The effect of erbium on the adsorption and photodegradation of orange I in aqueous Er3+-TiO2 suspension.
Pure TiO(2) and erbium ion-doped TiO(2) (Er(3+)-TiO(2)) catalysts prepared by the sol-gel method were characterized by means of XRD and diffusive reflectance spectra (DRS). The XRD results showed that erbium ion doping could enhance the thermal stability of TiO(2) and inhibit the increase of the crystallite size, and the DRS results showed that the optical absorption edge slightly shifted to red direction owing to erbium ion doping and the Er(3+)-TiO(2) catalysts had three typical absorption peaks located at 490, 523 and 654 nm owing to the transition of 4f electron from (4)I(15/2) to (4)F(7/2), (2)H(11/2) and (4)F(9/2). With a purpose of azo dyes degradation, orange I was used as a model chemical. And the adsorption isotherm, degradation and mineralization of orange I were investigated in aqueous suspension of pure TiO(2) or Er(3+)-TiO(2) catalysts. The results showed that Er(3+)-TiO(2) catalysts had higher adsorption equilibrium constants and better adsorption capacity than pure TiO(2). The adsorption equilibrium constants (K(a)) of Er(3+)-TiO(2) catalysts were about twice of that of pure TiO(2). The maximum adsorption capacity (Q(max)) of 2.0% Er(3+)-TiO(2) catalyst was 13.08x10(-5)mol/g, which was much higher than that of pure TiO(2) with 9.03x10(-5)mol/g. Among Er(3+)-TiO(2) catalysts, 2.0% Er(3+)-TiO(2) catalyst achieved the highest Q(max) and K(a) values. The kinetics of the orange I degradation using different Er(3+)-TiO(2) catalysts were also studied. The results demonstrated that the degradation and mineralization of orange I under both UV radiation and visible light were more efficient with Er(3+)-TiO(2) catalyst than with pure TiO(2), and an optimal dosage of erbium ion at 1.5% achieved the highest degradation rate. The higher photoactivity under visible light might be attributable to the transitions of 4f electrons of Er(3+) and red shifts of the optical absorption edge of TiO(2) by erbium ion doping.
Liang
Chun-Hua
CH
College of Resources and Environmental Sciences, Northwest Agriculture and Forestry University, Yangling, Shaanxi 712100, China.
Hou
Mei-Fang
MF
Zhou
Shun-Gui
SG
Li
Fang-Bai
FB
Liu
Cheng-Shuai
CS
Liu
Tong-Xu
TX
Gao
Yuan-Xue
YX
Wang
Xu-Gang
XG
Lü
Jia-Long
JL
D000327:Adsorption / Q000528:radiation effects; D001391:Azo Compounds / Q000737:chemistry*; D002384:Catalysis / Q000528:radiation effects; D004871:Erbium / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet; D013535:Suspensions / Q000737:chemistry; D014025:Titanium / Q000032:analysis / Q000737:chemistry*; D014466:Ultraviolet Rays; D014961:X-Ray Diffraction
D001391:Azo Compounds; D013535:Suspensions; C009495:titanium dioxide; D004871:Erbium; D014025:Titanium