Fly ash degree of reaction in hypersaline NaCl and CaCl2 brines: Effects of calcium-based additives

Marie Collin; Yu Song; Dale P Prentice; Ross A Arnold; Kirk Ellison; Dante A Simonetti; Mathieu Bauchy; Gaurav N Sant

doi:10.1016/j.wasman.2023.08.002

Fly ash degree of reaction in hypersaline NaCl and CaCl₂ brines: Effects of calcium-based additives

Waste Manag. 2023 Oct 1:170:103-111. doi: 10.1016/j.wasman.2023.08.002. Epub 2023 Aug 8.

Authors

Marie Collin¹, Yu Song², Dale P Prentice³, Ross A Arnold³, Kirk Ellison⁴, Dante A Simonetti⁵, Mathieu Bauchy⁶, Gaurav N Sant⁷

Affiliations

¹ Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; Institute for Carbon Management, University of California, Los Angeles, CA, USA. Electronic address: mariecollin03@ucla.edu.
² Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA.
³ Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; Institute for Carbon Management, University of California, Los Angeles, CA, USA.
⁴ Electric Power Research Institute, Charlotte, NC 28262, USA.
⁵ Institute for Carbon Management, University of California, Los Angeles, CA, USA; Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA, USA.
⁶ Institute for Carbon Management, University of California, Los Angeles, CA, USA; Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA.
⁷ Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; Institute for Carbon Management, University of California, Los Angeles, CA, USA; Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA; California Nanosystems Institute (CNSI), University of California, Los Angeles, CA, USA. Electronic address: gsant@ucla.edu.

PMID: 37562200
DOI: 10.1016/j.wasman.2023.08.002

Abstract

The pozzolanic reaction of fly ashes with calcium-based additives can be effectively used to solidify and chemically stabilize (S&S process) highly concentrated brines inside a cementitious matrix. However, complex interactions between the fly ash, the additive, and the brine typically affect the phases formed at equilibrium, and the resulting solid capacity to successfully encapsulate the brine and its contaminants. Here, the performances of two types of fly ash (a Class C and Class F fly ash) are assessed when combined with different additives (two types of cement, or lime with and without NaAlO₂), and two types of brine (NaCl or CaCl₂) over a range of concentrations (0 ≤ [Cl^-] ≤ 2 M). The best performing matrices - i.e., the matrices with the highest Cl-containing phases content - were identified using XRD and TGA. The experimental results were then combined with thermodynamic modeling to dissociate the contribution of the fly ash from that of the additives. All results were implemented in a machine learning model that showed good accuracy at predicting the fly ash degree of reaction, allowing for the robust prediction of extended systems performance when combined with thermodynamic modeling.

Keywords: Chemical reactivity; Fly ash; Hypersaline brine; Solidification and stabilization; Thermodynamic modeling.

MeSH terms

Calcium
Calcium Chloride
Coal Ash*
Refuse Disposal* / methods
Sodium Chloride

Substances

Coal Ash
brine
Calcium
Sodium Chloride
Calcium Chloride