Formation of a silicato complex of zinc in aqueous solution and its accelerating effect on the formation of silica scales in cooling water systems

Abstract

This study elucidates the effect of zinc (Zn), which is an anticorrosive water additive, on the formation of silica scales from cooling water. In these experiments, the silica scales were analyzed by EPMA, and the results indicate that Zn is sorbed into the silica scales during formation. Measurements of the solubility of Zn(OH)(2) at various concentrations of silicic acid demonstrate that Zn is present as a silicato complex of Zn (SCZ) in cooling water. From adsorption experiments of the SCZ on silica and alumina, which are major components of the silica scales, it can be concluded that the SCZ accelerates the formation of silica scales from cooling water.

Formation of Silica Scales in the Water Utilization Process and its Prevention Methods

“…Alkaline earth metal ions, such as calcium, magnesium and strontium etc promote polymerization of silicic acid. In contrast, other polyvalent cations like aluminum and zinc which added into cooling water as a coagulant to remove turbidity or as an anticorrosive are inhibited the polymerization process by the formation of soluble silicato-metal complexes in aqueous solution [19][20]. Fluoride anion accelerates the polymerization of silicic acid by expansion of the coordination number of silicon from four to six [21].…”