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Study of the Metal Precipitation from Decontamination Leachates of Municipal Wastes Fly Ash Incinerators.

Levasseur, Béatrice; Blais, Jean-François; Mercier, Guy (2005). Study of the Metal Precipitation from Decontamination Leachates of Municipal Wastes Fly Ash Incinerators. Environmental Technology , vol. 26 , nº 4. p. 421-432. DOI: 10.1080/09593332608618547.

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Résumé

This research work focuses on the development of a new process for the decontamination of municipal wastes incinerators fly ashes. The objective of this study was to evaluate different total and selective precipitation methods for metals removal from ash decontamination leachates. The tested options include 1) use of hydrated lime and caustic soda for selective (pH 5.0) and total (pH 8.5) metal precipitation; 2) addition of different chemicals (H3PO4, Na2S and FeCl3) in a pH range from 6.0 to 9.0. Fly ash decontamination assays using alkaline and acid washing steps were initially performed using optimal conditions previously established. Treated fly ashes respected the standards based on the TCLP leaching test for all studied metals and SPLP. Total metal precipitation tests carried out at pH 8.5 achieve removal yields for all metals ≥ 90% using hydrated lime and ≥ 83% using caustic soda. Selective precipitation tests alone at pH 5.0 show removal yields ≥ 97% for Cr and between 75 and 87% for Al and Pb. Moreover, assays carried out using a stoechiometric addition of Na2S have allowed the separation of Cd (≥ 99%) and Zn (≥ 71%) as metal sulphides (CdS and ZnS). From an economical point of view, the most interesting option seems to be the leachates neutralization at pH 7.0 using Ca(OH)2 combined with the reuse of the treated leachates in the fly ash leaching steps. Metal precipitation cost at pH 7.0 has been estimated to be 22.7 CAN$ tct−1 using Ca(OH)2, and 26.7 CAN$ tct-1 using NaOH.

Type de document: Article
Mots-clés libres: fly ash; leaching; metals; TCLP; SPLP; removal; precipitation
Centre: Centre Eau Terre Environnement
Date de dépôt: 08 janv. 2021 15:52
Dernière modification: 08 janv. 2021 15:52
URI: http://espace.inrs.ca/id/eprint/10997

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