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Editorial

Manne Anupam Kumar

Vedagiri Lakshminarayanan

Sai Sathish Ramamurthy

Platinum nanoparticles–decorated graphene-modified glassy carbon electrode toward the electrochemical determination of ascorbic acid, dopamine, and paracetamol

Siti Kholijah Abdul Mudalip

Fatmawati Adam

Mohd Rushdi Abu Bakar

Evaluation of the intermolecular interactions and polymorphism of mefenamic acid crystals in N,N-dimethyl formamide solution: A molecular dynamics simulation and experimental study

Thouraya Barhoumi

Imene Bekri-Abbes

Ezzeddine Srasra

lable at ScienceDirect
C. R. Chimie 22 (2019) 126e131Contents lists avaiComptes Rendus Chimie
www.sciencedirect.comFull paper/MemoirePhysicochemical characteristics and suitability of curative
pastes made of Tunisian clay minerals and thermal waters for
use in pelotherapy
Thouraya Barhoumi a, b, *, Imene Bekri-Abbes a, Ezzeddine Srasra a
a Laboratory of Composite Materials and Clay Minerals, National Center of Materials Research, Borj Cedria Technopole, Tunis, Tunisia
b Faculty of Sciences of Tunis, University of Tunis El Manar, Tunis, Tunisiaa r t i c l e i n f o
Article history:
Received 18 May 2018
Accepted 13 November 2018
Available online 15 December 2018
Keywords:
Pelotherapy
Clay
Thermal water
Peloids
Plasticity* Corresponding author. Laborotory of Composit
Minerals, National Center of Materials Research, Bo
Tunis, Tunisia.
E-mail address: thourayabarhoumi186@gmail.co
https://doi.org/10.1016/j.crci.2018.11.006
1631-0748/© 2018 Académie des sciences. Publishea b s t r a c t
This study presents the physicochemical characteristics of peloids prepared from two
Tunisian clays, CZ (clay from the region of Zaghouan) and CS (from the region of Siliana),
and two thermal mineral waters. The samples were analyzed by several physicochemical
techniques: X-ray diffraction, chemical composition (major and minor elements), grain-
size distribution, cation-exchange capacity, plasticity index, and thermal properties
(cooling kinetic). The results prove that the two clays are suitable for use in Tunisian spa
with differences in their characteristics, especially with regard to their composition,
plasticity, grain size distribution, and thermal properties.
© 2018 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.1. Introduction
Peloids or thermal muds are hot cataplasm formed
essentially by clay minerals (bentonite, kaolinite, illite
associatedwith carbonate, quartz, and otherminerals) with
seawater, thermal water, or medicinal water. Pelotherapy is
the local or generalized application of thermal muds for
recovering rheumatism, arthritis, and boneemuscle trau-
matic damages. It is considered as one of the popular
procedures, used in wellness and rehabilitation centers.
The history of balneotherapy dates way back to the ancient
times. The use of thermal andmedicinal waters and peloids
for health and cosmetic face care is a Tunisian traditional
activity, which is practiced in traditional “Hammam” (a
collective bath) and in Tunisian spa resorts. The medicinale Materials and Clay
rj Cedria Technopole,
m (T. Barhoumi).
d by Elsevier Masson SAS. Awater has multiple virtues and it is recognized that Tunisia
has exceptional thermal springs.
During the past few years a number of scientific studies
on the thermophysical properties of peloids have been
carried out all over the word (Greece, Italy, France, Spain,
etc.) [1e3], However, in Tunisia, although the number of
spas, clay deposit, and thermal water are widely spread all
over the country, the number of studies and scientific ar-
ticles dealing with pelotherapy are limited in number [4,5].
Jamoussi and co-workers have been interested in the
suitability of some Tunisian clay to be used as semisolid
health care paste and cosmetic products. Very recently,
heavy metals' mobility during maturation of silty-clay
peloid has been carried out [6] Therefore, more character-
izations and investigations are needed.
In this article, we present an experimental investigation
of the mineralogical and thermal characterization of
peloids prepared from two Tunisian clays and medicinal
waters.ll rights reserved.
T. Barhoumi et al. / C. R. Chimie 22 (2019) 126e131 1272. Materials and methods
2.1. Materials
Two clay samples were used in this work. They were
collected from Tunisian formations: Sample CZ was
collected from Zaghouan, one of the richest areas in the
country for this type of clays, and CS clay was from Siliana.
The samples were wet sieved (<63 mm) and dried at 80 C
for 24 h. The thermal waters were collected from two
sources designated as A (Ain Atrous in Korbos region) and B
(Ain El Eryan in Megrine region).
2.2. Preparation of peloids
The peloid was prepared by dispersing 45 g of CS or CZ
dried powder in 75 g of water A or B and mixing them at
10,000 rpm for 120 min. The mixtures were left for 7 days
for maturation. Four peloid samples were obtained: CZþ A,
CZ þ B, CS þ A, and CS þ B.
2.3. Characterization
2.3.1. Mineralogy and geochemistry
Mineralogical analyses of the samples were carried out
by X-ray diffraction using PAN analytical powder diffrac-
tometer with Cu Ka radiation at 40 kV and 40 mA. All
samples were scanned in the 2q range of 3e70.
The chemical composition for major, minor, and trace el-
ements of the<63-mmsieved sampleswas determinedusing
a ParkinElmer optima inductived coupled plasma apparatus
after digestion with a mixture of HCl þ H2SO4 þ HNO3.
2.3.2. Granulometry
The granulometric distribution of samples was
measured by means of a Laser granulometer Microtrac
S3500.Table 1
Mineralogical composition of the studied clays (in %).
Samples Smectite Kaolinite Calcite Quartz Dolomite
CS 33 20 33 11 4
CZ 41 39 14 6 e
Fig. 1. X-ray diffraction patterns of the samples. I ¼ illite, Sm ¼ sm2.3.3. Cation-exchange capacity
Cation-exchange capacity of clays was determined using
Tucker's method [7].
2.3.4. Specific heat
The specific heat has been determined for each clay in
dry powder form using a differential scanning calorimetry
(Shimadzu) using a mass 10 mg of clay minerals with a
heating rate of 10 C/min.
2.3.5. Determination of cooling rate curves
The paste was introduced in a closed 50 mL cylindrical
Teflon container and was heated at temperature constancy
(70 C), and then it was introduced in a thermostatic bath at
35 C. The temperature of the paste was measured every
60 s until the temperature of the clay paste and the ther-
mostatic bath attain equilibrium [8,9].
2.3.6. Plasticity index
The Atterberg limits (WL, liquid limit; WP, plastic limit;
PI, plasticity index) were determined following the norm
NP 143-1969 using a standard Casagrande cup.
3. Results and discussion
3.1. Physicochemical characteristic of clays
3.1.1. Mineralogy and geochemistry
The mineralogical composition of the two samples is
shown in Table 1 and Fig. 1. CZ sample is rich in calcite and
presents a very limited quantity of quartz. On the other
hand, CS sample showed high amounts of calcite (33%),
quartz, and a small amount of dolomite. Concerning clay
fraction, CZ presents a higher amount of clay minerals,
which is composed of 41% of smectite and 39% kaolinite.
For CS clay, the proportion of clay fraction is about 53%,
which is composed of 33% and 20% kaolinite. The two clays
present a high quantity of kaolinite (between 20% and
39%).
3.1.2. Major and trace element composition
In the field of pelotherapy, the application of clays is
directly related to their chemical and mineralogical
composition.ectite, Kln ¼ kaolinite, Q ¼ quartz, C ¼ calcite, D ¼ dolomite.
T. Barhoumi et al. / C. R. Chimie 22 (2019) 126e131128The chemical analysis values for the two samples are
represented in Table 2 and show that for both clays SiO2,
Al2O3, Fe2O3, MgO, and CaOwere the elements constituting
the major composition. The Si concentration was found in
the two clays with the same quantity. According to Carre-
tero and Pozo [10], high amounts of Si mean that the clay
could be used in skin tissue reconstruction. Al is the second
element found in highest amounts in the samples. On theTable 2
Chemical composition and trace element content in the studied clays with
safety concerns according to European and USA pharmacopoeias.
Samples CZ CS Acceptable limit (ppm)
Major element (%)
SiO2 40.65 44.02
Al2O3 1.93 10.57
Fe2O3 6.91 6.46
CaO 12.14 1.29
MgO 2.05 1.83
Na2O 0.26 0.18
K2O 1.45 1.16
SO3 1.46 1.64
LIO (loss in ignition) 1.73 2.21
Trace element (ppm)
As 1.1 3 <8
Cd 9.2 8 e
Pb 0.3 1 <50
Cr 19 20 1100
Cu 5.8 4 130
Mn 161.5 120.1 e
Ni 9.1 5.6 60
V 71.6 6.5 e
Ba 76 74 1300
Sr 224.4 183.9 e
Zn 109.3 94 200
Table 3
Geotechnical parameters of clays.
Parameter (%) CZ CS
Cation-exchange capacity (mmol/100 g) 40 37
Liquid limit 59 65
Plastic limit 27 28
Plastic index 32 37
Granulometry
Sand (2 mme63 mm) (%) 1.3 6.1
Silt (63e2 mm) (%) 88.7 84
Clay (<2 mm) (%) 10 9.9
Fig. 2. Distribution of particle size and cumulative weigother hand, the identified trace element concentrations
presented in Table 2 show no significant differences be-
tween studied samples. Clay selection for peloid applica-
tions must be safe. For that reason, Cd, Pb, and As should be
essentially absent, as they are known to be toxic to humans
and environmentally hazardous. Mo, Ni, V, Cr, and Cu have
been reported to have less toxicity effects than Cd, Pb, and
As, but should be limited in pharmaceutical formulations.
Tl and Te have also been classified as unwanted for
cosmetic products, including clays and for pelotherapy. In
addition, Ba, Se, Zn, and Sbwere considered as impurities in
cosmetic products. Both samples CS and CZ exhibit
acceptable trace element concentrations for official regu-
lations because the measured concentrations of trace
metals were found to be in the range of other healingmuds.
3.1.3. Grain size analysis
The two samples were characterized by very low per-
centage of sand fraction (better than 1.6%, Table 3 and
Fig. 2), thus the composition is being extremely preferable
for use as medicinal paste [11,12]. On the other hand, the
particle size of CZ presents a bimodal distributionwith two
maxima at 11 and 5 mm and the particle size distribution of
CS is very narrow, with a maximum around 10 mm. With
regard to the clay fraction, CZ showed the highest per-
centage of particles inferior to 2 mm and CS having the
lowest, and the two clays showed a wide range of particle
sizes.
3.1.4. Cation-exchange capacity
The two studied clays showed a greatest cation-
exchange capacity (40 mequiv/100 g for CZ and
37 mequiv/100 g for CS) (Table 3). These values agree with
the mineralogy composed essentially of smectitic clay.
3.1.5. Plasticity index
The PIs of the samples are between 32 and 37 (Fig. 3 and
Table 3). CS sample has a higher value of PI than CZ sample.
This is mainly due to the higher value of the liquid limit
(Table 3). Both studied samples were grouped in high
plasticity clays because liquid limit is50% [13]. The plastic
limit WP of the samples was 27% and 28%. Referring to
Jenkins classification [14], the samples were considered
with high plasticity because their PI is 15%.ht percentage (green curves) of the studied clays.
Fig. 3. Casagrade's chart [12] for the evaluation of the plasticity of the
samples.
T. Barhoumi et al. / C. R. Chimie 22 (2019) 126e131 1293.2. Thermal behaviors of peloids
3.2.1. Presentation and classification of thermal waters
The chemical composition and some physical properties
of the two mineral waters are presented in Tables 4 and 5,Table 4
Chemical composition of the two minerals waters.
A (Ain Atrous water) B (Ain El Aryan)
Cl (ppm) 4970.00 7923.00
SO42 (ppm) 2110.13 1116.00
HCO3 (ppm) 597.00 536.80
Ca2þ (ppm) 89.70 124.02
Mg2þ (ppm) 240.76 162.94
Kþ (ppm) 89.70 124.02
Naþ (ppm) 2953.20 3776.60
F (ppm) 3.20 2.70
CO32 (ppm) 106 133.4
Table 5
Physical properties of the two minerals waters.
A B
pH 6.7 6.6
Solid residue (110 C) (mg$L1) 1230 1570
Conductivity (mS/cm) 15.8 19.7
Fig. 4. Tickel's diagram of mineralemedicinal waters: (a) Ain Atrous (respectively. On the basis of their fixed residues, water B
could be classified as rich mineral content water because
solid residue was better than 1500 mg/L and A as medium
mineral content water (500e1500 mg/L). The two waters
are slightly acid and hard [15].
On the basis of the chemical composition, thermal water
takes its name from the element or group of elements from
which it is composed. Although determining what kind of
ionic composition there is in thewater, first we have to take
account of the prevalent anion (or anions) and then of the
cation. When an ion is >20 mequiv/L, this gives the water
its name. According to prevalent ionic composition, min-
eral waters are classified as bicarbonate waters/salt waters
or with sodium chloride/sulfurous waters, arsenical ferru-
ginous waters/sulfated waters Thus, referring to Tickel's
classification [16] (Fig. 4), both waters A and B could be
classified as sodium chloride-rich sulfated waters; howev-
er, water A contains more sulfate and bicarbonate. In
addition both waters are not calcic. The presence of chlo-
ride and sulfate confers to the anti-inflammatory activity of
these waters [15].
3.2.2. Specific heat
The thermal characteristic of clay mineraleforming
peloids is related to their specific heat and cooling ki-
netics. The average of specific heat of the two clays in dry
powder form has been determined using differential
scanning calorimetry curves of the two samples for tem-
perature ranging from 35 to 45 C, they were between
868 J/kg$K for CS to 1044 J/kg$K for CZ clay. These values
are in accordance with that reported for montmorillonite
clay in the literature (Table 6).
The variance of specific heat between the two clays can
be explained by the difference in clay fraction between the
two samples (80% for CZ as compared to 53% for CS) as
shown in the literature, the specific heat capacity increases
with increase in clay content [17]. On the other hand, these
values are in accordancewith that reported in the literature
for specific heat capacity of powder clays determined by
differential scanning calorimetry measurement [18]. It was
established that specific heat of clay in dry powder form
decreases in the following order: the Cp of sepiolite is su-
perior to that of montmorillonite and to that of illite and
kaolinite [18].region of Korbos) and (b) Ain El Eryan (region of Megrine) [16].
Table 6
A list of some Cp values of some clays cited in the literature.
Cp (J/kg$K) Temperature
(C)
Clay References
1720e4630 44e64 Sepiolites [17]
440e660 Caemontmorillonite
1510e1990 NaeCa montmorillonite
895e900 36e45 Na-activated magnesium
bentonite
[18]
873e892 Mg-bentonite and
sepiolite
751e776 Palygorskite
1245e1264 Sepiolite
1044 35e45 33% Smectite and 20%
kaolinite
Our study
868 41% Smectite and 39%
kaolinite
T. Barhoumi et al. / C. R. Chimie 22 (2019) 126e131130For peloids that represent a mixture of clay and water,
the specific heat capacity of the system is given, in a first
approximation, by the sum of those of their components
according to the general Eq. (1) [19]:
Cppeloid ¼

C% Cpclay powder þW% Cpwater

100 (1)
where C% represents the percentage of solid fraction, W%
is the percentage of water in the peloid given by Eq. (2)
and considered corresponding to 4180 J/kg$K.
W% ¼ 100 C% (2)
The calculated Cp values of the paste are, respectively,
2110 and 1696.5 J/kg$K for CS and CZ clay and they are inFig. 5. Kinetic cooling curves of CZ and CSaccordance with that of peloids suitable for use in pelo-
therapy [19].
3.2.3. Cooling kinetics of the peloids
The cooling kinetic is defined as the capacity of paste to
slowly release heat to the body. Heat loss from the peloid to
the body is defined by the Newton law and is represented
by the following Eq. (3):
dT=dt ¼ kðT  T0Þ (3)
where T is the temperature at instant t, T0 is the tempera-
ture of the cold surroundings, and k is a constant that de-
fines the rate of cooling. The mathematical solution to this
equation is defined by Eq. (4):
TðtÞ ¼ T0 þ A ekt (4)
where k is equal to 1/tr, and tr is the relaxation time.
It can be seen that different samples presented
acceptable cooling kinetic. The t37 parameter is defined as
time required for the paste to cool from 45 to 37 C. These
parameters for different pastes prepared with the two
clays and mineral waters have been calculated from ki-
netic cooling rate curves and are represented in Fig. 5. It
could be seen that peloid prepared in water A, which
contains less solid residues and cations, presents the
slowest cooling kinetic. This trend could be explained by
the fact that specific heat (Cp) of pure water is
4.18 J$K1$g1 and decreased with salinity and its content
in cations [20].clays prepared with waters A and B.
T. Barhoumi et al. / C. R. Chimie 22 (2019) 126e131 1314. Conclusion
The main objective of this study was the characteriza-
tion of the physicochemical characteristics of two Tunisian
clays and thermal waters for potential use as curative
pastes. They were characterized in terms of mineralogy,
granulometry, plasticity, adsorptive property, heat capacity,
and cooling behavior. The two samples are suitable for
application as curative pastes for the reasons below.
1. The two samples contain smectite and kaolinite as major
clay fractions and calcite and calcite þ dolomite þ quartz
as associate minerals; however, CZ contains more clay
fraction with a proportion of 80%. These compositions
explain the high cation-exchange capacity and plasticity,
which are suitable for curative application. On the other
hand, the two samples are characterized by their very low
percentage of sand fraction (>1.6%). These compositions
are preferable for this application.
2. The chemical analysis values for the two samples proves
that Si is the principal major element and that both
samples CS and CZ exhibit acceptable trace element
concentrations for official regulations because the
measured concentrations of trace metals were found to
be in the range of other healing muds.
3. Concerning their thermal characteristics, it was shown
that pastes prepared with thermal water containing less
solid residues and cations present preferable thermal
capacity.Acknowledgments
This work was supported by the Tunisian Ministry of
Higher Education and Scientific Research of Tunisia.References
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