In this study, four geopolymer sorbents GP0, GP10, GP30 and GP50 were synthesized using volcanic ash (VA) and metakaolin (MK) blends as precursors with 0, 10, 30 and 50% MK content by mass, respectively. The materials were characterized
by X-ray fuorescence (XRF), X-ray difraction (XRD), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface
area analyses, revealing successful geopolymerization of the precursors and increasing surface area with increasing MK
content. The sorption performance of the VA, MK and VA-MK geopolymers was then evaluated for the removal of cationic
methylene blue (MB) dye from aqueous media. Sorption capacity was independent of composition, providing fexibility in
sorbent synthesis. Sorption rate, on the other hand, was 3–8 times greater for the VA-MK geopolymers than the precursor
materials. The equilibrium adsorption data were suitably explained by the Freundlich model, denoting multilayer adsorption onto a heterogeneous adsorption surface with higher Freundlich afnity constant (KF) for geopolymers than VA. The
adsorption kinetics obeyed the pseudo-second-order (PSO) kinetic law with an average of 98% removal efciency in 30 min.
MB uptake was pH-dependent and driven by electrostatic chemisorption interactions. These results motivate further studies
on the use of locally sourced geopolymers for water purifcation applications.
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Study on the immersion test of geopolymers made by recycling of coal ash
Abstract A geopolymer was produced from coal ash generated from an integrated gasification combined cycle (IGCC) plant and its water resistance was evaluated. For this purpose, the geopolymer specimens were immersed in water for 30 days to measure changes in microstructure and alkalinity of the immersion liquid. Particularly, the experiment was carried out with foaming status of the geopolymers and parameters of room temperature aging condition, and immersion time. The foamed geopolymer containing 0.1 wt% Si-sludge had pores with a diameter of 1 to 3 mm and exhibited excellent foamability. Also, the calcium-silicate-hydrate crystal phase appeared in the foamed geopolymer. In the geopolymer immersion experiment, the pH of the immersion liquid increased with time, because the un-reacted alkali activator remained was dissolved in the immersion liquid. From the pH change of the immersion liquid, it was found that geopolymer reaction in the foamed specimen was completed faster than the non-foamed specimen. Through this study, it was possible to successfully produce foamed and non-foamed geopolymers recycled from IGCC coal ash. Also the necessary data for the safe application of IGCC coal ash-based geopolymers to areas where water resistance is needed were established; for example, the process conditions for room temperature aging time, effect of foaming status, immersion time and so on.
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- Award ID(s):
- 1829245
- NSF-PAR ID:
- 10099829
- Date Published:
- Journal Name:
- Han-guk gyeoljeong seongjang hakoeji
- Volume:
- 28
- Issue:
- 5
- ISSN:
- 2234-5078
- Page Range / eLocation ID:
- 199-205
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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