Analytical Methods in Environmental Chemistry Journal Vol 1(2018) 29-38
Research Article, Issue 1
Analytical Methods in Environmental Chemistry Journal
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Investigation of Adsorption of Cobalt-phthalocyanine from
Aqueous Waste Stream Using UVM-7/Ag
Amir Vahida*, Majid Abdousb, and Shahnaz Nayyerib
a Research institute of petroleum industry, Tehran, Iran.
b Faculty of chemistry, Amirkabir University of Technology, Tehran, Iran.
A R T I C L E I N F O:
Received 21 Aug 2018
The effect
tetrasulfonicacid tetrasodium salt
[Co(tsPc)-4•4Na+] onto UVM-7/Ag
Revised form 12 Nov 2018
mesoporous material was investigated. In addition, X-ray diffraction
Accepted 19 Nov 2018
(XRD), scanning electron microscopy (SEM), and nitrogen adsorption-
Available online 30 Dec 2018
desorption measurement were used to examine the morphology and the
microstructure of the obtained composite. Various parameters including
solution adsorbent dosage, contact time, initial dye concentration and
temperature were systematically studied. Equilibrium data fitted well
the Langmuir models; moreover, the fitness suggests that the adsorption
be monolayer and physical in nature. Kinetic studies showed that the
adsorption process could be better described by the Lagergren pseudo-
second-order models. Thermodynamic constant values (∆G < 0, ∆H<
0 and ∆S< 0) demonstrated that the adsorption reactions of Co(tspc)-4
onto UVM-7/Ag were feasible, spontaneous, and exothermic under the
examined conditions.
Mesoporous silica
1. Introduction
at the center [5, 6].
Mercaptan and sulfur compounds present in the
One of the most important applications of MPCS has
crude oil and petroleum cuts cause corrosion of
been in catalysis, including large-scale industrial
pipes and different environmental pollutions[1].
processes. For instance, the Merox process,
There are various methods to remove mercaptan
referred to as
“sweetening” in the petroleum
but the major one is the catalytic oxidation in the
refining industry, involves catalytic oxidation of
presence of caustic solution and air. phthalocyanine
mercaptans in the presence of sulfonated cobalt
are effective catalysts for thiol and hydrosulfide
phthalocyanines to remove a major part of sulfur
oxidation by dioxygen[2-4]. Metal phthalocyanines
from petrol [7]. The catalytic properties of MPCS
(MPCS) are two dimensional (2D) organic macro
depend on the metal and complex structure and can
cyclic molecular catalysts (MN4) with metal atoms
be tuned by appropriate structural modifications
[8, 9]. This is the basis of the redox mechanism of
* Corresponding Author Email:
catalytic oxidation of sulfur-containing compound.
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
Fig. 1. Schematic representation of Merox unit.
These catalysts have found wide application in the
as shown if Figure 2, makes this derivative easily
catalytic oxidation of mercaptans in oil fraction as
soluble in aqueous solution. sulfonated metal
shown if Figure 1 [10].
phthalocyanine (MSPC) complexes, highly water-
In many systems using transition metal compounds
soluble molecule and very well recognized for its
as catalysts, the mechanism suggested by Wallace
unique physicochemical properties and wide range
et al.[11] is:
of applications ranging from catalysis to sensing
and photocatalysis .
RSH + NaOH → RS- + H2O
The Merox catalyst is a heterogeneous blue powder
RS- + CO+3 → CO+2 + RS
dissolved in water.
Merox catalyst of caustic solution creates problems
O 2_2 + H2O → 2OH- + 1/2 O2
that in this work, co (II) tetra sulfophthalo cyanine
CoPC has a low solubility in water , the substitution of
Co(TSPc)-4 catalyst removal from caustic solutions
CoPc with hydrophilic sulfonic groups [Co(tsPc)-4]
by using meso porous silica UVM-7 is studied.
Functionalized with Ag and
, γ-Alumina was
prepared by sol-gel method and the synthesized
nanoparticle was characterized by scanning
electron microscopy (SEM) and X-ray diffraction
Mesoporous materials can have large adsorption
capacity, excellent selectivity and improved powder
recoverability for removal of toxic compounds
from aqueous solutions[12,
13]. The effects of
adsorbent dosage, initial Co(tspc)-4 concentration
and contact time were studied. The adsorption was
fit to different adsorption isotherms and also to
kinetics of the adsorption was studied. Parameters
Fig. 2. Structure of the Co (II) tetra sulfophthalocyanine
affecting the removal of Co(tspc)-4 from the
-4.4Na+[ organometal.
aqueous solution was investigated and validated by
Adsorption of cobalt-phthalocyanine by UVM-7/Ag; Amir Vahid, et al
using three factorial Box- Behnken Design (BBD).
2. Experimental
2.1. Synthesis and characterization
The general procedure for the synthesis of UVM-
7 is the atrane route, in which the presence of the
polyalcohol is the key to balancing the hydrolysis
and condensation reaction rates [18]. In a typical
synthesis, TEOS was added to determined
amounts of TEAH3
(tri ethanolamine). The
solution was heated up to 140ºC under vigorous
stirring. After cooling down to 90ºC, CTAB (cetyl
Fig. 3. TEM image of UVM-7/Ag.
trimethylammonium bromide) was added to this
solution. After that, water was added slowly to this
which reached to
601 m2g-1 after doping with
solution under stirring until a white suspension
silver. These are direct and indirect evidences of
resulted. This suspension was aged for 4 hours at
formation of ordered UVM-7 which contains silver
room temperature. The solid was filtered, washed
with sufficient amounts of water and acetone
XRD pattern of the as-synthesized and calcined
and dried in an oven at 80ºC overnight. Thermo
UVM-7 are illustrated in Figure 4. As can be
calcination of the as synthesized UVM-7 was
seen, a sharp peak at low angle about 1.5×2theta
carried out under a flow of air up to 550ºC for 6
is characteristic of mesoporous materials. In case
hours with a heating rate of 1 C/min to remove both
of calcined UVM-7 higher order diffraction, i.e.
the surfactant and TEAH3 from the as-synthesized
d110 and d200 are sign of better structural order
UVM-7. The final molar composition of the
which is usually seen in mesoporous materials
reactants was 1.0 TEOS : 3.5 TEAH3 : 0.25 CTAB:
after thermocalcination and condensation of silanol
90 H2O.
2.2. Modification of UVM-7
3.2. Adsorption studies
For the modification of UVM-7 with Ag, 1 gram of
Adsorption behavior was studied by a batch method,
calcined UVM-7 is mixed with 100 mL of distilled
which parameters that influence the adsorption
water contains 0.1 gram of AgNO3 and stirred for 24
process such as contact time, initial concentration,
hours. The water was distilled using and automatic
adsorbent dose, surfactant template, and reaction
evaporator and calcined at 450 ºC for 5 hours.
temperature was investigated. In addition, aqueous
solutions of Co(tsPc)-4 which its chemical structure
3. Results and Discussion
is shown in Figure 1; moreover, with concentration
3.1. Characterization UVM-7/Ag
ranging from 100 to 500 mg L1-were prepared by
TEM image of UVM-7/Ag is displayed in Figure
dissolving Co(tsPc)-4 in double distilled water. In
3. Mesochannels of the UVM-7 is obviously
each adsorption experiment, 10 mg adsorbent was
visible in this image. Furthermore, dark points in
added in 10 mL Co(tsPc)-4 solutions. to study the
the image related to the higher contrast of heavy
effect of temperature the adsorption was carried
silver atoms with incident electron beam. BET
out at four different temperatures (27, 35, 40 and
surface area of the calcined UVM/7 was 838 m2g-1
50 0C) and for contact time studies the samples
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
Fugire 4. XRD pattern of as-synthesized and calcined UVM-7.
were taken at predetermined time intervals (10, 20,
determined according to the following equation:
30, 40, 60, 80 and 100 min). After equilibrium,
the concentration of the adsorbate in the residual
solution was analyzed by a UV-spectrophotometer
at λ max of 661 nm. The amount of Co(tsPc)-4
adsorbed per unit mass of UVM-7/Ag the qe (mg
3.2.1. Effect of adsorbent dosage
g-1) was calculated by the following equation:
The effect of adsorbent dosage (m) on the amount
of Co(tsPc)-4 adsorbed at equilibrium
(qe, mg
g-1), was investigated by adding different weights
of adsorbent UVM-7/Ag into 10 ml of solution
where qe is the adsorption capacity (mg g-1) of the
500 mg l-1 Co(tsPc)-4 and shaking the mixture
adsorbent at equilibrium; C0 and Ce are the initial
for 60 min at ambient temperature. It is evident
and equilibrium concentrations of solute (mg L-1)
from figure 5، qe increases by increasing m, can
respectively. Also, V is the volume of the aqueous
be attributed to the availability of greater surface
solution (L). and W is the mass (g) of adsorbent
area and more adsorption sites. that adsorption
used in the experiments.
capacity of Co(tspc)-4 increased when UVM-7/Ag
The adsorptive removal efficiency
(R) was
dosage varied from 2 mg to 10 mg. However, the
Figure 5. .Effect of adsorbent dosage on the adsorption of Co(tsPc)-4 by UVM-7/Ag.
Adsorption of cobalt-phthalocyanine by UVM-7/Ag; Amir Vahid, et al
adsorption capacity slowly as the adsorbent dosage
adsorption is
60 min. The adsorption rate was
increased from 10 mg to 15 mg. Thus 10 mg was
related to the content of the active adsorption sites
chosen as the optimal UVM-7/Ag dosage in this
on the matrix of the adsorbent[15].
3.2.3. Effect of temperature
3.2.2. Effect of contact time
The effect of temperature on the adsorption of
It is visible from Figure 6, that the amount of the
Co(tsPc)-4 onto UVM-7/Ag was investigated by
adsorbed Co(tsPc)-4 increases with time and then
adding 10 mg of the adsorbent into 10 mL of solution
reaches a constant value. At this point, the amount
500mg L-1 Co(tsPc)-4 and shaking the mixture for
of Co(tsPc)-4 desorbing from the adsorbent is in a
60 min at different temperatures of 27, 35, 40 and
state of dynamic equilibrium with the amount of
50 C in a water bath. The results indicated that the
Co(tsPc)-4 being adsorbed onto the mesoporous.
equilibrium adsorption amount (qe) decreases with
The time required to attain this state of equilibrium
increasing temperature (Figure 7), indicating that
is termed equilibrium time. estimate equilibration
the adsorption process is exothermic in nature[16].
time for Calculation maximum adsorption
In order to understand the effect of temperature on
Capacity and to know the kinetics of the adsorption
the adsorption process, thermodynamic parameters
It is seen that the rate of uptake is rapid.Required
should be determined at various temperatures. For
at the beginning, and time required for equilibrium
this reason, three basic thermodynamic parameters
Fig. 6. .Effect of contact time on the adsorption of Co(tsPc)-4 by UVM-7/Ag
Fig. 7 .Effect temperature on the adsorption of Co(tsPc)-4 by UVM-7/Ag
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
were studied: the Gibbs free energy of adsorption
Therefore the optimal reaction temperature was
(∆G), the enthalpy change (∆H), and the entropy
300 K.
change (∆S).The Gibbs free energy change of the
adsorption process is related to the equilibrium
3.2.4. Effect of initial dye concentration
(Kc). The thermodynamic parameters
The effect of initial Co(tsPc)-4 concentration on
∆G, ∆S and ∆H for this adsorption process were
adsorption behaviors was investigated in Figure
calculated from the following equations:
8. It can be seen that the majority of Co(tsPc)-4
was removed by UVM-7/Ag in lower initial
∆G = - RT ln KC
where R is the gas constant (8.314 J mol-1 K-1), T is
Co(tsPc)-4 concentration, the Co(tsPc)-4 removal
the absolute temperature. Kc values were estimated as
efficiency decreased with increase
Co(tsPc)-4 concentration. also This effect can has
Kc = Ca /
been attributed to the ratio of surface active site to
where Ca is the equilibrium concentration of
the total Co(tsPc)-4 ions in the solution .while The
Co(tsPc)-4 on adsorbent
(mg L-1), Cb is the
result reveals that the amount of capacity adsorbed
equilibrium concentration of Co(tsPc)-4 in the
(qe) increases as the concentration increases. The
(mg L-1). the ∆H and ∆S values were
initial concentration of Co(tsPc)-4 can serve as an
calculated from slope and intercept of the linear
essential driving force for overcoming the mass
plot of lnKc versus 1/T[17, 18].
transfer resistance of dye molecules between the
aqueous solution and solid-phase adsorbent. As
ln Kc = -∆H/RT + ∆S/R
the initial concentrations of Co(tsPc)-4 increased,
The corresponding values of thermodynamic
the driving force became higher as well, which
parameters are presented in Table 1. It shows that
facilitated more dye molecules adsorbing onto the
∆H, ∆S and ∆G are negative for all experiments.
adsorbent, contributing to better adsorptive removal
The negative value of the standard enthalpy change
performance and higher adsorption capacity[21].
for Co(tsPc)-4
sorption indicates exothermic
nature of adsorption[19] .The values of ∆G were
3.3. Effect of presence of surfactant template
calculated to be
-3.7 kJ mol-1
When the surfactants in aqueous solution are
at the temperatures of 300, 308, 313 and 323 K,
beyond the critical micelle concentrations (CMC),
respectively. The negative ∆G indicates that the
micelles are formed and they act as templates for
adsorption is a spontaneous process. The increase
preparing UVM-7 materials. The existence of
of ∆G values with rising temperature demonstrate
cationic template within the framework of UVM-
a negative influence of temperature on the
7 materials causes the change in the surface
adsorption reaction. Moreover, negative ∆S values
chemistry and porosity of the sorbate, which in turn
indicate a reduction of randomness at the solid-
affects the sorption behavior of sorbate. CTAB/
liquid interface during the adsorption process[20].
UVM-7 possesses high adsorption energy of
Table 1. Thermodynamics parameters for Co(tspc)-4 adsorption onto UVM-7/Ag
Thermodynamics quantities
Temperature (k)
∆H(KJ mol-1)
∆G(kj mol-1)
∆S(kj mol-1k-1)
Adsorption of cobalt-phthalocyanine by UVM-7/Ag; Amir Vahid, et al
Figure 8. Effect initial concentration on the adsorption of Co(tsPc)-4 by UVM-7/Ag.
quaternary alkyl ammonium groups (Si-C-C-C-
for the adsorption of dyes, various isotherm
[N+-(CH3)3]) contributed from cationic template.
equations like those of Freundlich, Langmuir and
Apparently, the surfactant template can alter the
Temkin have been used to describe the equilibrium
surface chemistry and population of sorption sites
characteristics of the adsorption. For describing
of the materials. The cationic templates improve
the relationship between the amount of adsorbate
the sorption towards those species containing
adsorbed on adsorbents at equilibrium (qe) and the
anionic groups. It is known that hydrophobicity,
concentration cu(tspc)-4 of the remaining in aqueous
p-p interactions,
(ce). The Langmuir relation assumes
hydrogen bonding, dipole-dipole interactions,
monolayer sorption on to the homogeneous surface
steric hindrance as well as a combination of them,
with a specific number of equivalent sites. The
are among the most important interactions which
Langmuir isotherm[23] is represented by the
determine the retention behavior of substances
following linear equation:
in the absorbent. When the adsorbent is CTAB-
containing mesoporous silica, the aromatic cycles
could interact with the alkyl part of CTAB by
hydrophobicity; the sulfonic acid groups interact
where Ce (mgL−1) is the equilibrium concentration,
with the positive polar heads of surfactants by
qe (mgg-1) the amount of adsorbate adsorbed per
electrostatic interactions. It is mentioned multiple
unit mass of adsorbent, qm (mg g−1) is the Langmuir
interactions which give the surfactant-containing
constant representing maximum monolayer capacity
adsorbent excellent adsorption capability. As
and b is the Langmuir constant related to the energy
shown if Figure 9, The adsorption capacity of
of adsorption. The Langmuir constants b and qm were
‘‘calcined’’ adsorbent is weak and is generally due
calculated from this isotherm and their values are
to the van der Waals interactions present between
listed in Table 2. The Freundlich isotherm is derived
the molecules of dyes and adsorbent [22].
by assuming a heterogeneous surface with a non-
uniform distribution of heat of adsorption over the
3.4. Adsorption isotherms
surface. Finally, the Freundlich isotherm as follows:
To optimize the design of an adsorption system
Analytical Methods in Environmental Chemistry Journal; Vol. 1 (2018)
Fig. 9. Effect presence of surfactant template.
it provides information about the mechanism of
the adsorption process such as mass transfer and
= log
chemical reaction. In this context, the mechanism
where Kf is the Freundlich constant (mg g−1 (mg L−1)
of the adsorption of Co(tspc)-4 ion onto adsorbents,
n) and 1/n is the heterogeneity factor. The slope 1/n
different kinetic models such as the pseudo-first-
ranging between 0 and 1 is a measure of adsorption
order and pseudo-second-order has been studied.
more intensity or surface heterogeneity, becoming
The pseudo- first-order equation can be used to
heterogeneous as its value gets closer to zero. The
determine the rate constant for the adsorption
plot of log qe versus log Ce, gives straight lines
process and describe the initial stage of the
with slope 1/n [24].
adsorption processas follows [27]:
The Temkin isotherm equation assumes that the
heat of adsorption of all the molecules in the layer
) +
decreases linearly with coverage due to adsorbent-
adsorbate interactions, and that the adsorption
where qe and qt are the amounts of adsorbed
is characterized by a uniform distribution of the
Co(tspc)-4 at equilibrium and any time t (mg g−1),
binding energies, up to some maximum binding
respectively, k1 is the equilibrium rate constant of
energy [25, 26]. Temkin isotherm is given as:
the first-order sorption (min−1).
qe=B lnKt+BlnCe
The pseudo-second-order rate equation of can be
Kt is the equilibrium binding constant
represented in the following form [28, 29] :
corresponding to the maximum binding energy, and
constant B is related to the heat of adsorption. From
Table 2, the Langmuir isotherm model yielded the
best fit with the highest R2 value (0.99) compared
where K2 (g mg-1 min-1 ) is the rate constant of
to the other two models.
the second-order equation, qt
(mg g-1 ) and qe
(mg g-1 ) Co(tspc)-4 adsorbed at time t (min) and
3.5. Adsorption kinetics
at equilibrium respectively [30]. Pseudo-second-
The study of adsorption kinetics is desirable as
order kinetics is based on the adsorption capacity,
Adsorption of cobalt-phthalocyanine by UVM-7/Ag; Amir Vahid, et al
Table 2. Isotherm parameters for Co(tspc)-4 adsorption onto UVM-7/Ag.
Langmuir isotherm
Freundlich isotherm
Temkin isotherm
(mg g-1)
(L mg-1)
(mg g-1)
(L mg-1)
which usually gives a good description of the whole
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