Photochemical Oxidation
Jun Liu
What is the process of
photochemical oxidation?
• Photochemical oxidation is therefore the
reaction of a chemical change in a
substance which causes it to lose
electrons which is initiated by light.
A common example is photochemical
smog which is caused by hydrocarbons
and NOx reacting under the influence of
UV light.
Executive Summary
• The photochemical oxidation processes
generally involve generation and use of
powerful but relatively nonselective
transient oxidizing species, primarily the
hydroxyl radical (·OH) and in some cases
the singlet oxygen which can be generated
by photochemical means.
Photochemical oxidation processes include:
•
•
•
•
(1) vacuum ultraviolet (VUV) photolysis,
(2) ultraviolet (UV)/oxidation processes,
(3) the photo-Fenton process,
(4) sensitized photochemical oxidation
processes.
(1) vacuum ultraviolet (VUV) photolysis
Photolysis of water using UV radiation of a
wavelength shorter than 190 nanometers
yields ·OH and hydrogen radicals (H·).
(2) ultraviolet (UV)/oxidation processes
UV/oxidation processes generally involve
generation of ·OH through UV photolysis
of conventional oxidants, including
hydrogen peroxide (H2O2) and ozone (O3).
(3) the photo-Fenton process
Decomposition of H2O2, using ferrous iron
[Fe(ll)] or ferric iron [Fe(lll)] under acidic
conditions yields ·OH.
(4) Sensitized advanced photochemical
oxidation (APO).
• Sensitized APO processes can be broadly
categorized as dye-sensitized and
semiconductorsensitized processes.
In a dye-sensitized APO process, visible light is
absorbed by a sensitizing dye, which excites the
dye molecules to a higher energy state.
In a semiconductor-sensitized APO process,
metal semiconductors are used to destroy
environmental contaminants by means of lightinduced redox reactions.
Light source used in APO:
As implied by the term Photochemical
oxidation, light energy is one of the
essential components. Depending on the
type of Photochemical oxidation employed,
UV radiation [of wavelengths from 100 to
400 nanometers (nm)] or visible radiation
(400 to 700 nm) is used to produce ·OH.
Photochemical oxidation processes can be
used in:
• (1). Contaminated Water Treatment
• (2). Contaminated Air Treatment
• (3). Contaminated Solids Treatment
(1) Contaminated Water Treatment
•
•
•
•
•
•
Contaminated Groundwater Treatment
Industrial Wastewater Treatment
Municipal Wastewater Treatment
Drinking Water Treatment
Landfill Leachate Treatment
Contaminated Surface Water Treatment
(2) Contaminated Air Treatment
•
•
•
•
SVE Off-Gas Treatment
Air Stripper Off-Gas Treatment
Industrial Emissions Treatment
Automobile Emission Treatment
(3) Contaminated Solids Treatment
• Contaminated Soil Treatment
• Contaminated Sediment Treatment
• Contaminated Ashes Treatment
Some examples of photochemical oxidation
in organic chemistry
O2 N
O
1
CH 2I
light
air
O2 N
O
CHO
2
John Howard, George Klein. J. Org. Chem., 1959, 24 (2), 255–256.
NO 2
O
hv, 1c
+
N
BF4 OEt
3
-O
NO 2
+
+
N
BF4 OEt
3
hv
.
1. e -transfer
+
+
N
BF4 OEt
5
4
O + ON.
.
.
hv
H-transfer
+
N
BF4 OEt
+ OH
N.
HO
O
N
+N
6
BF4 OEt
NO
2.
H+-transfer
OH
7
O
+
+
N
BF4OEt
8
a reactor equipped with a high pressure 125 W Hg lamp.
Stephan Negele, Katja Wieser, and Theodor Severin. J. Org. Chem., 1998,
63 (4), 1138-1143
O
CH 3
HN
ROH 2C O
O
O
(1) CH3 COCOCl
N
CH 3
HN
(2) hv
ROH 2C O
O
N
O
OH
9
10
Roger W. Binkley, David G. Hehemann, Wendell W. Binkley J. Org. Chem.,
1978, 43 (13), 2573–2576
R2
R 1 C O S Ar
O2 , hv
H
R2
O
R 1 C O S Ar
H
11
12
R 1=-C 3H 7, -C 4H 9
R 2=H, CH 3
Daniel J. Pasto, Francois Cottard, Sandra Horgan J. Org. Chem., 1993, 58 (15),
pp 4110–4112
H3 C
CH3
13
hv
H3 C
CHO
14
Bulletin of the Chemical Society of Japan, Vol. 44, 1983-1984 (1971)
hv, O2
sens.
O
O
hv, O2
sens.
CHO
CHO
15
OOH Na S O
2 2 3
OH
16
Raj K. Bansal, Synthetic Approaches in Organic Chemistry, 1998, p272
hv, O2
sens.
17
O
O
18
H. H Wasserman and J. L. Ives, Tetrahedron, 1982, 38, 1825
Kiitos !