This document discusses the treatment of wastewater using photocatalysis with titanium dioxide (TiO2). It provides background on wastewater sources and contaminants. Wastewater treatment methods include physical, biological and chemical (tertiary treatment using photocatalysis). The mechanism of photocatalytic degradation using TiO2 is described where UV light excites the TiO2, generating electrons and holes that produce radicals to degrade organic pollutants. Experimental results show the degradation of S2O3 contaminant over time is greater with both UV light and TiO2 than with just UV light. The conclusions state that nanotechnology and solar light can enable practical wastewater treatment solutions.

2. Treatment Of Waste Water
Using Photocatalysis TiO2

3. Outline
Introduction
Methodology
Discussion
Conclusion

4.  According to the World Health Organization, more
than two million people per year die of water-borne
diseases, and one billion people lack access to a
source of improved drinking water…

5. What is wastewater ?
Water that has been utilized in some
capacity that negatively impacts the
quality of water.
Sewage is a subset of wastewater that
is contaminated with feces or urines.

6. Where does wastewater come from?
Residences (kitchen, bathroom)
Rainfall, Highway drainage
Industrial institution

7. Important Contaminants Of
Wastewater Treatment
Nutrients (P, N2&C)
Organic and inorganic compounds
Refractory organics
Heavy metals
Dissolved inorganics

8. What is wastewater treatment?
process of removing contaminants
from wastewater, both runoff and
domestic and making it suitable to
discharge back into the environment.
Municipal wastewater treatment
Industrial wastewater treatment

9. Methods involved in wastewater
treatment
Wastewater Treatment
 Mechanical (Physical) Treatment
a) Preliminary
b) Primary
 Secondary (Biological) Treatment
 Tertiary (Chemical) Treatment by
photocatalysis

10. History of Photocatalysis :-
 In 1967, professor Fujishima of the University of
Tokyo first discovered the Photocatalysis by chance.
 In 1972, the discovery of Photocatalysis was
published in British Science Journal Nature.
 In 1994, Dr. Ichinose of Saga Ceramics Research
Laboratory succeeded in manufacturing water
soluble titanium dioxide.

11. Among the many available techniques,
Semi-Conductor Photocatalysis
is gaining enormous interest in the field of environmental techniques
it is because of…..
Ambient condition for reaction
Use of air as a source of oxygen for oxidation
Abundantly available solar energy
No Secondary Pollution

12. Why only Semi-conductors?
Metals
 No Band Gap
 Only oxidation/reduction
Non-Metals
 Wide Band Gap
 High energy requirement
Semi-conductors
 Excited by UV/Visible light
 Suitable for redox reactions

13. How photocatalytic degradation (PCD)
occur?

14. Mechanism of photocatalytic process:
When photocatalyst titanium dioxide
absorbs Ultra violet radiation from sun
light or illuminated light source, it will
produce a pair of electrons and holes.
The electron of the valance band
titanium dioxide becomes excited
when illuminated by light.

15.  The excess energy of this excited electron
promoted the electron to the conduction
band of titanium dioxide therefore creating
the negative-electron(e-) and positive-
hole(h+) pair. This stage is reffered to as the
semiconductors photo-excited state.
 The energy difference between the valence
band and conduction band is known as the
“Band Gap”.

16. The positive-hole of titanium dioxide
breaks apart the water molecule to
form hydrogen gas and hydroxyl
radical. The negative-electron reacts
with oxygen molecule to form super
oxide anion.This cycle continues when
light is available.

18. Design Approach

19. Photoreactor during the experimental
run

20. Results and discussion
(Photocatalytic degradation of S2O3: Effect of UV light
and TiO2)
Time (min)
0 100 200 300 400
S2O3(mg/l)
0
20
40
60
80
100
120
140
160
180
200
220
S2O3 200 mg/l [UV and TiO2]
S2O3 200 mg/l [UV and no TiO2]

21. Advantage Of TiO2
TiO2 is mostly used as a photocatalyst
due to its:
Provide greater Efficiency.
Photochemical stability.
Non-toxic in nature.
Having low cost.

23. Conclusions
Nanotechnology has applications in
environmental protections.
Nanoengineering can enable practical
solutions to unmet needs.
Solar light in place of UV light lamp
can be used to reduce the pollutant