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O
O
O
P
O
OH
H
3
C
OH
NH
2
HO
TiO
2
+
O
-
etc.
OH
P
OCH
3
CH
3
COOH + NO
-
H
3
C
N
H
SCH
3
O
O
+ SO
2-
+ SO
2-
(on TiO
2
) + HCOOH
CO
2
P
H
3
C
N
H
TiO
2
OH
O
OH
+ SO
2-
+ SO
2-
(on TiO
2
) + HOCH
2
COOH
P
Glycolic acid
OH
H
2
N
O
OH
TiO
2
P
+ NO
-
HO
OH
OH
TiO
2
FIGURE 6.10
Proposedtentativepathwayforthephotocatalyticdegradationofacephate.(Reprintedfrom
Chemosphere,
76,
Echavia,G.R.M.,Matzusawa,F.,andNegishi,N.,Photocatalyticdegradationoforganophosphateandphos-
phonoglycinepesticidesusingTiO
2
immobilizedonsilicagel.,595-600,(2009),withpermissionfromElsevier.)
phosphateesterpesticidesrapidly;acidicandalkalinesolutionsarefavorableforthepho-
tocatalyticdegradation(ShifuandGengyu2005).
Photocatalytic degradation of phosphate ester pesticides takes place irst in the ester
group that has strong acidity. The pesticide is degraded into trimethyl phosphate ester,
formicacid,aceticacid,andsomesmallmoleculeorganics,andthenthetrimethylphos-
phateesterisphotocatalyticallydegradeddirectlyintoPO
3−
andformicacid(Shifuand
Gengyu2005).Photochemicaleffectsofhumicsubstancesonthedegradationoforgano-
phosphorus pesticides were described by Kamiya and Kameyama (1998). The effects of
selected ions on photodegradation of organophosphorus pesticides sensitized by humic
acidweredescribedbyKamiyaandKameyama(2001).Selectedmetalionshavingpara-
magneticpropertywerefoundtoexertinhibitioneffectsonaquaticphotodegradationof
organophosphoruspesticidessensitizedbyhumicacids,accordingtotheincreasingord
er:Cr(III)<Co(II)<Mn(II)<Cu(II). Basic factors dominating the metal-ion effects were
classiiedonthebasisoftheluorescencequenchingaswellasradicalscavengingabilities
ofthemetalionscomplexedwithhumicacids(KamiyaandKameyama2001).Inanother
SO
2-
(on TiO
2
)
O
S
OH
O
O
-
H
N
P
P
HO
etc.
P
H
3
C
S
S
OH
OCH
3
SO
2-
+
OH
HO
OCH
3
OH
TiO
2
TiO
2
OH
O
O
+
CO
2
HCOOH
NO
-
NO
-
H
3
C-NH
2
FIGURE 6.11
Proposedtentativepathwayforthephotocatalyticdegradationofdimethoate.(Reprintedfrom
Chemosphere,
76,
Echavia,G.R.M.,Matzusawa,F.,andNegishi,N.,Photocatalyticdegradationoforganophosphateandphos-
phonoglycinepesticidesusingTiO
2
immobilizedonsilicagel.,595-600,(2009),withpermissionfromElsevier.)
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