Nanotechnostructured Catalysts TiO Nanoparticles for Water Purification - Nanotechnologies for Water Environment Applications - page 63

specific surface to volume ratio; (b) improved light transparence; (c) increased degree of
mixing; (d) flexible design operation, which can be installed in other tube reactors, such
as a plug flow reactor and a CPC system; and (e) thin film coating, which allows
possible electron reclamation and energy recovery. It has been reported that the
treatment efficiency is proportional to the slides' number. When 12-slide configuration
is used, the reaction rate is only 1.8 times less than the slurry reactor, which is a very
promising result (Cernigoj et al., 2007).
Figure 3.10. Schematic representation of a Carberry type reactor (Redrawn from
Cernigoj et al., 2007).
3.4.1.4 Photoelectrochemical Cell (PEC) Reactor
In order to reclaim and maximize the electrons generated during the
photocatalytic process, various attempts have been developed. The PEC system is one
of them (Pecchi et al., 2001). The direction of electron flow in a TiO 2 /liquid junction
PEC system is manipulated by the relative energy position between the semiconductor
bandedges (E C and E V ) and the Fermi energy of the redox couple species (E F o redox ) at the
solid/liquid interface. To warren an efficient photoactivity, one has to maintain a large
reduction potential (φ O ) of the acceptor redox couples and an oxidation potential (φ R ) of
the donor redox couples. The PEC system, which consists of a photoelectrode, reference
electrode and counter electrode, is capable of maneuvering the φ O and φ R (Figure 3.11).
In a PEC system, the separation of the photoanode and the cathode is analogous
to the isolation of E V and E C in the semiconductor. The PEC system provides a high-