A study on the adhesion of calcium carbonate to glass. Energy balance in the deposition process

This work describes an experimental investigation on the adhesion of in situ synthesized calcite colloidal particles to rotating glass slides. The relative importance of the hydrodynamic processes involved was analyzed by measuring the amount adhered as a function of both the temperature and the rotation velocity. The adhesion was found to be temperature-dependent. At a given rotation speed of the slide, there exists a value of the temperature for which the adhesion is maximum. This value is lower, the higher the rotation speed. Comparison between experimentally determined particle fluxes (number of particles adhered per unit time and unit surface area of collector) and those calculated from Levich's theory (where laminar flow and absence of particle-collector repulsion are assumed) suggests that the hydrodynamic regime in the vicinity of the slide changes from laminar to turbulent when either the velocity or the temperature is increased above a certain critical value, corresponding to maximum adhesion. The effect of the electrolytes CaCl2 and MgCl2 on the adhesion was also studied in the range of concentrations between 0.7 and 70 mM. For fixed hydrodynamic conditions and temperature, the adhesion between the particle and the collector was found to be controlled by the interfacial interactions, including Lifshitz-van der Weals (LW), electrostatic double layer (EL), and acid-base (AB). The calcite-solution and glass-solution interfaces were completely characterized by using electrophoresis, contact angle, and thin-layer wicking techniques, together with van Oss et al.'s model of interfacial thermodynamics. From these data the total energy of interaction between the particle and the substrate was computed using either the classical DLVO model (EL + LW) or the extended theory (EL + LW + AB) for different electrolyte concentrations, and reasonably good agreement was found between the experimentally observed particle attachment and the predictions of the extended DLVO theory.