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

Spinthaki, Argyro; Petratos, George; Matheis, Juergen; Hater, Wolfgang; Demadis, Konstantinos D.

doi:10.1016/j.geothermics.2018.03.001

Cited by 30 publications

(17 citation statements)

References 24 publications

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“…An inset of images having a higher magnification (x30000) revealed that rigid deposits were formed by spherical-shaped subunits, which were approximately 30 nm in diameter. Recently, Demadis et al reported on the internal structure of metal silicates on the basis of example magnesium silicate system (Spinthakia et al, 2018). The authors proposed that the precipitates never correspond to true metal silicates, rather metal ions embedded or adsorbed in amorphous silica.…”

Section: Resultsmentioning

confidence: 99%

Increasing solubility of metal silicates by mixed polymeric antiscalants

et al. 2019

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The increase of silicate solubility is a big challenge for both hot and cold water because it reduces the deposition of metal silicates frequently observed in such systems and causes operational obstacles. The deposition of silicate coats the inner surface of the pipelines in an uncontrolled manner and reduces the harvesting of energy from brines. In this work, the solubility performance of two commercial water-soluble polymeric agents (poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA)) of various molecular weights employing dosage from 25 to 100 mg/L was examined. Along with dispersant-type antiscalant, poly(acrylamide) (PAM), poly(vinylsulfonic acid, sodium salt) (PVSA), and poly(vinylphosphonic acid) (PVPA) having chelating acidic groups were employed. Metal silicate deposits were obtained artificially in the lab-scale pressurized reactor. The experimental conditions employed were quite similar to a model power plant located in Çanakkale, Turkey. The concentration of dissolved silica was increased from 130 to 420 mg/L when 100 mg/L PEG 1500 and 25 mg/L PVSA were employed as a mixture. For the atomic-level understanding of the interaction of chelating groups with metal cations, DFT calculations were performed too.

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Section: Resultsmentioning

confidence: 99%

Increasing solubility of metal silicates by mixed polymeric antiscalants

et al. 2019

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“…In a recent paper on the precipitation of “magnesium silicate” (in the absence of additives) in geothermally relevant artificial waters, we reported that the inorganic precipitates formed under certain conditions (in the presence of variable amounts of Mg 2+ and silicate anions at pH 10) can best be described as “magnesium-containing amorphous silica”, with variable Mg 2+ content . It was also found that precipitate formation was pH-dependent (enhanced precipitation as pH increases).…”

Section: Resultsmentioning

confidence: 94%

“…In the prequel of the present work, we proposed the formation and characterization of “magnesium silicate” under geothermal stresses, coming one step closer in revealing the nature of so-called “magnesium silicate”. Recently, we published detailed studies on the precipitation of “magnesium silicate” (in the absence of additives) in geothermally relevant artificial waters . The variables studied were Mg 2+ and silicate concentrations, pH, and temperature.…”

Section: Introductionmentioning

confidence: 99%

Antiscalant-Driven Inhibition and Stabilization of “Magnesium Silicate” under Geothermal Stresses: The Role of Magnesium–Phosphonate Coordination Chemistry

Spinthaki

Matheis²,

Hater³

et al. 2018

Energy Fuels

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The formation, precipitation, and deposition of so-called “magnesium silicate” in geothermal waters have been subjects of intense interest. Such scaling poses a severe threat to the smooth process of industrial systems. The aim of our approach is the systematic study of the influence of phosphonate-based chemical additives on silica polycondensation chemistry in the presence of magnesium ions. The focus of this work is the prevention of “magnesium silicate” formation using a variety of well-known phosphonate additives. These are 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotris(methylenephosphonic acid) (AMP), hexamethylenediaminetetrakis(methylenephosphonic acid) (HDTMP), and bishexamethylenetriaminepentakis(methylenephosphonic acid) (BHMTPAMP). Inhibition experiments were carried out in supersaturated solutions of silicate (200 ppm, expressed as SiO2) and magnesium (200 ppm, as Mg) at pH 10.0. The phosphonate additives used were found to act as stabilizing agents, most likely by complexing the Mg2+ cations and, thus, preventing “magnesium silicate” formation. On the basis of a plethora of experimental data, a number of useful functional insights have been generated, which add to building a more complete and comprehensive picture of the mechanism of “magnesium silicate” formation and stabilization.

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“…The abundance and reactivity of authigenic Mg-phyllosilicate minerals on Earth's surface (Pozo and Galán, 2015;Tosca, 2015) suggest that their behavior, and the applicability of the PDB to their behavior, may differ from that observed for the feldspars. Al-poor Mg (Pozo and Galán, 2015), but also in geothermal production operations (Gunnarsson et al, 2002;Spinthaki et al, 2018). In addition, the formation of Mg-silicate gelis relatively straightforward to examine experimentally (Brady, 1992;Tosca et al, 2011;Tosca and Masterson, 2014;Tosca, 2015;Arizaleta et al, 2020;Chase et al, 2021).…”

Section: Mg-phyllosilicates As a Model System For Validating The Applicability Of The Pdbmentioning

confidence: 99%

Probing the application of kinetic theory to Mg-phyllosilicate growth with Si isotope doping

Che

Nightingale

Tutolo

2021

Geochimica et Cosmochimica Acta

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

Cited by 30 publications

References 24 publications

Increasing solubility of metal silicates by mixed polymeric antiscalants

Increasing solubility of metal silicates by mixed polymeric antiscalants

Antiscalant-Driven Inhibition and Stabilization of “Magnesium Silicate” under Geothermal Stresses: The Role of Magnesium–Phosphonate Coordination Chemistry

Probing the application of kinetic theory to Mg-phyllosilicate growth with Si isotope doping

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