Oxford-Princeton collaborative workshop

Oxford
-
Princeton collaborative workshop




Motivation: concerns in water purification


Water purification: goals of next generation
systems





Outlook: challenges of photocatalytic
microfluidic reactors




o
Solar photocatalytic water purification

o
Applications of micro/nanotechnology
(microfluidics) in water purification

80%
of urban rivers in China are


contaminated to varying degrees


1.2 billon
people globally

lack access to clean water

Millions

of people die

annually due to water

related diseases

Qu
, et al.
Critical Reviews in Environmental Science and Technology
, 2010
, 40,
519
–
560. Shannon, et al.

Nature
, 2008,
452
, 301
-
310.








Drinking water production
:
Disinfection:
extensive chemicals treatments, e.g., chlorine, and high
power UV expose.


Waste water treatment
(industrial and
municipal):
Decontamination (metal ions): extensive
chemicals treatments , e.g., chelating chemicals, and
absorbents, or membrane technology


Seawater desalination:
reverse osmosis
membrane



Next
-
generation

systems:
low
-
environmental
-
impact, low
-
energy
-
intensive, and high
efficiency

o
Micro/nanotechnology in water purification
: carbon
nanotubes

membranes,
nanofiber

membranes, nanoporous
ceramics, clays, and micro/
nanofluidics
.


Peters, et al.
Chem. Eng. Technol. 2010,
33
, 1233
–
1240
. Shannon, et al.
Nature
, 2008,
452
, 301
-
310.

Hochstrat
, et. al.
Desalination and water treatment
, 2010,
18
, 96
-
102.
Valli
, et al.
Int. J. Nuclear

Desalination,

2010 ,
4,
49
-
57. Blanco
-
Galvez, et al.
J Solar Energy Engineering.
2007,
129,
4
-
15.

o
Solar photocatalytic detoxification and
disinfection
:
solar reactors,
photocatalyts
, hybrid
photocatalytic
-
biological process, and photocatalytic
membrane process.

1. Photo
-
induced charge separation

3. Oxidation of organics

2. Generation of hydroxyl radicals

Belhacova
, et al.
J Chem Technol Biotechnol , 1999,
74
, 149
-
–154.

Blanco
-
Galvez, et al.
J Solar Energy Engineering.
2007,
129,
4
-
15.

Lin, et al.
J. Applied Electrochemistry
, 2005,
35
, 699
–
708. Lindstrom, et al.
AIChE

J.
2007,
53
,
3 695
-
702. Molinari, et al.
J Membrane Science, 2002,
206
, 399
–
415.

TiO2 on optical

fibers

TiO2 on

membranes

TiO2 in microfluidic

channels



Photocatalyst
:
slow kinetics,
low
photoefficiency
, and narrow
coverage of solar spectrum


Reaction

Efficiency

Commercial

viability

Overall

Efficiency


Characterization standards
:
detoxification efficiency is
strongly dependent on the
structure and reactivity of
pollutants, catalysts, and the
reaction environment.


Hybrid process
:
integrative
photocatalytic process with
biological and membrane process

Blanco
-
Galvez, et al.
J Solar Energy Engineering.
2007,
129,
4
-
15.
Friedmann

et al.
Applied Catalysis B:

Environmental

2010,
99,
398
–
406.


M
icrofluidics

act as sensors

for detection of toxic
compounds in water.
Cleary, et al.
IEEE sensors Journal.
2008,
5
, 508
-
515. Curtis, et al.
Lab on a chip
. 2009,
9
, 2176
–
2183







Micro/
nanofluidics

for water d
esalination
.

Kim, et al.
Nature Nanotechnology
. 2010,
5
, 297
-
301.


Microfluidics for detecting and capturing
microorganism in water.
Balasubramanian
, et al.
Lab on
a chip
2007,
7,
1315
–
1321. Liu, et al.

Water Science & Technology:
Water Supply,
2007,
7,
165
-
172. Chieko, et al.
J Microbiological
Methods

2007,
68,
643
-
647.





Microfluidic

m
odel

system to integrate
hydrodynamics with photochemical reactions

o
Quantitative understanding photocatalytic reactions under flow
conditions, e.g. flow in porous media

o
Establish protocols for standardize parameters for photocatalytic
water purification


Microfluidic approaches for synthesis of
effective photocatalytic nanoparticles

o
Nanoparticles with high
photoefficiency

and broad solar
spectrum coverage


Integrative photocatalytic microfluidic devices
with membrane or biological process

Clean water production

Effective device fabrication