ADSORPTION OF ORGANIC-COMPOUNDS FROM AQUEOUS-SOLUTIONS ON A SILICA-GEL AND ALPHA-ALUMINA

Adsorption of 25 substituted aromatic and heterocyclic hydrocarbons fr om aqueous solutions was studied by the static method in the concentra tion range 5 x 10(-4) to 1 x 10(-2) M. It was found that the adsorptio n of nitrogen-containing compounds is usually stronger than that of co mpounds with oxygen heteroatoms. The adsorption parameters of the Lang muir isotherm for the amines adsorbed on a silica gel decrease in the following order: mine>aminopyridine>diphenylamine>indole>benzamide. Al umina extracts less organic compounds from the aqueous solutions than a silica gel does. Additional n --> pi absorption bands are observed in the electronic spectra of the adsorbed molecules of quinoline, diph enylamine, aniline, and toluidine. Abnormally large shifts in the abso rption bands are discovered in the spectra of pyrogallol, pyrocatechol , and diphenylamine adsorbed on alumina. The conclusion is made that a silica gel in neutral aqueous solutions is a stronger electron donor and electron acceptor than alpha-alumina.