Modeling Dissolution–Precipitation Kinetics of Alkali-Activated Metakaolin

Valentini, Luca

doi:10.1021/acsomega.8b02380

Cited by 40 publications

(18 citation statements)

References 69 publications

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“…6). The clearly higher viscosity values of anionic SDS and cationic CTAB could be explained by interactions with the charged species in the fresh paste (e.g., Na 28 . Viscosity of pastes containing Triton X-405, X-100, and X-114 increased with molecular weight: Triton X-405 has a longer chain of -CH 2 -CH 2 -O-monomers (Supporting Information Fig.…”

Section: Resultsmentioning

confidence: 99%

Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation

Luukkonen

Sreenivasan

Ohenoja

et al. 2020

Sci Rep

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In this work, we compared the main characteristics of highly porous geopolymer components for water treatment applications manufactured by 3D printing, direct foaming, or granulation. Furthermore, different approaches to impregnate the materials with Ag or Cu were evaluated to obtain filters with disinfecting or catalytic properties. The results revealed that all of the investigated manufacturing methods enabled the fabrication of components that possessed mesoporosity, suitable mechanical strength, and water permeability, even though their morphologies were completely different. Total porosity and compressive strength values were 28 vol% and 16 MPa for 3D-printed, 70-79 vol% and 1 MPa for direct-foamed, and 27 vol% and 10 MPa for granule samples. Both the filter preparation and the metal impregnation method affected the amount, oxidation state, and stability of Ag and Cu in the filters. However, it was possible to prepare filters with low metal leaching between a pH of 3-7, so that the released Ag and Cu concentrations were within drinking water standards. Cellular ceramics have a high potential in water treatment applications, such as Ag impregnated point-of-use disinfecting filters 1 , slurry dewatering systems 2 , catalyst supports 3 , and micro-or ultrafiltration membranes 4. However, although ceramic materials have good chemical and physical stability, their higher price in comparison to organic polymers has hindered more widespread use in industrial water treatment 5,6. Geopolymers, on the other hand, are amorphous, low-calcium, aluminosilicate, ceramic-like materials with structural mesoporosity (i.e., pore diameter 2-50 nm) 7 ; good mechanical and chemical stability 8 ; and cation-exchange capacity 9. However, in contrast to conventional ceramics, geopolymers consolidate at (near) ambient conditions without high-temperature sintering. Consequently, geopolymer technology could offer a possibility for clean and low-cost production of ceramic-like filters, possessing better chemical stability, and a longer lifespan than polymeric components. In the context of water and wastewater treatment, geopolymers have already been investigated for a number of applications, such as adsorbents/ion exchangers, photocatalysts, and membranes, as summarized by Luukkonen et al. 10. Some of the outlined uses require modification of the geopolymers with metals. The proof-of-concept study for the use of geopolymers as antimicrobial materials was performed by O'Connor et al., who prepared an Ag +-exchanged, halloysite-based geopolymer and applied it successfully to inactivate Staphylococcus aureus on an agar plate 11. Metakaolin or fly ash geopolymers have also been modified with Ag-nanoparticles (AgNPs), and the resulting antimicrobial materials have been proposed to be used in construction 12,13. Furthermore, Cu 2+-exchanged metakaolin geopolymers have proved to be a promising antimicrobial material to be used against oyster mushroom hyphae 14. In (photo)catalytic water treatment applications, the successful impregnation of ca...

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Section: Resultsmentioning

confidence: 99%

Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation

Luukkonen

Sreenivasan

Ohenoja

et al. 2020

Sci Rep

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“…The primary reaction product after alkali-activation was C-(N)-A-S-H gel with a highly disordered structure, and PDF analysis revealed that atomic arrangements, as shown in primarily incorporated in the secondary reaction product, which is a hydrotalcite-like phase, as will be discussed in more detail below. In-situ X-ray total scattering measurements and PDF analysis are also starting to be widely used in the study of alkali-activated binders, as one of few techniques that can give time-resolved information about gel local structure during setting and hardening [91][92][93]. A method to investigate the chemistry of aluminosilicate-based cementitious binders by alkaliactivation of high-purity synthetic amorphous aluminosilicate powder has been proposed by Walkley et al [94].…”

Section: Setting Timementioning

confidence: 99%

Recent progress in low-carbon binders

Shi

Provis

2019

Cement and Concrete Research

490

131

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The development of low-carbon binders has been recognized as a means of reducing the carbon footprint of the Portland cement industry, in response to growing global concerns over CO2 emissions from the construction sector. This paper reviews recent progress in the three most attractive low-carbon binders: alkali-activated, carbonate, and belite-ye'elimite-based binders. Alkali-activated binders/materials were reviewed at the past two ICCC congresses, so this paper focuses on some key developments of alkali-activated binders/materials since the last keynote paper was published in 2015. Recent progress on carbonate and belite-ye'elimite-based binders are also reviewed and discussed, as they are attracting more and more attention as essential alternative low-carbon cementitious materials. These classes of binders have a clear role to play in providing a sustainable future for global construction, as part of the available toolkit of cements.

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“…Clay geology conditions its chemistry and mineralogy and therefore largely its reactivity, which can be stimulated with heat (500– 800°C), to convert all or part of a clay into an amorphous material. Dehydroxylation substantially alters the spatial arrangement of clay atoms, modifying the Al coordination number ( Valentini, 2018 ) and the degree of Si polymerisation ( Madani et al, 1990 ). The 27 Al and 29 Si, NMR findings in Figure 3 illustrate the significant changes taking place in a clay nanostructure after heating at 750°C and 1250°C ( Ruiz-Santaquiteria, 2013a ).…”

Section: Alkali Activated Binders (Aabs)*mentioning

confidence: 99%

Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability”

et al. 2021

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This review undertakes rigorous analysis of much of the copious literature available to the scientific community on the use of alkali-activated binders (AABs) in construction. The authors’ main intention is to categorically refute arguments of that part of the scientific community underestimating or even dismissing the actual potential of AABs as alternatives to Portland cement (PC). The main premise invoked in support of those arguments is a presumed lack of material resources for precursors that would make AAB industrial-scale production unfeasible anywhere on the planet (a substantial number of scientific papers show that the raw materials required for AAB manufacture are in abundance worldwide). The review also analyses the role of alkaline activators in the chemistry of AABs; it is important to clarify and highlight that alkaline activators are not, by any means, confined to the two synthetic products (caustic soda and waterglass) mostly employed by researchers; other sustainable and efficient products are widely available. Finally, the review deals with the versatility of AAB production processes. The technologies required for the large scale manufacturing of AABs are mostly already in place in PC factories; actually no huge investment is required to transform a PC plant in a AAB factory; and quality and compositional uniformity of Alkaline Cements (binders produced through an industrial process) would be guaranteed. The last conclusions extracted from this review-paper are related with: i) the low carbon footprint of one-part AABs and ii) the urgent need of exploring standardization formulas allowing the commercial development of (sustainable) binders different from PC.

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Modeling Dissolution–Precipitation Kinetics of Alkali-Activated Metakaolin

Cited by 40 publications

References 69 publications

Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation

Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation

Recent progress in low-carbon binders

Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability”

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