Surface chemical studies on alumina suspensions using ammonium poly(methacrylate)

The interaction of alpha-alumina with ammonium poly(methacrylate) (APMA) ha s been investigated through adsorption and electrokinetic measurements. The adsorption isotherms exhibit high affinity, Langmuirian behaviour at highl y acidic pH and the adsorption density is found to decrease with increasing pH. On the contrary, the percentage desorption increases with increasing p H. Electrokinetic studies indicate specific adsorption between alumina and APMA resulting in a shift of the isoelectric point to acidic pH values. Ele ctrophoretic mobility values indicate that the alumina suspension could be well dispersed in the pH range 5-11, consequent to polymer adsorption. Thes e results were corroborated by the dispersion tests. Dissolution tests reve al the release of aluminium species from alumina while co-precipitation exp eriments confirm the chemical interaction of aluminium species with APMA in the bulk solution. Hydrogen bonding, electrostatic and chemical interactiv e forces are postulated to govern the adsorption process. FTIR spectroscopi c data lend further support to the interaction mechanisms proposed. (C) 200 0 Elsevier Science B.V. All rights reserved.