CHEMISORPTION ON THIOL-SILICAS - DIVALENT-CATIONS AS A FUNCTION OF PHAND PRIMARY AMINES ON THIOL-MERCURY ADSORBED

The silylating agent 3-trimethoxysilyl-1-propanethiol was immobilized on silica gel. Sulphur analysis showed 0.98 mmol of thiol groups per g ram of support. These groups chemisorbed divalent cations: nickel, cob alt, copper, and mercury in the pH range from 1 to 6. The adsorption i s more significant for mercury in relation to the other cations in the pH range studied. The primary amines, methylamine, ethylamine, n-buty lamine, and benzylamine, were adsorbed on silica-thiol surface and on silica-thiol surface with mercury adsorbed. The values of adsorption c onstants were calculated using Langmuir isotherms data. Using these va lues, equilibrium constants and Delta G values for each adsorption sys tem were also obtained. When mercury is present on the silica surface, the adsorption of n-butylamine and benzylamine is significatively enh anced in relation to the other amines. This behavior suggests that the degree of adsorption of the studied amines is intimately related to t heir dissociation constants. (C) 1997 Academic Press.