Thermal treatment of soils contaminated with hexadecane. Temperature effects on removal efficiency and volatiles release

MERINO, JERÓNIMO; BUCALÁ, VERÓNICA

Rio de Janeiro, Brasil

Congreso; ENPROMER 2005; 2005

Universidade Federal do Rio de Janeiro (Brasil) y otras

  Abstract. Soils contaminated with hydrocarbons can be found in many industrial sites and oil refineries. Several technologies are used for the remediation of these sites. Thermal treatments are the most popular and versatile techniques because they can be effectively applied to a wide range of organic contaminants. According to their operational temperature, thermal treatments can be classified into desorption and destruction techniques. In the former, the contaminated soil is generally heated between 150 and 500°C, and a physical separation is produced transferring the pollutants to a gas stream. On the other hand, the latter involves working at high temperatures, usually 600-900°C or greater, and the contaminants often suffer chemical modifications. Several independent analyses to understand the fundamentals of contaminant release from soils have been performed. However, in most cases the studies are limited to clay soils, and it is assumed that soils behave as inert media throughout the thermal treatment. Moreover, the fate of the contaminants during the decontamination process and the quality of the generated gases are relevant aspects that have not been simultaneously addressed in depth to date. Therefore, in this work, we monitored the evolution of the soil quality as well as the quality and amount of volatile compounds generated during the process. This information was used to analyze the effect of temperature on the removal of both contaminants and the by-products generated from the soil matrix during the thermal treatment of the contaminated samples, so as to assess the overall efficiency of the treatment. An organic soil (2.5% of total organic carbon) was artificially contaminated with hexadecane, the contamination level being 3 wt%. Neat and contaminated samples were heated under an inert medium up to different final temperatures (150-800°C) for 30 minutes to simulate ex-situ thermal process conditions. Several technologies are used for the remediation of these sites. Thermal treatments are the most popular and versatile techniques because they can be effectively applied to a wide range of organic contaminants. According to their operational temperature, thermal treatments can be classified into desorption and destruction techniques. In the former, the contaminated soil is generally heated between 150 and 500°C, and a physical separation is produced transferring the pollutants to a gas stream. On the other hand, the latter involves working at high temperatures, usually 600-900°C or greater, and the contaminants often suffer chemical modifications. Several independent analyses to understand the fundamentals of contaminant release from soils have been performed. However, in most cases the studies are limited to clay soils, and it is assumed that soils behave as inert media throughout the thermal treatment. Moreover, the fate of the contaminants during the decontamination process and the quality of the generated gases are relevant aspects that have not been simultaneously addressed in depth to date. Therefore, in this work, we monitored the evolution of the soil quality as well as the quality and amount of volatile compounds generated during the process. This information was used to analyze the effect of temperature on the removal of both contaminants and the by-products generated from the soil matrix during the thermal treatment of the contaminated samples, so as to assess the overall efficiency of the treatment. An organic soil (2.5% of total organic carbon) was artificially contaminated with hexadecane, the contamination level being 3 wt%. Neat and contaminated samples were heated under an inert medium up to different final temperatures (150-800°C) for 30 minutes to simulate ex-situ thermal process conditions.