Solar Photocatalysis a green and novel technology for wastewater treatment. It is a sustainable way to harvest solar energy for treatment of wastewater at a lower cost thus helping in achieving some of the Sustainable Development Goals(i.e. Good Health and Wellbeing). This is based on the advanced oxidation process i.e. generation of reactive oxygen species which can help in the degradation of pollutants

1. Solar Photocatalysis
A green technology for waste water
treatment
Presented By:
Amit Kumar Bundela
M.Sc. Environment Science Env. Tech.
Roll No. 17430ENS008
Banaras Hindu University

2. Thermochemical Process
PhotonsHeat
Photochemical Process
SUN
INTRODUCTION

3. 1. The solar detoxification is a novel green technology for waste
water treatment .
2. Advanced Oxidation Process (AOP) depend on the generation
of reactive oxygen species which help in the degradation of the
pollutants .
Introduction (ctd.)
3. Solar photo-catalysis detoxification has developed
recently wherein the renewable and non-exhaustible solar
energy is used for irradiation and hence aiding to sustainable
use of energy.

4. Photo-catalysis mechanism
Adapted from Herman et.al. 1999; Hashimito et al. 2005

5. Photo-catalyst Materials
Photocatalyst Band Gap Energy (eV) Corresponding
Wavelength(nm)
Si 1.1
WSe2 1.2
Fe2O3 2.2 565
CdS 2.4 497
WO3 2.7 443
TiO2 (Rutile) 3.0 390
αFe2O3 3.1
ZnO 3.2 390
TiO2(Anatase) 3.2
SrTiO3 3.4
SnO2 3.5
ZnS 3.7 336
Modified from Bhatkhande et al 2001

6. Comparison of Concentrating System and Non
Concentrating System
CONCENTRATING SYSTEM
Advantages Disadvantages
Turbulent flow Only direct radiation
More practical use of a supported
catalyst
High cost (sun tracking)
More practical use of a supported
catalyst as
less is needed per unit collector surface
Low optical efficiency and usually expensive,
Low quantum efficiency (r = k I<1 with TiO2)
Smaller reactor tube area (shorter loop
in which to confine, control, and handle
the
water)
Lower optical efficiency and quantion of e-
/h+
than in non-concentration systems
There is no evaporation of volatile
compounds
Possible water overheating
( Modified from Minero et. al. 1996, Malato S. et. al. 1997, Blanco J. et. al. 2007)

7. NON CONCENTRATING COLLECTORS
Advantages Disadvantages
Direct and diffuse radiation Vaporization of reactants
No heating Laminar flow (low mass transfer)
Low cost and fewer maintenance
requirements
Reactant contamination and mass transfer
problems in photocatalysis
High optical efficiency Weather resistance, chemical inertness and
ultraviolet transmission
High quantum efficiency (r = k I with TiO2) Water overheating and Reactant contamination
Comparison of Concentrating System
and Non Concentrating System (ctd.)
( Modified from Minero et. al. 1996, Malato S. et. al. 1997, Blanco J. et. al. 2007)

8. 1. Parabolic trough reactor (PTR)
2. Thin-film-fixed-bed reactor (TFFBR)
3. Double skin sheet reactor (DSSR)
Types of Photo-catalytic Reactors:

9. Bacterial disinfection using solar photo-catalysis

10. 1.Photo-catalysis is a advantageous as it is not energy
intensive conventional method.
2. It can be used for the depletion of a wide range of
hazardous compounds in different wastewaters.
3. The reaction time for photo-catalysis is modest and
the chemical input that is required is very less. The
secondary waste that is generated is also minimum.
Benefits

11. Conclusions
• . The industrial application though is an infantile stage, is expected to
flourish soon.
• Some of the challenges that need to be overcome are the solar
utilization efficiency, the construction and operation of a
photoreacter and also the separation of catalyst.
• If all the aspects are taken care of and the photocatalytic process can
be carried out in a large scale then not only a solution for wastewater
treatment can be found out but also the use of renewable and
pollution less source of energy would lead to sustainable
development.