Research Article, Issue 1
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
1- Introduction
Nowadays, five major and hazardous pollutants
which can pollute and threaten drinking water,
groundwater, urban water, and bottled water are
known. The pollutants are arsenic, lead, fluoride,
chromium, and radioactive substances. Due to the
impossibility of biodegradation of arsenic in the
environment, it remains in contaminated water,
and thereby, it is considered as one of the most
hazardous pollutants in wastewaters and water
resources. In addition, the tendency of arsenic to
accumulate in the members of the body causes
dangerous diseases and cancers. The effects of
arsenic on the liver and nervous networks are
very prominent and cause a delay in mental
activity and anemia. In addition, arsenic enters
in the water, irrigated water, and environment
in various ways such as mining, printing, and
reproduction industries, petrochemical complexes,
and chemical industries or as a pollutant in their
effluent. According to available standards for
drinking water, the limit for arsenic is up to 10 ppm
Ahmad Ghozatlooa,*, Amir Zarei a,b and Mojtaba Arjomandi c,d
a Research Institute of Petroleum Industry, Tehran, Iran, Postal Box 14765-1376
b Department of Analytical chemistry, Payam Noor university, Kerman, Iran/ Department of Analytical chemistry Science and Research Branch, Islamic
Azad University, Tehran, Iran
c Department of Water Sciences and Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran/ Research Institute of Petroleum
Industry (RIPI), Tehran, Iran
d Department of Geophysics and Hydrogeology, Geological Survey and Mineral Explorations of Iran (GSI), Tehran, Iran
Synthesis and performance of graphene and activated carbon
composite for absorption of three-valance arsenic from wastewater
*Corresponding Author: Ahmad Ghozatloo
E-mail: ghozatlooa@ripi.ir
https://doi.org/10.24200/amecj.v2.i01.53
A R T I C L E I N F O:
Received 4 Dec 2018
Revised form 8 Feb 2019
Accepted 1 Mar 2019
Available online 21 Mar 2019
------------------------
Keywords:
Arsenic
Graphene
Activated carbon
Adsorption
Acidity of wastewater
A B S T R A C T
The presence of high levels of arsenic in the effluent is a major concern of human,
and the removal of it from the wastewater is hard and costly. The most common
techniques for removal of arsenic are membrane separation, ion exchange,
oxidation, and coagulation. All of these technologies eventually lead to the
separation of arsenic from wastewater and its accumulation among absorbent
materials, which are precipitated as sludge or extracted from liquid intermediate
phase. In this adsorption method, materials such as active alumina, active carbon,
titanium oxide, silicon oxide, and many natural and artificial elements are used.
Considering that active carbon is used as the most common arsenic adsorbent
in wastewater treatment processes, this study has been considered as the main
adsorbent and attempted to improve its surface properties by graphene nanosheets.
Thus, by adding 4.5 w.% graphene to the carbon structure, its porosity increases,
and the ion exchange behavior and surface load are corrected. In this research,
the effects of time process, concentration of arsenic, and adsorbent are evaluated
in different pH values. It has been observed that the maximum adsorption of
arsenic is 91.8%; in addition, when graphene is used, the rate of absorption of
Arsenic has increased about 5.2%, and the process time is shortened. In addition,
using graphene is cost-effective. It is also observed that the efficiency of the
adsorption process increases near neutral pH values; therefore, the adsorption
method by graphene/activated carbon composite in neutral cells can be used as
an additional method for industrial wastewater treatment.
Arsenic analysis in wastewater; Ahmad Ghozatloo, et al
Analytical Methods in Environmental Chemistry Journal Vol 2 (2019) 63-72
64 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
[1]. There are various methods for the adsorption
or removal of arsenic from contaminated water
sources, the most important of which are chemical
deposition [2], reduction by electron ultrafiltration
[3], ion exchange [4], and absorption process [5].
Among these approaches, the absorption method is
more cost-effective, efficient, and easy-to-absorb,
and extensive studies on the absorption of arsenic
by adsorption processes have been reported [7-5].
However, researches are looking for adsorbents
with a higher absorption rate, the identification of
an ideal adsorbent for the maximum absorption
of arsenic has not yet been suggested clearly.
Activated carbon has been used with the proper
properties as an efficient absorbent in treatment of
industrial wastewater for a Long time, especially
in the absorption of metal ions. In the meantime,
various technologies, including nanotechnology,
have increased the capacity of adsorbents used
to absorb more pollutants, including arsenic,
so that a new view has been opened in the field
of wastewater treatment. For example, carbon
nanotubes [8], graphene [9], graphene-oxide
[10], various graphene base materials, including
graphene hybrids [11] and graphene/metal oxide
nanocomposites [12], including nano-absorbents
which have been used in extensive researches,
and by using them, the best results have been
obtained. Moreover, no information is available
to use the adsorption of graphene/activated carbon
for removing arsenic from wastewaters. Graphene
oxide has shown good results in the removal of
some heavy metals from the effluent, which, in
its structure, oxygen acts as an absorption agent
for metal ions [13]. In graphene/activated carbon
composite, each of graphene and activated carbon
structures exhibits distinct effects on each other’s
performance. For example by considering the
effect of activated carbon on graphene behavior, it
can be admitted that the layer of graphene plate is
rolled onto activated carbon that not only prevents
the graphene from sticking together, but also
increases the porosity of the composite structure.
Consequently, it increases the specific surface of
adsorbents, which it is ideal target for sorbents.
On the other hand, graphene sheets, due to their
very small structures, act as a filler among the
active carbon structures and due to its conductive
behavior, and thereby, the absorption path in the
new structure of activated carbon is shortened.
It also facilitates the transfer of free electrons in
the composite structure and lowers its resistance.
This phenomenon is also the ideal goal of an
ideal adsorbent in sorption of ions [14]. In this
research, the graphene/activated carbon composite
synthesized as a porous adsorbent with a high
specific surface area is used for absorbing arsenic
from industrial effluent.
2. Experimental
2.1. Synthesis of Activated carbon/gra phene composite
absorbent
At First, graphene oxide has been obtained by
Hammers method with the mechanism of opening
of graphite layer sheets. After that, a double layer
dish with dilute sulfuric acid is washed, and while
the solution of sulfuric acid including graphite is
stirred, the temperature of the solution is reached to
0 °C using liquid cooling circulator. The amount of
2300 ml of sulfuric acid (98%) has been poured into
the reactor and mixed with 100 g of pure graphite
powder into the container, and the mixing operation
has been carried out for 30 minutes. Afterwards, the
amount of 300 g of solid potassium permanganate
powder is slowly added to the mixture during
6 hours, and the mixture is stirred for one hour
after completion. Then the temperature circulator
is increased to 40 °C, and after stabilizing the
temperature, the mixing operation continuous for
about three hours. For dilution, 500 ml of distilled
water is added with caution to the reactor, and the
circulator bleach and 3.5 liters of distilled water
are poured into a larger container, and then the
contents of the reactor are slowly transferred to a
larger container. Afterwards, the mixing operation
is carried out for one hour. The amount of 300 ml
hydrogen peroxide 30% has been slowly added to
the container, then mixing condition has continued
for 2 hours. Then 3 liters of chloride acid have
been added to 3 liters of distilled water separately.
65
Arsenic analysis in wastewater; Ahmad Ghozatloo, et al
Afterwards, the produced solution has been added
to the contents of the container. Then the process
continues for one hour. The stirrer has been turned
off, and the mixture has been subjected to the
intense ultrasound waves for 4 hours since the
opened plates do not adhere to each other. After
that, the container has been settled about eight
hours until the sediment is formed. Then from the
above part of the container, the produced solution
has been poured out, and the sediment contents
of the container are filtered. The strained cake is
transferred to a Chinese plant. Afterwards, the cake
is placed in a vacuum oven at 50 °C for two hours,
and then rinsed ultrasonically with distilled water
until neutral pH is achieved. After the neutralization
process, the powder formed is used as the graphene
oxide [15]. To prepare activated carbon, first 200 g
of powdered glucose is placed into a quartz tube.
The reactor is placed under nitrogen atmosphere
for 30 minutes. It is then gently warmed up to a
temperature of 350 °C and remained for 2 hours.
The glucose is carbonized under these conditions
and is colored as a black powder. In order to
increase the activated carbon efficiency, its surface
activation is carried out to perform a graphene
composite synthesis reaction under a two-step pre-
activation process. In the first step, at first, 10 g of
activated carbon powder is mixed with 20 g of zinc
chloride, and the mixed composite powder is added
to 300 ml of distilled water in a closed container.
Afterwards, the produced solution is exposed
to heat for 7 hours at 70 °C. During the heating
process, the water must not evaporate, and the
process is carried out in a dilute aqueous medium.
This action causes the activated carbon to become
more porous. Then, the mixture becomes smooth
with a filter paper, and the smooth mixture is dried
in an oven at 80 °C for 1 hour. The dried powder is
placed in a tubular quartz reactor, and the powder is
heated for one hour under neutral atmosphere while
temperature is equal to 400 °C. The powder has
been extracted from the reactor. Then the powder
has been poured into a one-molar chloride acid at
90 °C for 30 minutes. This has been carried out
to remove chloride from the remaining activated
carbon powder. The remaining mixture is filtered
and washed with warm distilled water several times
to remove remaining and additional chemicals. The
filter cake is dried in an oven at 65 ° C for 11 hours.
In the second step, 10 g of the carbon powder
obtained from the first step has been mixed with 30
g of potassium hydroxide, and the obtained mixture
has been placed in 300 ml of distilled water into the
container and brought to a temperature of 50 °C.
Then the mixture is mixed with alternating heat for
1 hour. The resulting mixture has been filtered with
filter paper. Afterwards, the filtered mixture has
been dried in an oven that its temperature is equal
to 80 °C for 1 hour. The dried powder is placed in a
tube quartz reactor and heated slowly at 700 ° C for
one hour under neutral atmospheres. The powder
has been brought out from the reactor. Afterwards,
it has been dried in an oven at 40 °C for one night.
Dried powder is a porous activated carbon that
is susceptible to participation in the graphene
composite structure. In order to synthesize the
active graphene / activated carbon composite, first
add 0.9 grams of dried graphene powder to 200
ml distilled water and add ultrasonic waves of 100
watts for a period of two hours, which appears as
a mixed mustard mixture. Then, the amount of 20
grams of activated carbon powder is slowly added
to the ultrasonic mixture for 3 hours. The mixture
is placed at 50 ˚C for one day, and then the water
evaporates. The remaining solids are introduced
into a quartz reactor formed in a tube, and under
a nitrogen atmosphere, it is slowly heated to 350
° C and left for 2 hours. The final product of this
reactor is the graphene/activated carbon composite
[16].
2.2. Study of structural properties of graphene/
activated carbon composite
In order to investigate the crystalline structure and
the phases present in the synthesized graphene/
carbon composite, X-ray analysis has been carried
out. In this study, a XRD spectrometer (Philips,
PW-1840) with a beam of 1.494 nm and a voltage
of 40 kV and a current of 30 mA has been used.
The spectrum obtained has been compared with
66 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
the Hammers graphene XRD. This comparison is
shown in Figure 1.
According to Fig. 1 (a), it is seen that the graphene
obtained from the Hammer’s process at 12.5
degrees has a sharp and narrow peak, which
indicates the crystalline structure of the graphene
oxide form, this means that the process of opening
graphite plates in the reaction of oxidation
with concentrated acid (Hammers process) is
successfully achieved. While in Figure 1 (b), the
peak has been shifted to a point of 26.5 degrees and
its intensity is very low. This criterion is a carbon-
crystalline structure with double bonds without the
presence of oxygenation groups, which has been
observed in pure graphene structure. As a result,
the process of making the graphene/activated
carbon composite, which has undergone a severe
heat stroke, causes the oxygen groups have been
removed from the composite structure. It also
shows that the synthesized composite structure is
free of any non-carbon bonding, in other words,
there is no additional contaminant in its structure.
In the following, a comparison of the two types of
graphite and synthesized composites is made, as
seen in Figure 2.
It is observed that the peaks of D and G in the area
of cm-1 of 1338 and 1611 cm-1 appear to be good
in this function respectively. The D-peak represents
stru c tural defects that appear due to its presence
in destructive environments such as concentrated
(or s trong) acidic environments or the presence
of d i fferent operating groups on the graphene’s
structural surface, while the G-peak is due to the
grap h ite crystalline network produced by the
carbon bonds. Thus, the ratio of the intensity of the
D/G peaks is an indicator of the structural state of
graphene, which is equal to 0.88, as shown in Fig.
2a. This ratio indicates the presence of high oxygen
groups on the structure of the Hammers graphene,
whil e in Fig. 2b, this value is increased to 1.69
due t o the elimination of oxygen’s groups of the
pres e nt graphene in the destructive environment.
Thes e results are also consistent with the XRD
anal y sis shown in Fig. 1. In order to study the
surf a ce properties of graphene/activated carbon
composite, the TEM image has been used, as seen
in Fig. 3. According to Fig. 3, it can be seen that the
Fig. 2. Raman spectrum: (a) Graphene (b) Graphene / activated carbon composite.
Fig. 1. XRD spectrum of graphene / activated carbon
composite
67
Arsenic analysis in wastewater; Ahmad Ghozatloo, et al
II BET device, the Japanese company BelJapan,
has been used. Preparation of samples is including
drying and degassing, which for this purpose, the
specimens should be heated in vacuum at 120 °C for
10 to 15 minutes for removing water vapor, carbon
dioxide, or other molecules that may occupy the
volume of the material cavities. Then the samples
cool down to the liquid temperature of the nitrogen
gas. Then the amount of nitrogen gas absorbed by
the composite or graphene structure is measured
by gradually increasing the relative pressure, and
its depletion rate is calculated by decreasing the
pressure at a constant temperature of 77 K. It has
been observed that in each case, with an increase in
relative pressure, the nitrogen uptake has increased,
and in the depletion mode, the same initial pattern
of absorbed nitrogen volume has been obtained.
The summary of the results is presented in Table 1.
According to the Table 1, graphene has shown an
increase in the specific surface area of activated
carbon by 87%. Also, the graphene composite with
Fig. 3. TEM image of graphene/active carbon composite.
layered structure of graphene nanosheet, which has
a micro-length, is well opened, and active carbon
particles are interacting. Small graphene layers are
randomly and irregularly distributed in activated
carbon particles.
Moreover, in circular shapes, in addition to carbon,
they also interact with each other, which have
created a structural network in activated carbon
and produced a total porosity. Moreover, this
phenomenon is due to a large amount of disruption
in the open graphene layers during the Hammers
process which is linked by functional groups
in the edges and structural defects of graphene
to activated carbon. The very narrow channels
created by the graphene plates inside the activated
carbon structure cause large structural porosity of
the composite to be obtained. To investigate the
structural porosity of synthesized composites, the
technique of nitrogen absorption and desorption
under different relative pressures has been used by
the BET method. In this research, the Belsorp mini
Table 1. pores status analysis based on BET analysis results.
Total pore
volumeMesoporous )%(
Average pore
diameter (nm)
Specific surface
area (m2 / g)
Isotherm absorption
typeStructure
0.373037.661Type I absorptionHammers graphene
2.4588.2982Type II absorptionActivated carbon
2.9195.61841Type IV absorptionGraphene composite
68 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
a specific surface area of 1841 m2/g exhibits a
very active surface structure that is very attractive
in the absorption region. In addition, the process
of synthesis of graphene composites has increased
the volume of activated carbon cavities up to 18%,
indicating an increase in the absorption capacity of
this structure. However, the size of the cavities is
not larger and, as a result, the number of each of
them is much larger. The presence of graphene in
the active carbon structure reduces the size of the
cavities, so that the average diameter of the cavities
in the composite is reduced b y 22%. In other
words, the hypothesis of the interaction between
graphene and activated carbo n on each other in
the composite structure is v i sible from the point
of view of the positive effec t of graphene on the
active carbon structure and g raphene reduces the
size of the cavities and increases their number in
the activated carbon structure. Based on the results
of the structural analysis of synthesized composite,
which indicates the proper position of this structure
as a sorbent, it is further used to absorb arsenic in
water.
2.3. The evaluation system of absorbent performance
and process variables
In this study, a batch reactor system has been used
in a laboratory scale to carry out the process of
adsorption and removal of arsenic in water, the
schematic illustration is shown in Fig. 3.
In accordance with Fig. 4, the system, which has
been used, consists of a double-headed reactor of
Pyrex with an internal volume of 300 cc, which is
an environment for an adsorption reaction. During
the absorption process, a circulator has been used
to transfer the required temperature and to maintain
the flow of the agent into the reactor’s second
wall. The reactor is equipped with a mechanical
agitator system that can control the speed of the
stirrer in different periods. At the end of the stirrer
rod, two parallel blades, with 2 cm in length, are
placed at an angle of 1 cm above the bottom of
the reactor, which is made of polymer and neutral,
with the aim of mixing the wastewater and the
lack of deposition of the adsorbent at the end of
the container is used during the absorption process.
Also, this system provides an opportunity to study
the rate of mixing speed in the absorption process.
To provide the required heating, a magnetic stirrer
equipped with an electric heater can also be
used. Arsenic adsorption process for two active
carbon adsorbents and graphene/activated carbon
composite for 200 cc wastewater containing three-
valence arsenic (Al3+) in water at 45 °C with an
abrasive stirrer 700 rpm has been carried out, and
their results have been compared with each other.
These processes have been repeated at different
times and at different concentrations of arsenic in
water and different concentrations of adsorbent and
pH values. These values are presented in Table 2.
3. Results and discussion
According to the variables defined, the arsenic
adsorption process is performed by two adsorbents
including active carbon and active carbon-graphene
composite in two pH values. In these experiments,
the amount of adsorbent is used, and the time of the
adsorption process with the initial concentration of
arsenic in the wastewater is changed in two levels.
Upon completion of the test, the amount of arsenic
in the wastewater is measured by atomic absorption
analysis with the PerkinElmer 2380 machine. The
amount of adsorption of arsenic after the adsorption
process is calculated by the following equation
(Eq. 1).
Fig. 4. Schematic of the absorption reactor system.
69
Arsenic analysis in wastewater; Ahmad Ghozatloo, et al
qe=(C0-Ce).V/m (Eq.1)
where qe is the amount of absorption after reaching
the equilibrium state with unit mg/g, C0 and Ce are
the initial and final concentrations of arsenic in the
wastewater, which their units are mg/L, obtained
by atomic absorption analysis and V is the volume
of wastewater used per Liter, and m is the absorbent
weight used in grams. Then based on the initial
concentration of arsenic in the wastewater, the
efficiency of arsenic adsorption is calculated. The
absorbent absorption efficiency is obtained using
the following equation (Eq. 2):
% Removal=(C0-Ce)/C0 ×100 (Eq.2)
Table 2 summarizes the number and conditions of
absorption experiments. For more precision and
the possibility of repeatability of the experiments,
each experiment has been repeated three times,
and its mean value as absorption efficiency has
been calculated and reported. In addition, Table 3
summarizes the results of arsenic adsorption under
various laboratory conditions.
According to Table 3, it is generally observed that
the adsorption rate in activated carbon/graphene
composites is higher than of activated carbon, so
that under the same conditions due to the positive
effect of graphene on porosity. The total amount of
adsorption increased from 6.6% to 9.3%, and the
highest amount of arsenic adsorption occurred when
using 200 mg graphene/activated carbon composite
in 120 minutes for effluent with concentration
of 100 mg which is 42.4%. It is observed that
increasing the concentration of arsenic in
wastewater decreases the amount of absorption due
to the presence of more arsenic in the wastewater
Table 2. The absorption Process Variables.
High Level of variationLow variation levelNon-dependent variableNumber of variables
200100
concentration of absorbers (mg)1
12060time of adsorption2
200100Amount of absorbent (mg As / L)3
63pH4
Table 3. The Summary of the results of arsenic adsorption under various laboratory conditions
Absorbent
type
The
amount of
adsorbent
(mg)
Time of
absorption
(minute)
Initial
concentration
(mg As/L)
Absorption
Test
Conditions
pH=6 pH=3
Absorption
rate (%)
Secondary
concentration
(mg As/L)
Absorption
rate (%)
Secondary
concentration
(mg As/L)
Activated carbon
100
60 100 AC1 79.2 79.2 74.4 74.4
200 AC2 77.1 154.2 74.0 148.0
120 100 AC3 80.3 80.3 74.2 74.2
200 AC4 79.7 159.4 76.4 152.8
200
60 100 AC5 86.4 86.4 80.2 80.2
200 AC6 85.9 171.8 83.4 166.7
120 100 AC7 84.5 84.5 78.4 78.4
200 AC8 86.6 173.2 83.3 166.6
Composite
100
60 100 AC/G1 83.8 83.8 77.6 77.6
200 AC/G2 82.2 164.4 79.1 158.2
120 100 AC/G3 85.3 85.3 80.4 80.4
200 AC/G4 83.1 166.2 79.9 159.8
200
60 100 AC/G5 91.8 91.8 85.5 85.5
200 AC/G6 90.7 181.4 87.6 175.2
120 100 AC/G7 92.4 92.4 86.1 86.1
200 AC/G8 91.6 183.2 88.5 176.9
70 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
and the creation of mass transfer resistance in its
transfer to the absorbent level. In this case, by
comparing the absorbance value for active carbon,
the same phenomenon is observed, as the amount
of adsorption decreases by about 2.5%. Therefore,
the amount of arsenic adsorption by active carbon
with the presence of arsenic in large concentrations
is inversely proportional, and it can be used as a
supplementary method in adsorption. It can be seen
that the presence of graphene in the activated carbon
structure due to electron exchange in the sites at the
edges and structural defects of graphene humors
increases the absorption performance. However,
the time of the absorption process does not have
any significant effects on it, based on this study,
if it is required to absorb less than 1% of arsenic
in wastewater by using graphene/activated carbon,
the time of absorption must be increased twice. In
addition, if it is required to absorb less than 1% of
arsenic in wastewater by using activated carbon,
the time of absorption must be increased 2.3 times.
As a result, graphene has increased the adsorption
rate, which has accelerated the absorption process,
and has a positive effect on the economy of this
process. Therefore, due to the negligible difference
and the very little effect of absorption time with
the presence of graphene, the absorption time at
60 minutes as an optimal point of the process is
suggested. By changing the amount of acidity of the
effluent from 6 to 3, the empirical values obtained
in Fig. 2 are reported.
According to Fig. 5, it is observed that with
increasing pH in all experiments, the amount of
adsorption increases. Generally, it is seen that
the reduction of the pH of the effluent is strongly
influenced by the amount of absorption due to
the competition of adsorption of arsenic in the
acidic environment. In addition, it is observed
that in lower pH values, the amount of adsorption
decreases, but the intensity varies in different
conditions. When only activated carbon adsorbent
is used, the greatest effect of pH is on AC3
adsorption conditions, which changes 6.1% of
absorption, whereas when composite absorbent is
used, the most effect of pH is on AC/G7 adsorption
conditions, of which 6.3 units change the absorption
percentage. In general, the maximum amount of
arsenic adsorption decreased by 6.3%, which is
related to dilute arsenic concentrations when 200
mg of composite absorbent is taken at 60 and 120
minutes. Therefore, it is noted that the time of
adsorption process has no significant effect on the
amount of arsenic adsorption. To better evaluate the
effect of time on adsorption, absorption processes
Fig. 5. Comparison of the effect of pH on arsenic removal under various laboratory conditions.
71
Arsenic analysis in wastewater; Ahmad Ghozatloo, et al
are compared with each other over a period of 60
minutes. According to Table 4, it is observed that
in the same condition, the presence of graphene
increases the amount of arsenic absorption.
According to Table 4, the presence of graphene
in neutral pH (pH = 6) has a greater effect on the
absorption rate due to the intrinsic effect of more
graphene porosity on the total of the adsorbent.
Moreover, the lack of ionic resistance in adsorption
of arsenic could also point to the phenomenon of
favorable spatial inhibition between graphene
sheets in neutral media due to the negative charge
found in the graphene agent groups of Hammers.
That way, by increasing the pH of the environment,
the presence of positive ions in the wastewater
decreases, and the tendency to converge graphene
plates in the composite weakens. As a result,
adsorption of arsenic by composite adsorbent with
less resistance and more surfaces by graphene is
done. This subject occurs with the same intensity
in the 120-minute adsorption period. Due to the
presence of graphene in the structure of activated
carbon, the effect of absorbing time is insignificant.
In addition, due to the structural nature of the
adsorbent and the low concentration of arsenic,
better adsorption is there in the process. Therefore, it
is observed that with the presence of less adsorbent,
the greatest effect of pH in the adsorption process
is due to the presence of graphene in the adsorbent
structure which increases the absorption to about
1.4 times. That is, graphene greatly enhances
the effect of the pH of the wastewater, in other
words, when the composite absorbent is used, the
sensitivity of the adsorption process to higher pH
changes should be controlled with greater precision
and be limited to higher pH.
4- Conclusion
Activated carbon as one of the most suitable
and efficient adsorbents in adsorption of arsenic
in industrial effluents has a good performance,
so that it can separate about 86.6% of arsenic
from wastewater during 120 minutes. Because
the adsorption process carried out by activated
carbon is related to porosity and ion exchange, it is
attempted to upgrade these parameters by changing
its structure. For this purpose, the graphene
structure of Hammers, which has a very high
porosity and anionic surface charge, as a modern
idea is used in this research. It has been observed
that the presence of graphene in the adsorbent
structure has caused a significant increase in the
amount of adsorption of arsenic, so that in optimum
conditions, the adsorption rate increased up to
91.8%. On the other hand, the absorption time of
more than 60 minutes have not had any significant
effects on absorption, and this process causes the
more economical due to requiring of shorter time
for balancing the maximum absorption. Moreover,
by observing the effect of wastewater pH, graphene
performance has been improved at higher pH
values due to the force of dissolved ion potential
difference at the rate of adsorption of arsenic by
composite absorber. Therefore, it can be controlled
by adjusting the pH of wastewater, and the use of
corrected graphene structures easily controls the
absorption process and increases the efficiency of
absorption. Also, it has been observed that with
increasing arsenic concentration, the absorbent
performance of the composite is weakened. Due to
the sensitivity of the presence of arsenic in released
wastewater, these types of adsorbents are suitable
for final purification and dilute wastewater.
Table 4. The Increasing adsorption of arsenic by the presence of graphene in the adsorbent structure.
amount of adsorbent
(mg)
Initial concentration
(mg As/L)
Time of absorption
(min)
pH=3
Increase in
absorption (%)
pH=6
Increase in
absorption (%)
100 100 60 3.2 4.6
100 200 60 5.1 5.1
200 100 60 5.3 5.4
200 200 60 4.2 4.8
72 Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
5. References
[1] M. A. P. Cechinel, A. A. U. de Souza, Study of arsenic
adsorption onto activated carbon originating from
cow bone, J. Clean. Prod., 65 (2014) 342–349.
[2] J. H. Park, Y. S. Han, J. S. Ahn, Comparison of arsenic
co-precipitation and adsorption by iron minerals
and the mechanism of arsenic natural attenuation
in a mine stream, Water Res., 106 (2016), 295–303.
[3] L. R. Molinari, P. Argurio, Arsenic removal from
water by coupling photocatalysis and complexation-
ultraltration processes: A preliminary study, Water
Res., 109 (2017) 327-336.
[4] B. Pakzadeh, J. R. Batista, Surface complexation
modeling of the removal of arsenic from ion-
exchange waste brines with ferric chloride, J.
Hazard. Mater., 188 (2011) 399–407.
[5] D. Santra, M. Sarkar, Optimization of process
variables and mechanism of arsenic (V) adsorption
onto cellulose nanocomposite, J. Mol. Liquids, 224
(2016) 290–302.
[6] O. P. Chen, Y. J. Lin, W. Z. Cao, C. T. Chang, Arsenic
removal with phosphorene and adsorption in
solution, Mater. Lett., 190 (2017) 280–282.
[7] A. Sigdel, J. Park, H. Kwak, P. Pyung-Kyu, Arsenic
removal from aqueous solutions by adsorption onto
hydrous iron oxide-impregnated alginate beads, J.
Ind. Eng. Chem., 35 (2016) 277–286.
[8] A.A.H. Izzeldin, S.M. Bice, J. Catherine, O.N.
Vincent, Adsorption studies of aqueous Pb(II) onto
a sugarcane bagasse/multi-walled carbon nanotube
composite, Phys. Chem. Earth 66 (2013) 157–166.
[9] R. Soni Dericks, P. Shukla, Data on Arsenic(III)
removal using zeolite-reduced graphene oxide
composite, Data in Brief, 22 (2019) 871-877.
[10] G. Zhao, X. Ren, X. Gao, X. Tan, J. Li, C. Chen,
Y. Huang, X. Wang, Removal of Pb(II) ions from
aqueous solutions on few-layered graphene oxide
nanosheets, Dalton Trans., 40, (2011) 945–952.
[11] L. Cui, Y. Wang, L. Gao, L. Hu, L. Yan, Q. Wei, B.
Du, EDTA functionalized magnetic graphene oxide
for removal of Pb(II), Hg(II) and Cu(II) in water
treatment: adsorption mechanism and separation
property, Chem. Eng. J., 281 (2015) 1–9.
[12] Z. Goharibajestani, A. YudaYürüm, Effect of
transition metal oxide nanoparticles on gas
adsorption properties of graphene nanocomposites,
Appl. Surface Sci., 475 (2019) 1070-1076.
[13] G. Zhao, J. Li, X. Ren, C. Chen, X. Wang, Few-
layered grapheme oxide nano-sheets as superior
sorbents for heavy metal ion pollution management,
Environ. Sci. Technol., 45 (2011) 454–462,
[14] C. Zheng, X. Zhou, H. Cao, G. Wang, Z. Liu,
Synthesis of porous graphene/activated carbon
composite with high packing density and large
specic surface area for supercapacitor electrode
material, J. Power Sources, 258 (2014) 290–296.
[15] M. Sohail, M. Saleem, S. Noor Saeed, A. Afridi, M.
Khan, M. Arif, Modied and improved Hummer’s
synthesis of graphene oxide for capacitors
applications, Modern Elec. Mater., 3 (2017) 110-
116.
[16] A. Ganesan, M. M. Shaijumon, Activated graphene-
derived porous carbon with exceptional gas
adsorption properties, Micropor. Mesopor. Mater.,
220 (2016) 21-27.
