George Chousos completed an 11-month work placement at the Institute of Nuclear & Radiological Sciences & Technology in Greece. He gained training in chemical analyses of air pollutants like particulate matter, organic compounds, and ions. He also researched air quality remediation methods like photocatalysis using titanium dioxide. As part of a project with CEN, he analyzed filters from various European sites using different protocols to investigate consistency in results. His work involved chemically analyzing approximately 600 filters to support the project.

1. Work placement portfolio
GEORGE CHOUSOS
JULY 2015

2. Work placement at Demokritos
Cardiff University:
◦ Course: Environmental Geoscience (sandwich year)
◦ Placement year: an extension of the course, takes place between the
2nd and 3rd educational year.
Institute of Nuclear & Radiological Sciences & Technology, Energy &
Safety:
◦ Energy, Safety and Environmental Technologies Division
◦ Environmental Research Lab (air quality and climate change studies, solar energy
systems, alternative fuels energy carriers, human exposure assessment)
Duration of placement: 11 months (September 2014- July 2015)

3. Training
CHEMICAL ANALYSES:
Chemical analysis of particulate
matter (PM):
◦ Organic/elemental carbon (OC/EC)
◦ Ions
◦ Cations (Na+, K+, Ca+)
◦ Anions (F-, SO4
2-, NO3-)
Chemical analysis of volatile
organic compounds (VOCs).
Bibliography
AIR QUALITY REMEDIATION
METHODS:
Heterogeneous photocatalysis.
Bibliography

4. Chemical analyses

5. What is air pollution?
“The presence in or introduction into the air of a substance which has harmful or
poisonous effect”
Types of substances:
◦ Particulate matter (acids, organic chemicals, metals, soil or dust particles)/ heart attacks, irregular
heartbeat ,aggravated asthma, decreased lung function etc.
◦ Nitrogen oxides (highly reactive gasses, emissions from cars, trucks and buses, power plants and off-road
equipment/ respiratory problems)
◦ Volatile organic compounds (VOCs) [(benzene, toluene, ethylbenzene, xylenes.)/ concentration in the
indoor environment higher (up to 10 times) than outdoors/ paints, cleaning supplies, pesticides, building
materials, copiers and printers etc./ eye, nose, throat irritation, headaches, nausea, damage to liver,
kidney, and central nervous system.]
◦ Ozone (ground-level) [chemically created from the interaction NOx, VOCs + sunlight]/ Harmful for people
with asthma]
◦ Carbon monoxide [colourless, odourless gas emitted from combustion processes (mobile sources)/ reduce
the oxygen delivery to the body’s organs, death at high levels)]
◦ Sulphur dioxide (highly reactive gasses, fossil fuel combustion from power plants (73%), extraction of
metal ores, burning of high sulphur containing fuels e.g. locomotives, large ships etc/ respiratory system
problems)
◦ Lead (fuels in on-road motor vehicles, e.g. cars and trucks, industrial sources/ today: ore and metal
processing and piston-engine aircraft/ nervous system, kidney function, immune system, reproductive and
development systems and cardiovascular system + oxygen carrying capacity in blood)

6. Particulate matter (PM)
Complex mixture of extremely small
particles and/or liquid droplets.
Acids (nitrates and sulphates), organic
chemicals, metals and soil or dust
particles.
Sources: tobacco smoke, combustions,
resuspension of accumulated dust,
cooking, use of spray.
Sizes:
 PM10 (coarse particles)- <10μm
 PM2.5 (fine particles)- <2.5μm
 PM1 (ultrafine particles)- <1μm

7. Particulate matter (PM)
OC/EC
OC/EC (organic/elemental carbon) aerosol analyser.
Measurements of carbon concentration in particulate matter,
specifically PM2.5 and PM10.
Theory of operation:
◦ Quartz filter placed in a quartz oven.
◦ Oven is purged with helium (He).
◦ Temperature ramp increases the temperature in oven  thermally
desorbing organic compounds  pyrolysis them into a manganese
dioxide (MnO2) oven.
◦ Carbon fragments flow through the MnO2 oven  converted into CO2
gas  swept out and mixed with hydrogen gas.
◦ The mixture flows through a heated nickel catalyst  converted to
methane, which is measured using a FID (flame ionization detector).
◦ Oven temperature drops and the flow stream is altered to an oxidizing
He/O2 carrier gas mixture.
◦ A second temp ramp occurs and any elemental carbon is oxidized off
the filter and into the oxidizing oven.
Thermal-optical transmittance/reflectance method.
Protocols followed:
 EUSAAR2
 NIOSH870
 IMPROVEA

8. Particulate Matter
Ions
Ion chromatographer system DIONEX 1100 & DIONEX
5000
Fields of application:
◦ Investigation of aqueous systems, e.g. drinking water,
rivers, rain water.
◦ Analysis of ions in chemical products, foods, cosmetics.
◦ Ultra-trace analysis, such as the semi-conductor and
power industry.
Theory of operation:
◦ Tissue quartz filters subjected to ultrasonic extraction
using 6ml of nanopure water and 0.5ml isopropanol.
◦ Sample is introduced via a sample loop in the injector.
◦ Sample is the pumped with the eluent onto the column 
sample ions are attracted to the charged stationary phase
of the column.
◦ The charged eluent elutes the retained ions  go through
the detector and are depicted as peaks on a
chromatograph.
What do the results mean/ how can we use them

9. Volatiles organic compounds (VOCs)
GC (gas chromatographer) equipped
with an FID (flame ionization
detector), a thermal desorption unit
and a cryotrapper (GERSTEL TDS3)
EN ISO 16017 method
Calibration  using a 10μl syringe,
spike in the glass tube 1μl of the
standard solution  inert helium (He)
flew though the tube for 30min, rate
about 100 ml/min
What do the results mean/ how can
we use them

10. Project
CEN, European Committee for Standardization, an association that unites the National Standardization
Bodies of 33 European countries.
One of the three organizations recognised by the European Free Trade Association (EFTA) 
developing and defining voluntary standards at European level. Its activities relate to a wide variety of
fields, amongst one of them is the environment.
Project’s goal  to investigate which of the protocols used had the least amount of deviation amongst
the results.
Filters obtained from four different sites all over Europe  Italy, Germany and (2) the Netherlands.
OC/EC instrument
Protocols used:
 EUSAAR2
 NIOSH870
 IMPROVEA
My obligations towards the campaign:
◦ Chemically analysed the filters/ record the results in the logbook.
◦ The filters that I analysed were approximately 600.

11. Air quality
remediation methods
PHOTOCATALYSIS

12. Photocatalytic decomposition of atmospheric gas pollutants
using building materials infused with titanium dioxide
(TiO2).

13. Basic principles of heterogeneous photocatalysis
Photocatalysis is the acceleration of a
chemical reaction, e.g. oxidation, by
the use of light energy.
System requirements:
◦ Photocatalyst: a semiconductor
material e.g. metal oxides (TiO2, ZnO,
ZrO2,CdS etc.)
Electronic structure: electrons present in
Valence Band (VB), empty Conduction
Band (CB).
◦ Intermediate: gas or liquid form
◦ Irradiation: hv>EBG (UV light <410nm)

14. Basic principles of heterogeneous photocatalysis

15. Mechanics of the photocatalytic activity
◦ Photons with energy larger than the
EBG
◦ Electrons from VB are transferred to
CB, creating pairs of free electrons
(eCB
-) and positive holes (hVB
+).
◦ Transfer of electrons (e-) to the
surface and reaction with the
adsorbed receivers and donors or
recombination (heat and light
production)
◦ Formation of reductive oxygen
radicals (O2
-) and hydroxyl radicals
(OH-) by reacting with the electrons
and the holes, respectively, which in
turn can oxidize organic and inorganic
compounds.

16. Fields of application of the photocatalytic activity
Applications:
◦ Air purification.
◦ Smell elimination.
◦ Protection of urban environment,
such as road domain and buildings.
◦ Development of super-hydrophilic
surfaces with self-cleaning and
anti-fogging attributes.
◦ Limitation of the bacterial
proliferation in a hospital or
medical environment.
◦ Purification and cleaning of the
water

17. Titanium dioxide (TiO2) as a photocatalyst
Titanium dioxide (TiO2) is a [1]
n –type
semiconductor  electrical
conductivity value is between that of a
conductor and an insulator.
Current uses:
◦ Pharmaceutical products
◦ Cosmetic products
◦ Grooming and toiletries
◦ Paints
◦ Food colouring (E171)
Mainly found in the naturally
occurring mineral Ilmenite.
[1]
LARGE ELECTRON CONCENTRATION THAN HOLE CONCENTRATION

18. Titanium dioxide (TiO2) as a photocatalyst
A) Rutile:
◦ Tetragonal crystal system
◦ Energy gap: 3.02 eV  413nm
◦ Stable at high temperatures
B) Anatase:
◦ Tetragonal crystal system
◦ Energy gap: 3.23 eV  388nm
◦ Stable at low temperatures:
◦ If subjected to temperatures over 450o C , it transforms into
rutile.
◦ Higher photocatalytic action:
◦ Difference in EG. Higher reduction activity since its energy
gap is higher than of rutile, thus requiring less energy to
initiate redox reactions
◦ Difference in crystal structure
C) Brookite:
◦ Rare form
◦ At temperatures over 750oC it transforms into
rutile
A
B
C

19. Photocatalytic advantages of TiO2 against other
semiconductor materials
◦ High photocatalytic activity
◦ High availability.
◦ Low cost.
◦ Low to no toxicity.
◦ Biological and chemical inertness and
stability
◦ Activation at environment conditions (low
energy costs).
◦ High resistance to photo-corrosion.
Semiconductor
Energy
gap (eV)
Wavelength
(nm)
ZnO 3.2 390
WO3 2.8 443
TiO2 3.0 380
CdS 2.5 497
CdSe 1.7 730

20. Factors affecting the photocatalytic performance
Material
◦ Particle size (1-100 nm)
◦ Surface features (method of preparation)
◦ Chemical modification of crystal lattice
◦ Insertion of metal or non-metal ions (doping)
◦ Combing TiO2 with other semiconductor compounds
◦ Deposition of noble metals
Increase the active surface of the catalyst 
stronger photon absorption  better surface
coverage from pollutant  higher reaction rates
Increase of complexity, geometric roughness
and surface porosity  increase active
surface area  higher absorption
percentages
• Improving photo-activity of
semiconductor under UV radiation, while
extending the activity to larger
wavelengths (visible light)
• Easier separation of the photo-induced
charge carriers (e-, h+)
• Hindrance of recombination

21. Factors affecting the photocatalytic performance
External factors
◦ Type/Intensity of radiation
◦ Initial concentration
◦ Temperature
◦ Humidity
◦ Oxygen
◦ Chemical compounds mixture
Low wavelengths  photons energy  higher activity
Increase in intensity  photon flux  higher
photocatalytic performance
Directly related to the present conditions and the type of
compound
Photocatalytic activity at ambient temperature scale (20o-40oC)
Small variations have no particular influence
Water molecules assist to the formation and regeneration of OH
.
humidity rates suspension of photocatalytic oxidation  emergence
of competitive adsorption phenomena between the water and pollutant
molecules
the concentration  the photocatalytic activity
An excess of oxygen  full oxidation and to limitation of by-product
formation
Acceleration or deceleration

22. Factors affecting the photocatalytic performance
Deactivation
◦ Photocatalyst deactivation
◦ Recovery methods
Formation of by-products that remain
adsorbed on the surface of the catalyst,
taking away active sites and blocking
the adsorption of new water molecules,
preventing the formation of OH.
• Exposure of catalyst in dry or humidified
air stream
• Irradiation with UV light
• Heat treatment at high temperatures
• Surface treatment with the usage of
humidified stream of hydrogen peroxide

23. Humidity (%RH)
1) TCE, Acetone, Methanol:
◦ The increase of water molecules
(water vapour concentration) works
antagonistically with the gas
molecules at occupying active sites
on the surface  lower reaction
rates
2) Toluene:
Water molecules suspend the
accumulation of carbon on the surface
of the semiconductor  accelerating
the photocatalytic activity.

24. Initial concentration
The photocatalytic reaction rate
increases as the initial concentration
increases, for all the pollutants, but
at a particular concentration and
above it remains stable.
The kinetics can be expressed by:
r = (k*K*C)/ (1+ K*C)
r: reaction rate
k: reaction rate constant
K: adsorption equilibrium constant
The photocatalytic degradation rate
relates to k and K; therefore, a higher
adsorption constant does not always
result in a higher reaction rate.

25. Intensity of UV radiation
◦ For illumination levels below
1000-2000 μW cm-2, the
photocatalytic degradation rate
increases linearly with photon
flux, but for levels above 1000-
2000 μW cm-2 the rate increases
with the square root of photon
flux.
◦ Wavelength of UV light:
◦ Germicidal lamp (200-300 nm, max at 254
nm)
◦ Black light (315-400 nm, max at 352nm)
Both lamps have sufficient energy to promote
photocatalytic reaction, but germicidal lamp’s
photo flux was higher  higher degradation
rate.

26. Chemical compound mixture
◦ Presence of NO:
◦ The conversion of BTEX is higher than BTEX
solely.
◦ This enhancement is due to the formation
of hydroxyl radicals (OH.) according to this
reaction:
NO + HO2
.  NO2 + OH.
The degree of influence for each of the
organic compounds depends on the
reaction rate of each with the hydroxyl
radicals (OH.).
◦ Presence of BTEX:
◦ NO conversion decreased and generated a
lower secondary pollutant, NO2.

27. Photocatalytic experiments:
Instrumentation and experimental conditions
Chamber characteristics:
◦ Chamber volume : 0.125m3
◦ 10 UV lamps, 20cm distance from
the material
◦ 2 fans for the prevention of heat
fluctuations that might affect the
photocatalytic process
◦ Cubic cell: 0.001 m3

28. Photocatalytic experiments:
Instrumentation and experimental conditions
FLOW METRE
CHEMILUMINESCENT NITROGEN
OXIDES ANALYSER

29. Photocatalytic experiments:
Instrumentation and experimental conditions
Materials:
◦ Photocatalytic cement in cube form
◦ Photocatalytic cement in powder form
Experimental conditions:
◦ Flow rate:
◦ 2.3 L/min (synthetic air)
◦ 0.8 L/min (nitrogen oxides)
◦ Duration of radiation: 4-5 hours

30. Photocatalytic experiments:
Experimental calculation procedure
In the chamber there are 4 pollutant removal mechanisms:
◦ Absorption from the chamber walls
◦ Photo-degradation from the radiation
◦ Adsorption to the surface of the material
◦ Photocatalytic oxidation from TiO2
Photocatalytic activity expression parameters:
◦ Ph% decomposition =
◦ Destruction Rate (μg/m2s)=
◦ Destruction Velocity (m/s)=
100
]/)[(
x
C
CCC
initial
initialfinalinitial 
Asa
xFCC finalinitial ])[( 
finalC
nRateDestructio

31. Photocatalytic experiments:
Results
SAMPLE (cubes) BRB3 B3 BRA3
Concentration (ppb) 370-380 360-370 340-350
Ph % 17.6145 13.0808 11.5318
Destruction Rate (μg/m2s) 0.21230 0.15454 0.12662
Destruction Velocity
(m/s)
0.00068 0.00048 0.00041
0.0
100.0
200.0
300.0
400.0
500.0
13.50
13.58
14.06
14.14
14.22
14.30
14.38
14.46
14.54
15.02
15.10
15.18
15.26
15.34
15.42
15.50
15.58
16.06
16.14
16.22
16.30
16.38
16.46
16.54
Time
BRB3
NO NOx
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
450.0
12.00
12.13
12.26
12.39
12.52
13.05
13.18
13.31
13.44
13.57
14.10
14.23
14.36
14.49
15.02
15.15
15.28
15.41
15.54
16.07
16.20
16.33
Time
B3
NO NOx
UV lamps
UV lamps

32. 0.0
100.0
200.0
300.0
400.0
10.50
11.06
11.22
11.38
11.54
12.10
12.26
12.42
12.58
13.14
13.30
13.46
14.02
14.18
14.34
14.50
15.06
15.22
15.38
15.54
16.10
B2 (100% grey)
NO NOx
UV lamps
Photocatalytic experiments:
Results
Sample
(powder)
W1
(100% white)
B2
(100% grey)
R1
(100% ref)
WRAs
(50% ref- 50% white)
BRC2
(90% ref- 10% grey)
Concentration
(ppb)
330-340 300-310 340-350 330-340 310-320
Ph % 19.1950 41.9706 11.1456 15.6579 3.5148
Destruction
Rate (μg/m2s)
0.24593 0.56604 0.15668 0.20627 0.04482
Destruction
Velocity (m/s)
0.00094 0.00287 0.00050 0.00074 0.00014
0.0
100.0
200.0
300.0
400.0
10.47
11.02
11.17
11.32
11.47
12.02
12.17
12.32
12.47
13.02
13.17
13.32
13.47
14.02
14.17
14.32
14.47
15.02
15.17
15.32
15.47
W1 (100% white)
NO NOx
UV lamps

33. 0.0
100.0
200.0
300.0
400.0
10.46
11.03
11.20
11.37
11.54
12.11
12.28
12.45
13.02
13.19
13.36
13.53
14.10
14.27
14.44
15.01
15.18
15.35
15.52
16.09
16.26
R1 (100% reference)
NO NOx
UV lamps
Photocatalytic experiments:
Results
0.0
100.0
200.0
300.0
400.0
11.00
11.16
11.32
11.48
12.04
12.20
12.36
12.52
13.08
13.24
13.40
13.56
14.12
14.28
14.44
15.00
15.16
15.32
15.48
16.04
16.20
WRAs (50% ref- 50% white)
NO NOx
UV lamps
0.0
100.0
200.0
300.0
400.0
10.15
10.20
10.25
10.30
10.35
10.40
10.45
10.50
10.55
11.00
11.05
11.10
11.15
11.20
11.25
11.30
11.35
11.40
11.45
11.50
11.55
12.00
12.05
12.10
12.15
12.20
12.25
12.30
12.35
12.40
12.45
12.50
12.55
13.00
13.05
13.10
13.15
13.20
13.25
13.30
13.35
13.40
BRC2 (90% ref- 10% grey)
NO NOx
UV lamps

34. Placement learning outcomes
◦ Enhanced my skills on teamwork, communication and co-operation.
◦ Development of my critical thinking on issues regarding decisions in the laboratory.
◦ Broadening the horizons and expanding my knowledge on subjects concerning air pollution
and methods of remediation.
◦ Contribution to tasks I was assigned by my supervisors, e.g. participating in lab’s chemical
analyses.
◦ Got acquainted with the usage and functionality of instruments specialised for recording
and measuring air pollution.
◦ Enhanced my skills on researching for appropriate and beneficial bibliography and creating a
thematic library.
◦ Practised and developed my scientific speech by giving short lectures to students, discussing
photocatalysis as a concept while presenting them the instruments that are being used.
◦ Improved my abilities on utilizing Microsoft Word & Excel through assignments given to me
by my supervisors.
◦ Participated as co-author in one scientific paper, that is to be submitted in a scientific
journal, and in 2 abstracts submitted to the 3rd international conference for photocatalytic
and advanced oxidation technologies in Gdansk, Poland and EAC, the European Aerosol
Conference in Milan, Italy.