Figure - available from: Journal of Chemistry
This content is subject to copyright. Terms and conditions apply.
Source publication
Chlorinated alkanes were heavily used in a wide range of industrial applications including as degreasers, paint strippers, chemical intermediates, and soil fumigants. These compounds are an environmental concern due to the adverse health effects associated with them and have been detected in environmental matrices including soils and groundwater. C...
Citations
... L·g −1 ·h −1 for PLP-QA vs 4.27 × 10 −2 L·g −1 ·h −1 for PLPpy + vs 0.01−1.9 × 10 −3 L·g −1 ·h −1 for ZVI/ZVZ).1,2,62 ...
... One of the agents that can be used to detoxify these organic compounds is vitamin B12. The dehalogenation of these organic halide compounds can occur through the direct use of vitamin B12 [15] or through bacterial activity in the mechanism of which the participation of vitamin B12 or similar compounds is well known [16][17][18][19]. Anaerobic reductive bacteria can be a solution for the dehalogenation of organic halide compounds in natural environments. ...
... It is interesting that the experimental data point to the interaction model between the reactants, in which the organic halide compound is quasi-perpendicular to the corrin ring of the cob(I)alamin cofactor so that the reactants interact through the central cobalt atom of the first with a halogen atom of the second reactant [17][18]. In particular, the dehalogenation of 3,5-dibromo-4-hydroxobenzoic acid, 3-bromo-4hydroxobenzoic acid [19], and 1,2-dichloroethene organic halide compounds have been reported [15]. These organic halide compounds were selected to create common computational models for CASSCF geometry optimizations (Figure 2). ...
... TCP is hard to deal with in the groundwater because of its migration ability, durability in the environment, and large water solubility. However, numerous studies have attempted to remediate sites contaminated by such pollutant, including adsorption by granular activated carbon (GAC), reduction by zero-valent metals, biodegradation, and chemical oxidation [10][11][12][13][14][15]. Babcock Jr et al. took six kinds of GAC to adsorb three different groundwater samples and found no GAC could completely remove TCP, but this method can reduce remediation time [16]. ...
In this research, zero-valent iron (ZVI) was chosen as a reductant in the classic Fenton system to accelerate the generation of Fe(II). The removal of 1,2,3-trichloropropane (TCP) was only 65.3% in classic Fenton system, while with the addition of ZVI its removal could be enhanced to 95.4% in 120 min. Hydroxyl radicals (HO•) was confirmed to be the major radical during TCP degradation by electron paramagnetic resonance (EPR) detection and radical quenching tests. Moreover, the mechanism of TCP degradation in H2O2/Fe(II)/ZVI system was proposed. In the presence of ZVI, Fe(III) was reduced to Fe(II), further reacted with H2O2 and produced more HO• for TCP removal. 2,3-Dichloro-1-propene and 2-chloro-2-propen-1-ol were the main intermediates in TCP degradation and two possible pathways were proposed. Finally, TCP removal in different solution matrixes and for other chlorinated contaminants removal were tested, revealing the broad-spectrum reactivity and excellent performance of ZVI-enhanced Fenton system in the remediation of chlorinated organic compounds.
... Many types of paraffins (e.g. n-hexanes) are well known for their ability to negatively affect the nervous system, and thus depending on the exposure, can cause dizziness, headaches, fatigue, numbness in the limbs, incoordination, tremors, temporary limb paralysis, and unconsciousness (Kuppusamy et al. 2020a, b;Lapeyrouse et al. 2019). Paraffins have lower solubility in comparison to aromatics with comparable molecular weight (i.e., equal carbon numbers) and tend to biodegrade faster than aromatics, and hence, are less toxic (Kuppusamy et al. 2020a). ...
Nonaqueous phase liquids (NAPL) tend to be trapped within aquifers. The review first covers conventional technologies that rely on pumping water, hot water, and/or air sparging with vapor extraction. The review then addresses polymer and foam delivery, which are intended to directly add solutions to low-permeability zones, where NAPL resides. Based on data from the literature, the removal of hydrocarbons by any of the flushing techniques, including polymer and foams apply well for porous media whose hydraulic conductivity is greater than 10 −4 m=s, excluding silt and clay materials. For those lower permeability soils, electrokinetics (EK) appears appropriate. EK relies on imposing a voltage of DC current across the soil, which would engender three types of flows: electromigration, which causes ions to move to the electrode of opposite sign; electrophoresis, which causes charged particles, such as negatively charged clay particles or bacteria (mostly negatively charged but also some positively charged) to the electrode of the opposite sign; and electroosmosis, which occurs only when a zeta potential exists in the soil (typical of clay and silt) that would cause the movement of water and potentially NAPL. EK could be used to deliver anionic surfactants through electromigration or nonionic surfactants through electroosmosis (in clay or silt). An emerging hydraulic technique is chaotic advection, and it maximizes the contact between the delivered solution and the soil region of interest. The main challenge of applying EK in field studies is the familiarity of operators and scalability, as the electrodes cannot be more than 15-20 m apart.
For decades, the comparison of experimental data with theoretical results in studying the biochemistry of vitamin B12 has been very confusing. While the methylcobalamin cofactor-dependent Methionine Synthase process can undergo unlimited turnovers, and some of the adenosylcobalamin-dependent processes run with close-to-unity equilibrium constants (e.g., with close-to-zero energy barriers), the DFT and QM/MM based on density functional theory, the most used and appreciated methods for calculating the electronic structure of molecules, have been showing a much shorter than experimental-determined Co-N distances in the vitamin B12 cofactors of Co+2 and the inadequate large energetic barriers of their enzymology bioprocesses. The confusion was even larger since some in vitro experimental data showed large barriers to the vitamin B12 cofactor reactions (which in fact play a destructive role in the Methionine Synthase process and which barriers were caused mostly by the influence of the solvents in which the reaction took place). It reached the point where solid contributions to the study of the biochemical processes of vitamin B12 were almost officially questioning the correctness of the experimental determination of the Co-N chemical bond distances in the cobalt(II) cofactors of vitamin B12. Unexpectedly, all the theoretical biochemistry of the vitamin B12 cofactors began to agree with all in vivo experimental data only when they were treated with the MCSCF method, the method that considers the orbital mixing, or in other words, the Pseudo-Jahn–Teller Effect. MCSCF data establish unknown mechanistic details of the methyl radical and hydrogen transfers, the origin of the electronic transfers between bioreagents, and the nature and the relationship between the bioreactions. The Pseudo-Jahn–Teller Effect, e.g., orbital mixing, governs vitamin B12 chemistry in general and provides insight into particular details of vitamin B12-dependent reactions in the human body. It turns out that the DFT or QM/MM based on DFT method theoretical data are incongruent with the experimental data due to their limitations, e.g., the unaccounted-for effects of orbital mixing.
1,2,3-trichloropropane (TCP), a refractory contaminant, can be reductive dehalogenated to allyl chloride (AC) by microorganisms, which has been shown a potential in situ bioremediation (ISB) strategy for TCP remediation in groundwater. In practice, however, it is hard to monitor the bioreduction extent because the TCP concentrations may also be decreased by non-biodegradation processes. Compound specific isotope analysis (CSIA) can be promising in determining the extent of degradation by quantifying the isotope enrichment factors (ε) of relevant degradation mechanisms. To date, no CSIA study has been reported on TCP degradation. In this study, a novel TCP-to-AC transformation enrichment culture (dominated by Azotobacter, Parabacteroides, Fusibacter, Hydrogenophaga, Trichococcus Desulfovibrio, etc) in the absence of the already identified TCP anaerobic reductive dechlorinating microorganisms (e.g., Dehalogenimonas) was derived from a chlorinated hydrocarbon-contaminated aquifer. A TCP degradation experiment was carried out by adding yeast extract to produce hydrogen as an electron donor. The TCP-to-AC transformation was found to conform to zero-order conversion kinetics with the rate constant 11 ± 0.34 μmol L⁻¹ d⁻¹ during the main biodegradation stage. The bulk carbon isotope enrichment factor (εbulk) of the TCP-to-AC transformation was firstly evaluated as −5.2 ± 0.1‰. This study for the first time characterized the carbon isotope fractionations during TCP biodegradation using a novel enrichment culture, which would provide a promising tool for the incorporation of ISB for TCP removal in the future.
Degradation of 1,2,3-trichloropropane (TCP) to allyl chloride (AC) by Dehalogenimonas (Dhg), the only reported TCP anaerobic reductive dechlorinating microorganism so far, has been demonstrated to be effective for in-situ bioremediation (ISB) of groundwater. This process is found viable when augmented with the fermentable organic substrate, yet its environmental implication is not yet clear and limited due to the complex environmental conditions and indigenous microbial communities. In this study, using yeast extract as biostimulant, an enrichment culture capable of dechlorinating TCP derived from groundwater well sludge at a chlorinated aliphatic hydrocarbon (CAH)-contaminated site was incubated. Geochemical methods, 16 S rRNA gene and shotgun metagenomic sequencing were used to systematically monitor the TCP biodegradation kinetics and unravel the functional microbial communities that play pivotal roles in this process. The decrease of TCP, along with the increase of AC (the product of TCP degradation) and δ¹³C-TCP values indicated active biodegradation of TCP. The 16 S rRNA phylogenetic tree showed the absence of Dhg, suggesting a putative novel culture for dechlorinating TCP. Several potential anaerobic reductive functional genes and dominant microorganisms were identified and mutualistic interactions were found. Hydrogenase (H2ase) genes, responsible for producing the hydrogen, were harbored by Desulfovibrio. Cobalamin synthase (CobS) genes, responsible for synthesizing the cobalamin, an important co-factor for dehalogenation, were harbored by Desulfovibrio, Gracilibacter, Thermococcus. By obtaining the electron donor (hydrogen) and essential cofactors (cobalamin), the reductive dehalogenase (Rdh) gene were harbored by Parabacteroides, Caldisalinibacter, and Desulfovibrio. Based on these findings, Desulfovibrio was deduced to be the most promising genus for TCP degradation. The identified microbial community could collaboratively play critical roles in TCP degradation, and therefore, a new method is expected to be developed.
