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- Title
Stepwise extraction and utilization of silica and alumina from coal fly ash by mild hydrothermal process.
- Authors
Xing, Lang; Li, Xinran; Cao, Pengxu; Luo, Jun; Jiang, Hao
- Abstract
Coal fly ash (CFA) is a potential secondary resource. In this study, silica and alumina from CFA were leached and utilized through a gentle alkali hydrothermal process. The results of CFA desilication with a single NaOH solution showed that amorphous silica was dissolved at a relatively low temperatures. Under optimized conditions, the leaching rate of SiO 2 reached 33.81 %, while that of Al 2 O 3 only was 1.37 %. Amorphous honeycomb calcium silicate hydrate was then well prepared by using silicon-rich liquid with CaO. The new aluminosilicate structures (sodalite) were detected in desilicated coal fly ash (DSCFA), which hinder the silica dissolution. After the optimal hydrothermal leaching in Ca(OH) 2 +NaOH system, the leaching rate of Al 2 O 3 in DSCFA reached 39.84 %. The dealuminated CFA were mainly composed of friendly nano-flake tobermorite. With the increase of temperature, time, alkali concentration and Ca/Si, the tobermorite phase gradually changed to hibschite. The obtained alumina lixivium was well transformed into valuable porous boehmite via a carbonation process. Finally, the pilot tests excellent results, leaching about 41 % of SiO 2 and 42 % of Al 2 O 3, further demonstrating the feasibility of the whole hydrothermal process of desilication with a single alkali followed by aluminum extraction with mixed alkali. [Display omitted]
- Subjects
FLY ash; COAL ash; CALCIUM silicates; ALUMINUM oxide; CALCIUM silicate hydrate; LEACHATE
- Publication
Process Safety & Environmental Protection: Transactions of the Institution of Chemical Engineers Part B, 2024, Vol 182, p918
- ISSN
0957-5820
- Publication type
Article
- DOI
10.1016/j.psep.2023.12.035