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Organic complexing agents for remediation of heavy metal contaminated soil
Örebro University, School of Science and Technology. (MTM)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil washing of heavy metal contaminated soil may be enhanced by the addition of synthetic chelators. Since many of these chelators may imply stress to soil organisms and are poorly biodegraded, identification and evaluation of effective biodegradable or recyclable chelators (synthetic and/or naturally produced) is of great interest. The efficiency of biodegradable synthetic chelators was evaluated both in bench- (0.3 kg) and meso- (10 kg) scale. Results demonstrated that the solubilization of copper, lead, and zinc was similar in bench- and meso-scale systems, which indicated that these systems could be used in a technical scale. However, the arsenic extraction in meso-scale system, were non-conclusive. Due to the high cost involved in the purchase of synthetic chelating agents, recycling of the solutions is of great interest, and this was achieved in five consecutive washing cycles. Considering the economy of a full-scale process, recycling of complexing solutions with sulfide addition at each cycle, both at the 100 mM-level, appears feasible. Naturally derived chelators were produced by saprotrophic fungi and through alkaline degradation of humic substances and cellulose. The results demonstrated that these types of complexing agents are not as effective as the synthetic chelators. In the fungal systems, desorption of metals was related to production of organic complexing acids, but mainly to the pH-decrease. Nonetheless, in some systems, formation of soluble complexes was indicated (copper). Enhancement of copper, lead, and zinc release with the use of alkaline leachates from wood and peat appeared possible. Since these agents have a natural origin and are derived from rather cheap raw material, recycling is not an issue.

 

Place, publisher, year, edition, pages
Örebro: Örebro universitet , 2009. , 59 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 12
Keyword [en]
soil washing, heavy metals, chelators, recycling
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
URN: urn:nbn:se:oru:diva-7913ISBN: 978-91-7668-680-5 (print)OAI: oai:DiVA.org:oru-7913DiVA: diva2:235033
Public defence
2009-10-02, HSP1, Fakultetsgatan 1, Örebro, 10:15 (English)
Opponent
Supervisors
Available from: 2009-09-11 Created: 2009-09-11 Last updated: 2011-04-29Bibliographically approved
List of papers
1. Remediation of Metal Contaminated Soil by Organic Metabolites from Fungi I—Production of Organic Acids
Open this publication in new window or tab >>Remediation of Metal Contaminated Soil by Organic Metabolites from Fungi I—Production of Organic Acids
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2008 (English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 205, no 1-4, 215-226 p.Article in journal (Refereed) Published
Abstract [en]

Investigations were made on living strains offungi in a bioremediation process of three metal (lead)contaminated soils. Three saprotrophic fungi (Aspergillusniger, Penicillium bilaiae, and a Penicillium sp.) wereexposed to poor and rich nutrient conditions (no carbonavailability or 0.11 M D-glucose, respectively) andmetal stress (25 μM lead or contaminated soils) for5 days. Exudation of low molecular weight organicacids was investigated as a response to the metal andnutrient conditions. Main organic acids identified wereoxalic acid (A. niger) and citric acid (P. bilaiae).Exudation rates of oxalate decreased in response tolead exposure, while exudation rates of citrate were lessaffected. Total production under poor nutrient conditionswas low, except for A. niger, for which nosignificant difference was found between the poor andrich control. Maximum exudation rates were 20 μmoloxalic acid g^−1 biomass h^−1 (A. niger) and 20 μmolcitric acid g^−1 biomass h^−1 (P. bilaiae), in the presenceof the contaminated soil, but only 5 μmol organic acidsg^−1 biomass h^−1, in total, for the Penicillium sp. Therewas a significant mobilization of metals from the soilsin the carbon rich treatments and maximum release ofPb was 12% from the soils after 5 days. This was notsufficient to bring down the remaining concentration tothe target level 300 mg kg^−1 from initial levels of 3,800,1,600, and 370 mg kg^−1in the three soils. Target levelsfor Ni, Zn, and Cu, were 120, 500, and 200 mg kg^−1,respectively, and were prior to the bioremediationalready below these concentrations (except for Cu Soil1). However, maximum release of Ni, Zn, and Cu was28%, 35%, and 90%, respectively. The release of metalswas related to the production of chelating acids, but alsoto the pH-decrease. This illustrates the potential to usefungi exudates in bioremediation of contaminated soil.Nonetheless, the extent of the generation of organicacids is depending on several processes and mechanismsthat need to be further investigated.

Place, publisher, year, edition, pages
Berlin, Germany: Springer, 2008
Keyword
Bioremediation, Citric acid, Fungi, Lead, Organic acids, Oxalic acid
National Category
Natural Sciences Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
urn:nbn:se:oru:diva-11843 (URN)10.1007/s11270-009-0067-z (DOI)000272851000016 ()2-s2.0-75049083063 (Scopus ID)
Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-02-22Bibliographically approved
2. Remediation of Metal-Contaminated Soil by Organic Metabolites from Fungi II-Metal Redistribution
Open this publication in new window or tab >>Remediation of Metal-Contaminated Soil by Organic Metabolites from Fungi II-Metal Redistribution
2010 (English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 207, no 1-4, 5-18 p.Article in journal (Refereed) Published
Abstract [en]

Exudation of low molecular weight organic acids by fungi was studied in a project focusing on bioremediation of metal-contaminated soils. The production of acids (mainly oxalic and citric acid) as a response to nutrient variations and presence of metals has recently been reported (Arwidsson et al. 2009). A significant release of metals was observed and was related not only to the production of organic acids but also to the resulting pH decrease in the systems. The processes governing the release and redistribution of metals in the soil-water fungus system were the focus of the present continuation of the project, based on observations of Aspergillus niger, Penicillium bilaiae, and a Penicillium sp. The release of lead was 12% from the soil with the second highest initial load (1,600 mg kg(-1)), while the release of copper was 90% from the same soil (140 mg kg(-1)). The dominating mechanism behind the release and subsequent redistribution was the change in pH, going from near neutral to values in the range 2.1-5.9, reflecting the production of organic acids. For some of the systems, the formation of soluble complexes is indicated (copper, at intermediate pH) which favors the metal release. Iron is assumed to play a key role since the amount of secondary iron in the soils is higher than the total load of secondary heavy metals. It can be assumed that most of the heavy metals are initially associated with iron-rich phases through adsorption or coprecipitation. These phases can be dissolved, or associated metals can be desorbed, by a decrease in pH. It would be feasible to further develop a process in technical scale for remediation of metal-contaminated soil, based on microbial metabolite production leading to formation of soluble metal complexes, notably with copper.

Keyword
Bioremediation, Fungi, Metals, Oxalic acid, Citric acid
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-13015 (URN)10.1007/s11270-009-0222-6 (DOI)000274550700002 ()
Available from: 2011-01-03 Created: 2011-01-03 Last updated: 2017-02-14Bibliographically approved
3. Leaching of metals from contamined soil with polyhydroxycarboxylic acids of natural origin
Open this publication in new window or tab >>Leaching of metals from contamined soil with polyhydroxycarboxylic acids of natural origin
(English)Manuscript (preprint) (Other academic)
National Category
Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-15427 (URN)
Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2016-12-13Bibliographically approved
4. Remediation of heavy metal contaminated soil washing residues with amino polycarboxylic acids
Open this publication in new window or tab >>Remediation of heavy metal contaminated soil washing residues with amino polycarboxylic acids
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2010 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 173, no 1-3, 697-704 p.Article in journal (Refereed) Published
Abstract [en]

Removal of Cu, Pb, and Zn by the action of the two biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS) and methylglycinediacetic acid (MGDA), as well as citric acid, was tested. Three soil samples, which had previously been treated by conventional soil washing (water), were utilized in the leaching tests. Experiments were performed in batches (0.3 kg-scale) and with a WTC-mixer system (Water Treatment Construction, 10 kg-scale). EDDS and MGDA were most often equally efficient in removing Cu, Pb, and Zn after 10-60 min. Nonetheless, after 10 d, there were occasionally significant differences in extraction efficiencies. Extraction with citric acid was generally less efficient, however equal for Zn (mainly) after 10 d. Metal removal was similar in batch and WTC-mixer systems, which indicates that a dynamic mixer system could be used in full-scale. Use of biodegradable amino polycarboxylic acids for metal removal, as a second step after soil washing, would release most remaining metals (Cu, Pb and Zn) from the present soils, however only after long leaching time. Thus, a full-scale procedure, based on enhanced metal leaching by amino polycarboxylic acids from soil of the present kind, Would require a pre-leaching step lasting several days in order to be efficient. (C) 2009 Elsevier B.V. All rights reserved.

Keyword
Heavy metals, Amino polycarboxylic acids, Soil, Remediation, EDDS, MGDA
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-13043 (URN)10.1016/j.jhazmat.2009.08.141 (DOI)000273135600098 ()
Available from: 2011-01-03 Created: 2011-01-03 Last updated: 2017-02-15Bibliographically approved
5. Recycling of amino polycarboxylic acids in soil washing of heavy metal contaminated soil
Open this publication in new window or tab >>Recycling of amino polycarboxylic acids in soil washing of heavy metal contaminated soil
(English)Manuscript (preprint) (Other academic)
National Category
Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-15428 (URN)
Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2016-12-14Bibliographically approved
6. Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site: Changes in concentration and toxicity
Open this publication in new window or tab >>Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site: Changes in concentration and toxicity
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2009 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 172, no 2-3, 1033-1040 p.Article in journal (Refereed) Published
Abstract [en]

Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2xCMC* of a nonionic, alkyl glucoside surfactant at pH 12 (Ca(OH)2). This combination managed to reach Swedish threshold values within 10 min of treat­ment when performed at elevated temperature (50°C), with initial conta­minant concentrations of As = 105±4 mg/kg and US-EPA PAH16 = 46.0±2.3 mg/kg. The main mechanisms behind the removal were the pH-effect for As and a combina­tion of SOM-ionization as a result of high pH and micellar solu­bilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characte­ristics of the leaching solution due to the elevated pressure utilized. The ecotox­icological evaluation, Microtox®, demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to in­creased availability of contaminants and toxicity of soil washing solutions to the test organism.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2009
Keyword
Arsenic, Microtox®, PAH, Soil washing, Surfactant
National Category
Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-7988 (URN)10.1016/j.jhazmat.2009.07.092 (DOI)000271980800068 ()19699582 (PubMedID)2-s2.0-71049155866 (Scopus ID)
Available from: 2009-09-23 Created: 2009-09-23 Last updated: 2017-02-17Bibliographically approved

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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
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  • en-GB
  • en-US
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  • nn-NO
  • nn-NB
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  • Other locale
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Output format
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  • asciidoc
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