Mechanisms Of Polycyclic Aromatic Hydrocarbons Degradation Research Articles

Efficiency of Hydrogen Peroxide and Fenton Reagent for Polycyclic Aromatic Hydrocarbon Degradation in Contaminated Soil: Insights from Experimental and Predictive Modeling

This study investigates the degradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil using hydrogen peroxide (H2O2) and the Fenton process (H2O2/Fe2+). The effect of oxidant concentration and the Fenton molar ratio on PAH decomposition efficiency is examined. Results reveal that increasing H2O2 concentration above 25 mmol/samples leads to a slight increase in the rate constants for both first- and second-order reactions. The Fenton process demonstrates higher efficiency in PAH degradation compared to H2O2 alone, achieving decomposition yields ranging from 84.7% to 99.9%. pH evolution during the oxidation process influences PAH degradation, with alkaline conditions favoring lower elimination rates. Fourier-transform infrared (FTIR) spectroscopy analysis indicates significant elimination of PAHs after treatment, with both oxidants showing comparable efficacy in complete hydrocarbon degradation. The mechanisms of PAH degradation by H2O2 and the Fenton process involve hydroxyl radical formation, with the latter exhibiting greater efficiency due to Fe2+ catalysis. Gaussian process regression (GPR) modeling accurately predicts reduced concentration, with optimized ARD-Exponential kernel function demonstrating superior performance. The Improved Grey Wolf Optimizer algorithm facilitates optimization of reaction conditions, yielding a high degree of agreement between experimental and predicted values. A MATLAB 2022b interface is developed for efficient optimization and prediction of C/C0, a critical parameter in PAH degradation studies. This integrated approach offers insights into optimizing the efficiency of oxidant-based PAH remediation techniques, with potential applications in contaminated soil remediation.

New insights into the Ferrate-Sulfite system for the degradation of polycyclic aromatic Hydrocarbons: A dual role for sulfite

The presence of polycyclic aromatic hydrocarbons (PAHs) in water is a significant environmental concern due to their potential health risks. While sulfite activation of ferrate (Fe(VI)) has shown promise in enhancing the degradation of antibiotics and pesticides in water systems, its applicability to the degradation of PAHs remains largely unexplored. Here, we investigated the efficiency and mechanisms of PAH degradation via sulfite-activated ferrate. The ferrate-sulfite system significantly accelerated PAH degradation, achieving a 1.53 to 3.13-fold rate increase compared to ferrate-only treatment. Key active species involved in PAHs degradation were Fe(V), Fe(IV), and SO4●−. Sulfite accelerated the degradation of PAHs by undergoing a swift reaction with Fe(VI), leading to the formation of Fe(V) and SO4●−. Sulfite accelerated the degradation of PAHs by undergoing a swift reaction with Fe(VI) resulting in the production of Fe(V) and SO4●−. Through the reduction of ferrate species by sulfite, Fe(III) were produced and accelerated the decomposition of residual Fe(VI) into Fe(IV). Sulfite accelerates the degradation of PAHs by ferrate through these two processes. It promotes Fe(V) and Fe(IV) production from ferrate in a different way. Importantly, the toxicity of PAHs degradation intermediates is significantly reduced. Overall, these findings indicate that the ferrate-sulfite combination has significant potential to address environmental and health concerns associated with PAHs in water sources.

Oxidative degradation of polycyclic aromatic hydrocarbons in contaminated industrial soil using chlorine dioxide

In situ chemical oxidation can be used to remediate soils contaminated with polycyclic aromatic hydrocarbons (PAHs). However, typical oxidation systems are limited by the acidic environment needed for Fenton reactions, cost and soil effects of activated persulfate, and large pores required for ozone or selected oxidation by permanganate. Chlorine dioxide (ClO2) is an environmentally friendly strong oxidant that is highly reactive with PAHs and produces limited halogenated byproducts. In this study, the kinetics, products, and mechanisms of PAH degradation in industrial soil using ClO2 were investigated. The degradation rate was approximately 84.24% for 0.90 mol kg−1 of ClO2; it increased with ClO2 concentration and temperature had little effect. The degradation process was divided into quick (<1h) and slow (1–48 h) reaction stages. PAH removal was significantly inhibited at higher pH levels, but > 70% of the PAHs were degraded at a typical soil pH of 5.0–7.0. Chemical pretreatment is favorable for PAH removal during ClO2 oxidation and the degradation rate was passively correlated with the desorbing fraction of the PAHs in the soil. Quenching experiments indicated that HOCl was the most important active species responsible for degradation. Among five representative PAH congeners, the degradation products of anthracene, phenanthrene, and benzo[a]pyrene were all oxygenated products. However, the degradation product of pyrene was the Cl substitution product and fluoranthene oxidation produced ring rupture oxygenated transformation and Cl substitution products. The mechanisms of PAH degradation by ClO2 oxidation include one-electron transfer, HOCl as a second oxidant, and •OH participation.

Draft Genome Sequence of Ochrobactrum anthropi Strain W13P3, a Halotolerant Polycyclic Aromatic Hydrocarbon-Degrading Bacterium.

Ochrobactrum anthropi W13P3 was isolated from saline soil contaminated by polycyclic aromatic hydrocarbons (PAHs) and could degrade PAHs with 5% NaCl. We report the 5.3-Mb draft genome sequence of this strain, which is helpful for understanding the diversity of Ochrobactrum spp. and the mechanism of PAH degradation in saline environments.

Enrichment, Isolation, and Phylogenetic Identification of Polycyclic Aromatic Hydrocarbon-Degrading Bacteria from Elizabeth River Sediments

The diversity of indigenous bacteria in sediments from several sites in the Elizabeth River (Virginia) able to degrade multiple polycyclic aromatic hydrocarbons (PAHs) was investigated by the use of classical selective enrichment and molecular analyses. Enrichment cultures containing naphthalene, phenanthrene, fluoranthene, or pyrene as a sole carbon and energy source were monitored by denaturing gradient gel electrophoresis (DGGE) to detect changes in the bacterial-community profile during enrichment and to determine whether the representative strains present were successfully cultured. The DGGE profiles of the final enrichments grown solely on naphthalene and pyrene showed no clear relationship with the site from which the inoculum was obtained. The enrichments grown solely on pyrene for two sample sites had >80% similarity, which suggests that common pyrene-degrading strains may be present in these sediments. The final enrichments grown on fluoranthene and phenanthrene remained diverse by site, suggesting that these strains may be influenced by environmental conditions. One hundred and one isolates were obtained, comprising representatives of the actinomycetes and alpha-, beta-, and gammaproteobacteria, including seven novel isolates with 16S rRNA gene sequences less than 98% similar to known strains. The ability to degrade multiple PAHs was demonstrated by mineralization of 14C-labeled substrate and growth in pure culture. This supports our hypothesis that a high diversity of bacterial strains with the ability to degrade multiple PAHs can be confirmed by the combined use of classical selective enrichment and molecular analyses. This large collection of diverse PAH-degrading strains provides a valuable resource for studies on mechanisms of PAH degradation and bioremediation.