Rl. Pozzo et al., Towards a precise assessment of the performance of supported photocatalysts for water detoxification processes, CATAL TODAY, 54(1), 1999, pp. 143-157
The performance of Degussa P-25 titanium dioxide photocatalyst in a water e
nvironment and two different forms of operation was studied. The finely div
ided powder was used in a suspended bed (slurry) reactor, and the same cata
lyst was physically supported on quartz sand and employed in a fluidized be
d reactor. Both reacting systems were operated under conditions of a fully
irradiated photoreaction space (FLP reactor) and the comparison was made fo
r the same mass concentration of catalyst per unit reactor volume (250 ppm)
using different combinations of bed expansion and surface coverage of the
support. A tubular black light lamp was placed inside an annular reactor, w
here the photocatalytic oxidation of a model compound (oxalic acid) was inv
estigated.
Results were analyzed in terms of initial reaction rates per unit reactor v
olume and per unit of the liquid phase volume inside the reactor. Likewise,
apparent quantum efficiencies were evaluated for the initial conditions, u
sing the concept of apparent captured radiation power. It was found that th
e efficiency of the slurried photocatalyst is approximately five times larg
er than in the supported form. Among the different fluidized bed operations
the highly expanded bed, with 100% coverage of the support surface, was fo
und to be the most convenient condition for the immobilized titania. (C) 19
99 Elsevier Science B.V. All rights reserved.