Synthesis and comparison of the photocatalytic activities of antimony, iodide, and rare earth metals on SnO2 for the photodegradation of phenol and its intermediates under UV, solar and visible light irradiations
Al-Hamdi, Abdullah M. (2017-08-18)
Väitöskirja
Al-Hamdi, Abdullah M.
18.08.2017
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-335-117-2
https://urn.fi/URN:ISBN:978-952-335-117-2
Tiivistelmä
The tremendous amounts of pollutants being dumped into the water have become a major
problem all over the world which let researchers to focus on. These chemicals are
stubborn toxins not easily eliminate, difficult to keep up can go transformations under
certain conditions, after conversion might become more toxic than their parent molecule.
There are many ways to withdraw these organic compounds from the water sources, the
cheapest way is to use photocatalytic material oxides like SnO2 through harnessing the
sunlight and using it for photocatalytic degradation processes. Photocatalysis by
advanced oxidation processes is a most popular and promising method of taking away
these contaminants such as phenol and its intermediates form water.
Tin dioxide (SnO2) has already been used in detecting some of toxic gases and involved
in many other technological applications. SnO2 is a strong oxidizing agent and a powerful
reducing catalyst, a variety of techniques utilized to improve the photocatalytic activities
of SnO2 including doping and others. Photodegradation of phenol in the presence of SnO2
Nps under UV light irradiation is known to be an effective photocatalytic process.
However, phenol photodegradation under solar and visible light irradiation is less
effective due to the large band gap (BG) of SnO2. In this study, pure SnO2 catalysts been
synthesized by a sol-gel method using tin tetrachloride, ethanol and water. For the
synthesis of SnO2 doped with species containing different ions such as [gadolinium (Gd),
cerium (Ce), Lanthanum (La), neodymium (Nd), iodine (I) and antimony (Sb)], different concentrations of these dopants such as (0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%,
1.0%, and 1.1%) were mixed and dissolved separately in ethanol and water later added to
the precursor solution. At the final stages ammonia was added to cause gelation of the
sol. The sol-gel formed was washed and prepared at low temperature to obtain the SnO2
nanoparticles (Nps).
SnO2 powders been characterized by X-ray diffraction (XRD), scanning electron
microscope (SEM), transition electron microscope (TEM) and the specific surface area
was estimated by Brunauer–Emmett–Teller (BET) analyser. Several analytical
techniques were used in the analysis of phenol and its byproducts such as high
performance liquid chromatography (HPLC), UV-Vis spectrophotometry, gas
chromatography (GC), capillary electrophoresis (CE), total organic carbon (TOC)
measurements, Fourier transformer infrared (FTIR) and by determining chemical oxygen
demand (COD) from the pollutant. The results show that a decrease in the particle size
from 8 to 1.8 nm and increase in the surface area up to 58 m2/g upon increasing of
different doping contents from 0% to 1.1% as they incorporate into SnO2. In this study, The optimum parameters were found to be catalyst loading (65 mg/50.00
mL), light intensity (8 W mercury lamp, 300 W xenon lamp or sunlight during full sunny
days), reaction time (2-3 h), phenol concentration (10 ppm), 4 L/min of an optimum air
flow, sampling time (12-13), sample volume (250.00 mL), and pH of the reaction medium
was (5.7). The GC study shows that the irradiation of the catalyst by UV light was found
to enhance phenol photodegradation in the first 30 min of the experiment. The UV-Vis
investigation of the treated phenol samples indicates that phenol molecules initially
transform to byproducts, which also optically absorb in the similar region as phenol. In
this study, for photocatalysis experiments on phenol photodegradation the optimum
condition applied under UV light irradiation allowed more than 95% of phenol
degradation with SnO2/La 0.6 wt. % after 2 h. Also, 95% of phenol was found to degrade
with the photoactivity of SnO2/Sb 0.6 wt. % under solar light irradiations, the same
amount of phenol photodegradation was found with SnO2/Gd 0.6 wt. % under visible
light irradiation and with exactly the same optimum conditions only changing the light source. HPLC results show that the intermediates are in the order catechol (Cat)>
resorcinol (Res) > hydroquinone (HQ) > benzoquinone (BQ), but the last stages of phenol
photodegradation show isopropanol (2-P) and acetic acid (AA). The reaction of phenol
photodegradation results indicate that it takes place when light radiation photoexcites a
catalyst in the presence of oxygen, hydroxyl radical (•OH) is generated to attack phenol
and reacts with OHˉ to produce Cat or HQ, which on continuous oxidation breaking them
down leading to the formation of aliphatic acids and finally yielding carbon dioxide (CO2)
and water (H2O). In fact, the mineralization process starts early during the photocatalytic
degradation process as Fourier transform infrared FTIR results showed that the phenol
molecules are converted to CO2 in the early stages and continued until all phenol are
removed. The change in the concentration of phenol affects the pH of the solution due to
the intermediates formation during the photodegradation of phenol. Clear correlations
between the results obtained from these multiple measurements were found, and a kinetic
pathway for the degradation process was proposed. A maximum of 0.02228 min-1 of
propanol and a minimum of AA 0.013412 min -1 were recorded.
problem all over the world which let researchers to focus on. These chemicals are
stubborn toxins not easily eliminate, difficult to keep up can go transformations under
certain conditions, after conversion might become more toxic than their parent molecule.
There are many ways to withdraw these organic compounds from the water sources, the
cheapest way is to use photocatalytic material oxides like SnO2 through harnessing the
sunlight and using it for photocatalytic degradation processes. Photocatalysis by
advanced oxidation processes is a most popular and promising method of taking away
these contaminants such as phenol and its intermediates form water.
Tin dioxide (SnO2) has already been used in detecting some of toxic gases and involved
in many other technological applications. SnO2 is a strong oxidizing agent and a powerful
reducing catalyst, a variety of techniques utilized to improve the photocatalytic activities
of SnO2 including doping and others. Photodegradation of phenol in the presence of SnO2
Nps under UV light irradiation is known to be an effective photocatalytic process.
However, phenol photodegradation under solar and visible light irradiation is less
effective due to the large band gap (BG) of SnO2. In this study, pure SnO2 catalysts been
synthesized by a sol-gel method using tin tetrachloride, ethanol and water. For the
synthesis of SnO2 doped with species containing different ions such as [gadolinium (Gd),
cerium (Ce), Lanthanum (La), neodymium (Nd), iodine (I) and antimony (Sb)], different concentrations of these dopants such as (0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.6%, 0.8%,
1.0%, and 1.1%) were mixed and dissolved separately in ethanol and water later added to
the precursor solution. At the final stages ammonia was added to cause gelation of the
sol. The sol-gel formed was washed and prepared at low temperature to obtain the SnO2
nanoparticles (Nps).
SnO2 powders been characterized by X-ray diffraction (XRD), scanning electron
microscope (SEM), transition electron microscope (TEM) and the specific surface area
was estimated by Brunauer–Emmett–Teller (BET) analyser. Several analytical
techniques were used in the analysis of phenol and its byproducts such as high
performance liquid chromatography (HPLC), UV-Vis spectrophotometry, gas
chromatography (GC), capillary electrophoresis (CE), total organic carbon (TOC)
measurements, Fourier transformer infrared (FTIR) and by determining chemical oxygen
demand (COD) from the pollutant. The results show that a decrease in the particle size
from 8 to 1.8 nm and increase in the surface area up to 58 m2/g upon increasing of
different doping contents from 0% to 1.1% as they incorporate into SnO2. In this study, The optimum parameters were found to be catalyst loading (65 mg/50.00
mL), light intensity (8 W mercury lamp, 300 W xenon lamp or sunlight during full sunny
days), reaction time (2-3 h), phenol concentration (10 ppm), 4 L/min of an optimum air
flow, sampling time (12-13), sample volume (250.00 mL), and pH of the reaction medium
was (5.7). The GC study shows that the irradiation of the catalyst by UV light was found
to enhance phenol photodegradation in the first 30 min of the experiment. The UV-Vis
investigation of the treated phenol samples indicates that phenol molecules initially
transform to byproducts, which also optically absorb in the similar region as phenol. In
this study, for photocatalysis experiments on phenol photodegradation the optimum
condition applied under UV light irradiation allowed more than 95% of phenol
degradation with SnO2/La 0.6 wt. % after 2 h. Also, 95% of phenol was found to degrade
with the photoactivity of SnO2/Sb 0.6 wt. % under solar light irradiations, the same
amount of phenol photodegradation was found with SnO2/Gd 0.6 wt. % under visible
light irradiation and with exactly the same optimum conditions only changing the light source. HPLC results show that the intermediates are in the order catechol (Cat)>
resorcinol (Res) > hydroquinone (HQ) > benzoquinone (BQ), but the last stages of phenol
photodegradation show isopropanol (2-P) and acetic acid (AA). The reaction of phenol
photodegradation results indicate that it takes place when light radiation photoexcites a
catalyst in the presence of oxygen, hydroxyl radical (•OH) is generated to attack phenol
and reacts with OHˉ to produce Cat or HQ, which on continuous oxidation breaking them
down leading to the formation of aliphatic acids and finally yielding carbon dioxide (CO2)
and water (H2O). In fact, the mineralization process starts early during the photocatalytic
degradation process as Fourier transform infrared FTIR results showed that the phenol
molecules are converted to CO2 in the early stages and continued until all phenol are
removed. The change in the concentration of phenol affects the pH of the solution due to
the intermediates formation during the photodegradation of phenol. Clear correlations
between the results obtained from these multiple measurements were found, and a kinetic
pathway for the degradation process was proposed. A maximum of 0.02228 min-1 of
propanol and a minimum of AA 0.013412 min -1 were recorded.
Kokoelmat
- Väitöskirjat [1037]