| Popis: |
Dioxins and furans are persistent, highly hazardous and ubiquitous compounds that have become the focus of many investigations due to the contamination of food and the ecosystem. Dioxins and furans refer to a class of polyhalogenated aromatic hydrocarbons generated by various chemical processes occurring often at high temperature. The main sources of dioxins and furans have been classified into four categories, namely: incineration, combustion, industrial processes and natural processes such as volcanic eruptions. Dioxins and furans are present in flue gas and fly ash from combustion, in contaminated soils, sediments and water bodies. The expression toxic equivalency (TEQ) factor has been defined to assess their toxicity. Dioxins and furans have adverse effects on human health because they are bioaccumulated in tissues and cells. They are carcinogenic and cause reproductive alterations. They are a threat to the ecosystem because they persist in nature, affecting marine and terrestrial living organisms, and subsequently ending up in the food chain. We review remediation techniques of dioxins and furans. The most common techniques are landfill cap system and deep well injections, high temperature incineration and cement kilns. This chapter focuses on the principal destruction, removal and remediation techniques based on flue gas, fly ash and soil treatment. Basic techniques are selective catalyst reduction technologies, adsorption by means of activated carbon, base catalysed reactions, photolytic degradation processes, thermal desorption processes, alkaline polyethylene glycolate (APEG) process, bioslurry treatment and vitrification. |
