University of Oulu

Laukkanen, J., Ojala, S., Luukkonen, T., & Lassi, U. (2022). Effect of material age on the adsorption capacity of low-, medium-, and high-calcium alkali-activated materials. Applied Surface Science Advances, 12, 100345.

Effect of material age on the adsorption capacity of low-, medium-, and high-calcium alkali-activated materials

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Author: Laukkanen, Johanna1,2; Ojala, Satu3; Luukkonen, Tero4;
Organizations: 1University of Oulu, Kerttu Saalasti Institute Pajatie 5, Nivala FI-85500, Finland
2University of Oulu, Research Unit of Sustainable Chemistry, P.O. Box 4300, FI-90014, Finland
3University of Oulu, Environmental and Chemical Engineering, P.O. Box 4300, FI-90014, Finland
4University of Oulu, Fibre and Particle Engineering Research Unit, P.O. Box 4300, FI-90014, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
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Language: English
Published: Elsevier, 2022
Publish Date: 2022-11-24


Alkali-activated materials (AAMs) are actively studied as adsorbents in wastewater treatment. They are frequently classified as low-, medium-, or high-calcium content since the gel nanostructure of AAMs changes upon the introduction of network-modifying cations (e.g., Ca²⁺). Furthermore, AAMs undergo changes in the phase composition and pore structure upon aging. In the present study, these two aspects were assessed for the first time in the context of adsorption: three typical mix designs involving metakaolin, blast furnace slag, or their mixture were prepared and studied for ammonium (NH₄⁺) uptake at 7-, 28-, or 90-day age. The adsorption capacity of the “zeolite-like” metakaolin-based geopolymer increased from 34 to 87 mg/g when material was cured up to 90 days at room temperature. However, the adsorption capacity increase appears to be also depending on the metakaolin structure as approx. 1-month and 8-year old samples prepared with another metakaolin grade indicated almost similar adsorption capacity. Adsorption was clearly hindered when blast furnace slag was introduced in the mix designs, which turns the gel into “tobermorite-like” chain structures. Thus, this study demonstrated that using the Ca-content of precursors and material age are significant parameters for the interpretation of the adsorption results and practical development of AAM-based adsorbents.

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Series: Applied surface science advances
ISSN: 2666-5239
ISSN-E: 2666-5239
ISSN-L: 2666-5239
Volume: 12
Article number: 100345
DOI: 10.1016/j.apsadv.2022.100345
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
215 Chemical engineering
216 Materials engineering
218 Environmental engineering
Funding: This work was supported by University of Oulu & The Academy of Finland Profi5 326291, the Finnish Cultural Foundation, the Central Ostrobothnia Regional Fund (grant #25171220), and the European Regional Development Fund (projects WaterPro A74635 and KAIVASU A75259). Part of this work was carried out with the support of the Centre for Material Analysis, University of Oulu, Finland.
Copyright information: © 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (