Involvement of chloride anion in photocatalytic process.
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 (OII) in aqueous TiO2 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 OII. In the presence of 0.50 mol/L Cl-, the rate decreased by 70% for MB while increased 7.5-fold for OII. Furthermore, two bands in the ultraviolet region of OII were rapidly broken down. The proposed mechanism was discussed in detail.
Yang
Shi-ying
SY
Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, China. shiningpup@hotmail.com
Chen
Ying-xu
YX
Lou
Li-Ping
LP
Wu
Xiao-na
XN
D001391:Azo Compounds; D001557:Benzenesulfonates; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry*; D008751:Methylene Blue / Q000737:chemistry; D010782:Photolysis / Q000528:radiation effects*; D013056:Spectrophotometry, Ultraviolet; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
D001391:Azo Compounds; D001557:Benzenesulfonates; D002712:Chlorides; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; C014722:2-naphthol orange; D008751:Methylene Blue