1/n > 1), Concave type L (1/n < 1) and type H (1/n << 1).

second order model. The differential equation is generally known

and described as [25]:

2.6 Adsorption studies

The required initial dye concentrations were prepared by

dissolving the desired weight of each dye in distilled water. The

sorption processes were carried out in a series of 200 mL beakers

containing the desired clay weight and 200 mL of the colouring

solution at a given concentration. These experiments were carried

out with constant agitation by varying the clay mass from 1 to 4

g/L, the contact time from 0 to 360 min, the pH of the solution,

the initial dye concentration from 10 to 50 mg/L and the

temperature from 10, 30 and 50°C. The pH of the solution was

adjusted by adding NaOH (0.1 N) or HCl (0.1 N) and using a

푑푞_ꢆ

푡

푘 (ꢀ − ꢀ )

(3)

푒

푑푡

The integration of equation (3) gives:

ꢄꢇ푞ꢈ^ꢇ 푡

ꢀ_푡= ₁

(4)

+ꢄꢇ푞ꢈ푡

where k (g/mg. min) is the rate constant of pseudo-second order

adsorption.

sensION pH meter. Temperature was controlled using a

Cryothermostat. After each adsorption test, the solid phase was

separated from the liquid phase by syringe filters, and the

concentration was determined from its UV–Vis absorbance

characteristic with the calibration curve method at the maximum

absorption wavelength at 461 nm for methyl orange and 661 nm

.5 Adsorption isotherms

The relationship between the quantity fixed of adsorbate and

the equilibrium solution concentration have been described by

theoretical or empirical models proposed by several authors.

These are non kinetic relationships, called isotherms. In general,

such isotherms are processed by several models, including

Langmuir, Dubinin-Radushkevich, Freundlich, Temkin, Elovich,

BET etc….

for methylene blue.

TOMOS V-1100 UV-Vis

spectrophotometer was used. The adsorption capacity was

calculated using the following equations:

The Freundlich and Langmuir isotherms are the most commonly

used models in the literature.

(퐶0ꢃ퐶)

ꢀ

(7)

푅

and the removal efficiency (%) can be calculated as follows:

.5.1 Langmuir isotherm

The adsorption model of Langmuir [26] is based on the

(

퐶0ꢃ퐶)

퐶0

following assumptions: uniform energetic adsorption sites,

single-ply coverage, and no lateral interaction between adsorbed

molecules. Graphically, a tray characterizes the isotherm of

Langmuir. Therefore, at equilibrium, a saturation point is reached

where no further adsorption can occur. A theoretical expression

of the Langmuir isotherm is given by the following equation:

% ꢋꢂꢌ표푣푎푙 =

× ꢁꢍꢍ

(8)

Where q is the adsorbed quantity (mg/g), C

concentration (mg/L), C is the dye concentration at a time t

mg/L) and R is the mass adsorbents per liter of solution (g/L).

is the initial dye

(

푞_푚퐾 퐶

3 Results and discussions

3.1 Characterization

퐿

ꢈ

ꢀ_푒⁼1

(5)

+퐾 퐶

퐿

ꢈ

.1.1 Chemical analysis by X-ray fluorescence

The value of K

is related to the interaction force between the

The analytical results obtained by X-ray fluorescence are

adsorbed molecule and the surface of the solid, the value of q

grouped in table 2. It can be seen from these values that the

percentage of silica and alumina is very high, indicating the

expresses the quantity of solute fixed per gram of solid the surface

of which is considered to be totally covered by a monomolecular

layer [27].

presence of Kaolinite (Al

(OH)

). As well as for calcium

which is relatively high, so this material is rich in calcite (CaCO

The Alumina/Silica ratio provides information on the

permeability of the material vis-à-vis moisture, the greater this

ratio the greater the permeability [31]. In our case, this ratio is

.5.2 Freundlich isotherm

In this model, the number of sites likely to adsorb the

small Al

the low percentage of moisture. The overall composition of the

other oxides (Fe , MgO and K O) reaches a percentage of 8.353

2 3 2

O /SiO =0.38 for both samples; this low value indicates

compound is unlimited. Thus, the Freundlich isotherm has no

maximum unlike that of Langmuir. This empirical model is

widely used for the practical representation of adsorption

equilibrium. Freundlich isotherm can be given as follows [28]:

for the raw clay not calcined and of 9.987 for the calcined which

shows that our clays are not pure [32]. After the treatment

thermic, an increase of composition of clay is observed, due

mainly to the loss of physically adsorbed water and departure of

structural OH from Kaolinite (confirmed by XRD).

/푛

ꢀ_푒= ꢉꢊ_푒

(6)

is amount adsorbed per gram of solid, C

is concentration of

adsorbent at adsorption equilibrium, K and n being two constants

where K is a parameter essentially related to the maximum

capacity, and n is a parameter related to coefficients of variation

of the energies interacting with the overlap rate [29]. The shape

of obtained isotherms may suggest the interfacial interaction type

between the adsorbent and the adsorbate. Giles [30] classified the

.1.2 X-ray diffraction

The mineralogical composition evolution of the raw and

calcined clay sample is illustrated by figure 1. X-ray diffraction

analysis indicates that the both samples have almost the same

composition. They are composed of Quartz (SiO ), Calcite

Ca(CO )), and reveal the presence of a weak line that can be

(

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2020, Volume 8, Issue 4, Pages: 1258-1267

attributed to the Illite ((NH

Montmorillonite ((Na0.3(Al,Mg) Si

the presence of the Kaolinite phase (Al

clay not calcined. This later phase decomposes under effect of

calcination at 500°C. The diffractograms show the presence of a

more intense peak, corresponding to the Quartz. The clay fraction

of our materials consists of Quartz and Calcite as a major

compound in our samples, this confirms the results of

,K)(Si,Al)

.8H

(OH)

10(OH)

)

and

O) phases, with

) in the raw

OH units in their mineral structure [33]. A band centered at 1450

2−

antisymmetric stretching mode

O10(OH)

cm is attributed to the ν

of carbonate, where as the band at 880 cm is assigned to the

binding vibration of carbonate ν . These bands confirm the

presence of calcium carbonate CaCO [34]. Langford et al. [35]

(CO

)

show that the peaks from 900 to 1150 cm could be the

characteristic bending of Al-OH and stretching of Si-O vibrations

of weathered sheet silicates, principally illite and kaolinite.

However, an intense and wide absorption band centered at 1052

Fluorescence X which show high proportions of SiO (Quartz).

cm characterizes the valence vibrations of the Si-O bond [36].

Table 2: Mineralogical composition of clays

The doublet peak observed at 802 and 799 cm are attributable to

the Si-O link elongation vibrations of quartz mineral, where as the

Composition

SiO

CaO

% Raw clay

30,552

11,846

9,409

% Calcined clay in 500°C

peak at 695 cm is assigned to the Si-O perpendicular vibration

36,741

14,254

10,574

5,929

2,682

1,376

0,905

0,799

of silicates minerals [35]. The vibration bands of the Si-O-M

bonds (M denotes the Al, Mg and Fe metals located in the

octahedral position) appear in 538 and 486 cm . Therefore, the

absorption bands found by infrared confirm the results obtained

by X-ray diffraction.

4,878

2,294

.1.4 Scanning electron microscope SEM

MgO

TiO

1,181

The surface morphology of the raw and calcined clays was

0,769

observed by scanning electron microscope SEM. This technique

makes it possible to highlight the "macroporosity" character of the

samples. The resulting images are shown in figure 3. The

morphologies observed by scanning electron microscope of the

different phases are in the form of clusters of fine aggregates with

irregular contours. On the other hand, the morphology of the

natural clay not calcined is more compact than that of the

calcined, this is explained by the efficiency of the calcination by

allowing to increase the specific surface of the clay by pores

creation. In addition, we observe that the interparticular pores of

uncalculated clay are smaller than those in calcined clay.

0,231

0,405

.1.3 FTIR spectroscopy

The IR spectra of raw and calcined clays (figure 2) show the

different characteristic absorption bands of clays recorded

between 4000 and 400 cm . For both clay samples (raw and

calcined), we observe a broad absorption band around 3650 cm

characterizing the O-H bond, indicating the presence of water and

Figure 1: Clay diffractograms: Quartz (Q), Calcite (C), Illite (I), Montmorillonite (M) and Kaolinite (K)

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2020, Volume 8, Issue 4, Pages: 1258-1267

Figure 2: FT-IR spectra of raw and calcined clays

Figure 3: SEM image of raw clay (a) and SEM image of calcined clay (b)

.2 Adsorption study

.2.1 Adsorbent mass

Figures 4 and 5 represent, respectively, the variation in the

On the basis of the results obtained from the adsorption of

methylene blue, we note that the adsorption capacity of the raw

clay is almost the same as that of the calcined clay. The maximum

adsorption capacity is recorded for gross with 98% removal and

96% for the other with a mass of 1g per liter of solution. the

residual concentration of MB in the solution was 0,17 mg/L and

0,4 mg/L after the adsorption over the raw and calcined clay,

respectively. the optimum value of the residual concentration

amounts adsorbed by clay to MB and MO and the percentage of

removal. The curves show that the quantities retained are

maximum for the low ratios and decrease with the increase in this

ratio. This variation is due to an increase in the free surface area

of clay grains for low ratios.

(0,07 mg/L) was obtained after 180 min of adsorption of MB on

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2020, Volume 8, Issue 4, Pages: 1258-1267

g/L of raw clay, this corresponds to 99,4% optimum removal of

MB.

For the adsorption of orange methyl, the adsorption capacity

initial (20, 30, 40, 50 mg L ) dye concentrations. The recorded

curves show that the amount of adsorbate fixed on the material

increases with the increase in the content of the methylene blue

solution. In fact, the increase in concentration induces an increase

in the driving force of the concentration gradient, thus increasing

the diffusion of dye molecules in solution through the adsorbent

surface [37].

is very low compared to methylene blue. This result can be

interpreted by the anionic nature of MO, and the cationic nature

of BM which gives it a great affinity with the clays. Both types of

clay give almost the same results with a removal percentage equal

to 8% with a mass of 4g per liter of solution. in this case, the final

concentration of MO in the solution was 18 mg/L for both

supports raw and calcined clay.

.2.2 pH effect on methyl orange adsorption

We have limited ourselves only to the study of MO just to

improve the percentage of elimination, because in the case of MB

the percentage is reached 99% without modifying the working

conditions. Figure 6 shows the influence of pH variation on the

adsorption of methyl orange (MO) on uncalcined raw clay.

In our study, for the MO dye, there is a low adsorbability

regardless of the pH value (acid or basic), this is due to the anionic

nature of the MO which in its anionic form is repelled by the clay

surface due to the electrostatic effects (electrostatic repulsion

phenomenon).

Figure 6: pH effect on adsorption of MO. C =20mg/L, R=4 g/L,

Contact time = 180 min, RT

We also notice a rapid adsorption at the beginning instead in

5 minutes, then a spreading with saturation. The first phase

constitutes the main part of the adsorption phenomenon because

the fixation kinetics are limited by the low residual dye

concentration. In the second stage, the occupation of the deep

adsorption sites requires the diffusion of adsorbent within the

adsorbent micropores. After this phase we observe a saturation

step.

Figure 4: Effect of adsorbent mass on MB adsorption. C = 10 mg/L,

Contact time = 180 min, RT

Figure 7: Change in the amount of BM adsorbed at equilibrium as a

function of contact time and initial dye concentration

.2.4 Adsorption kinetics

The adsorption kinetics of methylene blue and methyl orange

on the crude clays were carried out at initial pH of the solution

8,3 for MB and 6,6 for MO) and at an initial concentration of 10

(

mg/L, with a clay mass of 1 g/L for methylene blue and an initial

concentration of 20 mg/L, with a clay mass of 4 g/L for methyl

orange. The results are presented in figure 8. The latter indicates

that the removal of cationic dye (BM), from the solution, is very

rapid. During the first 10 to 15 minutes of contact, more than 98%

dye was removed. For methyl orange, the kinetics were much

slower, and the percentage of elimination is 8% observed after 30

min of contact between the dye and the clay. In order to

characterize the kinetics involved in the adsorption process, the

Figure 5: Effect of adsorbent mass on MO adsorption. C = 20 mg/L,

Contact time = 180 min, RT

.2.3 Effect of initial MB dye concentration

Figure 7 shows the evolution of the adsorbed amount of BM

dye per gram of raw clay as a function of contact time at different

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pseudo-first-order and pseudo-second-order parameters were

estimated using non-linear regression. The data obtained and the

correlation coefficients, r , are given in table 3 and figures 9 and

Figure 9: Adsorption kinetics, pseudo-first order and pseudo-second

order of MB, C =10mg/L, R=1g/L, pH = 8.3, RT

Figure 8: MB and MO adsorption kinetics

.5.5 Adsorption isotherms

The adsorption isotherms were made with different initial

concentrations for a ratio of R = 1 g/L for MB, and R = 4 g/L for

MO, a contact time is 3 hours at RT and at initial pH.

The adsorbed amounts of each dye at equilibrium (q ) as a

function of the equilibrium concentration of each dye were

determined in figures 11 and 12. The experimental results

obtained were compared with the models of the adsorption

isotherms of Langmuir and Freundlich and the constants

appearing in each equation of these models were determined by

nonlinear regression analysis. The constants characterising each

of the systems were determined and given in table 4.

Figure 10: Adsorption kinetics, pseudo-first-order and pseudo second-

order of MO, C =20mg/L, R=4g/L, pH= 6,6, RT

The adsorption isotherm of methylene blue is the type H in

the Giles classification [30]. Generally, isotherms of this type H

are the result of the dominance of strong adsorbate-adsorbent

interactions [38]. A chemical adsorption of the functional groups

of the MB positively charged on the negatively charged groups

on the clay surface is proposed. The experimental data for MB are

best described by the Langmuir model. This result suggests that

the adsorption process of BM on clay is a single-ply adsorption,

and the maximum adsorption capacity was estimated at 15,82

mg/g. This result showed that methylene blue is uniformly

adsorbed by ionic adsorption from the negatively charged surface

of the clay.

The adsorption isotherm of methyl orange is the type S. The

isotherms of this class correspond to an adsorption in which the

adsorbate-adsorbent interactions occur, but also adsorbate-

adsorbate. Thus, a cooperative adsorption of molecules can be

observed. Type S isotherm occurs when the binding energy of the

first layer is less than the binding energy between water

molecules. This is due to the fact that methyl orange is an anionic

molecule that has the same surface charge of clays.

Table 3: Kinetic adsorption parameters of BM and MO on raw clay

pseudo-first-ordre

(1/min)

pseudo-second-ordre

Dyes

e (exp)

(mg/g)

r²

(mg/g)

(g/mg min)

0.79591

r²

10,01597

0,395021

9.98299

0.37727

0.76544

0.07142

0.99997

0.99195

10.0147

0.41154

0.99999

0.99907

0.27514

Table 4: Constants for isothermal models of dye adsorption on clays

Langmuir

Freundlich

Dyes

(mg/g)

(L/mg)

r²

(mg¹⁻¹^/ⁿ/L¹^/ⁿ.g)

r²

15.82816

13.7147

2.48567

0.00243

0.9055

0.99169

9.51471

3.62124

0.97771

0.84616

0.9936

0.02808

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Therefore, a low adsorption affinity is observed. This

suggests a physisorption provided by Van der Waals bonds.

Linearity shows that the number of free sites remains constant

during adsorption, this means that the sites are created during

adsorption.

The adsorption of methyl orange on clays depends mainly on

working conditions (pH, temperature, pressure, etc.). Other

authors [15,39] have shown that the adsorption of methyl orange

on other clays from the Safi region is greater at low temperatures

and the adsorption capacity is high in acidic medium. They

showed that kinetic parameters strongly influence adsorption.

the covalent bonds are high, make their breakup very difficult.

The slower decrease in the adsorption capacity of the MO with

the increase in temperature is due to the measurement of the

desorption step in the adsorption mechanism indicating that the

process is exothermic. It is known that, the decrease in adsorption

capacity with the increase in temperature is mainly due to the

attenuation of adsorptive forces between the active sites on

natural clay and dye molecules; anionic compound, and also

between dye molecules adjacent to the adsorbed phase [41].

Figure 13: Effect of temperature on adsorption of MB and MO

For such equilibrium reactions, K

can be expressed as:

, the distribution constant,

Figure 11: MB adsorption isotherms: V = 200 mL, R = 1 g/L,

pH = 8,3, RT

푞ꢈ

퐶ꢈ

ꢉ_퐷

(9)

Gibbs free energy is defined as:

훥퐺 = −ꢋ푇푙ꢎ(ꢉ )

(10)

퐷

where R is the universal gas constant (8.314 mole J/K), and T is

the temperature of the solution in (K). The enthalpy (ΔH°) and the

entropy (ΔS°) of adsorption were estimated from the slope and

the ordinate at the origin of the curve of ln(K ) function of 1/T,

respectively.

ꢏꢐ

ꢏ퐻

ꢒ

푅ꢑ

ꢏ푆

푅

푙ꢎ(ꢉ ) = −

= −

(11)

퐷

푅ꢑ

The constants calculated are illustrated in Table 5. We can

Figure 12: MO adsorption isotherms: V = 200 mL, R = 4 g/L,

pH = 6,65, RT

.2.6 Effect of temperature

conclude that the adsorption process was judged to be exothermic

(

ΔH negative) in the case of the both dyes MB and MO. In the

The effect of temperature on the adsorption of dyes plays a

case of MO, the value of the entropy is negative this suggests a

decrease in the randomness at the solid/solution interface during

very important role in the application of adsorption of various

textile effluents such as organic dyes. In fact, the temperature

favours the diffusion of the molecules through the outer boundary

layer to the internal pores of the adsorbent particles, probably

because of the decrease in the viscosity of the solution [40].

Figure 12 represents the variation of the percentage sorption of

MO and MB on the clay as function of the temperature. The

curves indicate that the temperature has no effect on the

adsorption of the MB to the clay, which confirms what happened

previously, that the adsorption of the MB is chemically similar,

adsorption. Gibbs energy (ΔG ) increases as the temperature

increases from 10 to 50 C indicating a decrease in the feasibility

of adsorption at higher temperatures. In the case of MB, the

adsorption is accompanied by a decrease in the values of ΔG with

the increase in temperature. This result indicates an increase in

the feasibility of adsorption at higher temperatures. The value ΔS

was found positive, which suggests an increase in the randomness

at the solid / solution interface during adsorption.

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2020, Volume 8, Issue 4, Pages: 1258-1267

Table 5: Thermodynamic parameters calculated for the adsorption of dyes by clays

BM OM

T(°C)

ΔG°

(KJ/mol)

ΔH°

(kJ/mol)

ΔS°

(J/K mol)

ΔG°

ΔH°

(kJ/mol)

ΔS°

(J/K mol)

(

mg/g)

9,914 115,35

9,907 107,6

9,901 100,81

(mg/g)

0,591

0,564

0,451

(KJ/mol)

7,9597

8,6554

9,8974

-11,177

-11,791

-12,394

0,034

0,032

0,025

-25,61

30,43

-56,69

-47,85

Hossen MZ, Hussain ME, Al Hakim, Islam K, Uddin MN, Azad

AK. Biodegradation of reactive textile dye Novacron Super Black

G by free cells of newly isolated Alcaligenes faecalis AZ26 and

Bacillus spp obtained from textile effluents. Heliyon 2019; 5(7):

e02068.

Yang C, Xu W, Nan Y, Wang Y, Hu Y, Gao C, Chen X.

Fabrication and characterization of a high performance polyimide

ultrafiltration membrane for dye removal. J. Colloid Interf. Sci.,

Conclusion

In summary, we have characterized the natural clay from the

south-east of Morocco and studied its adsorption capacity in the

elimination of organic pollutants from aqueous solutions.

Adsorption was rapid and complete in the case of methylene blue

and the pseudo-second-order model is the most suitable to

describe the adsorption dynamics. The rate of adsorption can be

controlled by a chemical absorption process, making this type of

adsorption irreversible. The adsorption isotherm can be well

described by the Langmuir equation and the optimal mass of the

adsorbent evaluated is 1 gram, corresponding to a yield of 98%.

The increase in temperature does not affect the amount of

methylene blue adsorbed. In the case of methyl orange, the

adsorption reaction is slower, reaching only 8% dye removal, at

different pH of the solution. The adsorption dynamics are

described by the pseudo-second order model and the adsorption

isotherm can be well described by the Freundlich equation.

Increased temperature reduces the amount of dye adsorbed.

020; 562(7): 589-597.

Basha CA, Selvakumar KV, Prabhu HJ, Sivashanmugam P, Lee

CW. Degradation studies for textile reactive dye by combined

electrochemical, microbial and photocatalytic methods. Sep. Purif.

Technol., 2011; 79(3): 303-309.

Herrera-González AM, Caldera-Villalobos M, Peláez-Cid A.

Adsorption of textile dyes using an activated carbon and

crosslinked polyvinyl phosphonic acid composite. J. Environ.

Manage., 2019; 234: 237-244.

Mahjoubi FZ, Khalidi A, Elhalil A, Barka N. Characteristics and

mechanisms of methyl orange sorption onto Zn/Al layered double

hydroxide intercalated by dodecyl sulfate anion. Sci. African 2019;

: e00216.

Das I, Das S, Chakraborty I, Ghangrekar M.M. Bio-refractory

pollutant removal using microbial electrochemical technologies: A

short review. J. Indian Chemical Society, 2019; 96(4): 493-497.

Barka N, Assabbane A, Ichou Y, Nounah A. Decantamination of

textile wastewater by powdered activated carbon. J. Appl. Sci.

Aknowledgment

The authors would like to thank University Sultan Moulay

Slimane of Beni Mellal for supporting this study.

006; 6: 692–695.

Ethical issue

Authors are aware of, and comply with, best practice in

publication ethics specifically with regard to authorship

Kausar A, Iqbal M, Javed A, Aftab K , Nazli Z, Bhatti HN, Nouren

S. Dyes adsorption using clay and modified clay: A review. J.

Molec. Liquids 2018; 256: 395–407.

Gomes C, Silva JB. Minerals and Clay Minerals in Medical

Geology. Appl. Clay Sci., 2007; 36: 4-21.

Carretero MI, Pozo M. Clay and non-clay minerals in the

pharmaceutical industry: Part I. Excipients and medical

applications. Appl. Clay Sci., 2009; 46: 73-80.

Williams L, Hillier S. Kaolins and Health: From First Grade to

First Aid. Elements, 2014; 10: 207-211.

(avoidance of guest authorship), dual submission, manipulation

of figures, competing interests and compliance with policies on

research ethics. Authors adhere to publication requirements that

submitted work is original and has not been published elsewhere

in any language.

Elmoubarki R, Mahjoubi FZ, Tounsadi H, Moustadraf J,

Abdennouri M, Zouhri A, El Albani A, Barka N. Adsorption of

textile dyes on raw and decanted Moroccan clays: Kinetics,

equilibrium and thermodynamics. Water Resour. Ind. 2015; 9: 16–

Competing interests

The authors declare that there is no conflict of interest that

would prejudice the impartiality of this scientific work.

Authors’ contribution

16.

Yariv S, Cross H. Organo-clay Complexes and Interaction, Marcel

Dekker New York, 2002, viii +688 pages.

Das I, Das S, Dixit R, Ghangrekar M.M. Goethite supplemented

natural clay ceramic as an alternative proton exchange membrane

and its application in microbial fuel cell. Ionics (2020).

All authors of this study have a complete contribution for data

collection, data analyses and manuscript writing

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