EGU22-4272
https://doi.org/10.5194/egusphere-egu22-4272
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Environmental suitability of MSWI fly ash geopolymers: evaluation by leaching tests 

Caterina Caviglia1, Enrico Destefanis1, Davide Bernasconi1, Linda Pastero1, Alessandro Pavese1, Alberto Viani2, Petra Mácová2, and Lucie Zárybnická2
Caterina Caviglia et al.
  • 1Università degli Studi di Torino, Earth Science Department, Torino, Italy (caterina.caviglia@unito.it)
  • 2Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Centre Telč, Prosecká 809/76, Praha 9, 190 00, Czech Republic

This work is focused on the possible reutilization of municipal solid waste incinerator (MSWI) fly ash as a metakaolin replacement in the acid-based geopolymer. This type of geopolymer, obtained by the reaction between an aluminosilicate source (metakaolin) and phosphoric acid to form an Al-O-P/Si-O-P matrix (Wang et al, 2019), have displayed better performance than the traditional alkali-silicate geopolymer, in terms of corrosion resistance (Wagh et al, 2011), thermal stability and mechanical strength (Celerier et al, 2019). The replacement of up to 30 % wt has proved to not significantly alter the remarkable performance of the material, obtaining compressive strength values higher than 30 MPa. However, since fly ash contains dangerous substances as chlorides, sulfates, and heavy metals, which must be stabilized, it is important to evaluate the leching stability of the final materials.

Therefore, test cube blocks of 1x1x1 cm size, containing 10, 20 and 30 % wt of previously washed fly ash replacement with respect to metakaolin are prepared, with Al/P molar ratio of 1, liquid-to-solid ratio raging from 0.95-1 and 3 days at 60°C as curing temperature. 

Leaching tests, according to the European standards EN-12457 (2002), using deionized water at a ratio liquid to solid of 10, are applied to geopolymers blocks to evaluate the concentration of salts and heavy metals that usually exceeds the law threshold in the raw fly ash. Leachates are analyzed by ionic chromatography and ICP-MS: the results show that the concentrations of chlorides are under the legislation limits provided for not dangerous waste, as well as sulfates and fluorides; relatively to heavy metals Zn, Pb, Cd exceed the concentrations limits. Further tests and analyses are carried out to evaluate the impact of synthesis parameters on the leaching stability of these materials.

 

Reference

 

  • Wang, Y. Alrefaei, J. Dai. Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review, Frontiers in Materials, 6 (2019), 106.

 

A.S. Wagh. Phosphate geopolymers, Ceramic Engineering and Science Proceeding, 32, 10 (2011), 91-103.

 

  • Celerier, J. Jouin, A. Gharzouni, V. Mathivet, I. Sobrados, N. Tessier-Doyen, S. Rossignol. Relation between working properties and structural properties from 27Al, 29Si and 31P NMR and XRD of acid-based geopolymers from 25 to 1000 °C, Materials Chemistry and Physics, 228 (2019), 293-302.

How to cite: Caviglia, C., Destefanis, E., Bernasconi, D., Pastero, L., Pavese, A., Viani, A., Mácová, P., and Zárybnická, L.: Environmental suitability of MSWI fly ash geopolymers: evaluation by leaching tests , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4272, https://doi.org/10.5194/egusphere-egu22-4272, 2022.