Adsorption Properties of Alumina Modified by Stearic and Oleic Acids

摘要

Two sets of alumina samples were prepared, one chemically modified by stearic acid and the other by oleic acid, with modifier concentrations within 0.1-4.0 groupsm~2. The adsorption of nitrogen, water, and benzene vapors, as well as Acid Orange dye (from aqueous solution), was studied as a function of modifier concentration. In the highest concentration (2.7 groupsm~2), stearate generates a dense surface monolayer, which is hardly accessible to the penetration of molecules of the test compounds. Alumina with stearate concentrations of about one-half the monolayer coverage is the most active adsorbent of organic ions from aqueous solutions. Alumina with the limiting oleate concentration adsorbs a large benzene volume (three times the specific pore volume of the support), because oleate exists on the surface in a liquid state.