Immobilization of (aqueous) cations in low pH M-S-H cement

Marsiske, Maximilian R.; Debus, Christian; Di Lorenzo, Fulvio; Bernard, Ellina; Churakov, Sergey V.; Ruiz-Agudo, Cristina (2021). Immobilization of (aqueous) cations in low pH M-S-H cement. Applied Sciences, 11(7), pp. 1-18. MDPI 10.3390/app11072968

[img]
Preview
Text
applsci-11-02968.pdf - Published Version
Available under License Creative Commons: Attribution (CC-BY).
© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Download (4MB) | Preview

Incorporation of heavy metal ions in cement hydrates is of great interest for the storage and immobilization of toxic, hazardous, and radioactive wastes using cementitious matrix. Magnesium silicate hydrate (M-S-H) is a low pH alternative cementitious binder to commonly used Portland cement. Low pH cements have been considered as promising matrix for municipal and nuclear waste immobilization in the last decades. It is however crucial to assure that the incorporation of secondary ions is not detrimental for the formation of the hydration products. Herein, we investigate the early stages of formation of M-S-H from electrolyte solutions in presence of a wide range of metal cations (LiI, BaII, CsI, CrIII, FeIII, CoII, NiII, CuI, ZnII, PbII, AlIII). The final solid products obtained after 24 h have been characterized via powder X-ray diffraction (PXRD), attenuated total reflectance-Fourier transformed infrared spectroscopy (FTIR-ATR), elemental analysis via energydispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). In all the experiments, the main precipitated phase after 24 h was confirmed to be M-S-H with a ratio (total metal/Si) close to one. The obtained M-S-H products showed strong immobilization capacity for the secondary metal cations and can incorporate up to 30% of the total metal content at the early stages of M-S-H formation without significantly delaying the nucleation of the M-S-H. It has been observed that presence of Cr, Co, and Fe in the solution is prolonging the growth period of M-S-H. This is related to a higher average secondary metal/total metal ratio in the precipitated material. Secondary phases that co-precipitate in some of the experiments (Fe, Pb, Ni, and Zn) were also effectively trapped within in the M-S-H matrix. Barium was the only element in which the formation of a secondary carbonate phase isolated from the M-S-H precipitates was detected.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Di Lorenzo, Fulvio and Churakov, Sergey

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

2076-3417

Publisher:

MDPI

Language:

English

Submitter:

Fulvio Di Lorenzo

Date Deposited:

11 Apr 2022 14:53

Last Modified:

11 Apr 2022 14:53

Publisher DOI:

10.3390/app11072968

BORIS DOI:

10.48350/168609

URI:

https://boris.unibe.ch/id/eprint/168609

Actions (login required)

Edit item Edit item
Provide Feedback