Photochemical reactions between superoxide ions and 2,4,6-trichlorophenol in atmospheric aqueous environments

Mercury transformations in algae, plants, and animals: The occurrence, mechanisms, and gaps

Mercury (Hg) is a global pollutant showing potent toxicity to living organisms. The transformations of Hg are critical to global Hg cycling and Hg exposure risks, considering Hg mobilities and toxicities vary depending on Hg speciation. Though currently well understood in ambient environments, Hg transformations are inadequately explored in non-microbial organisms. The primary drivers of in vivo Hg transformations are far from clear, and the impacts of these processes on global Hg cycling and Hg associated health risks are not well understood. This hinders a comprehensive understanding of global Hg cycling and the effective mitigation of Hg exposure risks. Here, we focused on Hg transformations in non-microbial organisms, particularly algae, plants, and animals. The process of Hg oxidation/reduction and methylation/demethylation in organisms were reviewed since these processes are the key transformations between the dominant Hg species, i.e., elemental Hg (Hg0), divalent inorganic Hg (IHgII), and methylmercury (MeHg). By summarizing the current knowledge of Hg transformations in organisms, we proposed the potential yet overlooked drivers of these processes, along with potential challenges that hinder a full understanding of in vivo Hg transformations. Knowledge summarized in this review would help achieve a comprehensive understanding of the fate and toxicity of Hg in organisms, providing a basis for predicting Hg cycles and mitigating human exposure.

Formation of Environmentally Persistent Free Radicals from the Irradiation of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) provide a complex matrix for environmentally persistent free radicals (EPFRs) to stabilize in particulate matter, allowing them to be transported over long distances in the atmosphere while participating in light-driven reactions and causing various cardiopulmonary diseases. In this study, four PAHs ranging from three to five rings (anthracene, phenanthrene, pyrene, and benzo[e]pyrene) were investigated for EPFR formation upon photochemical and aqueous-phase aging. Through electron paramagnetic resonance (EPR) spectroscopy, it was found that approximately 10¹⁵ to 10¹⁶ spins g^-1 of EPFRs were formed from the PAH upon aging. EPR analysis also revealed that carbon-centered and monooxygen-centered radicals were predominantly formed by irradiation. However, oxidation and fused-ring matrices have added complexity to the chemical environment of these carbon-centered radicals, as observed by their g-values. This study showed that atmospheric aging results not only in the transformation of PAH-derived EPFR but also in an increase in EPFR concentrations of up to 10¹⁷ spins g^-1. Therefore, because of their stability and photosensitivity, PAH-derived EPFRs have a major impact on the environment.

Effective degradation of 2,4,4'-trichlorodiphenyl by Fe3C@Fe-800 activated peroxymonosulfate: Superoxide radical and singlet oxygen-dominated advanced oxidation process

Polychlorinated biphenyls (PCBs) degradation by peroxymonosulfate (PMS) activation through •OH and SO₄^•- radical oxidation process was the effective technology in the last decades; however, there were few research focusing on removing PCBs by O₂^•- and ¹O₂ induced by PMS activation. In this work, 90.86% of 2,4,4-trichlorodiphenyl (PCB 28) was degraded by 0.3 g/L Fe₃C@Fe-800 activated 0.5 mM PMS system under the synergistic action of O₂^•- and ¹O₂. The structures of Fe₃C@Fe-800 were identified by Scanning electron microscope (SEM), High resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), Raman spectra and Fourier transform infrared (FT-IR) spectra. Electron paramagnetic resonance (EPR) measurements and quenching tests verified that O₂^•- and ¹O₂ were the primary reactive species in Fe₃C@Fe-800/PMS/PCB 28 ternary reaction system. Density functional theory (DFT), Linear sweep voltammetry (LSV), and chronoamperometry test revealed that electron-deficient Fe atoms on Fe₃C were the main active sites in Fe₃C@Fe-800 for PMS activation to generate ¹O₂. Unlike the reported •OH and SO₄^•- mediated degradation induced by the iron-based catalyst, both O₂^•- and ¹O₂ contributed to PCB 28 degradation： nucleophilic dichlorination reaction by O₂^•- and then ring-open oxidation process by ¹O₂. Fe₃C@Fe-800/PMS system had excellent catalytic performance under different reaction conditions and possessed desirable inorganic salt and natural organic matter resistance. This work elucidated the important role of Fe₃C in PMS activation to generate O₂^•- and ¹O₂ for PCB 28 decontamination by nonradical way and provided a clue to design rationally catalysts in polychlorinated biphenyl pollution remediation.

Sulfurized nano zero-valent iron prepared via different methods: Effect of stability and types of surface corrosion products on removal of 2,4,6-trichlorophenol

Sulfurization improves the stability and activity of nano zero-valent iron (nZVI). The sulfurized nZVI (S-nZVI) were prepared with ball milling, vacuum chemical vapor deposition (CVD) and liquid-phase reduction techniques and the corresponding products were the mixture of FeS₂ and nZVI (nZVI/FeS₂), well-defined core-shell structure (FeS_x@Fe) or seriously oxidized (S-nZVI(aq)), respectively. All these materials were applied to eliminate 2,4,6-trichlorophenol (TCP) from water. The removal of TCP was irrelevant with the structure of S-nZVI. Both nZVI/FeS₂ and FeS_x@Fe showed remarkable performance for the degradation of TCP. S-nZVI(aq) possessed poor mineralization efficiency to TCP due to its bad crystallinity degree and severe leaching of Fe ions, which retarded the affinity of TCP. Desorption and quenching experiments suggested that TCP removal by nZVI and S-nZVI was based on surface adsorption and subsequent direct reduction by Fe⁰, oxidation by in-situ produced ROS and polymerization on the surface of these materials. In the reaction process, the corrosion products of these materials transformed into crystalline Fe₃O₄ and α/β-FeOOH, which enhanced the stability of nZVI and S-nZVI materials and was conductive to the electron transferring from Fe⁰ to TCP and strong affinity of TCP onto Fe or FeS_x phases. All these were contributed to high performance of nZVI and sulfurized nZVI in removal and minerazilation of TCP in continuous recycle test.

Self-assembled nanorods with reduced graphene oxide as efficient nano-catalyst for dual modality sensing of hazardous phenolic compound

The modern development in the agricultural production has huge influential factors being highly beneficial and also includes some health hazards. Under the class of chlorophenols, 2,4,6-trichlorophenol is a widely used chemical which remains as a major pollutant in the environment. The detection of 2,4,6-trichlorophenol was initiated as a controlling measure to decrease the seriousness prevailing in the ecosystem. The electrochemical and UV-vis absorption sensing platform are simple and low-cost detection techniques with precise and sensitive analysis. Cadmium tin oxide integrated with the reduced graphene oxide was employed as a nanohybrid for the construction of the working electrode. The structural and morphological analysis confirmed the high degree of crystallinity of the nanocomposite with nanorod formation. The high surface area, with high charge carrier mobility, and increased electrical conductivity of the material boosted the 2,4,6-trichlorophenol detection. The active surface area was calculated to be 0.068 cm^-1, 0.089 cm^-1, 0.118 cm^-1 and 0.146 cm^-1 for all the modified electrodes. The resistance of the electrodes was about 91.4 Ω, 72.9 Ω, 48.8 Ω and 41.6 Ω. The linear range of 2,4,6-trichlorophenol was 0.019 μM-0.299 μM and 1.299 μM-1678.97 μM in electrochemical sensing and 10.99 μM-24.84 μM in UV detection. The obtained limit of detection with the formulation 3σ/SD was about 3.05 nM and 80 nM with sensitivity about 14.01 μA μM^-1 cm^-2. The real sample detection in environmental real samples showed good recovery results. The specific selectivity, good repeatability, reproducibility and stability analysis proves the good sensing parameters. Thus, the fabricated electrode is highly sufficient of sensing 2,4,6-trichlorophenol. These excellent features of the material can be applied for several other applications which will provide good performances.

The performance and pathway of benzothiazole degradation by electron beam irradiation

Benzothiazole (BTH) is a typical refractory heterocyclic compound that can be used as a photosensitive material in organic synthesis and conditional plant resource research. The extensive use of BTH has led to high BTH concentrations in natural environment, such as in tap water and urine, which tend to inhibit animal hormone synthesis and induce genotoxicity. Traditional wastewater treatment processes cannot effectively remove BTH. Therefore, we aimed to use the electron beam method, an emerging method for pollutant degradation, to degrade BTH in water. Experiments showed that BTH can be effectively degraded (up to 90%) when the electron beam reaches 5 kGy and irradiation conformed perfectly to the pseudo first-order kinetics model. Experimental results showed that acidic conditions are more favorable for electron beam degradation of BTH, while the degradation of most other inorganic ions is inhibited (except SO₄^2-). Hydroxyl radicals (•OH) was confirmed to play a major role in degradation by the experiment, and the mineralization rate was greatly increased by the addition of H₂O₂ and K₂S₂O₈. In addition, our experimental and theoretical calculations showed that the degradation of BTH occurred mainly through the opening of the benzene ring. Theoretical calculations showed that the toxicity of BTH decreased significantly after electron beam degradation, making it an effective way to degrade BTH.

Fabricating BiOI nanostructures armed catalytic strips for selective electrochemical and SERS detection of pesticide in polluted water

We have constructed a dual mode catalytic strip equipped with 2D BiOI nanostructures and deployed for dual mode detection sensing of hazardous trichlorophenol (TCP). Synthesized BiOI nanostructures are investigated for its crystal architecture, morphology and chemical composition. The BiOI are loaded onto the catalytic strips with the assistance of gravity offered drying process. The BiOI nanostructures offers a very less charge transfer resistance indicating its superior catalytic properties upon the electrochemical impedance studies. It reflected on providing an excellent limit of detection (LOD) and linear sensing range for TCP in electrochemical mode. For SERS, a thin plasmonic Au layer is sputter coated on BiOI equipped catalytic strips (Au@BiOI) for the TCP detection. An impressive enhancement factor of 10⁷ is obtained for SERS detection of TCP with good LOD of 10^-10 M. Fabricated dual mode BiOI based strips are thoroughly examined for operational stability and performance in real time conditions. The fabricated high performance dual mode platform for the detection of hazardous pesticides appears to be a promising prospect for the on-the-spot investigation.

Degradation of anticorrosive agent benzotriazole by electron beam irradiation: Mechanisms, degradation pathway and toxicological analysis

Benzotriazole (BTA), which is extensively served as household and engineering agent, is one of the emerging and persistent contaminants. Despite the spirit to remove BTA is willing, the traditional wastewater treatments are weak. Therefore, the degradation of BTA via electron beam was systematically explored in this study. It turned out that after 5.0 kGy irradiation, even 87.5 mg L^-1 BTA could be completely removed, and the irradiation conformed perfectly to the pseudo first-order kinetics model. The effects of solution pH, inorganic anions (CO₃^2-, HCO₃^-, NO₃^-, NO₂^-, SO₄^2-, SO₃^2-, Cl^-), and gas atmosphere were all explored. And results indicated that oxidative hydroxyl radicals played critical role in BTA irradiation. Additionally, presence of H₂O₂ and K₂S₂O₈ promoted significantly not only degradation extent but also mineralization efficiency of BTA due to they both augmented the generation of oxidative free radicals. Moreover, by combining theoretical calculations with experimental results, it could be inferred that degradation of BTA was mainly carried out by the benzene ring-opening. Further toxicity evaluation proved that as irradiation proceeded, the toxicity alleviated. Taken together, there were various indications that BTA could be effectively eliminated by electron beam irradiation in aquatic environments.