Pollutants actually existing in various types of soil, ranging from rural, agricultural soils to urban or factory soils, belong to a wide range of chemical compounds, both organic and inorganic. The modern decontamination methods were each specifically designed for a particular pollutant. Reagents and procedure conditions targeted only one particular contaminant, more rarely several pollutants, all usually belonging to the same family (e.g., several heavy metals or polychloro-p-dibenzodioxins and polychloro-p-dibenzofurans). Most reviews on the subject presented soil decontamination processes under the same auspices: specific process with specific reagent for a specific pollutant. Unfortunately, soils are often cross-contaminated with various types of pollutants, which make the decontamination procedure much more complicated: indeed, for each contaminant, a certain procedure must be carried out. This transforms the whole decontamination process in a multi-step procedure, enhancing the costs. Therefore, any method that could realize a simultaneous decontamination for at least two different types of pollutants would be extremely advantageous. In the recent years, such methods made an interesting appearance in the environmental science and engineering literature. We wish to review these dual decontamination methodologies that deal simultaneously with at least one organic and one inorganic contaminant in the same soil matrix.
Part of the book: Soil Contamination
Defunctionalization of organochlorines through reductive dechlorination (also known as hydrodechlorination—replacement of chlorine atoms by hydrogen—is one of the main methodologies used in the detoxification of these harmful compounds. Most of the published papers on this particular matter focused on specific reagents, reaction conditions, and mainly result efficiency. Some of the authors were also concerned with reaction pathways (e.g., the order in which chlorine atoms were removed from a polychlorinated aromatic substrate—polychlorinated biphenyls, PCBs; polychlorinated dibenzo-p-dioxins, PCDDs; or polychlorinated dibenzofurans, PCDFs). However, the papers that dealt with the investigation of reaction mechanism were rather scarce. This chapter presents the advances made by researchers in understanding, from a mechanistic point of view, the hydrodechlorination process, along with our own assumptions. In doing so, it would be easier to predict the behavior of such compounds in a specific environment, showing more clearly the scope and limitations of each process, depending on the reaction conditions and reagents.
Part of the book: Organochlorine