Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash

Qadeer Alam (Corresponding author), Alberto Lazaro, Katrin Schollbach, H.J.H. Brouwers

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2%, 1.4%, 2.1% and 1.3%, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly soluble alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.

LanguageEnglish
Article number124985
Number of pages7
JournalChemosphere
Volume241
DOIs
StatePublished - 1 Feb 2020

Fingerprint

Ashes
Chemical speciation
Coal Ash
Incineration
Solid Waste
bottom ash
speciation (chemistry)
Waste incineration
Municipal solid waste
incineration
municipal solid waste
Leaching
Chlorides
leaching
chloride
Slags
Oxides
Microanalysis
Solid wastes
Sodium chloride

Keywords

  • Bottom ash
  • Chloride speciation
  • Leaching
  • MSWI
  • Washing treatments

Cite this

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title = "Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash",
abstract = "Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2{\%}, 1.4{\%}, 2.1{\%} and 1.3{\%}, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly soluble alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.",
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Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash. / Alam, Qadeer (Corresponding author); Lazaro, Alberto; Schollbach, Katrin; Brouwers, H.J.H.

In: Chemosphere, Vol. 241, 124985, 01.02.2020.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Chemical speciation, distribution and leaching behavior of chlorides from municipal solid waste incineration bottom ash

AU - Alam,Qadeer

AU - Lazaro,Alberto

AU - Schollbach,Katrin

AU - Brouwers,H.J.H.

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AB - Municipal solid waste incineration (MSWI) bottom ash is an environmentally harmful solid waste that cannot be recycled without pre-treatment. The chloride content in bottom ash (BA) is a major obstacle that restricts its application as secondary building materials. Here, the chemical speciation of the chlorides in BA is systematically studied with multiple analytical techniques, i.e., quantitative XRD, microanalysis and XPS. In addition to halite (NaCl), several chloride-rich minerals are present in BA. These phases are hydrous metal oxides, ettringite, decomposed hydration products (C4A3) and incineration slag with a chloride content of 3.2%, 1.4%, 2.1% and 1.3%, respectively. For the first time, the real-time leaching profiles of chloride (up to 80 h) from BA were obtained with a chloride-ion specific electrode to explain the leaching mechanism. In the initial stage of leaching, highly soluble alkali salts (NaCl) and physisorbed chlorides (especially those adsorbed on hydrous metal oxides) are released, which is controlled by diffusion. Later, the leaching is controlled by the solubility/reactivity of the chloride-containing phases, such as ettringite and incineration slag. The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.

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