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Remediation of Metal-Contaminated Soil by Organic Metabolites from Fungi II-Metal Redistribution
Örebro University, School of Science and Technology. SAKAB AB, Kumla, Sweden.
Örebro University, School of Science and Technology.ORCID iD: 0000-0002-2104-4593
2010 (English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 207, no 1-4, p. 5-18Article 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.

Place, publisher, year, edition, pages
2010. Vol. 207, no 1-4, p. 5-18
Keywords [en]
Bioremediation, Fungi, Metals, Oxalic acid, Citric acid
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-13015DOI: 10.1007/s11270-009-0222-6ISI: 000274550700002OAI: oai:DiVA.org:oru-13015DiVA, id: diva2:382799
Available from: 2011-01-03 Created: 2011-01-03 Last updated: 2018-04-19Bibliographically approved
In thesis
1. Organic complexing agents for remediation of heavy metal contaminated soil
Open this publication in new window or tab >>Organic complexing agents for remediation of heavy metal contaminated soil
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. p. 59
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 12
Keywords
soil washing, heavy metals, chelators, recycling
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-7913 (URN)978-91-7668-680-5 (ISBN)
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: 2017-10-18Bibliographically approved

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Arwidsson, ZandraAllard, Bert

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