inorganic chemistry

irradiation time. These conditions should favor photodesorption
(vide supra) and therefore a long-term irradiation was conducted
in the presence of NaHCO 3 to neutralize the acid generated. In
this experiment, the concentration of 4-CP was readjusted to its
original value when thec/c 0 values approached zero. Whereas
in the absence of bicarbonate the activity decreased to 50% of
its original value already at the third cycle, it changed only little
even after 19 cycles when bicarbonate was present. This clearly
proofs the catalytic nature of the photodegradation reaction.
Also other pollutants like atrazine, dichloroacetic acid, lindane,
and trichloroethylene were almost completely mineralized
(l455 nm). The degradation of atrazine in general affords
cyanuric acid as the final product when unmodified titania were
employed as photocatalysts( 34 ). However, when 4.0%H 2 [PtCl 6 ]/
TH was used, even cyanuric acid was mineralized as indicated
by TOC and nitrate determinations.

C. PHOTODEGRADATION WITHNATURAL
INDOOR ANDOUTDOORDAYLIGHT

The excellentphotocatalyticactivityof4.0%H 2 [PtCl 6 ]/TH became
even more evident, when the reaction was conducted in diffuse
indoor laboratory daylight (4–10 Wm^2 at 400–1200 nm). Under
these conditions both unmodified P25 and TH were inactive

0 20 40 60 80 100 120

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

d

c

b

a

TOC/TOC

0

4-CP,

c/

c^0

Time (min)

FIG. 4. 4-CP degradation upon visible light irradiation; H 2 [PtCl 6 ]/
Ald (a), 1.1%H 2 [PtCl 6 ]/P25 (b), 4.0%H 2 [PtCl 6 ]/TH (c), 4-CP mineraliza-
tion as catalyzed by 4.0%H 2 [PtCl 6 ]/TH (d) (19).

382 HORST KISCH