ELSEVIER Applied Surface Science 75 (1994) 197-203 iiii iii iiiii! i!iiiiiiiiiiii i i iiiiiiiiiiiii !iiiiiii i applied surface science Adsorption of anionic and cationic polymers on porous and non-porous calcium carbonate surfaces Robert B. Bjorklund *, Hans Arwin Laboratory of Applied Physics, Link6ping University, S-581 83 Link6ping, Sweden Lars J~irnstr6m Swedish Pulp and Paper Research Institute, Box 5604, S-114 86 Stockholm, Sweden (Received 15 May 1993; accepted for publication 8 June 1993) Abstract The adsorption of anionic and cationic polymers onto calcium carbonate surfaces was studied by ellipsometry. Sodium polyacrylate was observed to both adsorb on and promote dissolution of polished limestone surfaces in 5 mM CaSO4 solution at pH 10.3. It was not possible to differentiate between the two processes when they occurred simultaneously. Cationic starch adsorbed on the limestone surfaces at low concentrations and caused mineral dissolution at higher concentrations. The adsorbed amount of starch was higher on surfaces which were first made porous by partial dissolution than on freshly polished surfaces. Surfaces created by cleavage of Iceland spar calcite were quite stable against dissolution and the amount of starch adsorbed determined by ellipsometry agreed well with the adsorbed mass determined from batch adsorption experiments on ground calcite. 1. Introduction Calcium carbonate is an important industrial mineral used in both its natural and synthetic forms in the rubber, plastic and paper industries. In these applications, surface properties play an important role in determining the effectiveness of calcium carbonate as a bulk filler or as a func- tional component in the final product. When used as a pigment in the coating of paper and board, the nature of the calcium carbonate is a * Corresponding author. major factor in determining many important properties of the final product, such as dusting, ink interactions and de-inking of waste paper. Even the surface morphology of the mineral plays a key role in this regard as reported by Keller and Luner [1] that physi- and chemisorbed water bound within the pore structure significantly in- fluences the properties of calcium carbonates. Surface studies of calcium carbonates often deal with the colloidal properties of small calcite particles in aqueous suspensions. The surface charge has been extensively studied and has been reported by Siffert and Fimbel [2] to be depen- dent on the concentration of the dispersed cal- cium carbonate, i.e. on the total surface area in 0169-4332/94/$07.00 © 1994 Elsevier Science B.V. All rights reserved SSDI 0169-4332(93)E0193-P