Adsorption at inorganic surfaces. II. Adsorption of dyes and related compounds by silica
| Autor: | C. H. Giles, Margaret M. Allingham, J. M. Cullen, S. K. Jain, J. S. Woods |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Applied Chemistry. 8:108-116 |
| ISSN: | 1934-998X 0021-8871 |
| Popis: | A study has been made of the adsorption by varieties of silica of a number of aromatic compounds, (chiefly dyes), from aqueous solution. Basic dyes are adsorbed by ion-exchange in the form of a monolayer of cationic micelles, the amount adsorbed being considerably in excess of that required to cover the surface with a normal monolayer. In the case of methylene blue and pseudocyamine chloride, micellar adsorption is confirmed by spectroscopic examination of the solution before and after adsorption. This form of adsorption is very rapid (complete in a few minutes at room temperature) and is not temperature-dependent. Two typical anionic (sulphonated azo) dyes, Orange I and II, are also adsorbed, but much more slowly and to a less extent than basic dyes. Orange I is adsorbed probably by hydrogen bonding as a monolayer. Both of these dyes are oriented perpendicularly as single anions, but some micellar adsorption may occur. Orange II has no free phenolic group and is adsorbed probably by accompanying sodium ions themselves adsorbed by ion-exchange, and its extent of coverage is much less than a monolayer. It is suggested that the low adsorption rates are a result of the difficulty the dye anions have in penetrating to the negatively charged silicon surface. p-Nitrophenol is adsorbed as a monolayer, probably by hydrogen bonding. There is no clear evidence that forces other than ion-exchange and hydrogen-bonding are effective in adsorption of any aromatic compounds on silica. |
| Databáze: | OpenAIRE |
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