Calcium Silicate Crystal Structure Impacts Reactivity with CO₂ and Precipitate Chemistry

Journal Article · Fri Aug 24 00:00:00 EDT 2018 · Environmental Science & Technology Letters (Online)

DOI:https://doi.org/10.1021/acs.estlett.8b00386· OSTI ID:1481253

Plattenberger, Dan A. ^[1]; Ling, Florence T. ^[2]; Tao, Zhiyuan ^[3]; Peters, Catherine A. ^[2]; Clarens, Andres F. ^[3]

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1. Univ. of Virginia, Charlottesville, VA (United States); NETL
2. Princeton Univ., Princeton, NJ (United States)
3. Univ. of Virginia, Charlottesville, VA (United States)

The reaction of CO_2(aq) with calcium silicates creates precipitates that can impact fluid flow in subsurface applications such as geologic CO₂ storage and geothermal energy. These reactions nominally produce calcium carbonate (CaCO₃) and amorphous silica (SiO_x). Here we report evidence that the crystal structure of the parent silicate determines the way in which it reacts with CO₂ and the resulting structures of the reaction products. Batch experiments were carried out using two polymorphs of a model calcium silicate (CaSiO₃), wollastonite (chain-structured) and pseudowollastonite (ring-structured), at elevated temperatures and CO_2(aq) concentrations. Reaction of CO_2(aq) with wollastonite produced CaCO₃ and SiO_x, whereas reaction of CO_2(aq) with pseudowollastonite produced numerous plate-like crystalline calcium silicate phases, along with CaCO₃ and SiO_x. A reaction mechanism is proposed that explains the observations in relation to dissolution rates of ions from the parent silicate, the pH of the solution, and the presence of nucleation sites. The mechanism is supported with ICP-OES measurements of the aqueous phase and SEM/TEM-SAED characterization of solid products. As a result, these findings are important for a number of reasons among them the fact that the crystalline silicate precipitates are more stable than CaCO₃ at low pH conditions, which would be very valuable for creating permanent seals in subsurface applications.

• Research Organization: Univ. of Virginia, Charlottesville, VA (United States)
• Sponsoring Organization: USDOE Office of Fossil Energy (FE)
• Grant/Contract Number: FE0026582
• OSTI ID: 1481253
• Journal Information: Environmental Science & Technology Letters (Online), Journal Name: Environmental Science & Technology Letters (Online) Journal Issue: 9 Vol. 5; ISSN 2328-8930
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES