Feasibility study of soil washing to remediate mercury contaminated soil
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Mercury (Hg) cannot be degraded. Therefore only two principal processes are available for the treatment of Hg-contaminated soil: (1) the separation of Hg from the soil or (2) the stabilisation of Hg within the soil. Prior to selecting a suitable treatment technique, it is necessary to have an understanding of Hg behaviour in contaminated soil, i.e., distribution in particle size fractions, dissolution at different pH and in the presence of chlorides, and mobilisation using various extractants. The thesis aims to evaluate the potential for applying soil washing to decontaminate the Hg-contaminated soil. The Hg contamination originated from inappropriate waste disposal, chlor-alkali process and harbour activities, and the soil was also polluted by other trace elements, i.e., Zn, Cu and Pb, etc. The soil was fractionated from fine to coarse particles to study the effectiveness of physical separation. A pH-static titration ranging from pH 3 to 11 was performed to assess the mobility of Hg in response to pH changes. The chloride influence on Hg mobilisation was studied using an HCl solution of different concentrations as the leachant. Batch leaching tests were used to evaluate Hg solubility in water, and extraction efficiency by various extractants. The extractants derived from wastes were acidogenic leachates generated from biodegradable wastes, and alkaline leachates produced from fly/bottom ashes. The studied soil consisted of dominant coarse-grained fractions, which is usually suitable for particle size separation. However, dry sieving has been shown to be insufficient to separate clean from contaminated soil fractions although the Hg concentrations decreased with increasing particle sizes. The reasons are likely to be: (i) the physical attachment of fines to coarse particles; (ii) the strong chemical bond of soil organic matter (OM) and minerals for Hg. Distilled water could barely mobilise the Hg from the soil, most likely due to firm chemical bonding between the soil and Hg. Despite the fact that enhanced Hg dissolution was observed at pH 5 and 11 in this study, soil washing by pH adjustment was insufficient for Hg removal. The introduction of chlorides did not facilitate the Hg mobilisation either. Retention of Hg in the soil by OM seemed to be predominant over Hg mobilisation by chlorides. Chemical extraction by leachates from wastes as well as EDTA solution and NaOH solutions showed that neither alkaline nor acidic leachates could facilitate Hg removal from the soil. Mercury was firmly bound in the soil matrix and no more than 1.5% of the total Hg could be removed by any of the tested extractants. Future research should therefore focus on the development of Hg immobilisation techniques.
Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013. , 92 p.
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
soil remediation, pH-dependentdissolution, organic matter, mobilisation, Other technology - Environmental engineering
Övriga teknikvetenskaper - Miljöteknik
Other Environmental Engineering
Research subject Waste Science and Technology
IdentifiersURN: urn:nbn:se:ltu:diva-18669Local ID: 9ba07408-a2c8-44e2-bc45-962d3c35f6c0ISBN: 978-91-7439-734-5 (print)ISBN: 978-91-7439-735-2 (electronic)ISBN: 978-91-7439-776-5 (electronic)OAI: oai:DiVA.org:ltu-18669DiVA: diva2:991679
Godkänd; 2013; 20130904 (xuajin); Tillkännagivande licentiatseminarium 2013-10-07 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Jingying Xu Ämne: Avfallsteknik/Waste Science and Technology Uppsats: Feasibility Study of Soil Washing to Remediate Mercury Contaminated Soil Examinator: Associate Professor, Lecturer Jurate Kumpiene, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Associate Professor, Chalmers; Dep. Director General, SGI Bo Lind, Swedish Geotechnical Institute (SGI), Göteborg Tid: Tisdag den 29 oktober 2013 kl 14.30 Plats: F531, Luleå tekniska universitet2016-09-292016-09-292017-02-10Bibliographically approved