Generation Of Hydroxyl Radicals Research Articles

Promotive Effects of Chloride and Sulfate on the Near-Complete Destruction of Perfluorocarboxylates (PFCAs) in Brine via Hydrogen-tuned 185-nm UV Photolysis: Mechanisms and Kinetics.

Hydrogen-tuned 185 nm vacuum ultraviolet (VUV/H2) photolysis is an emerging technology to destroy per- and polyfluoroalkyl substance (PFAS) in brine. This study discovered the promotive effects of two major brine anions, i.e., chloride and sulfate in VUV/H2 photolysis on the hydrated electron (eaq-) generation and perfluorocarboxylates (PFCAs) destruction and established a kinetics model to elucidate the promotive effects on the steady-state concentration of eaq- ([eaq-]ss). Results showed that VUV/H2 achieved near-complete defluorination of perfluorooctanoic acid (PFOA) in the presence of up to 1000 mM chloride or sulfate at pH 12. The defluorination rate constant (kdeF) of PFOA peaked with a chloride concentration at 100 mM and with a sulfate concentration at 500 mM. The promotive effects of chloride and sulfate were attributed to an enhanced generation of eaq- via their direct VUV photolysis and conversion of additionally generated hydroxyl radical to eaq- by H2, which was supported by a linear correlation between the predicted [eaq-]ss and experimentally observed kdeF. The kdeF value increased from pH 9 to 12, which was attributed to the speciation of the H·/eaq- pair. Furthermore, the VUV system achieved >95% defluorination and ≥99% parent compound degradation of a concentrated PFCAs mixture in a synthetic brine, without generating any toxic perchlorate or chlorate.

H2O2 self-supplying Ce6@ZIF-8/PDA/CuO2/HA (CZPCH) nanoplatform for enhanced reactive oxygen species (ROS)-mediated tumor therapy

Tumor hypoxia, limited H2O2 levels, and abundant glutathione (GSH) in the tumor microenvironment (TME) pose challenges for high-efficiency reactive oxygen species (ROS)-mediated therapies. To address these limitations, an intelligent ROS-mediated nanoplatform, Ce6@ZIF-8/PDA/CuO2/HA (CZPCH), with photodynamic activity, self-supplied H2O2, Fenton-like reaction, GSH-depletion and photothermal activity was designed for efficient tumor treatment. In the acidic TME, CuO2 in CZPCH deposits into Cu2+ and H2O2, consuming GSH and triggering Fenton-like reactions to generate hydroxyl radical (•OH), enabling efficient chemodynamic therapy (CDT). Moreover, the presence of Ce6 and PDA enables CZPCH to exhibit excellent singlet oxygen (1O2) and temperature increase performance 660 nm and 808 nm laser irradiation, respectively, resulting in efficient photodynamic therapy (PDT) and photothermal therapy (PTT) efficacy. Interestingly, the temperature increase from PTT significantly enhances •OH and 1O2 generation, achieving high-efficiency ROS-based therapeutic efficacy. This synergistic CDT/PDT/PTT treatment demonstrates excellent anti-tumor efficacy and illuminates novel ROS-based therapeutic strategy design.

Insights into the Crystallinity-Dependent Photochemical Productions of Reactive Oxygen Species from Iron Minerals.

Iron minerals are widespread in earth's surface water and soil. Recent studies have revealed that under sunlight irradiation, iron minerals are photoactive on producing reactive oxygen species (ROS), a group of key species in regulating elemental cycling, microbe inactivation, and pollutant degradation. In nature, iron minerals exhibit varying crystallinity under different hydrogeological conditions. While crystallinity is a known key parameter determining the overall activity of iron minerals, the impact of iron mineral crystallinity on photochemical ROS production remains unknown. Here, we assessed the photochemical ROS production from ferrihydrites with different degrees of crystallinity. All examined ferrihydrites demonstrated photoactivity under irradiation, resulting in the generation of hydrogen peroxide (H2O2) and hydroxyl radical (•OH). The photochemical ROS production from ferrihydrites increased with decreasing ferrihydrite crystallinity. The crystallinity-dependent photochemical •OH production was primarily attributed to conduction band reduction reactions, with the reduction of O2 by conduction band electrons being the rate-limiting key process. Conversely, the crystallinity of iron minerals had a negligible influence on photon-to-electron conversion efficiency or surface Fenton-like activity. The difference in ROS productions led to a discrepant degradation efficiency of organic pollutants on iron mineral surfaces. Our study provides valuable insights into the crystallinity-dependent ROS productions from iron minerals in natural systems, emphasizing the significance of iron mineral photochemistry in natural sites with abundant lower-crystallinity iron minerals such as wetland water and surface soils.

A Stimulus-Responsive Ternary Heterojunction Boosting Oxidative Stress, Cuproptosis for Melanoma Therapy.

Cuproptosis, a recently discovered copper-dependent cell death, presents significant potential for the development of copper-based nanoparticles to induce cuproptosis in cancer therapy. Herein, a unique ternary heterojunction, denoted as HACT, composed of core-shell Au@Cu2O nanocubes with surface-deposited Titanium Dioxide quantum dots and modified with hyaluronic acid is introduced. Compared to core-shell AC NCs, the TiO2/Au@Cu2O exhibits improved energy structure optimization, successfully separating electron-hole pairs for redox use. This optimization results in a more rapid generation of singlet oxygen and hydroxyl radicals triggering oxidative stress under ultrasound radiation. Furthermore, the HACT NCs initiate cuproptosis by Fenton-like reaction and acidic environment, leading to the sequential release of cupric and cuprous ions. This accumulation of copper induces the aggregation of lipoylated proteins and reduces iron-sulfur proteins, ultimately initiating cuproptosis. More importantly, HACT NCs show a tendency to selectively target cancer cells, thereby granting them a degree of biosecurity. This report introduces a ternary heterojunction capable of triggering both cuproptosis and oxidative stress-related combination therapy in a stimulus-responsive manner. It can energize efforts to develop effective melanoma treatment strategies using Cu-based nanoparticles through rational design.

Near‐Infrared Light‐Triggered MXene Nanocomposite for Tumor‐Specific Mild Photothermal‐Enhanced Chemodynamic Therapy

AbstractMild photothermal therapy (PTT) is an emerging and elegant approach with minimal adverse effects, demonstrating itself as an effective treatment for cancer. However, potential challenges may arise from the overexpression of heat shock protein 90 (HSP90) and the reliance on monotherapy. Here, a near‐infrared (NIR) light‐triggered MXene nanocomposite (FA@MXene/CuO2/GA) is developed to synergistically combine mild PTT and chemodynamic therapy (CDT) for remarkably effective tumor eradication without any notable tissue damage. Under the irradiation of NIR light, the nanocomposite effectively enhances the mild PTT by suppressing HSP90 expression through the release of gambogic acid (GA) due to the excellent photothermal performance of Ti3C2 MXene nanosheets as well as the tumor‐targeting ability and biocompatibility of the surface‐modified FA‐PEG‐SH. The copper‐based catalyst CuO2 in this system releases Cu2+ in an acid‐triggered manner within the tumor microenvironment, activating the Fenton‐like reaction to generate hydroxyl radicals, and the simultaneous production of H2O2 serves to alleviate the deficiency of endogenous H2O2 within the tumor. Overall, the current work showcases a remarkable synergistic anticancer effect of PTT and CDT, and also proposes new avenues for research in utilizing MXene nanomaterials for tumor treatment.

Dissolved Organic Matter-Mediated Photosensitized Activation of Monochloramine for Micropollutant Abatement in Wastewater Effluent.

Utilizing solar light and water matrix components in situ to reduce the chemical and energy demands would make treatment technologies more sustainable for micropollutant abatement in wastewater effluents. We herein propose a new strategy for micropollutant abatement through dissolved organic matter (DOM)-mediated photosensitized activation of monochloramine (NH2Cl). Exposing the chlorinated wastewater effluent with residual NH2Cl to solar irradiation (solar/DOM/NH2Cl process) degrades six structurally diverse micropollutants at rate constants 1.26-34.2 times of those by the solar photolysis of the dechlorinated effluent (solar/DOM process). Notably, among the six micropollutants, the degradation rate constants of estradiol, acetaminophen, bisphenol A, and atenolol by the solar/DOM/NH2Cl process are 1.13-4.32 times the summation of those by the solar/DOM and solar/NH2Cl processes. The synergism in micropollutant degradation is attributed to the generation of reactive nitrogen species (RNS) and hydroxyl radicals (HO·) from the photosensitized activation of NH2Cl. Triplet state-excited DOM (3DOM*) dominates the activation of NH2Cl, leading to the generation of RNS, while HO· is produced from the interactions between RNS and other photochemically produced reactive intermediates (e.g., O2·- and DOM·+/·-). The findings advance the knowledge of DOM-mediated photosensitization and offer a sustainable method for micropollutant abatement in wastewater effluents containing residual NH2Cl.

Oxidative photocatalysis on membranes triggers non-canonical pyroptosis

Intracellular membranes composing organelles of eukaryotes include membrane proteins playing crucial roles in physiological functions. However, a comprehensive understanding of the cellular responses triggered by intracellular membrane-focused oxidative stress remains elusive. Herein, we report an amphiphilic photocatalyst localised in intracellular membranes to damage membrane proteins oxidatively, resulting in non-canonical pyroptosis. Our developed photocatalysis generates hydroxyl radicals and hydrogen peroxides via water oxidation, which is accelerated under hypoxia. Single-molecule magnetic tweezers reveal that photocatalysis-induced oxidation markedly destabilised membrane protein folding. In cell environment, label-free quantification reveals that oxidative damage occurs primarily in membrane proteins related to protein quality control, thereby aggravating mitochondrial and endoplasmic reticulum stress and inducing lytic cell death. Notably, the photocatalysis activates non-canonical inflammasome caspases, resulting in gasdermin D cleavage to its pore-forming fragment and subsequent pyroptosis. These findings suggest that the oxidation of intracellular membrane proteins triggers non-canonical pyroptosis.

Electrochemically produced nano-TiO2-coated SiC membranes for photocatalytic water treatment: Preparation, characterization, and hydroxyl radical formation

ABSTRACT Photocatalytically active ceramic flat sheet membranes based on a nanostructured titanium dioxide (TiO2) coating were produced for photocatalytic water treatment. The nano-TiO2 layer was produced by a novel combination of magnetron sputtering of a thin titanium layer on silicon carbide (SiC) membranes, followed by electrochemical oxidation (anodization) and subsequent heat treatment. Characterization by Raman spectra and field emission scanning electron microscopy proved the presence of a nanostructured anatase layer on the membranes. The influence of the titanium layer thickness on the TiO2 formation process and the photocatalytic properties were investigated using anodization curves, by using cyclovoltammetry measurements, and by quantifying the generated hydroxyl radicals (OH•) under UV-A irradiation in water. Promising photocatalytic activity and permeability of the nano-TiO2-coated membranes could be demonstrated. A titanium layer of at least 2 μm was necessary for significant photocatalytic effects. The membrane sample with a 10 μm Ti/TiO2 layer had the highest photocatalytic activity showing a formation rate of 1.26 × 10−6 mmol OH• s−1. Furthermore, the membranes were tested several times, and a decrease in radical formation was observed. Assuming that these can be attributed to adsorption processes of the reactants on the TiO2 surface, initial experiments were carried out to reactivate the photocatalyzer.

Accelerated peroxidase-like activity of ultrathin amine-tagged bimetallic MOF-74 nanozyme for construction of versatile bioassays from small molecules to enzymes and bacteria

The exquisite design of nanostructures for enzyme-biocatalyzed active sites mimicking has become a prospective method to significantly boost biocatalytic properties, which is profitable to response amplification for bioanalysis scenarios. Metal-organic frameworks (MOFs) with customizable compositions, diverse microstructures and open catalytic sites are considered to deal with challenges in conventional materials of unfriendly microenvironment and inexact coordination. Herein, by combining a metal doping and post-synthetic modification approach, amine-tagged Fe-Ni bimetallic MOF-74 nanozyme (FeNi-MOF-74-NH2) with ultrathin structure and improved peroxidase-mimicking bioactivity is synthesized through a layered double hydroxide (LDH) directed method. The boosted biocatalytic property largely benefits from the synergistic effects of Fe-Ni species, attributing to the dual mechanism (electron transfer and generation of hydroxyl radicals). On the basis of the enhanced enzyme-mimicking property and accessible amino functionalization of FeNi-MOF-74-NH2, versatile applications were carried out for the ultrasensitive detection of analytes from bioactive small molecules (H2O2 and ascorbic acid), biomacromolecules (alkaline phosphatase, ascorbic acid oxidase, and α-glucosidase), and pathogenic bacteria (Staphylococcus aureus). The nanozyme-based biosensing platform without complex enzymatic techniques serves as a proof-of-concept to facilitate the application of MOF nanozymes in biochemical analysis, clinical diagnosis, and biomedical research.

Innovative carbon materials from lignocellulosic wastes for electrochemical hydrogen peroxide production: Bridging biomass conversion and material properties

This study aims to assess the electrochemical generation of hydrogen peroxide and hydroxyl radicals (*OH) using carbon cathodes synthesized from three different lignocellulosic residues, Phragmites australis (PA), Cladium mariscus (CM) and Typha domingensis (TD). These vegetal species are commonly used in natural wetlands and phytoremediation processes and can accumulate recalcitrant pollutants within these treatment processes, generating a waste that should be properly managed. To convert these residues into valuable carbon materials, they underwent hydrothermal carbonization (HTC) followed by either chemical activation with KOH or pyrolysis at 1000 ºC. The best results were obtained with chemically activated materials, yielding a maximum H2O2 concentration of 313 mg L−1 with the carbon cathode produced from PA. The specific surface area, oxygenated functional groups and presence of structural defects in carbonous structures, were key parameters related to a good performance as catalysts towards the 2e- Oxygen Reduction Reaction (ORR). It was also demonstrated, in comparison with previous studies, that the presence of heavy metals in the structure of the lignocellulosic residue enhanced the decomposition of H2O2 into *OH. However, in the study of the degradation of a model organic contaminant as methylene blue (MB), it was shown that these *OH were not the main contributors to degradation, as direct H2O2 chemical degradation and adsorption on the carbon materials played the most significant role. Therefore, the outstanding capacity of these lignocellulosic residues as catalysts for the electrogeneration of H2O2 was confirmed, suggesting their potential future application in advanced oxidation processes for water decontamination.

Cell-Membrane-Coated Metal-Organic Framework Nanocarrier Combining Chemodynamic Therapy for the Inhibition of Hepatocellular Carcinoma Proliferation.

Chemodynamic therapy (CDT) employs hydrogen peroxide (H2O2) within the tumor microenvironment (TME) to initiate the Fenton reaction and catalyze the generation of hydroxyl radicals (·OH) for targeted therapy. Metal ion-based nanomaterials have garnered significant attention as catalysts due to their potent anti-tumor effects. Hypoxia in the TME is often associated with cancer cell development and metastasis, with HIF-1α being a pivotal factor in hypoxia adaptation. In this study, an organic framework called MIL-101 (Fe) was designed and synthesized to facilitate H2O2-induced ·OH production while also serving as a carrier for the HIF-1α inhibitor Acriflavine (ACF). A biomimetic nanomedical drug delivery system named MIL-101/ACF@CCM was constructed by encapsulating liver cancer cell membranes onto the framework. This delivery system utilized the homologous targeting of tumor cell membranes to transport ACF, inhibiting HIF-1α expression, alleviating tumor hypoxia, and catalyzing ·OH production for effective tumor eradication. Both in vivo and in vitro experiments confirmed that combining ACF with chemotherapy achieved remarkable tumor inhibition by enhancing ROS production and suppressing HIF-1α expression.

Oxygen-Evolving Radiotherapy-Radiodynamic Therapy Synergized with NO Gas Therapy by Cerium-Based Rare-Earth Metal-Porphyrin Framework.

The efficacy of traditional radiotherapy (RT) has been severely limited by its significant side effects, as well as tumor hypoxia. Here, the nanoscale cerium (Ce)-based metaloxo clusters (Ce(IV)6)-porphyrin (meso-tetra (4-carboxyphenyl) porphyrin, TCPP) framework loaded with L-arginine (LA) (denoted as LA@Ce(IV)6-TCPP) is developed to serve as a multifarious radio enhancer to heighten X-ray absorption and energy transfer accompanied by O2/NO generation for hypoxia-improved RT-radiodynamic therapy (RDT) and gas therapy. Within tumor cells, LA@Ce(IV)6-TCPP will first react with endogenous H2O2 and inducible NO synthase (iNOS) to produce O2 and NO to respectively increase the oxygen supply and reduce oxygen consumption, thus alleviating tumor hypoxia. Then upon X-ray irradiation, LA@Ce(IV)6-TCPP can significantly enhance hydroxyl radical (•OH) generation from Ce(IV)6 metaloxo clusters for RT and synchronously facilitate singlet oxygen (1O2) generation from adjacently-coordinated TCPP for RDT. Moreover, both the •OH and 1O2 can further react with NO to generate more toxic peroxynitrite anions (ONOO-) to inhibit tumor growth for gas therapy. Benefitting from the alleviation of tumor hypoxia and intensified RT-RDT synergized with gas therapy, LA@Ce(IV)6-TCPP elicited superior anticancer outcomes. This work provides an effective RT strategy by using low doses of X-rays to intensify tumor suppression yet reduce systemic toxicity.

Universality of hydroxyl radical generation in irradiated nanoenhancer suspensions: Vital role of concentration

Concentration plays an essential role in generating hydroxyl radicals in irradiated nanoenhancer suspensions. In this paper, we used coumarin-3-carboxylic acid as a hydroxyl radical-specific probe to investigate the hydroxyl radical production of different concentration nanodiamonds (NDs) and CeO2 NPs in phosphate-buffered saline under x-ray irradiation. NDs significantly enhanced hydroxyl radical production, and the maximum enhancement of hydroxyl radical production was observed at a concentration of 10 µg/ml, with an enhanced factor of 1.398 ± 0.262. CeO2 NPs can increase and scavenge hydroxyl radicals at different concentration ranges, with the lowest and highest enhanced factors of 0.623 ± 0.069 and 1.738 ± 0.264, respectively. We tested the hydrodynamic diameter at various concentrations to explore the concentration effect further. We found that with increasing concentration, there might be factors, such as hydroxyl radical recombination and nanoparticle agglomeration, that lead to changes in the enhancement factor. Based on the data from previous and present studies, the experimental results indicate that the concentration factor is essential for hydroxyl radical generation in nanoenhancer suspensions under ionizing radiation. We also provide possible mechanisms for enhancing hydroxyl radical production by nanoenhancers in water under ionizing radiation and the decrease in enhancement factor at high concentrations of nanoenhancers.

Multi-mechanism antitumor/antibacterial effects of Cu-EGCG self-assembling nanocomposite in tumor nanotherapy and drug-resistant bacterial wound infections

Chemotherapy and surgery stand as primary cancer treatments, yet the unique traits of the tumor microenvironment hinder their effectiveness. The natural compound epigallocatechin gallate (EGCG) possesses potent anti-tumor and antibacterial traits. However, the tumor’s adaptability to chemotherapy due to its acidic pH and elevated glutathione (GSH) levels, coupled with the challenges posed by drug-resistant bacterial infections post-surgery, impede treatment outcomes. To address these challenges, researchers strive to explore innovative treatment strategies, such as multimodal combination therapy. This study successfully synthesized Cu-EGCG, a metal-polyphenol network, and detailly characterized it by using synchrotron radiation and high-resolution mass spectrometry (HRMS). Through chemodynamic therapy (CDT), photothermal therapy (PTT), and photodynamic therapy (PDT), Cu-EGCG showed robust antitumor and antibacterial effects. Cu+ in Cu-EGCG actively participates in a Fenton-like reaction, generating hydroxyl radicals (·OH) upon exposure to hydrogen peroxide (H2O2) and converting to Cu2+. This Cu2+ interacts with GSH, weakening the oxidative stress response of bacteria and tumor cells. Density functional theory (DFT) calculations verified Cu-EGCG’s efficient GSH consumption during its reaction with GSH. Additionally, Cu-EGCG exhibited outstanding photothermal conversion when exposed to 808 nm near-infrared (NIR) radiation and produced singlet oxygen (1O2) upon laser irradiation. In both mouse tumor and wound models, Cu-EGCG showcased remarkable antitumor and antibacterial properties.

Ti-MOG derived TiO2 facet heterojunction rich in C/Ti3+/Ov for adsorption-photocatalytic removal of pharmaceutical pollutants from water

Developing efficient, stable, and broad-spectrum responsive photocatalysts is an effective way to degrade pharmaceutical pollutants in water. In this work, using concentrated hydrochloric acid (HCl) as a modulator, titanium metal–organic gel (Ti-MOG) was prepared and used as a template for calcination in air to obtain anatase TiO2 facet heterojunction rich in C/Ti3+/oxygen vacancy (Ov) (MOG-TiO2), which has a hierarchical porous structure, large specific surface area, and highly dispersed active site. Compared to P25, P25 + C and MIL-125(Ti) derived TiO2 (MOF-TiO2), MOG-TiO2 exhibited obviously enhanced adsorption-photocatalytic performance for tetracycline (TC) and low concentrations ethenzamide (ETH) under broad-spectrum light irradiation. The photocatalytic degradation efficiency of ETH by MOG-TiO2 reached 92.8, 100 and 98.7 % within 240, 60 and 6 min under Vis, UV and VUV light illumination, respectively, which were much higher than those of P25 (62.7, 33.2 and 73.0 %), P25 + C (61.7, 31.2 and 72.5 %) and MOF-TiO2 (79.2, 86.8 and 88.7 %). Furthermore, concentrated HCl promoted the formation of Ti3+/Ov in MOG-TiO2, which was conducive to the improvement of its photocatalytic performance. MOG-TiO2 also displayed great adsorption-photocatalytic stability and reusability. Moreover, the biotoxicity of TC toward E. coli DH5a obviously decreased after photocatalytic degradation. Based on the TiO2 facet heterojunction rich in C/Ti3+/Ov and the generation of hole, hydroxyl radicals, and superoxide radicals, the possible photocatalytic degradation mechanism of MOG-TiO2 was proposed. Overall, this work provides insights into constructing a novel hierarchical porous carbon-doped facet heterojunction photocatalyst for efficient pharmaceutical contaminants removal.

Sustainable electro-Fenton simultaneous reduction of Cr (VI) and degradation of organic pollutants via dual-site porous carbon cathode driving uncoordinated molybdenum sites conversion

Simultaneous removal of heavy metals and organic contaminants remains a substantial challenge in the electro-Fenton (EF) system. Herein, we propose a facile and sustainable “iron-free” EF system capable of simultaneously removing hexavalent chromium (Cr (VI)) and para-chlorophenol (4-CP). The system comprises a nitrogen-doped and carbon-deficient porous carbon (dual-site NPC-D) cathode coupled with a MoS2 nanoarray promoter (MoS2 NA). The NPC-D/MoS2 NA system exhibits exceptional synergistic electrocatalytic activity, with removal rates for Cr (VI) and 4-CP that are 20.3 and 4.4 times faster, respectively, compared to the NPC-D system. Mechanistic studies show that the dual-site structure of NPC-D cathode favors the two-electron oxygen reduction pathway with a selectivity of 81 %. Furthermore, an electric field-driven uncoordinated Mo valence state conversion of MoS2 NA enchances the generation of dynamic singlet oxygen and hydroxyl radicals. Notably, this system shows outstanding recyclability, resilience in real wastewater, and sustainability during a 3 L scale-up operation, while effectively mitigating toxicity. Overall, this study presents an effective approach for treating multiple-component wastewater and highlights the importance of structure-activity correlation in synergistic electrocatalysis.

Enhanced electro-catalytic activity of TNTs/SnO2-Sb electrode through the effect mechanism of TNTs architecture

The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.

Design of a washing ejector and column flotation based on the microbubble for heavy metal contaminants removal from contaminated soils: A pilot and laboratory-scale studies

This study mainly examines the effects of combined washing ejector and column flotation process by remediation equipment for heavy metal remediation at a contaminated site. A washing ejector system is a sustainable technology that considers the concept of hydrodynamic cavitation. Soil aggregates strongly binding to poorly crystalline minerals and Fe oxide bonding with the soil create challenges for their elimination from soils contaminated with complex contaminants. The effects of the operating conditions of the cavitation flow on increasing the separation of fine particles were evaluated by determining the mass balance during the washing system process on a pilot scale. Cavitation flow in the washing ejector system can increase the dispersion of soil aggregates owing to the generation of hydroxyl radicals (•OH) and the increase in mixing intensity. Cavitation flow during the process can increased the dispersion of soil aggregates owing to the release of Fe oxides into the soil. The coarse and fine particles were readily separated from the bulk soil, and the fine particle distribution per mass increased after washing. The levels of Fe in the coarse fraction soil met the KS requirements after separation, whereas the Fe levels in the fine fraction soil were above than the KS limits. To reduce waste volume, column flotation was used to selectively separate Fe oxides from contaminated soil. Microbubbles in column flotation have the important function of facilitating the collision and attachment between air bubbles and Fe oxides and subsequently recovering the Fe oxides. When AF65 as a frother and oleic acid as an anionic collector were used in the column flotation, the concentration of Fe oxides increased from 9.67% to 13.76%, a recovery of approximately 10% from the fine soil. According to the mass balance of the study area, after treatment using the washing ejector system, coarse (60%) and fine (40 %) soils in the total soil were separated. Column flotation can be applied to fine soil to achieve a volume reduction of approximately 30% of the total soil volume. The results of this study illustrate the feasibility of the proposed remediation process to reduce waste volume and improve sustainability while meeting Korean standards for heavy metal pollution in soil, thereby minimizing environmental risk.

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream and the treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals could be the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration of CAP, because part of hydroxyl radicals could be consumed by a low concentration of CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could also react with some reductive species, such as eaq- and •H, which could compete with Cr(VI) and inhibit the reduction of Cr(VI). In addition, the presence of Cr(VI) could enhance the degradation and mineralization of CAP, and the identification of obtained intermediates indicated that the presence of Cr(VI) could change the degradation path of CAP as Cr(VI) would react with reductive species and enhance the generation of hydroxyl radicals, leading to more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology could be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environment.

Effects of chemical composition of ambient PM2.5 measured in Seoul on potential health risks and generation of reactive oxygen species

This study assesses the health effects associated with the chemical species of ambient particulate matter (PM) with an aerodynamic diameter ≤ 2.5 μm (PM2.5) in Seoul, focusing on identifying key chemical constituents and their sources. We employed two approaches to estimate health risks: (1) evaluating carcinogenic and noncarcinogenic risks using IRIS (Integrated Risk Information System) data from the US EPA (Environmental Protection Agency), and (2) quantifying the generation of hydroxyl radicals (·OH) following exposure to PM2.5 in surrogate lung fluid (SLF). Our results show a significant impact on human health from certain elements (Cr, Ni, As, and Cd) and polycyclic aromatic hydrocarbons (PAHs) (DaeP, DahA, and BaP for carcinogenic risks; BaP and BeP for noncarcinogenic risks). Notably, Cr and BaP, which are influential in both risk assessment and ·OH generation, highlight their significant roles in human health impacts. However, other components (e.g., CPP, BaP, BghiP, BaA, CHR, PYR, FLT, Ca, Mg, and Cu), though contributors to ·OH generation, were not included in the EPA’s health risk assessment, suggesting a need for a broader PM2.5 compositional analysis to more accurately determine exposure concentrations and assess inhalation risks. These components predominantly originate from anthropogenic sources, such as combustion, vehicles, and industrial activities, underscoring the significant health implications of the pollutants emitted from these sources. The study concluded that focusing solely on the mass reduction of PM2.5 may not suffice; a dual approach that reduces both mass concentration and chemical-specific health risks is imperative for effective public health protection.