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Title: Solubilization of Trace Metals from FGD Gypsum Using a Continuously Stirred Tank Reactor

Abstract

A continuous, stirred-tank extractor (CSTX) is an effective technique for evaluating the leachability of contaminants from flue gas desulfurization (FGD) products and other materials with low permeability or cementitious properties and allows the chemistry of the leaching process to be studied at a level unachievable through more traditional batch and column techniques. In this study, metal release patterns were examined in detail over a range of pH values extending from the material’s natural, slightly alkaline pH to acidic pH conditions. Understanding the fundamental mechanisms operating during the leaching process provides a basis for evaluating the safety of FGD byproducts and ensuring these materials are used and disposed of appropriately. The results indicate that the leaching behavior of individual elements depends on several factors including, but not limited to, the solubility of the mineral phases present, sorption properties of the remaining phases, behavior of the solubilized material in the tank, the type of species in solution and the neutralization capacity of the minerals. Bulk gypsum is moderately soluble; dissolution is controlled by its solubility product and hydration reactions rather than pH. Elution and pH profiles indicate the presence of alkaline material(s) that buffer the system during the initial leaching. Iron andmore » aluminum are not leached until the buffering capacity is exhausted. Any elements bound to these phases can be mobilized during this dissolution. Arsenic, lead and mercury are not released during the leaching of most samples and become concentrated in a minor, insoluble residue remaining at the end of each experiment« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV, and Albany, OR (United States)
Sponsoring Org.:
USDOE - Office of Fossil Energy (FE)
OSTI Identifier:
916969
Report Number(s):
DOE/NETL-IR-2007-234
DOE Contract Number:  
None cited
Resource Type:
Conference
Resource Relation:
Conference: World of Coal Ash, Covington, KY, May 7-10, 2007
Country of Publication:
United States
Language:
English
Subject:
flue gas desulfurization; FGD; leaching; continuous stirred tank reactor

Citation Formats

Kairies, C L, Schroeder, K T, Thompson, R L, Cardone, C R, and Rohar, P C. Solubilization of Trace Metals from FGD Gypsum Using a Continuously Stirred Tank Reactor. United States: N. p., 2007. Web.
Kairies, C L, Schroeder, K T, Thompson, R L, Cardone, C R, & Rohar, P C. Solubilization of Trace Metals from FGD Gypsum Using a Continuously Stirred Tank Reactor. United States.
Kairies, C L, Schroeder, K T, Thompson, R L, Cardone, C R, and Rohar, P C. 2007. "Solubilization of Trace Metals from FGD Gypsum Using a Continuously Stirred Tank Reactor". United States.
@article{osti_916969,
title = {Solubilization of Trace Metals from FGD Gypsum Using a Continuously Stirred Tank Reactor},
author = {Kairies, C L and Schroeder, K T and Thompson, R L and Cardone, C R and Rohar, P C},
abstractNote = {A continuous, stirred-tank extractor (CSTX) is an effective technique for evaluating the leachability of contaminants from flue gas desulfurization (FGD) products and other materials with low permeability or cementitious properties and allows the chemistry of the leaching process to be studied at a level unachievable through more traditional batch and column techniques. In this study, metal release patterns were examined in detail over a range of pH values extending from the material’s natural, slightly alkaline pH to acidic pH conditions. Understanding the fundamental mechanisms operating during the leaching process provides a basis for evaluating the safety of FGD byproducts and ensuring these materials are used and disposed of appropriately. The results indicate that the leaching behavior of individual elements depends on several factors including, but not limited to, the solubility of the mineral phases present, sorption properties of the remaining phases, behavior of the solubilized material in the tank, the type of species in solution and the neutralization capacity of the minerals. Bulk gypsum is moderately soluble; dissolution is controlled by its solubility product and hydration reactions rather than pH. Elution and pH profiles indicate the presence of alkaline material(s) that buffer the system during the initial leaching. Iron and aluminum are not leached until the buffering capacity is exhausted. Any elements bound to these phases can be mobilized during this dissolution. Arsenic, lead and mercury are not released during the leaching of most samples and become concentrated in a minor, insoluble residue remaining at the end of each experiment},
doi = {},
url = {https://www.osti.gov/biblio/916969}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jul 01 00:00:00 EDT 2007},
month = {Sun Jul 01 00:00:00 EDT 2007}
}

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