Kinetic mechanism of desilicated fly ash lime consumption

T. Falayi, F.N. Okonta, F. Ntuli

Research output: Contribution to journalArticle

Abstract

This paper presents study of the kinetic mechanism of lime consumption using desilicated fly ash (DFA). Desilicated fly ash (DFA) a residue from leaching of silica from fly ash was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40 ºC, 80 ºC and 100 ºC for 4 days. 80 ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.6 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol and a reaction grade of 3 meaning that the reaction was controlled by diffusion of reactants through a dense layer of reaction products. The main hydration products were calcium silicate hydrate and tricalcium aluminate. Toxicity leaching tests showed a 79 % reduction in the leachability of trace and heavy metals. Therefore, DFA can successfully be stabilised using lime. © 2018, Kauno Technologijos Universitetas. All rights reserved.
Original languageEnglish
Pages (from-to)192-196
Number of pages5
JournalMedziagotyra
Volume24
Issue number2
DOIs
Publication statusPublished - 2018

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Coal Ash
Fly ash
Lime
Kinetics
Leaching
Silicic Acid
Calcium silicate
Heavy Metals
Hydrates
Reaction products
Silicon Dioxide
Hydration
Heavy metals
Toxicity
Curing
lime
Moisture
Activation energy
Silica
Temperature

Cite this

Falayi, T. ; Okonta, F.N. ; Ntuli, F. / Kinetic mechanism of desilicated fly ash lime consumption. In: Medziagotyra. 2018 ; Vol. 24, No. 2. pp. 192-196.
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author = "T. Falayi and F.N. Okonta and F. Ntuli",
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Kinetic mechanism of desilicated fly ash lime consumption. / Falayi, T.; Okonta, F.N.; Ntuli, F.

In: Medziagotyra, Vol. 24, No. 2, 2018, p. 192-196.

Research output: Contribution to journalArticle

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T1 - Kinetic mechanism of desilicated fly ash lime consumption

AU - Falayi, T.

AU - Okonta, F.N.

AU - Ntuli, F.

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AB - This paper presents study of the kinetic mechanism of lime consumption using desilicated fly ash (DFA). Desilicated fly ash (DFA) a residue from leaching of silica from fly ash was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40 ºC, 80 ºC and 100 ºC for 4 days. 80 ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.6 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol and a reaction grade of 3 meaning that the reaction was controlled by diffusion of reactants through a dense layer of reaction products. The main hydration products were calcium silicate hydrate and tricalcium aluminate. Toxicity leaching tests showed a 79 % reduction in the leachability of trace and heavy metals. Therefore, DFA can successfully be stabilised using lime. © 2018, Kauno Technologijos Universitetas. All rights reserved.

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