Transition metal modified TiO2-loaded MCM-41 catalysts for visible- and UV-light driven photodegradation of aqueous organic pollutants

被引:143
作者
Reddy, EP [1 ]
Sun, B [1 ]
Smirniotis, PG [1 ]
机构
[1] Univ Cincinnati, Dept Chem & Mat Engn, Cincinnati, OH 45221 USA
关键词
D O I
10.1021/jp047419m
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A number of transition metal (Cr, V, Fe, Cu, Mn, Co, Ni, Mo, and La) incorporated MCM-41 mesoporous molecular sieves with Si/Me = 80 have been synthesized by a hydrothermal method. It was demonstrated that the presence of transition metal salts in the gel during synthesis hinders the action of the template, which results in pores of MCM-41 that are not well-formed. These materials were then loaded with TiO2 via the sol-gel method, and the resulting materials were explored for the destruction of 4-chlorophenol in the presence of visible, as well as UV, light. A combination of various physicochemical techniques such as N-2 physisorption, O-2 chemisorption, X-ray diffraction (XRD), diffuse reflectance UV-vis (DR UV-vis), and temperature program reduction (TPR) were used to characterize the chemical environment of these transition metals in the prepared catalysts. The dispersion of transition metals as determined by O-2 chemisorption suggests that they are well dispersed inside the MCM-41 framework, but the dispersion values decrease with the loading of TiO2. This indicates that the loaded titania promotes the transformation of incorporated metal ions into different phases. The UV-vis spectroscopy results of TM-MCM-41 (where TM = Cr, V, Fe, Cu, Mn, Co, Ni, Mo, and La) showed enhancement of light absorption in the visible range by some composite materials. The same materials loaded with titania show higher absorption in the UV range (250-400 nm) due to the presence of titania. Among all TM-MCM-41 materials, only Cr- and Cu-MCM-41 showed strong reduction transitions at lower temperatures; all other TM-MCM-41 materials showed very broad reduction transitions. Titania-loaded Cr-MCM-41 showed an interesting reduction transition at 321 degreesC due to Cr6+-->Cr5+. This transition was obtained as a result of the strong interaction of Cr-O-Ti inside the MCM-41. The photocatalytic activity under visible and UV light for the degradation of aqueous 4-chlorophenol was tested. Among all of the catalysts, only 25% TiO2/Cr-MCM-41 exhibited significant activity in visible light. Other 25% TiO2/TM-MCM-41 samples demonstrated low or no activity to operate with visible light. In contrast, the activities of all 25% TiO2/TM-MCM-41 catalysts under UV light were found to be more comparable with each other. Their catalytic performances are correlated with the UV-vis spectrum of each synthesized catalyst to reveal the specific role played by each metal ion.
引用
收藏
页码:17198 / 17205
页数:8
相关论文
共 31 条
[1]   Photocatalysis in water environments using artificial and solar light [J].
Alfano, OM ;
Bahnemann, D ;
Cassano, AE ;
Dillert, R ;
Goslich, R .
CATALYSIS TODAY, 2000, 58 (2-3) :199-230
[2]   Iron and copper immobilised on mesoporous MCM-41 molecular sieves as catalysts for the oxidation of cyclohexane [J].
Carvalho, WA ;
Wallau, M ;
Schuchardt, U .
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL, 1999, 144 (01) :91-99
[3]   UV PHOTOLYTIC DEGRADATION OF PHENYLMERCURY COMPOUNDS IN WATER-ACETONITRILE (1/1)-MEDIA [J].
CERRILLOS, C ;
ADRIAN, MAP ;
NAVIO, JA .
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 1994, 84 (03) :299-303
[4]   THE ROLE OF METAL-ION DOPANTS IN QUANTUM-SIZED TIO2 - CORRELATION BETWEEN PHOTOREACTIVITY AND CHARGE-CARRIER RECOMBINATION DYNAMICS [J].
CHOI, WY ;
TERMIN, A ;
HOFFMANN, MR .
JOURNAL OF PHYSICAL CHEMISTRY, 1994, 98 (51) :13669-13679
[5]   Transition-metal-substituted titania-loaded MCM-41 as photocatalysts for the degradation of aqueous organics in visible light [J].
Davydov, L ;
Reddy, EP ;
France, P ;
Smirniotis, PG .
JOURNAL OF CATALYSIS, 2001, 203 (01) :157-167
[6]   REACTIVITY OF SUPPORTED VANADIUM-OXIDE CATALYSTS - THE PARTIAL OXIDATION OF METHANOL [J].
DEO, G ;
WACHS, IE .
JOURNAL OF CATALYSIS, 1994, 146 (02) :323-334
[7]   Yttria-stabilized zirconia supported copper oxide catalyst .1. Effect of oxygen vacancy of support on copper oxide reduction [J].
Dow, WP ;
Wang, YP ;
Huang, TJ .
JOURNAL OF CATALYSIS, 1996, 160 (02) :155-170
[8]   Mesoporous oxide junctions and nanostructured solar cells [J].
Grätzel, M .
CURRENT OPINION IN COLLOID & INTERFACE SCIENCE, 1999, 4 (04) :314-321
[9]   Redox behaviour of La-Cr compounds formed in CrOx/La2O3 mixed oxides and CrOx/La2O3/ZrO2 catalysts [J].
Hoang, DL ;
Dittmar, A ;
Radnik, J ;
Brzezinka, KW ;
Witke, K .
APPLIED CATALYSIS A-GENERAL, 2003, 239 (1-2) :95-110
[10]   ENVIRONMENTAL APPLICATIONS OF SEMICONDUCTOR PHOTOCATALYSIS [J].
HOFFMANN, MR ;
MARTIN, ST ;
CHOI, WY ;
BAHNEMANN, DW .
CHEMICAL REVIEWS, 1995, 95 (01) :69-96