Journal Published Online: 23 June 2022
Volume 11, Issue 2

How Brine Composition Affects Fly Ash Reactions: The Influence of (Cat-, An-)ion Type

CODEN: ACEMF9

Abstract

Hypersaline brines can be solidified and stabilized via the hydraulic and pozzolanic reactions between fly ash(es) and calcium-based additives. Although recent work has examined fly ash reactivity in single-salt (“simple”) hypersaline brines (ionic strength, Im > 1 mol/L), the effects of mixed-salt solutions on fly ash reactivity remain unclear. Herein, the reactivity of a Class C (calcium oxide [CaO]-rich) or Class F (CaO-poor) fly ash mixture with calcium hydroxide is reacted in solutions bearing sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), sodium sulfate (Na2SO4), or combinations thereof for 1.5 ≤ Im ≤ 2.25 mol/L, from 1 week until 24 weeks. Expectedly, sulfate anions promote the formation of sulfate phases (i.e., ettringite, monosulfoaluminate, U-phase), while chloride anions induce the formation of Cl-AFm compounds (i.e., Kuzel’s and Friedel’s salt). Although the Class C fly ash’s reactivity is similar across different anions (for a fixed cation and Im), Class F fly ash shows a small change in reactivity depending on the anion present. NaCl suppresses (Class C and Class F) fly ash reactivity by up to 30 % as compared to neat CaCl2 and MgCl2-based brines. Thermodynamic modeling reveals that NaCl induces a considerable increase in pH—up to 13.7, where many hydrated phases of interest cease to be the major phase expected—as compared to CaCl2 and MgCl2 brines (pH < 13). In mixed-salt brines, anion immobilization is competitive: sulfate achieves a greater level of incorporation into the hydrates, as compared to chloride. These results offer new understanding of how the brine composition affects solidification and stabilization and thereby yield new insight into improved approaches for wastewater disposal.

Author Information

Collin, Marie
Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, USA Institute for Carbon Management, University of California, Los Angeles, Los Angeles, CA, USA
Prentice, Dale P.
Institute for Carbon Management, University of California, Los Angeles, Los Angeles, CA, USA Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, USA
Arnold, Ross A.
Institute for Carbon Management, University of California, Los Angeles, Los Angeles, CA, USA Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, USA
Ellison, Kirk
Electric Power Research Institute, Charlotte, NC, USA
Simonetti, Dante A.
Institute for Carbon Management, University of California, Los Angeles, Los Angeles, CA, USA Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, CA, USA
Sant, Gaurav N.
Institute for Carbon Management, University of California, Los Angeles, Los Angeles, CA, USA Laboratory for the Chemistry of Construction Materials (LC), Department of Civil and Environmental Engineering, University of California, Los Angeles, Los Angeles, CA, USA Electric Power Research Institute, Charlotte, NC, USA Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, CA, USA California Nanosystems Institute, University of California, Los Angeles, Los Angeles, CA, USA
Pages: 20
Price: $25.00
Related

ASTM License Agreement

Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Stock #: ACEM20210155
ISSN: 2379-1357
DOI: 10.1520/ACEM20210155
Copyright © 1996 - 2025 ASTM. All Rights Reserved. ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959 USA