Trace concentrations of metal ion impurities, such as Fe<sup>2+</sup>, Fe<sup>3+</sup> and Mg<sup>2+</sup>, which are commonly
encountered in water, can retard significantly the precipitation of CaCO<sub>3</sub>. In view of the paucity of viable
techniques for overcoming scale deposition difficulties, it is important to examine options
for CaCO<sub>3</sub> scale control by trace amounts of inhibiting metal ions. The literature cites Zn <sup>2+</sup> ions as being
particularly effective in suppressing CaCO<sub>3</sub> scale deposition.
This paper reviews phenomena induced by the presence of ion impurities. Literature data relating to the
retardation of CaCO<sub>3</sub> nucleation and crystal growth processes by adsorption of impurities on crystal
growth sites are analyzed and correlated. The effect of the presence of Zn<sup>2+</sup> ions on CaCO<sub>3</sub> scale
deposition from hard waters having a Langelier saturation index of 1.0 to 1.5 was measured in two
experimental heating systems. A marked scale suppression effect was obtained with as little as 1 to 1.5
PPM Zn<sup>2+</sup> ion, added to the water either by dosing a Zn<sup>2+</sup> solution or by the release of Zn<sup>2+</sup> ions through
contact with a redox Zn-Cu alloy medium such as a granular bed of KDF-55®. Includes references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 11/15/2004 |
