ON THE SORPTION OF ANIONS BY FERRIC-OXIDE GEL .3. RATE-CONTROLLING MECHANISM AND EFFECT OF ORGANIC-SOLVENTS IN CHLORIDE-ION EXCHANGE

被引:3
作者
MIKHAIL, EM
GHONEIMY, HF
MISAK, NZ
机构
[1] HOT LAB CTR,DEPT CHEM,CAIRO,EGYPT
[2] HOT LAB CTR,DEPT ISOTOPE PROD & LABELLED CPDS,CAIRO,EGYPT
关键词
ANIONS; FERRIC OXIDE GEL; SORPTION;
D O I
10.1016/0927-7757(94)02917-2
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 ferric oxide gel (Fe-I), prepared by adding ammonia to ferric chloride and washing with dilute ammonia and water, and the gel (Fe-II), obtained by further washing of Fe-I with more concentrated ammonia (which removed more of the Cl- ions from the gel) and water were studied. It was found that the apparent capacity for Cl- ion adsorption by ligand exchange with surface OH groups is much higher for Fe-II than for Fe-I. The Fe-II displayed a complex variation of this capacity with alcohol addition, whereas Fe-I displayed a continuous increase in sorption with alcohol concentration. The latter increase is in the order propan-1-ol > ethanol > methanol, and may be attributed to a stronger interaction of Cl- ions with the surface. For Fe-II, the complex behaviour may in part be connected with the development of micropores. The latter effect changed the rate-controlling mechanism from chemical for Fe-I to particle diffusion for Fe-II, and may be accompanied by an increase in the surface area, leading to an increase in the capacity. For the Cl- ion exchange, the values of the rate constant for Fe-I and the internal diffusion coefficient ($) over bar D-i for Fe-II decreased progressively with alcohol addition. This pointed to an imbibition of alcohols by both gels. The order of the ($) over bar D-i values for the various anions is not changed by the addition of alcohol, which probably shows that ($) over bar D-i is governed by the complexing ability of the anions with the surface.
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页码:209 / 220
页数:12
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