Granular activated carbon (GAC)- extraction of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans from soil washing liquids of contaminated soils
(English)Manuscript (Other academic)
Ethanol washing has been recently shown to be a potentially useful technique for remediating soils contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). During this process, the contaminants are transferred from the soils to the washing liquid, producing a highly toxic extract. Consequently, there is a need for a post-treatment technique that removes the PCDD/F from the washing liquid, enabling its recirculation. In this study, the potential utility of granular activated carbon (GAC) as an adsorbent for extracting PCDD/Fs from soil-washing liquids was investigated. The washing liquids were produced by extraction of two former sawmill sites, at which chlorophenol based preservatives had been used. The PCDD/F levels in the washing liquids were 42 and 540 pg TEQ PCDD/F /g soil, and the organic contents in the soils differed greatly prior to the washing procedure. Ten 80 mL aliquots of the extracts of each soil, each corresponding to approximately 25 g of soil, were treated with 0-1.5 g GAC to adsorb the contaminants. In both cases, a removal efficiency of 96% was attained, but 15-fold more GAC was needed to clean the liquid used to treat the soil with the high organic content to this degree (1.5 g versus 0.1 g for the liquid used to wash the other soil). Hence, the extraction efficiency of the GAC treatment appears to be influenced by the amount of organic matter in the soil, probably due to competition between PCDD/F and other organic compounds (natural organic matter and other contaminants) in the soil for the GAC adsorption sites, since GAC adsorbs non-specifically. The results in this study provide promising indications that GAC can be used to remove dioxins from soil-washing liquid, thereby facilitating recirculation and reducing treatment costs. We also propose a number of additional procedures that may be needed for a complete soil-solvent washing process.
Soil remediation, pollutants, PCDD, PCDF, solvent washing, carbon, adsorption
IdentifiersURN: urn:nbn:se:umu:diva-21009OAI: oai:DiVA.org:umu-21009DiVA: diva2:210299