Dispersion of Al 2 O 3 suspension with acrylic copolymers bearing carboxylic groups M. Ramzi Ben Romdhane a , Sami Boufi b , Samir Baklouti a , Thierry Chartier c, , Jean-Franc ¸ois Baumard c a Laboratoire de Chimie Industrielle, Equipe Ce ´ramique, ENIS, BP W 3038 Sfax, Tunisia b Laboratoire de Sciences des Mate ´riaux et Environnement, Faculte ´ des Sciences de Sfax, BP 802-3018 Sfax, Tunisia c Laboratoire de Science des Proce ´de ´s Ce ´ramiques et de Traitements de Surface, SPCTS, UMR CNRS 6638, 47 Avenue Albert Thomas, 87065 Limoges Cedex, France Received 15 March 2002; accepted 2 July 2002 Abstract The interaction between acrylic copolymers carrying carboxylic groups and the surface of an alumina powder in water has been studied. The trends of the adsorption isotherms suggest the formation of a monolayer according to the Langmuir model. The quantity absorbed on the plateau increases when the fraction of carboxylic groups on the polymer decreases. The electrokinetic properties of the alumina suspensions were also analysed. Results indicate that the copolymer adsorption leads to a shift in the IEP towards acidic pH. Moreover, the density of charge of the surface of alumina particle at pH 8 /9 was found to depend on the quantity of adsorbed carboxylic groups and on the configuration of the adsorbed polymer. The stability of dispersions was investigated through particle size distribution and rheological properties after addition of various amounts of copolymers. The ability of the acrylic copolymer to stabilise alumina suspensions was found to be greatly affected by the content of carboxylic groups contained in the macromolecular chain. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Dispersion; Copolymers; Carboxylic groups; Alumina 1. Introduction Polymer adsorption at solid/liquid interfaces continues to receive considerable attention nowa- days [1  /4]. Many processes in ceramic, paint, wastewater treatment technologies are closely connected to adsorption phenomena. During ceramic processing, various polymeric additives are used to confer desired properties to the media [5  /9]. Quite often, polyelectrolytes are added to the suspension to get a homogenous dispersion of the powder in the liquid phase, thus leading to both high solid loadings and low viscosities [10  / 13]. After adsorption onto the surface of the powder, polyelectrolytes create an excess of charge which results in the formation of an electrical  Corresponding author. Tel.:  /33-5-5545-2222; fax:  /33-5- 5579-0998 E-mail address: t.chartier@ensci.fr (T. Chartier). Colloids and Surfaces A: Physicochem. Eng. Aspects 212 (2003) 271  /283 www.elsevier.com/locate/colsurfa 0927-7757/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0927-7757(02)00327-8