Princípios e aplicações de processos térmicos para remediação de áreas contaminadas

Abstract

Processos térmicos têm sido cada vez mais aplicados mundialmente para a remediação de áreas contaminadas. O tratamento térmico, in situ ou ex situ, baseia-se na elevação da temperatura do solo e da água subterrânea visando a degradação do contaminante ou a sua transferência para a fase vapor, facilitando sua extração. Existem diversas formas de aquecimento, sendo a condução de calor, o aquecimento por resistência elétrica e a injeção de vapor os métodos mais utilizados. A remediação térmica pode ser utilizada em áreas com concentrações elevadas de contaminantes dissolvidos e até mesmo em fase separada (NAPLs), além de ser aplicável em diferentes litologias. Apesar do seu potencial de utilização, no Brasil essa técnica ainda é pouco estudada e aplicada. Dessa forma, o presente trabalho apresenta uma análise das diversas técnicas de remediação por processos térmicos, suas aplicações, vantagens e desvantagens, assim como um panorama de sua utilização em nível nacional.

Ultrasound-Assisted Extraction of Saponins from Beet Leaves for Soil Decontamination

“…In order to comply with the reference values demanded by the regulatory authorities, the affected sites are subjected to mechanical, chemical, biological, and/or thermal interventions . Although bioremediation and phytoremediation techniques are simple and inexpensive to implement on-site, they require long treatment times and are not suitable for heavily contaminated areas or with difficult-to-degrade hydrocarbons, such as cycloaliphatic and aromatic hydrocarbons, resulting in low treatment efficiencies. , On the other hand, thermal methods such as incineration or pyrolysis enable a fast and effective soil treatment, but they consume a lot of energy, which is reflected in their high operating costs and greenhouse gas emissions. − In order to combine high treatment efficiencies with low operational costs, physical-chemical techniques have been the focus of recent research. − Soil washing is perhaps the most common remediation technique used in the removal of petroleum hydrocarbons from soils. − This technique uses a pre-treatment, which divides the soil according to its granulometry, separating the finest fraction of the soil, with a diameter of less than 2 mm, which typically corresponds to the most contaminated part, which is sent to the washing process, while the coarser soil fraction, which generally has a lower contaminant level, is sent to a less refined treatment. ,, Soil washing is carried out with aqueous solutions to which different components, namely surfactants, pH regulators, or chelating agents, are added depending on the target contaminants, making this technique very versatile . For the removal of petroleum hydrocarbons, surfactants are generally applied, as they can mobilize and solubilize pollutants in an aqueous medium, which can be subsequently easily treated with liquid–liquid separation techniques. ,,, …”