Research Article, Issue 4
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
------------------------
1. Introduction
One of the most important issues facing human
beings today and even endangering their health is
air pollution. Volatile organic compounds (VOCs)
are one of the most important pollutants, and
these compounds are listed as toxic [1, 2]. Global
warming, ozone depletion, photochemical smog,
and contributor of haze is the effect of this material
[3, 4]. The boiling point range of volatile organic
compounds is from 50 to 250 °C and because of
high vapor pressure creates a notable amount of the
molecules to evaporate and release in the air [5, 6].
Their health effects on humans are very important,
these compounds can irritate the respiratory system
and eyes, cause headaches and nausea, damage the
kidneys, liver, the central nervous system and even
in chronic exposure cause cancer [7-10]. Some of
the major industries producing volatile organic
compounds include petroleum refineries, chemical
industries, automotive industries, paint industry,
pharmaceuticals, cable and wire industries,
printing, aerospace, textile, etc. [1, 11]. BTEX
(Benzene, toluene, ethylbenzene, and xylene) are
the most common VOCs and usually used in the
Maling Gou
a,b
and Baharak Bahrami Yarahmadi
c,
*
a
State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu
610041, China
b
Department of Thoracic Oncology, Cancer Center, West China Hospital, Medical School, Sichuan University, Chengdu 610041, China
C,*
Occupational Health Engineering Department, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran
Removal of ethylbenzene from air by graphene quantum dots
and multi wall carbon nanotubes in present of UV radiation
*Corresponding Author: Baharak Bahrami Yarahmadi
Email: baharakb72@gmail.com
DOI: https://doi.org/10.24200/amecj.v2.i01.44
A R T I C L E I N F O:
Received 12 Sep 2019
Revised form 15 Nov 2019
Accepted 5 Dec 2019
Available online 28 Dec 2019
Keywords:
Graphene quantum dots,
Multi wall carbon nanotubes,
Ethylbenzene,
Air removal,
UV-radiation,
Solid gas removal
A B S T R A C T
Luminescent graphene quantum dots (GQDs) and multi wall carbon
nanotubes (MWCNTs) as photocatalytic sorbent based on was used for
removal of toxic ethylbenzene from air in present of UV-radiation. A novel
method based on solid gas removal (SGR) based on GQDs and MWCNTs
as an efficient adsorbent was used for ethylbenzene removal from air in
Robson quartz tubes (RGT). After synthesized and purified of GQDs and
MWCNTs, a system was designed for generation of ethylbenzene in air
with difference concentrations, and then the mixture was moved to quartz
tubes with UV radiation in optimized conditions. The ethylbenzene in
air was absorbed on the 25 mg of GQDs or MWCNTs, desorbed from
sorbent at 146
o
C and determined by GC-FID. The main parameters such
as, temperature, ethylbenzene concentration, amount of GQDs / MWCNTs
and flow rate were studied and optimized. The recovery of ethylbenzene
removal from air (more than 95%) and absorption capacity of adsorbent
(186.4 mg g
-1
) were achieved in present of UV radiation at room temperature
by GQDs. The flow rate and temperature were obtained at 300 mL min
-1
and less than 42
0
C, respectively. Based on results, the special surface area
and favorite porosity of GQDs caused to efficient removal of ethylbenzene
from air in present of UV as compared to other carbon compounds such as
MWCNTs, and graphene.
Removal of ethylbenzene from air Baharak Bahrami Yarahmadi et al
Analytical Methods in Environmental Chemistry Journal Vol 2 (2019) 59-70
60
Analytical Methods in Environmental Chemistry Journal; Vol. 2 (2019)
petrochemical industry and as reagents for the
synthesis of multiple C-based products [11-13].
Among BTEX, ethylbenzene is mainly used in the
manufacture of styrene. The release of Ethylbenzene
into the air could be carcinogenic, cause secondary
aerosol and photochemical smog. Ethylbenzene is a
colorless liquid that smells like gasoline. The odor
threshold for ethylbenzene is 2.3 parts per million
(ppm). The chemical formula for ethylbenzene is
C
8
H
10
, and the molecular weight is 106.16 g mol
-1
.
The vapor pressure for ethylbenzene is 9.53
mm Hg at 25 °C, and its octanol/water partition
coefficient is 3.13. In petrochemical factories,
BTEX and mercury vapor released in air and can be
absorbed in humans via the inhalation and dermal
routes of exposure. So determination BTEX and
mercury in air, water and human matrixes is very
important [14-17]. Previous study reported the
carcinogenic effects of ethylbenzene in humans.
EPA has classified ethylbenzene as a Group D, not
classifiable as to human carcinogenicity. ACGIH
recommends a TLV-TWA of 100 ppm and STEL/C
of 125 ppm for ethylbenzene based on irritation
and central nervous system effects [18-20]. Acute
(short-term) exposure to ethylbenzene in humans
results in respiratory effects, such as throat irritation
and chest constriction, irritation of the eyes, and
neurological effects such as dizziness. Chronic
(long-term) exposure to ethylbenzene by inhalation
in humans has shown conflicting results regarding
its effects on the blood. Animal studies have
reported effects on the blood, liver, and kidneys from
chronic inhalation exposure to ethylbenzene [21-
23]. There are many successful techniques which
have been developed and applied to control the
VOCs emission, such as condensation, membrane,
absorption, adsorption, thermal combustion,
catalytic, photocatalytic oxidation, non-thermal
plasma, and biofiltration [24-27]. Photocatalytic
oxidation (PCO) as the most current generation
of air cleaning technology has a magnificent
potential to eliminate vaporous pollutants even at
low concentrations [28]. Exceptional features of
this method are operating at ambient temperature
without notable energy supply, environmentally
friendly final products (CO
2
and H
2
O), and
applicable for various pollutants [29]. PCO
implemented using photocatalyst, ultraviolet (UV)
light and oxygen to decay chemical pollutants[30].
Numerous researchers have reviewed the materials
for the removal of VOCs [27, 31]. Most sources
have been reviewed based on a particular kind
of material, such as TiO
2
[32], graphene-based
materials [33], zinc indium sulfide [34] and silica-
nanosphere-based materials, etc., or concentrating
on the catalytic oxidation processes in a specific
condition such as low-temperature, visible light,
or based on a review of the aspect of different
VOCs[35].
In this study, a novel analytical method based
on UV- GQDs or UV-MWCNTs was used for
ethylbenzene removal from air by SGR technology.
All of important parameter for photocatalytic
process were optimized and the results validated
by spiking standard concentration of ethylbenzene
to real samples. The mixture of ethylbenzene vapor
in air was generated and storage in polyethylene
bags and its concentration determined by GC-
MS before moved to quartz tubes. The removal
efficiencies were calculated in UV- GQDs, GQDs
and MWCNT
S
by SGR procedure.
2. Experimental
2.1. Gas Chromatography (GC-FID)
The gas chromatography with flame ionization
detector (GC-FID) based on air sample loop
injection was used for ethylbenzene determination
in gas phase (Agilent GC, 7890A, FID, Netherland).
Before injection to GC-FID, Slide the plunger
carrier down and tighten. An air sample introduced
into the carrier gas by sampling valves which was
used to sample gases or liquids. Air sampling
bags were used by valve and septum port (Tedlar,
Germany). GC with a split injector (200
o
C), flame
ionization detector (250°C), and a column with
methylsiloxane was used. The oven temperature
was adjusted from 25°C to 250°C which was held
for 15 min. The carrier gas of hydrogen with flow
rate of 1.2 mL min
-1
–1
were tuned. For batch system,
the vials (PTFE) with air-tight cap (parker) were