Affiliations: Department of Environmental Engineering, Zhejiang
University, Hangzhou 310029, China | College of Environmental Sciences and Engineering,
Ocean University of China, Qingdao 266003, China
Abstract: The effect of Cl^- on photocatalytic degradation
(PCD) of pollutants is an important factor since it is ubiquitous in nature. In
general, Cl^- showed an inhibition on photodegradation due
to its scavenging HO^{·} radicals. In this paper,
experiments were carried out to examine the effects of Cl^-
on the PCD of Methylene Blue (MB) and Orange II (Oll) in aqueous
TiO_2 suspensions under UV light illumination. It was found
that low concentration of Cl^- (< 0.01 mol/L) showed
little influence on both dyes, however, high concentration of
Cl^- (> 0.10 mol/L) had a very different influence on the
decolorization of dyes: a significant inhibition for MB but a great promotion
for Oll. In the presence of 0.50 mol/L Cl^-, the rate
decreased by 70% for MB while increased 7.5-fold for Oll. Furthermore, two
bands in the ultraviolet region of Oll were rapidly broken down. The proposed
mechanism was discussed in detail.
