Reactivity of Pyrogenic Carbonaceous Matter (PCM) in mediating environmental reactions: Current knowledge and future trends

Redox Properties of Pyrogenic Dissolved Organic Matter (pyDOM) from Biomass-Derived Chars

“…Thermally altered plant biomass (char) is ubiquitous in the environment and has long been recognized as an important geosorbent for organic compounds and inorganic species, including pollutants. − More recent work has revealed that chars are also redox-active by accepting and donating electrons and, thereby, participate in biogeochemical electron transfer processes and pollutant redox transformations. − Chars accept electrons from anaerobic microbial respiration or from inorganic reductants in the environment (e.g., hydrogen sulfide). ,,,,− ,,,, Following reduction, chars may then transfer electrons to both organic and inorganic pollutants, thereby facilitating their reductive transformation. ,,− ,,,, Chars are also involved in electron transfer between microbial cells , or from metal-reducing bacteria to hematite or ferrihydrite. , In addition, electron transfer to and from chars was shown to mitigate emissions of the radiatively active trace gas N 2 O from agricultural soils. , The important role of chars in redox reactions has led to considerable interest in characterizing the redox chemistry and reactivity of chars. However, chars also release dissolved organic carbon (DOC), which herein we refer to as pyrogenic dissolved organic matter (pyDOM) (operationally defined as DOC from bulk chars that passes through 0.45 μm filters). − The released amounts of pyDOM are considered significant in the global carbon cycle: for instance, pyDOM is estimated to contribute ∼10% of the riverine flux of DOC to the oceans. , Yet, compared to bulk chars and non-pyrogenic DOM, only a few studies have characterized ...…”

New Mechanism via Dichlorocarbene Intermediate for Activated Carbon-Mediated Reductive Dechlorination of Carbon Tetrachloride by Sulfide in Aqueous Solutions

“…The findings from this study imply that the chemical, structural, and pore properties of these materials can be finely tuned and coordinated to develop efficient and cost-effective adsorption-reaction systems for pollution control and environmental remediation. For instance, the mediation facilitation properties of CMs on the reductive dechlorination of CCl 4 by sulfide shown herein can be readily improved by increasing pyrolysis temperature of CMs to enhance graphitization degree, microporosity, and pore wall hydrophobicity simultaneously. , …”

“…Several mechanisms have been proposed to explain the mediation ability of CMs in the sulfide-induced reductive reactions of HOCs. First, the graphitic regions of CMs have high electro-conductivity and can, thus, enhance electron transfer from sulfide to adsorbed HOCs ,– Second, the quinone moieties at the surface of CMs may act as electron shuttles to facilitate the electron transfer process though the quinone–hydroquinone redox cycling . Furthermore, the oxygenated functional groups (e.g., quinones and semiquinones) on CMs can oxidize sulfide to polysulfides, polysulfide free radicals, and other reactive sulfur species, which can reduce HOCs more quickly than sulfide. – …”

Electron exchange capacity of pyrogenic dissolved organic matter (pyDOM): complementarity of square-wave voltammetry in DMSO and mediated chronoamperometry in water

“…Natural organic matter (NOM) plays an essential role in the biogeochemistry of natural waters, including the global carbon cycle. [1][2][3] Pyrogenic carbonaceous matter (PCM) is the solid residue produced by pyrolysis of biomass or fossil fuels under oxygen-limited conditions, 4,5 and includes naturally existing black carbon and its engineering analogs, such as activated carbon and biochar. Recently, studies have found that dissolved organic matter (DOM) can be released from PCM and subsequently enter the aquatic environment.…”