Modeling the effect of anti-scalant on CaCO₃ precipitation in continuous flow

Scale inhibition by anti-scalants is known to involve blockage of active growth sites by adsorbed inhibitor molecules, but there is virtually no quantitative information on the kinetics of anti-scalant retarded precipitation. This paper presents a model integrating the process of anti-scalant adsorption on precipitated CaCO₃ particles with the kinetics of the ensuing retarded precipitation. Adsorption is analyzed according to the Langmuir, Freundlich and Langmuir-Freundlich models, and CaCO₃ precipitation is described by the commonly used surface reaction controlled model. The proposed model is validated by experimental data measured in a continuous flow precipitation system over a wide range of conditions.