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Distribution and chemical association of trace elements in incinerator residues and mining waste from a leaching perspective
Örebro University, School of Science and Technology.ORCID iD: 0000-0001-5215-5934
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Incineration is a mainstream strategy for solid waste management in Sweden and all over the world. Improved knowledge and understanding about the distribution of trace elements (in ashes) during incineration, and how trace element partitioning respond to the changes in waste composition, are important in terms of combustion process optimization and plant efficiency. Moreover, determination of chemical association of trace elements in ashes are vital for avoiding environmental concerns and to promote possible reuse. In this study, partitioning of trace elements in ashes during incineration as function of input waste fuel and incineration technology was investigated. Further, chemical association of trace elements in resulting ashes was studied. An evaluation was also performed about feasibility of metal extraction from sulfidic mining waste and flotation tailings. Moreover, green liquor dreg (GLD) was tested with respect to stabilization of metals within the sulfidic mining waste.

Findings showed that the total input of trace elements and chlorine affects the partitioning and increasing chlorine in the input waste caused increase in transfer of trace elements to fly ash especially for lead and zinc. Vaporization, condensation on fly ash particles and adsorption mechanisms play an important role for metal distribution. Firing mixed waste, especially biofuel mix, in grate or fluidized (CFB) boilers caused increased transfer into fly ash for almost all trace elements particularly lead and zinc. Possible reasons might be either an increased input concentration of respective element in the waste fuel, or a change in volatilization behavior due to the addition of certain waste fractions. Chemical association study for fly ashes indicated that overall, Cd, Pb, Zn, Cu and Sb are presenting major risk in most of the fly ashes, while in bottom ashes, most of elements are associated with stable fraction. Further, fuel type affects the association of elements in ashes. Chemical leaching of mining waste materials showed that sulfuric acid (under different conditions) is the best reagent to recover zinc and copper from sulfidic mining waste and also copper from flotation tailings. GLD indicates potential for metal stabilization in mining waste by reducing the metal mobility. Extraction methods could be applied to treat mining waste in order to meet the regulatory level at a specific mining site.Similarly stabilization/solidification  methods might be applied after leaching for recovery of metals.

Place, publisher, year, edition, pages
Örebro: Örebro university , 2016. , 92 p.
Series
Örebro Studies in Chemistry, ISSN 1651-4270 ; 15
Keyword [en]
trace elements, partitioning, fly ash, bottom ash, speciation, association, risk assessment, wood waste, incineration, mining waste
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-48933ISBN: 978-91-7529-128-4 (print)OAI: oai:DiVA.org:oru-48933DiVA: diva2:908881
Public defence
2016-05-03, Hörsalen, Musikhögskolan, Örebro universitet, Fakultetsgatan 1, Örebro, 13:15 (English)
Opponent
Supervisors
Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2017-10-17Bibliographically approved
List of papers
1. Trace element partitioning in ashes from boilers firing pure wood or mixtures of solid waste with respect to fuel composition, chlorine content and temperature
Open this publication in new window or tab >>Trace element partitioning in ashes from boilers firing pure wood or mixtures of solid waste with respect to fuel composition, chlorine content and temperature
2014 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 34, no 12, 2505-2519 p.Article in journal (Refereed) Published
Abstract [en]

Trace element partitioning in solid waste (household waste, industrial waste, waste wood chips and waste mixtures) incineration residues was investigated. Samples of fly ash and bottom ash were collected from six incineration facilities across Sweden including two grate fired and four fluidized bed incinerators, to have a variation in the input fuel composition (from pure biofuel to mixture of waste) and different temperature boiler conditions. As trace element concentrations in the input waste at the same facilities have already been analyzed, the present study focuses on the concentration of trace elements in the waste fuel, their distribution in the incineration residues with respect to chlorine content of waste and combustion temperature. Results indicate that Zn, Cu and Pb are dominating trace elements in the waste fuel. Highly volatile elements mercury and cadmium are mainly found in fly ash in all cases; 2/3 of lead also end up in fly ash while Zn, As and Sb show a large variation in distribution with most of them residing in the fly ash. Lithophilic elements such as copper and chromium are mainly found in bottom ash from grate fired facilities while partition mostly into fly ash from fluidized bed incinerators, especially for plants fuelled by waste wood or ordinary wood chips. There is no specific correlation between input concentration of an element in the waste fuel and fraction partitioned to fly ash. Temperature and chlorine content have significant effects on partitioning characteristics by increasing the formation and vaporization of highly volatile metal chlorides. Zinc and cadmium concentrations in fly ash increase with the incineration temperature.

Keyword
Ash; Incineration residue; Solid waste management; Trace element partitioning
National Category
Chemical Sciences Environmental Sciences
Research subject
Chemistry; Enviromental Science
Identifiers
urn:nbn:se:oru:diva-41179 (URN)10.1016/j.wasman.2014.08.025 (DOI)000347019700009 ()25263218 (PubMedID)2-s2.0-84910639884 (Scopus ID)
Available from: 2015-01-13 Created: 2015-01-13 Last updated: 2017-12-05Bibliographically approved
2. Distribution and leaching characteristics of trace elements in ashes as a function of different waste fuels and incineration technologies
Open this publication in new window or tab >>Distribution and leaching characteristics of trace elements in ashes as a function of different waste fuels and incineration technologies
2015 (English)In: Journal of Environmental Sciences(China), ISSN 1001-0742, E-ISSN 1878-7320, Vol. 36, no 1 Oct., 9-21 p.Article in journal (Refereed) Published
Abstract [en]

Impact of waste fuels (virgin/waste wood, mixed biofuel (peat, bark, wood chips) industrial, household, mixed waste fuel) and incineration technologies on partitioning and leaching behavior of trace elements has been investigated. Study included 4 grate fired and 9 fluidized boilers. Results showed that mixed waste incineration mostly caused increased transfer of trace elements to fly ash; particularly Pb/Zn. Waste wood incineration showed higher transfer of Cr, As and Zn to fly ash as compared to virgin wood. The possible reasons could be high input of trace element in waste fuel/change in volatilization behavior due to addition of certain waste fractions. The concentration of Cd and Zn increased in fly ash with incineration temperature. Total concentration in ashes decreased in order of Zn > Cu > Pb > Cr > Sb > As > Mo. The concentration levels of trace elements were mostly higher in fluidized boilers fly ashes as compared to grate boilers (especially for biofuel incineration). It might be attributed to high combustion efficiency due to pre-treatment of waste in fluidized boilers. Leaching results indicated that water soluble forms of elements in ashes were low with few exceptions. Concentration levels in ash and ash matrix properties (association of elements on ash particles) are crucial parameters affecting leaching. Leached amounts of Pb, Zn and Cr in > 50% of fly ashes exceeded regulatory limit for disposal. 87% of chlorine in fly ashes washed out with water at the liquid to solid ratio 10 indicating excessive presence of alkali metal chlorides/alkaline earths.

Place, publisher, year, edition, pages
Science Press, 2015
Keyword
Incineration residues; Leaching behavior; Biofuel incineration; Metal distribution; Waste incineration
National Category
Chemical Sciences
Research subject
Environmental Chemistry; Chemistry
Identifiers
urn:nbn:se:oru:diva-45103 (URN)10.1016/j.jes.2015.03.006 (DOI)000362983500002 ()26456601 (PubMedID)2-s2.0-84943225103 (Scopus ID)
Note

Funding Agency:

Varmeforsk (Thermal Engineering Research Association) Q4-251

Available from: 2015-07-04 Created: 2015-07-04 Last updated: 2017-12-04Bibliographically approved
3. Chemical association and mobility of trace elements in 13 different fuel incineration fly ashes
Open this publication in new window or tab >>Chemical association and mobility of trace elements in 13 different fuel incineration fly ashes
2015 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 165, 193-204 p.Article in journal (Refereed) Published
Abstract [en]

The migration of trace elements from waste incineration fly ash is problematic during utilization/ landfilling. This study investigated the chemical association and potential mobility of trace elements in fly ashes originating from incineration of different fuels [virgin wood, recovered waste wood (RWW), mixed wooden fuel/waste, household, industrial, and mixed waste]. Fly ashes were characterized for total content of trace elements, chemical association by sequential extraction and leaching behaviour by standard leaching method (EN 12457-3). Results showed that average total content of trace elements in 13 fly ashes decreased in the order Zn > Cu > Pb > Sb > Cr > As > Cd. Sequential extraction results indicated that overall, Cd, Pb, Zn, Cu and Sb were the most mobile elements and excessive leaching was associated with high content of acid exchangeable fractions. Sequential extraction showed thatthe average percentage of trace elements in labile and stable fractions for all 13 fly ashes decreased in the order:Cd > Cu > Sb > Zn > As > Pb > Cr (ion-exchangeable), Pb > Zn > Sb > Cd > Cu > As > Cr(acid soluble),Cr > As > Pb > Sb > Cu > Zn > Cd (residual). The standard leaching procedure of ashes indicated that the leached amount of Pb in all samples, Zn in 7 while Cu in 6 (out of 13) samples, respectively, exceeded the regulatory level for disposal. Moreover, principal component analysis (PCA) showed that fuel type affects the chemical association of trace elements in fly ash. Further, risk assessment code (RAC) suggested that most of fly ashes presented very high risk due to high RAC values for Cd, Zn, Cu and Sb.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Chemical speciation; Fly ash; Risk assessment; Trace elements mobility; MSWI
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-46305 (URN)10.1016/j.fuel.2015.10.062 (DOI)000364655000023 ()2-s2.0-84946087137 (Scopus ID)
Available from: 2015-10-23 Created: 2015-10-23 Last updated: 2017-12-01Bibliographically approved
4. Chemical association and mobility of trace elements in 13 different fuel incineration bottom ashes
Open this publication in new window or tab >>Chemical association and mobility of trace elements in 13 different fuel incineration bottom ashes
2016 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 172, 105-117 p.Article in journal (Refereed) Published
Abstract [en]

The release of trace elements from waste incineration bottom ash is problematic during utilization/landfilling. Thirteen bottom ashes (from various waste fuels and wooden/mixed wooden fuel) were investigated with respect to the total content, leaching behaviour by standard leaching procedure (EN 12457-3), and chemical association of trace elements by sequential extraction. Results showed that the content of trace elements in household/or industrial waste bottom ashes were of high level in comparison to in wooden/mixed wooden fuel/mixed wooden waste ashes. Type of fuel being treated greatly impacts the total inventory of trace elements. On average, trace element content in 13 ashes followed the decreasing order; Cu > Zn > Pb > Cr > Ni > Sb > As. In this study the average total content of Zn, Pb, Cu and Cr was higher in grate bottom ash treating household/industrial waste in comparison to fluidized boilers ash using same waste, however, there were too few data points and variation in data was large. By Standard leaching procedure, an excessive amount (more than disposal limit) of leached Cr, Pb, Sb and Cu (mostly in household/industrial waste ash) was observed in 6, 5, 5 and 4 of the 13 samples, respectively. Correlation coefficients (r) found between total and water leachable contents for Cu, Sb and As were 0.8, 0.7 and 0.6 respectively. Sequential extraction indicated that residual was the major fraction mostly, however, considerable amounts of trace elements had the potential to leach out. A large fraction of arsenic (57% based on average values) in 5 samples (mostly in waste/virgin wood and mixed wooden waste/fuel) and Zn (49% based on average values) in 4 of 13 samples (mostly household/or industrial) were found in the fractions that are easily available (acid soluble and exchangeable). Further, a considerable amount of Cu in 4 samples were found associated with the organic-bound phase. Dissolved organic matter might play an important role in leaching of Cu during utilization/landfilling. Moreover, principal component analysis (PCA) showed that fuel type affects the association of trace elements in bottom ash. Amounts of labile trace elements in wooden/mixed wooden fuel/waste bottom ashes were comparatively lower than other fuel bottom ashes. None of the samples exceeded the limit of disposal with respect to DOC leaching while chlorine in two and sulphate in three samples (household/industrial) exceeded limit. LOI (550 °C) values were higher for bottom ash from grate facilities probably due to no-pre-treatment of the waste fuel. While comparatively low values of LOI (1 000 °C) in few samples implies that the oxidation might have outweighed the loss of carbonates.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Bottom ash; Speciation; Trace elements; Incineration; Mobility
National Category
Inorganic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-47348 (URN)10.1016/j.fuel.2016.01.010 (DOI)000368881200013 ()2-s2.0-84954326717 (Scopus ID)
Note

Funding Agency:

Varmeforsk (Thermal Engineering Research Association)

Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2017-12-01Bibliographically approved
5. Chemical leaching of Zn, Cu and Pb from oxidized sulfidic mining waste followed by stabilization using green liquor dreg
Open this publication in new window or tab >>Chemical leaching of Zn, Cu and Pb from oxidized sulfidic mining waste followed by stabilization using green liquor dreg
(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-49743 (URN)
Available from: 2016-04-11 Created: 2016-04-11 Last updated: 2017-10-17Bibliographically approved
6. Flotation tailings as a copper resource - Extraction and characterization through chemical leaching
Open this publication in new window or tab >>Flotation tailings as a copper resource - Extraction and characterization through chemical leaching
(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-49744 (URN)
Available from: 2016-04-11 Created: 2016-04-11 Last updated: 2017-10-17Bibliographically approved

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