The precipitation of “magnesium silicate” under geothermal stresses. Formation and characterization

• Published in: Geothermics 2018-07, Vol.74, p.172-180
• Main Authors: Spinthaki, Argyro, Petratos, George, Matheis, Juergen, Hater, Wolfgang, Demadis, Konstantinos D.
• Format: Article
• Language: English
• Subjects: Chemical precipitation; Geology; Geothermal; Geothermal power; Industrial water; Magnesium; Magnesium silicates; Minerals; Morphology; Precipitates; Precipitation; Scale; Silica; Silicates; Silicic acid; Silicon dioxide; Stresses; Water treatment
• ISSN: 0375-6505; 1879-3576
• DOI: 10.1016/j.geothermics.2018.03.001

Inorganic precipitates formed in the presence of Mg2+ ions and soluble silica (silicic acid) can be characterized as “magnesium-containing amorphous silica”. [Display omitted] •Inorganic precipitates form in the presence of Mg2+ ions and soluble silica (silicic acid/silicate) at pH > 8.5.•These precipitates are better characterized as “magnesium-containing amorphous silica”.•They do not correspond to any of the known magnesium silicate minerals.•Precipitate formation is profoundly influenced by pH. Geology presents a well-defined family of minerals in the case of crystalline magnesium silicates. However, in industrial water processes deposits that contain both “Mg” and “Si” are usually referred to as “magnesium silicate” scales. In this paper we attempt to delineate the true nature of such Mg- and Si-containing precipitates formed under the severe stresses simulating geothermal-like conditions. The purpose of this work is to deliberately form precipitates in the presence of Mg2+ ions and soluble silica (silicic acid) and study these with a variety of analytical techniques, to reveal morphology, texture, structure and composition. Such precipitates are better described as “magnesium-containing amorphous silica”.