F. Aouaini, M. Ben Yahia and M. M. Alanazi
Journal of Molecular Liquids 340 (2021) 117108
Fig. 2a shows that the synthesis of H2TPP is performed via the
reaction between propanoic acid (2L) and benzaldehyde (40 mL).
Fig. 2b illustrates that H2TTPP is synthesized through the introduc-
tion of the 4-tolualdehyde (12.5 g) with the propanoic acid
(110 mL). It is to be noted that the synthesis of these two adsor-
bents are done through the application of the same procedure
based on the following steps: reflux for 30 min, then, allowing to
cool, after that, filtration and finally, drying under-vacuum for
3 h. The mass of the dried solid of H2TPP is equal to 9.76 g and
the one of the obtained solid H2TTPP is equal to 3 g. When dis-
solved in chloroform, the solid compounds of porphyrins result
Fig. 1. Chemical structure of the metalloporphyrins complexes.
hyperbilirubinemia- treatment [11]. The cooper-porphyrin com-
plexes started to be seen as a new synergic option as far as the
PET molecular imaging-applications are concerned [12]. They have
been used as well in medical chemistry as in the photodynamic-
therapy [13].
Although many papers have aimed at surveying metallopor-
phyrins complexes like the metal centers zinc, rhodium, and cobalt
[14,15], the porphyrins’ use as complexing compounds of copper
(II) and tin(II) (Fig. 1) has not gained the same importance inspite
of their contribution to the above-mentioned fields. In fact, this
paper presents the two metals’ adsorption done on two tested por-
phyrins (H2TPP and H2TTPP).
in two solutions having a concentration equal to 2.9 10ꢀ2 mol.Lꢀ1
.
2.2. Adsorption-measurements
Fig. 3 illustrates the QCM-setup.
The piezoelectric-quartz crystal is the main focusing point in
the QCM measurements [28,29]. A crystal is a tiny disc cleft from
the polished-quartz (AT-cut). The principal quartz- resonant-
frequency is 5 MHz and the disc diameter is 2.54 cm [29]. First,
the crystals are cleansed using a Piranha-solution at room-
temperature, then they are rinsed using ethanol finally, the crystals
are dried with high purity-nitrogen.
Many approaches have been used in order to investigate the
metals- adsorption mechanism as the heavy metal ions- sorp-
tion/reduction in environmental pollution-management [16,17].
Different experimental-methods have been used to investigate
the adsorption-mechanism [18–20]. In this paper, the QCM tech-
nique explores both the cooper chloride and cooper chloride
adsorption- mechanisms for several reasons. First, this method is
a simple-mass-detector technique which necessitates the por-
phyrins’ immobilization done on quartz-crystal- support. The
microbalance apparatus ensures the control of the complexed -
metal mass contained in the macromolecules cavities. Second,
the metal-porphyrin complexes do not need a motionless environ-
ment as they are steady in water. Third, QCM technique plots the
adsorption curves describing the metallic ions’ complexed amount
on porphyrins at different temperatures. Finally, the microscopic
properties of the resulting adsorbed-film can be pursued by simple
fitting of-isotherms curves as far as the analytical models are con-
cerned [21].
Many authors selected the physical models in order to inspect
the adsorption phenomenon. The empirical Langmuir and Fre-
undlich models’ expressions [22,23] have been used to depict the
isotherms curves but they did not result in substantial
physicochemical- adsorption process inquiry. The inventive statis-
tical physics theory of the current paper leads to establish analyt-
ical adsorption models which elaborate a new perception of the
metalloporphyrin description [24,25]. The fundamental purpose
of isotherms- modeling work is to search for the satisfactory
systematic-model which will foresee the physical insights of the
porphyrins’ adsorption-based on the physicochemical parameters
of the statistical physics-models [26].
As far the adsorption-measurement is concerned, 60 lL of the
adsorbents (porphyrins H2TPP and H2TTPP) are added to the clean
crystal-surface following the spin-coating-technique at 3500 rpm
for 30 s. The crystals in question are dried at 393 K during 2 h.
A Teflon probe, wrapped in a vigilant ring, englobes the crystal
or the adsorption cell, which is submerged in Vs = 100 mL of pure-
water in a bain-marie. The resonant frequency- stabilization in the
reactor lasts about 1 h, after that, the crystal-frequency F0 is being
considered. Then, volumes of stock-solutions of adsorbates(CuCl2/
SnCl2) are injected in the reactor. The next equation leads to deter-
mine the added volumes of adsorbates Vad
:
cf ꢁ Vs
Vad
¼
ð1Þ
c0
where, Vs is the initial-volume in the reactor, c0 is the concentration
of the prepared adsorbate-solution and cf is the final-concentration
in the reactor.
A micropipette is used to add 15 injections in the reactor. The
resonant frequency-variation which corresponds-to the new
adsorbate-concentration in the reactor is calculated as:
D
f ¼ Fi ꢀ F0
ð2Þ
with, Fi is the resonant-frequency after injection and F0 is the quartz
crystal hydrostatic pressure-effect. Referring back to the equation, it
is to be noted that the frequency-variation
Df is the result of the
metal-mass variation m on the porphyrins surface and it does
D
not take into account any consequence from the crystal on the
adsorption since the hydrostatic pressure- effect on the quartz (fre-
quency F0) is not taken into consideration in the measured
frequency-variation
Df.
2.3. The equation of Sauerbrey
2. Experiments
After each injection, metallic ions’ mass collected to the surface
is calculated in the light of Sauerbrey’s hypothesis associating the
mass-variation to the frequency-change [30–32]:
2.1. Materials
In this paper, the copper(II) chloride (CuCl2) and the tin(II) chlo-
ride (SnCl2) are considered as the tested adsorbates. For these
experiments, the used porphyrins, synthesized based on the
Adler-Longo strategy, are the tetrakis(4-tolylphenyl)porphyrin(H2-
TTPP) as well as the tetraphenylporphyrin (H2TPP) [27].
The synthesis methods of the two porphyrins H2TPP and H2-
TTPP are illustrated in Fig. 2.
D
f ¼ ꢀC ꢁ
D
m
ð3Þ
where C is the crystal sensitivity-factor (Hz.cm2.
l
gꢀ1). In this con-
text, it is noted that the relation should be only practiced if the
resonant-frequency-variation is basically the origin of the mass-
change on the adsorption-surface.
2
Aouaini, Fatma
