In Situ Chemical Reduction of Chlorinated Organic Compounds

Abstract

Chlorinated organic compounds (COCs) are common anthropogenic contaminants of soil and groundwater. COCs were industrially produced for different applications, such as dry cleaning, degreasing, or as pesticides. The presence of COCs in the environment is a major concern because of their toxicity and persistence.The most widely used method for their remediation is the conventional pump-and-treat system. However, this technology can hardly achieve a complete remediation because of geological characteristics and the presence of pore space pollution/adsorbed pollution, leading to a residual saturation. Hence, in addition to the improvement of pump-and-treat systems, in situ chemical processes have been largely developed. These chemical processes involve the injection of chemical reagents for the removal of residual source pollution and/or the treatment of plume contamination. Chemical degradation of COCs can be achieved by oxidative or reductive processes. If chemical oxidation has been first developed for in situ application, chemical reduction is one of the most important emerging remediation techniques for COCs treatment. Due to the electronegative character of chlorine substituents, COCs can effectively be transformed via reductive pathways. Moreover, reductive dechlorination has shown higher efficiency on highly chlorinated compounds. This chapter focuses on the presentation of the chemical reduction of the most common COCs pollutants, followed by kinetic and mechanistic approaches related to the use of iron-based particles. Developments on in situ chemical reduction technologies in order to enhance remediation rates are also exposed. Influence of environmental conditions for in situ applications is then developed. Finally, a case study is presented.

Photocatalytic Degradation of Alkyl Halide Molecules Promoted by CsPbBr3 Perovskite Quantum Dots

“…In a more recent study, Tamang and co-workers have reported that colloidal CsPbBr 3 QDs provide efficient visible-light photocatalysts to trigger organic transformations, namely, synthesis of a broad range of azaheterocycles, via oxidative aromatization . Conversely, in situ chemical reduction of chlorinated hydrocarbons using iron-based nanoparticles has been actively pursued, as these are common groundwater and soil pollutants. , Cyclic voltammetry was employed to investigate the electrochemical degradation routes of alkyl chloride molecules in either aqueous or organic solutions . These studies have shown that each medium produces different reaction pathways involving different intermediates .…”

Synthesis of Chlorine- and Nitrogen-Containing Carbon Nanofibers for Water Purification from Chloroaromatic Compounds

“…Therefore, the research aiming to improve the purification technologies for removing such dangerous chemicals from liquid waste and wastewater is of high demand. Various methods have been proposed for the removal of COCs from water, including catalytic oxidation [ 5 ]; biodegradation [ 6 ]; advanced oxidation processes, such as photocatalytic destruction [ 7 ] or electrochemical degradation [ 8 ]; reductive dechlorination [ 9 ]; as well as non-destructive methods, such as adsorption [ 10 , 11 , 12 ]. Each of these methods has its advantages and limitations [ 1 ].…”

Combined Strategies to Prompt the Biological Reduction of Chlorinated Aliphatic Hydrocarbons: New Sustainable Options for Bioremediation Application

“…The two major problems associated with aged CAHs-contaminated sites are the secondary source management and the containment and remediation of the contamination plume. Secondary source refers to the presence of the solvent in a separate phase, primarily accumulated in the low-permeability layers of the aquifer (clay lens), which work as a source of long-term contaminants [ 5 ]. On the other hand, contamination plume refers to prolonged contamination in the same direction of water flow due to the slow and steady release of secondary sources.…”