Removal Pharmaceutical Pollutants by Adsorption Competitive using Powdered Activated Carbon CAP (F400)

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal weblink: http://www.jett.dormaj.com

Removal Pharmaceutical Pollutants by

Adsorption Competitive using Powdered

Activated Carbon CAP (F400)

Abdelkarim Mellah¹, Djamila Harik¹

.2*

National Polytechnic School, Environmental Sciences and Technology Laboratory, Algiers, Algeria

Scientific and Technical Research Centre for Arid Areas (CRSTRA), Biskra

Received: 03/11/2019

Accepted: 14/12/2019

Published: 20/02/2020

Abstract

The aim of this study is to assess the competitive adsorption of two pharmaceutical products, phenobarbital and ibuprofen using

powdered activated carbon (PAC) F400. The adsorption tests were carried out in batch experiments. The kinetic adsorption results

–

–1

showed that the PAC adsorbs good lipophilic ibuprofen with an adsorption capacity reaching 101.46 mg g against 63.46 mg g

of phenobarbital. The adsorption capacity was negatively influenced by the presence of both adsorbates compared to their individual

adsorption onto PAC. logkow, pKa values, and molecular weights played a crucial role on the adsorption capacities of the target

compounds onto PAC. The results obtained show that the adsorption of both pharmaceuticals follows a pseudo-second order model

through a complex process including connecting layer and intra-particle diffusion in micropores. According to the results, the

isotherm models of Langmuir, Freundlich, and Temkin fit well the experimental data for each selected pharmaceuticals. The b

values show that the competitive adsorption process of each pharmaceutical is a physisorption without formation of links.

Keywords: Adsorption; Phenobarbital; Ibuprofen; PAC, Kinetics; Isotherms

Introduction¹

Pharmaceuticals play

decade [3, 10-12]. Many specialized research has been

reported in that field using several technologies of removal

pharmaceuticals such as activated sludge systems [13-16],

electro-coagulation coupled electro-flotation process [17],

membrane bioreactors [15, 18, 19], photocatalytic oxidation

processes [19,20], advanced oxidation processes [21-23],

magnetic ion-exchange resins [24], and adsorption [25].

In the present research we studied the efficacy of the

competitive adsorption of ibuprofen and phenobarbital as

products largely used in the world form water using the

powder activated carbon F400, in order to study the effect of

the simultaneous presence of two drug molecules.

a dominating role in the

improvement of quality and life expectancy of the

populations. Every year, thousands of tons of pharmaceutical

compounds are utilized in human medicine and veterinary

[

1]. Many drug molecules were detected in the different

effluents of the aquatic environments [2]. Pharmaceuticals

have been developed to have effects on the human organism

for treating diseases; therefore, their disposal in the

environment may cause harm to humans, plants, and animals

even at very low concentrations [3-6]. They can be

eliminated via the urine without transformation [7]. Thus,

they can present a considerable risk because of their direct

toxicity and their effects cumulative or synergistic with other

micropollutant. Many drugs have biological effects in the

organism not targeted such as certain synthetic hormones on

the fish [8, 9].

In recent years, their impact on the environment has

become a scientific and public health concern, and are the

matter of significant attention with respect to their

environmental fate, the circumstances of their contact with

the organisms and their toxicological risks during the last

2 Materials and methods

2.1 Materials

The activated carbon used PAC F400 is presented in the

form of a powder with a size granulometry of 50 µm. PAC

F400 is prepared by activation of bituminous oil under high

temperature in the presence of oxygen. It exhibits a

microporous structure with a variable specific surface area

–1

of 1050–1200 m g , iodine index of 1050 mg g and acid

–

function of surface 0.23 mEq g [26].

Corresponding author: Abdelkarim Mellah, National Polytechnic School, Environmental Sciences and Technology Laboratory,

Algiers, Algeria. E-mail: karim.epa2008@hotmail.fr.

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

Table 1: Physico-chemical properties of the pharmaceuticals

Mw^b

Compounds

Ibuprofen

Molecular formula

Chemical structure

pKa

4.91

logkow

206.28 206.28

3.97

Phenobarbital

232.23 232.23

.3;11.8

1.47

PSA = Polar Surface Area

–1

Sw = Water solubility (mg L ) at 25 °C

1

Mw = Molecular weight (g mol )

It is recommended to use clarifiers to increase the time

The residual pharmaceutical concentration was

determined by HPLC (Waters 600 Controller, iodine bar

detector: DAP Waters 2996) using column Nucleosil5 C18,

of contact between PAC and water [27]. Before each use,

PAC undergoes dehydration in the oven at 105 °C during 12

hours. All the chemicals and reagents used in the study are

all of analytic grade. Phenobarbital [5 -éthyl- 5phényl -

,4,6(1H, 3H, 5H) - pyrimidine trione and ibuprofen [acide

±) 2 - (4 - isobutyphényl) propionique] were supplied by

Sigma–Aldrich, Germany. The physico-chemical

characteristics and the structural formulas of both

pharmaceuticals are shown in Table 1. The pharmaceutical

solutions were prepared in ultrapure water (Millipore Milli-

Q Direct 8 Water Purification System).

L=250 mm, d =4.6 mm (OSI) at a wavelength of 210 nm for

phenobarbital and 220 mn for ibuprofen. The developed

conditions of analysis allowed the separation of the peaks of

two molecules with very reasonable retention times (3.0 and

4.0 minutes respectively for phenobarbital and ibuprofen),

which allow the analysis of a great number of samples per

(

–

day. Chromatograms of a solution containing 8 mg L of

each product are presented on Figure 1. Spectra UV relating

to each peak is presented on Figure 2.

A volume of 20 µL of the filtrate injected by the injection

loop is pulled by the mobile phase made up of a mixture

methanol–water (75:25, V : V). The mobile flow phase is

fixed at 1 ml min . Detection takes place in the field of UV,

the quantification and the qualification of the molecules

were carried out with the wavelengths corresponding to the

maximum of absorption in this field.

The retention times characteristic of the molecules allow

their identification. The method of the compared injections

(external calibration) and the determination of the

chromatographic peak area are used for quantify the residues

of the studied molecules.

.2 Adsorption experiments

For the purpose of our different studies, stock solutions

–

were prepared for the tow selected pharmaceutical products:

ibuprofen and phenobarbital, at a concentration of 1.0 g L

1

in the methanol. From these solutions, solutions were

prepared with the desired concentration. All solutions were

prepared with ultrapure water at pH = 67. Adsorption

experiments were carried out using a batch experimental

process. The adsorption kinetic experiments were first

performed in order to determine the necessary time to reach

the equilibrium (teq). Then, equilibrium tests were executed

to determine the adsorption isotherms. All experiments were

performed in duplicate by incubation under constant shaking

3 Results and discussion

3.1 Kinetics of adsorption

00 rpm, at a constant temperature of 21 ± 2 °C using a

magnetic stirrer (Fisher bioblock scientific), with a known

mass of the PAC of 40 mg L in ultrapure water. The initial

concentration of the pharmaceuticals in ultrapure water is 8

The influence of the agitation time on the mixed

1

adsorption of phenobarbital and ibuprofen at an initial

–

concentration of 8 mg L by PAC F400 at a concentration

1

–1

mg L .

of 40 mg L is presented in Figure 3. The adsorbed amount

can be calculated based on the Eq. (1):

.3 Sample analysis

To evaluate the residual concentrations of phenobarbital

푞 = (퐶 − 퐶 )푉/ 푚

(1)

푒

and ibuprofen (Cr), we developed the operating conditions

for the proportioning of these two molecules by High-

performance liquid chromatography (HPLC). This method

was already validated in our laboratory. The protocol

followed for this validation was inspired by that used in the

Center of Expertise in Environmental Analysis of Quebec

where q

is the adsorption capacity at the equilibrium, C

is the initial concentration of the adsorbate in the solution, m

is the mass of the adsorbent and V is the volume of the

solution.

[65].

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

Figure 1: Chromatograms of a solution made up of the mixture of phenobarbital and ibuprofen at concentration of 8 mg L to λ = 210 nm

In the present study, the adsorbed quantity of individual

pharmaceutical was clearly higher than that obtained for

120

mixed substrates solution, which proved visibly

competitive adsorption existing between the target

compounds in this research as shown in Figure 2. The

adsorption process of phenobarbital in mixture is not fast.

–

Indeed, only 23% equivalent of 45.24 mg

phenobarbital is adsorbed after 5 min, while the slope

becomes very weak with the approach of equilibrium after

–

80 min indicating a quantity adsorbed of 63.46 mg g

Ibuprofen mixed

equivalent of 32% of the quantity presents initially as shown

in Figure 2. The adsorbed quantity of ibuprofen in binary

mixture was very quickly reaching a rate of 31% after 5 min,

Phenobarbital mixed

Ibuprofen individual

Phenobarbital individual

–

which is equivalent of 62.22 mg g and pseudo-equilibrium

is established after 180 min with an adsorption percentage

100

200

t (min)

300

400

–

rate of 51% equivalent of 101.46 mg g . The mechanism of

the binary mixture adsorption is probably influenced by the

pKa and logkow of the substrates competing for the limited

adsorption sites. The dissociation of the electrolyte

substrates is governed by the pKa [28]. The pKa of

phenopbarbital (7.3; 11.8) indicated that it would remain at

molecular form over the operation. This property resulted

good competitive adsorption with ibuprofen. The logkow is

considered, as well, as a significant factor for the adsorption

capacity evaluation, in which the pharmaceutical pollutants

with higher logkow values should have a higher adsorption

affinity towards PAC [29].

Therefore, the adsorbed quantity of ibuprofen was higher

than that obtained with phenobarbital. Phenobarbital

presents the lowest logkow value, which indicates that is the

most hydrophilic compound among the tow selected

pharmaceuticals. However, logkow played out a crucial role

in controlling the adsorbed quantity in the competitive

adsorption of pharmaceuticals. At neutral pH, ibuprofen

exists in non-polar state, whereas the phenobarbital is

dissociated into anions. The PAC surface is principally non-

polar, which facilitates to adsorb non-polar molecules [30].

Some reported works confirm the low adsorption capacity of

PAC towards phenobarbital, such as the works mentioned

above, of Cooney using the activated carbons Instachar and

Liquichar to adsorb phenobarbital [31], and the reported

work of Papciak and co-workers about adsorption of

ibuprofen onto Norit SA super and Carbopol MB5 [32].

Figure 2: Adsorption Kinetics of ibuprofen with phenobarbital

mixed and individual expressed as quantity adsorbed (mg g ) by

–1

PAC F400 at 20 ± 2 °C in ultrapure water at pH = 6.6 ± 0.2

–1

(C (pharmaceutical) = 8 mg L ; C(PAC) = 40 mg L

The difference in the adsorption capacity for both

pharmaceuticals at equilibrium could be related to

competitive adsorption on the sites of PAC. Similar results

were reported by Weber and co-workers [33], were studied

the influence of solute size and molecular configuration in

which they found a relation between the speed of adsorption

and the molar mass. Hydrophobic phenobarbital exhibits a

higher molar mass and bit large molecular structure

compared to lipophilic ibuprofen, its adsorption get

equilibrium a bit slightly with less adsorption capacity than

ibuprofen. In addition, the least soluble compounds are

adsorbed more easily and the structure of the carbonaceous

chain plays a significant role in the case of competitive

adsorption. The molecules containing of the unsaturated

connections are more easily adsorbed than the molecules

with saturated connections (electronic exchanges) [34].

Carvalho and co-workers were reported similar times of

equilibrium in their study adsorption of ibuprofen onto

powdered activated carbons prepared from cork waste [35].

3.1.1. Kinetics the pseudo-first order

The Lagergren model governing the pseudo-first-order

adsorption kinetics is the most widely used in its linearized

form as shown the Eq. (2) [66]:

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

ln(푞 − 푞 ) = ln(푞 ) − 퐾 푡 /2.3ꢁ3

(2)

where q

and q

are the quantities of aqueous solution

푒

ꢀ

–

adsorbed out in mg g at equilibrium and at moment t, K

and q

are the amounts of solute adsorbed in mg g^

the speed constant of the pseudo-second order (g mg min^–

–1

where q

at equilibrium and at time t, respectively, and K

is the

pseudo-first-order rate constant (min ). The graphs given by

plotting ln(qe ) as a function of time are presented in Figure

for the adsorption of ibuprofen and phenobarbital at an

). The initial velocity of the adsorption h is given in this case



by the Eq. (4):

ꢂ

^ℎ⁼^퐾^푞e

(4)

ꢂ

1

initial concentration of 8 mg L on PAC at a concentration

1

The graphs given by plotting t/q

the adsorption of ibuprofen and phenobarbital at an intial

concentration of 8 mg L by PAC (F400) at a concentration

of 40 mg L are presented in Figure 4. The linear adjustment

of the experimental values obtained during the kinetic

adsorption tests for the pseudo-second order model were

as a function of time for

of 40 mg L . The pseudo first-order kinetic parameters are

presented in Table 2. A wide variance can be observed

between experience and theory using the Lagergren model

1

and the correlation coefficient (R ) values for the pseudo-

first-order kinetic model were 0.872 and 0.860 for

phenobarbital and ibuprofen, respectively, indicating that the

Eq. (2) does not adequately describe the adsorption

processes of ibuprofen and phenobarbital onto PAC.

given coefficients of correlation R very close to the unit

showing that this model is in perfect agreement with the

obtained experimental values. Some works were reported

that pseudo-second order is adequate to describe the

adsorption of ibuprofen and phenobarbital onto activated

carbons [35, 39-42]. The calculated q

and 76.92 mg

Ibuprofen

–

phenobarbital

values of 125 mg g

Linear (Ibuprofen)

Linear (phenobarbital)

–1

of ibuprofen and phenobarbital,

y = -0.0066x + 4.0407

R² = 0.8609

respectively, according to the pseudo-second order kinetic

model of the adsorption by PAC (F400) agreed well with the

experimental data as shown in Table 3. According to these

results, the ibuprofen presents an initial velocity h of 12.5

–

–1

mg g min higher than 6.21 mg g min of phenobarbital.

y = -0.006x + 3.641

R² = 0.8725

Ibuprofen

Phenobarbital

Linear (Ibuprofen)

Linear (Phenobarbital)

y = 0.0133x + 0.1611

R² = 0.9976

100

200

300

400

t (min)

Figure 3: Pseudo-first order kinetics results on the removal of

ibuprofen (λ = 220 nm) mixed with phenobarbital (λ = 210 nm), by

PAC (F400) at 21 °C in ultrapure water at pH 67,

1 1

(C (pharmaceutical) = 8 mg L ; C(PAC) = 40 mg L )

y = 0.0081x + 0.0804

R² = 0.9981

.1.2 Kinetics the pseudo-second order

The pseudo-second order model is suggested by certain

authors as being adapted to describe certain kinetics of

adsorption [36-38], it is especially used in the following

linearized form as it shown by the Eq. (3):

100

200

300

400

t (min)

Figure 4: Pseudo-second order kinetics results on the removal of

ibuprofen (λ = 220 nm) mixed with phenobarbital (λ = 210 nm), by

PAC (F400) at 21 °C in ultrapure water at pH 67,

ꢂ

푡/푞 = 1/퐾 푞 + 푡/푞

(3)

ꢂ

1 1

(C (pharmaceutical) = 8 mg L ; C(PAC) = 40 mg L ).

1

Table 2: Pseudo-first order kinetic parameters for mixed ibuprofen and phenobarbital at an initial concentration of 8 mg L by PAC ( F400) at a

concentration of 40 mg L^at 21 °C and pH=67

R²

e,exp (mg g^¹)

e,calc (mg g^¹)

(min )

Phenobarbital

Ibuprofen

0.013

0.014

0.872

0.860

74.45

124.31

38.13

56.82

= 8 mg L^by PAC (F400) at concentration of 40

e exp (mg g^–¹) e calc (mg g^–¹)

Table 3: Pseudo-second order kinetic parameters for ibuprofen mixed with phenobarbital at C

mg L^at 21 °C and pH=67

(g mg^h )

1

h (mg g min )

–1

Phenobarbital

Ibuprofen

0.0010

0.0008

6.21

12.5

0.997

0.998

124

76.92

125

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

The low speed of phenobarbital in mixture may be due

to the influence of the competition phenomenon, which

negatively affect its adsorption [34], and the lipophilic

ibuprofen would be adsorbed more quickly thus occupying

the sites and reducing the adsorption of phenobarbital

indicating a good affinity to PAC than phenobarbital.

the sites of PAC [52]. Therefore according to our study,

ibuprofen diffuses more easily onto the PAC. The results

suggested that organic PAC adsorbent could serve as a good

adsorbent for lipophilic organic pharmaceutical pollutants

[53].

.1.3 Intra-particle diffusion

The intra-particle diffusion of the adsorbates into

adsorbents during the process of adsorption is explored to

understanding the stage which controls the speed of

adsorption [43], using the Eq. (5):

100

t =

t¹^/²

(5)

where q

is the adsorbed quantity per unit mass of adsorbent

1

at time t (mg g ) and K

is the intra-particle velocity constant

1

1/2

(

mg g min ). According to the plotted data of the intra-

particle diffusion model (Figure 5) q

versus t exhibits

Ibuprofen

multilinear plots, where two steps could be influencing the

process. The plots for the adsorption of ibuprofen and

Phenobarbital

1

phenobarbital at an intial concentration of 8 mg L by PAC

(

F400) at a concentration of 40 mg L^do not result in a

linear relationship passing via the origin, but multimodal

graphs with two distinct regions, indicating that intra-

particle diffusion is affected by more than one process [44].

The plotted curves of the mixed pharmaceuticals were

presented the existence of two stages. In the first stage, both

ibuprofen and phenobarbital diffuse through the solution to

the external surface of the adsorbent. The second stage

relates to the equilibrium stage, in which the intra-particle

diffusion starts to slow down and level out [45, 46]. Thus, in

order to calculate the speed constants of diffusion of each

stage, the linear regression is applied to each section. The

coefficient of diffusion was also calculated for each element

using the Eq. (5). The multilinearity of the curves of the

intra-particle diffusion is described in the literature for many

couples adsorbate-adsorbent such us cations natural metal-

materials [47], diuron and metribuzine-activated carbon

t1/2 (min1/2)

Figure 5: Intra-particle diffusion model for the adsorption kinetics

of the mixed ibuprofen (λ= 220 nm) and phenobarbital (λ= 210 nm)

by PAC (F400) at 21 °C in ultrapure water at pH 67,

1 1

(C (pharmaceutical) = 8 mg L ; C(PAC(F400)) = 40 mg L )

3.2 Modeling of the isotherms

Equilibrium adsorption isotherms are the most

commonly data used to understand the adsorption

mechanisms, in which many isotherm models are available.

In this study, the three most used models in literature were

tested: the isotherms of Langmuir [54], Freundlich [55], and

Temkin [56].

3.2.1 Langmuir isotherm

The Langmuir isotherm model [54] for the adsorption of

[

48]. Only one part is regarded as limiting factor speed in a

mixed ibuprofen and phenobarbital at an initial

concentration of 8 mg L by PAC (F400) at varying

concentrations was tested using the Eq. (6) in its linear form:

1

particular field of time [49].

The intra-particle parameters are presented in Table 4.

The values of the correlation coefficients R for the intra-

particle diffusion model of Weber–Morris obtained for the

mixed pharmaceuticals are all above 0.901 indicating that

the intra-particle model fits well the obtained experimental

values. The slope of the linear part indicates the speed of

adsorption; and the weakest slope corresponds to the slowest

process of adsorption noting that the least soluble

compounds are adsorbed more easily.

퐶ꢃ/푞 = 퐶ꢃ/푞_ꢄ+ 1/푞 푏

(6)

푒

ꢄ

where q is the adsorbed amount of solute per unit weight of

−1

adsorbent at equilibrium (mg g ), C is the concentration of

the solute at the equilibrium in the bulk solution (mg L ),

−1

q is the maximum adsorption capacity (mg g ), and b is the

−1

constant related to the free energy of adsorption (L mg ).

The values of the intra-particle velocity constants kp1

and kp2 showed that the first stage due to the external mass

transfer is the fastest followed by the slowest intra-particule

diffusion stage confirmed by kp1 > kp2. Lipophilic ibuprofen

characterized by its high logkow of 3.97 than 1.47 of

phenobarbital was presented a highest initial velocity, that

can be explained by the good affinity of organic adsorbents

towards lipophilic adsorbates [29, 50, 51]. The adsorption of

both mixed pharmaceutical products supposed competing on

The graphs fitting C /q as a function of C is presented in

Figure 6. The Langmuir isotherm constants b, 1/b, q and

max

the correlation coefficients R are presented in Table 5.

The Langmuir isotherm model for the adsorption of

mixed ibuprofen and phenobarbital onto PAC (F400) fits

well the experimental data (Figure 6) based on the relatively

high values of correlation coefficient R 0.983 and 0.960 for

phenobarbital and ibuprofen, respectively (Table 5).

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

1

Table 4: Intra-particle diffusion parameters for the mixed ibuprofen and phenobarbital at an initial concentration of 8 mg L by PAC (F400) at a

concentration of 40 mg L^at 21 °C and pH=67

p1 (mg g^min^¹^/²

)

R²

p2 (mg g^¹min^¹^/²

)

R²

Phenobarbital

Ibuprofen

3.116

7.899

0.948

0.969

1.228

0.065

0.902

0.973

–

capacities towards ibuprofen arriving to 1000 mg g than

.035

.03

.025

.02

.015

.01

Phenobarbital

Ibuprofen

Linear (Phenobarbital)

Linear (Ibuprofen )

–1

phenobarbital with 333.3 mg g highlighting well the

y = 0.0036x + 0.0037

R² = 0.9837

competitive

adsorption

between

both

selected

pharmaceuticals. The b factor relates to the dissociation

constant of the adsorbate determined for the ibuprofen is

.25 L mg (b<1) showing the good affinity of PAC (F400)

–

towards ibuprofen compared to phenobarbital [60].

y = 0.0017x + 0.0074

R² = 0.9604

.2.2 Freundlich isotherm

Freundlich isotherm [55] presents an empirical model

for multilayer and heterogeneous adsorption sites. Its linear

form is commonly given by the Eq. (7):

.005

ln(푞 ) = ln푘 + 1/푛ln(퐶 )

(7)

푓

C (mg L^–¹)

where q

is the adsorbed amount of solute per unit weight of

Figure 6: Langmuir isotherm of adsorption of ibuprofen (λ= 220 nm)

mixed with phenobarbital (λ= 210 nm) by PAC (F400) at different

1

adsorbent (mg g ), C is the concentration of solute at

equilibrium in the bulk solution (mg L ), ^Kf is the

Freundlich constant indicative of the relative adsorption

capacity of the adsorbent (mg g ), and 1/n is the

heterogeneity factor.

1

–1

concentrations C(PAC) =20–280 mg L , at 21 °C in ultrapure water

1

at pH 67, (C (pharmaceutical) = 8 mg L )

1

These results were confirmed by Morley and co-werkers,

who indicated that Langmuir fits well their result of

adsorption of ibuprofen onto activated carbon F400 [57].

Carvalho and co-werkers have as well reported that

Langmuir model fits best their results of adsorption onto

activated carbons CAC and CPAC compared to Freundlish

model [35]. Papciak and co-workers were furthermore

reported that Langmuir fits well the results of adsorption of

ibuprofen onto Norit and Carbopol [32].

The Freundlich isotherms are presented in Figure 7 by

e e

fitting ln(q ) as a function of ln(C ) for the adsorption of

ibuprofen and phenobarbital at an initial concentration of 8

1

mg L by PAC (F400) at different concentrations. Straight

lines are obtained with origin lnK and slope 1/n. The

Freundlich isotherm parameters K , 1/n, n and the correlation

coefficients R are presented in Table 6. The values of the

coefficients of correlation (R ), 0.908 and 0.954 for the

Some works were indicated that Langmuir isotherm fits

very well the results of phenobarbital adsorption onto

activated carbons such us the adsorption onto activated

charcoal reported by El-Mabrouk and co-workers [58], and

onto activated carbons like SuperChar, Darco KB-B, Norit

B Supra, Norit USP XX by Wurster and co-woerkers [59].

Langmuir fits best the results of adsorption of phenobarbital

onto activated carbon Norit USP XX, Ch3J, and MI in which

adsorption of the mixed phenobarbital and ibuprofen,

respectively indicate that Freundlich isotherm model seems

good to adjust the obtained experimental results. Morley and

co-workers had reported that Freundlich model fits well their

results about adsorption of ibuprofen onto activated carbon

F400 [57]. Papciak and co-workers were furthermore

reported that Freundlich isotherm fits well the results of

adsorption of ibuprofen onto Norit and Carbopol [32]. The

application of the Freundlich isotherm model for the

adsorption of ibuprofen onto activated carbons F300 by

Ociepa–Kubicka and co-workers showed a best fitting of this

model [61].

presented a high R of 0.99, followed by Temkin and then

Freundlich models according to Gallardo and co-workers

[

41].

The calculated values of maximum adsorption capacities

max) show that the PAC (F400) exhibits better adsorption

(

Table 5: Langmuir isotherm parameters for adsorption of mixed ibuprofen and phenobarbital at initial concentration of 8 mg L^¹by PAC (F400)

at different concentrations at 21 °C and pH=67

R²

(mg g )

-1

b (L mg^–¹)

1/b (mg L^–¹)

Phenobarbital

Ibuprofen

0.983

0.960

333.33

1000

0.14

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

Table 6: Freundlich isotherm parameters for adsorption of ibuprofen and phenobarbital at initial concentration of 8 mg L^¹by PAC (F400) at

different concentrations, at 21 °C, and pH=67.

1/n

0.425

0.583

2.35

1.72

R²

0.908

0.954

.575 –1 0.425

g L

Phenobarbital

Ibuprofen

137.14 mg

123.10 mg

.417 –1 0.583

and phenobarbital have been presenting a values of

y = 0.5838x + 4.8132

R² = 0.9542

1

adsorption energy variation b

of 17.92 and 29.85 kJ mol ,

respectively, indicating a physical adsorption [46,62,63].

The positive values of the adsorption energy variation b

Table 7) indicate an endothermic adsorption process [64].

y = 0.4255x + 4.9215

R² = 0.9082

(

y = 136.41x + 98.297

R² = 0.924

Phenobarbital

250

y = 81.933x + 131.52

R² = 0.8615

Ibuprofen

0.5

1.5

2.5

^Lⁿ⁽^Ce⁾

Phenobarbital

Ibuprofen

Figure 7: Freundlich isotherm of adsorption of mixed ibuprofen (λ=

20 nm) and phenobarbital (λ= 210 nm) by PAC (F400) at different

–1

concentrations C(PAC) =20–280 mg L , at 21 °C in ultrapure water

1

at pH 67, (C (pharmaceutical) = 8 mg L )

0.5

1.5

2.5

Ln (C_e)

The calculated values of Freundlich constant (1/n) 0.425,

and 0.583 for phenobarbital and ibuprofen, respectively, are

less than 1, indicating that the adsorption of the selected

drugs is favorable. A high adsorbent capacities were

Figure 8: Temkin isotherm of adsorption of mixed ibuprofen (λ= 220

nm) and phenobarbital (λ= 210 nm), by PAC (F400) at different

–1

concentrations C(PAC) =20–280 mg L at 21 °C in ultrapure water



at pH 67, (C (pharmaceutical) = 8 mg L )

.507 –1 0.493

g L

indicated by the K values 137.14 mg

0.257

, 123.10

.743

–1

for phenobarbital and ibuprofen,

respectively.

4 Conclusion

The adsorption processes of tow pharmaceuticals,

ibuprofen and phenobarbital onto PAC were evaluated in

ultrapure water. The PAC F400 can effectively eliminate the

pharmaceutical pollutants from the water. logkow, pKa

values, and molecular weights were affected the adsorption

capacities of the trajet compounds onto PAC. Non-polar

ibuprofen had have a good adsorption capacity compared to

phenobarbital. Activated carbon had had a less affinity to

soluble organic compounds. Competitive adsorption

influenced negatively on the kinetics of the pharmaceuticals.

The kinetic of pseudo-second order appears more suitable

model to describe the competitive adsorption process. The

investigation results are best described by the Langmuir

model for both ibuprofen and phenobarbital, followed, in

decreasing order, by the Freundlich and Temkin models.

This study carried out on a synthetic water and for two

molecules, gave very promising results as for the possibility

of eliminating the residues of pharmaceutical products from

water. It would be interesting to continue this research by

studying the behavior of other pharmaceutical molecules and

especially to apply it in real waters (rejections of

manufacturing plant of drugs, drinking water…) to seek and

eliminate the residues of pharmaceutical products which can

harm human health.

.2.3 Temkin isotherm

The derivation of the Temkin isotherm model presumes

that the diminution of the adsorption heat is linear rather than

logarithmic, as applied in the Eq. (7) of Freundlich model.

The Temkin isotherm is mostly presented in its form given

by the Eq. (8) [56]:

푞 = (푅푇/푏 )log퐴 + (푅푇/푏 )log퐶

(8)

푒

ꢅ

푒

where: T is the temperature (°K); R is the universal gas

constant (8.314 J mol K ); b

heat of adsorption (J mol ), and A is the Temkin isothermal

constant (L g ).

1

is the constant relative to the

1

The application of the Eq. (8) of Temkin isotherm model

e e

is presented in Figure 8 by fitting q as a function of ln(C )

for the adsorption of ibuprofen and phenobarbital at an intial

concentration of 8 mg L by PAC (F400) at different

concentration. The adsorption isotherms derived from the

experimental data for each of the tested adsorbate and

adsorbent are presented in Table 7. According to the

1

correlation coefficient values R of 0.861 and 0.924 for

ibuprofen and phenobarbital, respectively, the Temkin

isotherm model for the adsorption of selected

pharmaceuticals by PAC (F400) do not fit well the

experimental data (Figure 8). The adsorption of ibuprofen

Journal of Environmental Treatment Techniques

2020, Volume 8, Issue 1, Pages: 336-345

Table 7: Temkin isotherm parameters for adsorption of mixed ibuprofen and phenobarbital at an initial concentration of 8 mg L^by PAC (F400)

at different concentrations at 21 °C and pH=67.



1

R²

(kJ mol )

A (L g )

Phenobarbital

Ibuprofen

29.85

17.92

4.98

2.06

0.924

0.861

challenges. Journal of Environmental Management.

Acknowledgements

009;90:2354–2366

The authors would like to acknowledge the Laboratory

of Environmental Sciences and Technology (LSTE) of the

National Polytechnic School (ENP) for the support during

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