PMBRs for waste water treatment

1. PHOTOCATALYTIC
MEMBRANE REACTORS
MR.BASITALI SADIQUE NEVAREKAR
B-Tech (Chemical)
20160480
PRESENTED BY

2. INTRODUCTION

3. WHY PMRs ???
A very promising method
for solving problems
concerning separation of
the photo-catalyst as well
as products and by-
products of photo-
decomposition from the
reaction mixture is
application of
photocatalytic membrane
reactors (PMRs).
PMRs are hybrid reactors
in which photo-catalysis
is coupled with a
membrane processes.
The membrane would
play both the role of a
simple barrier for the
photo-catalyst and a
selective barrier for the
molecules to be degraded.

4. HETEROGENEOUS PHOTOCATALYSIS
“Heterogeneous photocatalysis can be described as
acceleration of photoreaction in the presence of catalyst”

5. External
mass
transfer
Internal
mass
transfer
adsorption
Surface
reaction
Desorption
Internal
mass
transfer
External
mass
transfer
Steps involved in heterogeneous
photocatalysis

6. Figure. 1 Schematic of semiconductor excitation by band gap
illumination leading to the creation of “electrons” in the conduction
band and “holes” in the valance band ( Mozia 2010)
MECHANISM OF PHOTOCATALYTIC
OXIDATION

7. CHARACTERISTIC OF
PHOTOCATALYST
A Photocatalyst should possess;
High activity.
Resistance for poisoning.
Mechanical stability and resistance to attiration.
Physical and chemical stability.
Inexpensive.
Able to utilize not only UV light but also visible
light.

8. MEMBRANE
SEPARATION
PROCESSES

9. Membrane
techniques
Pressure driven
Microfiltration
Ultrafiltration
Nano-filtration
Concentration
difference
driven
Dialysis
Pervaporation
DCMD
CLASSIFICATION OF MEMBRANE
TECHNIQUES

10. PMRs Configurations and
designs
PMRs
Reactors with
catalyst suspended in
feed solution
Reactors with
catalyst immobilized
in/on the membrane

11. Reactors with
catalyst suspended
in the feed solution
Irradiation of
membrane module
Irradiation of feed
tank
Irradiation of an
additional reservoir
PMRs with suspended TiO2

12. Figure. 3. PMR utilizing photocatalyst in suspension: irradiation of
the feed tank (Mozia 2010)

13. Figure. 2. PMR utilizing photocatalyst in suspension: irradiation of
the membrane module (Mozia 2010)

14. Figure. 4. PMR utilizing photocatalyst in suspension: irradiation of
the additional reservoir (photoreactor) located between the feed
tank and membrane module ( Mozia 2010).

15. PMRs with suspended TiO2
Reactors with
catalyst suspended
in feed solution
With pressure
driven membrane
techniques
Nanofiltration
Ultrafiltration
microfiltration
With concentration
driven techniques
DCMD
Dialysis
Pervaporation

16. PMRs coupling photocatalysis with
pressure-driven membrane processes
Figure 5. Schematic diagram of laboratory scale slurry PMR with submerged
membranes and internal (immersed) UV lamps [Fu et. al. 2006].

17. Advantages
Higher
photocatalytic
efficiency
Convenient to
adjust
Membrane
damage could
be avoided
Disadvantages
Higher
operating cost
Membrane
fouling
Low quality
of permeate

18. PMRs with TiO2 immobilized
in/on membrane

19. Figure 6. Possible types of asymmetric photocatalytic membranes
.

20. Advantages
No need to separate
and recycle the
catalyst
No membrane
fouling
Contaminants
could be
decomposed either
in feed or permeate
Disadvantages
Low photocatalytic
efficiency
Adjustment of
catalyst loading is
impossible
Risk of damage of
polymer
membranes
Necessity of
membrane
exchange