MECHANISTIC ASPECTS OF THE DEPOSITION OF THE CR(VI) SPECIES ON THE SURFACE OF TIO2 AND SIO2

被引:21
作者
SPANOS, N [1 ]
SLAVOV, S [1 ]
KORDULIS, C [1 ]
LYCOURGHIOTIS, A [1 ]
机构
[1] UNIV PATRAS,INST CHEM ENGN & HIGH TEMP CHEM PROC,DEPT CHEM,GR-26500 PATRAI,GREECE
关键词
CHROMIA CATALYSTS; EQUILIBRIUM DEPOSITION FILTRATION; MICROELECTROPHORESIS; PREPARATION OF SUPPORTED CATALYSTS; SILICA CATALYSTS; TITANIA CATALYSTS;
D O I
10.1016/0927-7757(95)03087-T
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
The deposition of the negatively charged Cr(VI) species on TiO2 and SiO2 surfaces suspended in aqueous electrolyte media has been studied in the pH range 3.0-8.0. The investigation included deposition isotherm and microelectrophoretic mobility measurements. From the experimental results and a theoretical analysis of the deposition isotherms, it was concluded that the CrxOyz- ions taken up were located in energetically equivalent sites at the inner Helmholtz plane (IHP) of the electric double layer that had developed between the support particles and the impregnating solution. The deposition sites were mainly created by protonated surface hydroxyl groups in the case of SiO2 and by protonated and undissociated surface hydroxyl groups in the case of TiO2. The lateral interactions operative among the deposited Cr(VI) species were, in general, strong, being stronger in SiO2 supports in comparison with those of TiO2. Moreover, it was found that upon a pH decrease from 6.0 to 3.0, the extent of deposition of the Cr(VI) species on silica increased from 0.01 to 0.13 mu mol Cr(VI)m(-2). The extent of deposition of the Cr(VI) species on titania increased also from 0.23 to 1.68 mu mol Cr(VI)m(-2) with a pH decrease from 8.0 to 4.8. Further decrease in the pH in the case of titania resulted in a considerable decrease in the extent of deposition.
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页码:109 / 117
页数:9
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