A new kinetic models analysis for CO adsorption on
palladium zeolite nanostructure by roll-coating technique
Nastaran Mozaffari
a
, Alireza Haji Seyed Mirzahosseini
a,*
and Niloofar Mozaffari
b
a
Department of Environmental Engineering, Faculty of Natural Resources and Environment,
Science and Research Branch, Islamic Azad University, Tehran, Iran
b
Department of Physics, Faculty of Sciences, Science and Research Branch,
Islamic Azad University, Tehran, Iran
ABSTRACT
The aim of this article was the fabrication of zeolite@Pd/Al
2
O
3
nanostructure through roll-coating technique for CO gas adsorption
      
scanning electron microscopy (FESEM), X-ray diffraction (XRD),
and energy-dispersive x-ray spectroscopy (EDX) were performed to
investigate the morphological, structural, and elemental properties
of zeolite@Pd/Al
2
O
3
adsorbent. A continues carbon monoxide gas
analyzer KIGAZ 210 was applied for analyzing of CO gas adsorption
on as-present adsorbent in an experimental set-up. The adsorption
capacity at equilibrium time for CO molecules was studied by
zeolite@Pd/Al
2
O
3
adsorbent. The Elovich, Avrami, and Fractional
power kinetic models were used for this study. The equal value of
experimental and theoretical adsorption capacity at equilibrium time

Avrami kinetic model was the suitable model to describe CO removal
from air through zeolite@Pd/Al
2
O
3
nanostructure. The results showed
us, the CO 
adsorbent more than 95% from air at optimized conditions.
Keywords:
Carbon monoxide (CO),
Toxic gas analysis,
Adsorption,
Alumina palladium zeolite ,
Kinetic models
Anal. Method Environ. Chem. J. 3 (2) (2020) 92-107
ARTICLE INFO:
Received 19 Feb 2020
Revised form 25 Apr 2020
Accepted 20 May 2020
Available online 30 Jun 2020
Research Article, Issue 2
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
------------------------
*
Corresponding Author: Alireza Haji Seyed Mirzahosseini
Email: mirzahosseini@gmail.com
https://doi.org/10.24200/amecj.v3.i02.106
1. Introduction
The clean and high quality air is essential for human
health. The main contributors to climate change
belong to emission of toxic gases CO, CO
2
, NO
x
,
So
x
[1, 2]. Operations of industries and factories,
transportation, agricultural activities and post/
pre combustion of fuels are major reasons behind
the emissions of CO and CO
2
in environment air.
Carbon Monoxide (CO) as a main ecological
pollutant, can be formed by incomplete burning of
industrial fuels, automobiles and caused to a serious
of symptoms including dizziness, naupathia and
dyspnea [3, 4]. The acceptable limit of CO exposure
has reported by ACGIH chemical substances
[5]      
      
attention over the past few decades [6]. Among
these techniques, the process of adsorption shows
a fundamental surface phenomenon in which the
attachment of solute (adsorbate) into a solid surface
(adsorbent) can remove pollutants selectively from
air atmosphere [6, 7]. According to the previous
studies, some of toxic gases such as CO, CO
2
, SO
2
,
O
3
, VOC
s
, etc., have more concentration in air [3].
Nowadays, excellent properties of nanomaterials
such as high surface area and high adsorption
93
CO adsorption by Al
2
O
3
/Pd(NO
3
)
2
/Zeolite composite Nastaran Mozaffari et al
[8-10]. According
to the most valence of equilibrium cycle, the cycle

approximately when the adsorbent is started that

and or pressure can be applied for appraising of the
maximum capacity of equilibrium axle. Moreover,
the regeneration procedure can be estimated
through adsorbents’ recognizable characteristic
like thermal behavior of electricity. Electric swing
adsorption (ESA), moisture swing adsorption
(MSA), temperature swing adsorption (TSA), and
pressure swing adsorption (PSA), or techniques like
temperature vacuum-pressure swing adsorption
(TVPSA) that can be made by compilation of
these above methods [11]. Pressure/Vacuum swing
adsorption (PSA/VSA) and temperature swing
adsorption (TSA) techniques was used for trapping
of gas pollutions by above methods [12-15].
Carbon-based adsorbents such as activated carbons
are commercially cheaper than other adsorbents,
and also have known for toxic gas removal because
of its useful properties such as eco-dependence,
consistency of thermic and chemic, conductance
of heat and electricity, or high resistance [16-19].
However, its disadvantages such as lack of low
thermal and mechanical stability rather than other
materials should not be ignored [6]. Recently,
varieties of nonporous including metal-organic
frameworks (MOFs) [20-23], mesoporous alumina
(MA) [24, 25], and mesoporous silica (MS) [26,27]
have been used for detection and adsorption of toxic
gases, and are regarded as alternatives to commercial
adsorbents [28,29]. Metal-organic frameworks


surface area, ultra-high porosities, controllable
architectures, and low density [30, 31]. As an
important factor, the porosity of MOFs can help to
adsorb and desorbs micro molecules by providing a
fast and handy path [32,33]. Although considerable
fabricated and natural adsorbents such as activated
carbon [26]   [25]  
[24], biomaterials [4], metal-organic-frameworks
(MOFs) [23], zeolites [22,21], and nanomaterials
[27] have been studied for a long period of time,
there is still needs for advancements of adsorption
technology and developing recyclable, cost-
     
high capacity. Mesoporous alumina and other
alumina-based substances have high adsorption
capacity because of their interconnected channels,
uniformed porous structures, and united pore size
[34,35]    
2
O
3
is the
best candidate for gas molecules capturing rather
than other alumina phases known as “transition
alumina” owing to its pore-volume, large surface
area, and great catalytic activity [36, 37, 38]. The
properties with high surface area and acidic surface
   
2
O
3
) a unique
material with extensive application ranging from
adsorbents to heterogeneous catalysis [39-42]. The

2
O
3
indicates
one of various metastable stages (polymorphs) of
alumina [39, 43, 44]. A higher CO adsorption and
great capacity of adsorbents can be occurred by
covering of the small particle size of Pd clusters on
the Al
2
O
3
surface [45]. The application of palladium
is restricted due to its high material cost, even
though there has been extensive investigation of
nanopalladium or its alloy groups [46]. Therefore, in
this study, nano-scale palladium II nitrate has used
due to its similar unique and useful characteristics
with palladium nanoparticles, and because of
being cost-effective and easy to access compared
to palladium. The mesoporous silicates are one of
the promising kinds of nanoscale materials that
become well-known for researchers due to their
potential abilities and utilizations [47-53]. Several
researchers have been reported the advantages of
applying nanoscale zeolite (NPs) over micro-scale
zeolite (MPs). [54-58] For example, according to
results of comparing nano-scale (30-40 nm) and
micro-scale (2000 nm) of H-ZSM-5 for its catalytic
performance, it has found that the catalyst lifetime
for H-ZSM-5 in nano-scale particles is longer than
itself in micro-scale particles [58]. Synthesizing
and utilizing nanosized zeolite attract great interests
compared to zeolite with micron size, recently
[54-62]. The properties of high external surface
94
Anal. Method Environ. Chem. J. 3 (2) (2020) 92-107
area and high availability of active sites have been

and age of catalyst. Either a particular type of
nanoadsorbents like CNTs [63,64], or some kinds
of pollutants including heavy metal, antibiotic and
so on [65, 66], or organic and inorganic pollutants
removal [67] have totally been focused by most
of recent review articles even though over 500
technical papers published between 2000 to 2019
indicate the rapid growth of interest in this research
area. Hence, the current study concentrates on the
adsorption of carbon monoxide as a toxic gas by
     
      

2
O
3
, Pd(NO
3
)
2
and zeolite on glass substrates
through the roll-coating method, in order to
enhance the span of reactions between CO gas
molecules and adsorbents surface, and improve
the ability of adsorbents for CO capturing. Then,
the Elovich, the Avrami, and the Fractional power
kinetic models for CO adsorption by zeolite@Pd/
Al
2
O
3
nanoadsorbent were studied and analyzed.
2. Experimental
2.1. Materials
Nanoshel chemicals was provided alumina
nanoparticles (CASN: 1344-28-1, Molar mass:101.96 g
mol
-1

2
O
3
with purity >99.9%) and zeolite
nanoparticles (CASN:1318-02-01, Al
2
O
34
SiO
2
H
2
O
with purity 99%). Merck chemicals and Sigma-Aldrich
were two sources that 1-methyl-2-pyrrolidone and
palladium nitrate (Pd(NO
3
)
2
) were bought from them,
      
received chemicals in order to use them.
2.2. Preparation of Adsorbent
The roll-coating technique has been used to deposit
zeolite@Pd/Al
2
O
3
    
substrates. Four glass substrates (2 cm × 8 cm)
were used in this study. Disinfectant materials
such as acetone, ethanol and deionized water
were consumed for washing glass substrates three
times in an ultrasonic device. Then, the washed
substrates dried at room temperature. As the

2
O
3
,
1 g of zeolite and 1 g of Pd(NO
3
)
2
were mixed
in a container, then 1-methyl-2-pyrrolidone was
added dropwise into it as 10 mL in order to make
the adhesion of materials on the substrates easy and
stronger. After 1 day, the prepared coated substrates
were desiccated at room temperature. Finally, a
hollow cubic container was fabricated through
attaching these four Al
2
O
3
/Pd(NO
3
)
2
/Zeolite coated
substrates to each other whereby this tunnel-like
shape helps CO gas molecules to be channeled and
trapped readily [68]. In this case, the adsorption
      
by enhancing the rate of interaction between gas
molecules and adsorbents.
2.3. Characterization
Transmission Electron Microscopy (TEM) was
used in order to determine the shape and grain
distribution of nanoparticles with high resolution.
X-ray diffraction (XRD, STOE STADI MP) was
applied for extracting the crystalline structure of
pure initial materials. Topography and morphology
of as-present adsorbent (before and after adsorption
     
scanning electron microscope (FESEM, MIRA3
TESCAN), while energy-dispersive X-ray
spectroscopy (EDX) analysis was used in order to
specify and measure chemical elemental contents
of the sample.
2.4. Adsorption of CO
The schematic of designed experimental setup
for testing CO adsorption consists of main three
sections as a CO gas capsule, a compartment (20
cm length and 7 cm internal diameter) where an
adsorbent is placed, and a carbon monoxide gas
analyzer KIGAZ 210 (Sauermann Co, CO sensor
protection by solenoid valve) based on tunable diode
laser (TDL, LOD=1 ppm) for CO Measurement
for detection of 1-120 ppm CO and evaluation of
target gas (CO 99,999%) concentration [68]. The
temperature of 0-250 °C (23-482 °F); optional
(for probe installation) 0-600 °C (0-1112 °F) with
additional thermal barrier was used. The constant
pressure 1.5 bar was applied in this study. The
95
concentration of inlet CO gas and the saturation
level of CO gas concentration were 150 mg L
-1
and
5 mg L
-1
, respectively.
2.5. Adsorption mechanism of CO by Zeolite@
Pd/Al
2
O
3
       
     
Al
2
O
3
/Pd(NO
3
)
2
/Zeolite. The molecules of gases
like CO can attach to the adsorbent surface of
Al
2
O
3
/Pd(NO
3
)
2
/Zeolite when the molecules of
these gases achieve decreased free energy while the
molecules come towards the surface of adsorbent.
The value of CO molecules that come close to
the surface of Al
2
O
3
/Pd(NO
3
)
2
/Zeolite adsorbent
will be increased by decreasing of entropy that
occurs by interplay between solid surface and CO
molecules. The adsorption process based on van der
Waals forces called physically adsorption, while
chemical bond formation obtained between surface
of Al
2
O
3
/Pd(NO
3
)
2
/Zeolite adsorbent and adsorbate.
So, there are different mechanisms of physio-
chemisorption for adsorption procedure which
must be optimized. The MOFs’ surface has several
functional groups caused to act chemical reaction
in mechanism adsorption [16]. In Order to achieve

should possess some essential properties which are

adsorption can specify how many adsorbents are
required whereby the adsorption column’s volume
can be measured, it possesses high importance
for determining the main cost of the adsorption
mechanism. However, the value of adsorbent and
size of equipment for adsorption process must
be minimized due to high CO concentration. 2)
The ratio of CO to another gas capacity shows
the selectivity CO gas. 3) Another parameter for

adsorption/desorption that the fast rate of adsorption/
desorption kinetics for CO will be required by the
adsorbents. The cycle of time will be controlled
by processes of regeneration and the adsorption’s
kinetics that can form two types of curves that are
a sharp breakthrough curve for CO which indicates
a fast kinetics, and a budged breakthrough curve
occurs if there is slow kinetics for CO. The transfer
of mass through the surface of adsorbent, the
functional group on the surface of adsorbent, and
carbon monoxide’s reaction kinetics can together
        
porous substances. 4) In order to keep high kinetics,
it is necessary to have a property of the mechanical
stability for adsorbent. 5) The demanded energy
for regeneration of adsorbents should be measured.
The range of -25 to -50 kJ mol
-1
is allocated to heat
of physisorption and chemisorption cases possess
the heat of -60 to -90 kJ mol
-1
[17]. Regarding the
chemical adsorbents, physical adsorbents such as
carbonaceous and non-carbonaceous substances
need low energy desire for CO removal due to the
no generation of new bonds between these gases and
the adsorbents’ surface whereby the regeneration of
these gases requires less energy (Fig.1).
Fig.1. The adsorption mechanism of CO by zeolite@
Pd/Al
2
O
3
adsorbent
3. Results and discussion
3.1. TEM analysis
Figure 2a demonstrates the results of TEM
analysis of pure Al
2
O
3
nanoparticles (
2
O
3
)
that three dimensional porous structure are made
up by interconnected rod-like particles [69]. It is
obviously shown that the shape of nanoparticles
does not look accurately spherical [70]. The TEM
for nanoparticles of
zeolite and zeolite@Pd/Al
2
O
3
was
shown in Figure 2b and 2C, respectively.
CO adsorption by Al
2
O
3
/Pd(NO
3
)
2
/Zeolite composite Nastaran Mozaffari et al