Recent State-of-the-Art of Antiscalant-Driven Scale Inhibition Theory (Review)

Application of antiscalants is a worldwide practice for industrial scale formation mitigation. The range of reagents is constantly expanding, and new scale inhibitors are permanently elaborated, including biodegradable ones. An antiscalant-driven scale inhibition theory has formed in the mid-twentieth century, and is up to date with some minor refinements. However, in recent years, the classical views have been increasingly criticized on the grounds of such modern methods as dynamic light scattering, particle counter technique and fluorescent visualization of antiscalant location in industrial and model system’s deposits. These methods provide a better understanding of scale inhibition mechanisms. In a present review the major mechanisms of scale inhibition are critically examined, and a hypothesis on the dominating role of solid impurities interaction with antiscalant is formulated. According to this hypothesis, the scale crystals nucleation in the bulk aqueous medium is a heterogeneous process, catalyzed by foreign solid nano/microdust particles, serving as crystallization templates (seeds). Thus, an antiscalant competes for these templates with the scale forming ions, blocks the background seeds, and reduces therefore the number of potential crystallization centers. In this way, the scale inhibitor slows down the scale formation due to the foreign seeds isolation, but not via direct interaction with the nuclei of a sparingly soluble salt.