Deposition behavior of elements composing of a silica scale from a geothermal water

Abstract

Silica scales, which precipitate from geothermal waters, contain some elements such as Al, Na, K, Mg and Ca as major constituents in addition with Si. The movement of the elements from geothermal water to surface of stainless-steel (SUS) plates was examined by the metal plate immersion method. Change in the concentration of the elements deposited on the surface with time was measured by a LAICP-MS. From the plot of the concentration of each element against the immersion time of SUS plates in a geothermal water, the followings were made clear: (1) the deposition of Si (silicic acid) correlated with that of Al, suggesting that Al may contribute the deposition of silicic acid, (2) Na, K, and Ca may be incorporated in the silica scale due to neutralization of a permanent negative charge on the 4-coordinated Al.