Environmental Engineering Reference
In-Depth Information
as the electron scavenger. According to Wang
et al.
[44], the photocata-
lytic reaction could be terminated in the absence of dissolved oxygen and
the rate of photocatalytic decomposition of organic compound would be
affected by the steady state concentration of dissolved oxygen. Zhou and
Ray [40] performed an Eosin B photo-oxidation experiment in oxygen
atmosphere (saturated). They have used the Langmuir-Hinshelwood equa-
tion to describe the dependence of dye-degradation rate constant on the
concentration of dissolved oxygen as follows:
Kp
KP
OO
(4.4)
k
2
2
p
1
OO
2
2
where k
p
is the kinetic constant for organic compound degradation, K
O
2
is
the adsorption constant of dissolved oxygen on TiO
2
catalyst, and p
O
2
is the
partial pressure of dissolved oxygen.
4.7 Conclusions
Huge amounts of dye-containing wastewater released from textile indus-
tries contaminate water resources every year. Conventional treatment
methods are capable of color removal from wastewater but are incapable of
complete mineralization.
UV-light-driven photocatalysis is an emerging technique for the min-
eralization of dye-containing wastewater. Normal band gap excitation and
photo-oxidation process occur under UV light. In the presence of visible
light, dye degradation is also possible via dye-sensitization pathway in the
presence of a sensitizing dye.
As UV light is costly and hazardous, today solar-light-assisted photo-
catalysis is becoming popular around the world. There are several pho-
toreactors such as CPC, TFFBR, DSS, etc., that have shown potential
for dye degradation (mineralization) under natural sunlight. Like other
photo-oxidation processes, dye photo-oxidation also depends on different
parameters such as photocatalyst dose, solution pH, light intensity, and
electron scavenger.
Acknowledgement
The First author would like to thank the Natural Sciences and Engineering
Research Council of Canada (NSERC), for financial support.
Search WWH ::
Custom Search