ISSN 1070-4272, Russian Journal of Applied Chemistry, 2016, Vol. 89, No. 1, pp. 94−98. © Pleiades Publishing, Ltd., 2016.
Regeneration of Photocatalysts by In Situ UV Irradiation
in Photocatalytic Membrane Reactor
, Xu Xiangyanga
*, Liu Jun
, Bao Ruiling
, and Li Lizheng
College of Hydrology and Water Resources, Hohai University, Nanjing, China
China CMCU Engineering Corporation, Chongqing, China
Received June 25, 2015
Abstract—ZnO was successfully prepared by the conventional synthetic route. Polyvinylpyrrolidone was used
as soft-template to synthesize ZnO with controllable size and shape. It was found that ZnO was synthesized with
average crystal size of 49 nm, as reported by an X-ray diffraction experiment. Scanning electron microscopy and
transmission electron microscopy conﬁ rmed the hexagonal shape of the as-synthesized ZnO. The thus prepared
ZnO colloidal particles exhibited numerous opportunities for numerous applications.
The heterogeneous photocatalytic oxidation (HPO)
process with a catalyst, such as TiO
or ZnO, and UV
irradiation has yielded promising results in degradation
of contaminants in the liquid phase, such as persistent
organic pollutants, humic acid, etc. [1–4]. However,
the deactivation of photocatalysts in the course of pho-
tocatalytic degradation has been found to be a crucial
disadvantage of this technique in practice, which restricts
its industrial application [5, 6].
Recently, several research groups have been concerned
with clarifying the origin of photocatalyst deactivation
and ﬁ nding solutions to the problem of deactivation in the
liquid phase. However, batch photocatalytic reactors have
been mostly used, with the total reaction time referred to
as the photocatalyst lifetime [7, 8]. In the present study,
a photocatalytic membrane reactor (PMR) combining
photocatalysis with membrane ﬁ ltration was used. This
reactor enables a continuous process and describes the
practical photocatalyst lifetime in terms of the processed
volume more exactly.
Previous studies have shown that the deactivation of
a photocatalyst is induced by accumulation of reaction
intermediates during the photocatalytic oxidation, and a
physical or chemical method should be used to remove
species of this kind [9–11], such as thermal treatment, ul-
trasonication, UV-irradiation, ion exchange, washing with
solvents, and treatment with an oxidizing agent [11–15].
In many studies, completely deactivated photocatalysts
are regenerated after being separated from the reaction
mixture. In this study, photocatalysts are in situ regen-
erated by UV irradiation at regular intervals at stopped
functioning of the PMR. The in situ regeneration method
is simple and feasible in practical application.
Thus, a continuous photocatalytic reactor was used in
the present study to analyze the photocatalyst lifetime.
Furthermore, the photocatalyst lifetimes with and without
in situ intermittent UV regeneration were compared, with
emphasis on the deactivation process.
Titanium dioxide (P25 TiO
, Degussa, Germany)
was used as photocatalyst. TiO
particles have a 75/25
anatase/rutile ratio, an approximately 50 m
surface area, and average primary particle size of 21 nm.
In aqueous dispersions, TiO
particles tend to aggregate
and form fairly large agglomerates with size dependent on
various parameters. The TiO
concentration was 1 g L
Methyl orange (MO) stock solution was prepared and
fed into the PMR upon dilution with distilled water to an