The Inhibition of Calcium Carbonate Formation by Copolymers Containing Maleic Acid

Abstract

Calcium carbonate scale formation in geothermal wells and other industrial processes is a persistent problem. Remediation of this problem may be achieved through the addition of water soluble polymers which may influence nucleation, crystal growth and the particle characteristics of the precipitated calcium carbonate. In the present work we have investigated the effect of water soluble copolymers of maleic acid with N-Vinyl Pyrrolidone, Vinyl Acetate, Methyl Methacrylate and Styrene groups on the kinetics of calcium carbonate crystal growth. The effectiveness of the polymers tested on the kinetics of calcium carbonate scale formation was evaluated using the constant supersaturation methodology. The water soluble copolymers tested, were all found to be effective inhibitors of calcium carbonate formation at concentration levels lower than 1 ppm. The crystal growth rates of calcite showed a drastic decrease, while for inhibitor concentrations exceeding 0.25 ppm crystal growth was completely suppressed. It is suggested that the activity of the inhibitors is due mainly to the presence of the maleic acid entity in the copolymer, which promoted the adsorption of the copolymer onto the growing solid particles. Kinetics analysis of the rates measured in the presence and in the absence of the polymers, provided additional evidence that adsorption of the macromolecules on the active growth sites of calcite seed crystals was responsible for the inhibition of crystal growth.