Direct detection of calcium carbonate scaling via a pre-calcified sensitive area of a quartz crystal microbalance
Résumé
In an industrial cooling circuit supplied with raw river water, the scaling phenomenon can reduce cooling efficiency
and even lead to the shutdown of the power plant. During the last twenty years, various methods have
been developed in order to estimate the scaling propensity of natural waters, which involve the precipitation
of calcium carbonate (CaCO3), the main component of scale. FCP (Fast Controlled Precipitation) is a nonelectrochemicalmethodwhich
consists in CO2 degassing fromwater bymoderate stirring. FCP allows quantifying
the scaling propensity of natural water. However, FCP is not well adapted in the case of waters with low scaling
propensities, or for in situ measurements.
In this study, a quartz crystal microbalance with a pre-calcified sensitive electrode surface or SQCM (Scaling
Quartz Crystal Microbalance) was developed. The sensitive surface of this gravimetric sensor could be used as
an adsorption layer for calcium carbonate nuclei present in water. Thus, the SQCM method is able to detect the
phenomenon of scaling, even if the water does not precipitate, due to its high gravimetric sensitivity. Thismethod
is described in details in this paper, and was successfully applied to evaluate the scaling propensity of synthetic
waters. The SQCM could be used in situ to assess the efficiency of humic substances in synthetic water towards
scaling.
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