D.P. Das et al. / Journal of Molecular Catalysis A: Chemical 245 (2006) 217–224
223
of the semiconductor itself. During this photo-catalysis first
Acknowledgements
adsorption takes place which is a reversible process and also
takes place even in absence of light illumination. During the
light illumination electron–hole pairs are produced inside the
semiconductor catalyst. The species migrate to the surface of
the catalyst out of which electron reduces Cr(VI) to Cr(III) and
holes oxidize water:
The authors are thankful to Mr. L.B. Sukla, HOD, BP & EM
Department, for his constant encouragement and also thank-
ful to Dr. R.P. Das, Director, Regional Research Laboratory
(CSIR), Bhubaneswar. Authors are also thankful to Mr. S.K.
Sahoo, HM Department, Regional Research Laboratory (CSIR),
Bhubaneswar for doing the XRD analysis. One of the authors
DPD is obliged to CSIR, New Delhi for Senior Research Fel-
lowship.
hν
ZrP or TiP/TiO2 (semiconductor)−→ e− + h+
h+ + H2O(OH−) → OH•
(1)
(2)
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(5) The apparent rate constant values (k) were found to decrease
with increase in the initial concentration of Cr(VI).
(6) Comparing the effects of sacrificial electron donors like
EDTA and 4-nitrophenol, a significant effect was observed
for EDTA in case of 2 wt.% titania pillared ZrP.
(7) Among N2, O2 and air, the N2 has got more and significant
effect on the photo-reduction of Cr(VI) over titania pillared
ZrP and TiP. The dissolved oxygen has got almost no effect
or very negligible effect on this photo-reduction process.