Electrocatalytic hydrogenation (ECH) of aqueous phenol to cyclohexanone and cyclohexanol provides a sustainable strategy for simultaneous pollutant remediation and the synthesis of high-value chemicals. However, in both previous reports and our preliminary experiments, the liquid-phase product distributions often suffer from incomplete carbon balance that could not be explained by volatilization, adsorption, membrane crossover, or analytical error. Motivated by this imbalance, a sealed H-cell equipped with a gas-absorption trap was implemented to capture volatile products. A bimetallic PtRu electrode supported on carbon cloth, prepared by cyclic electrodeposition, was then evaluated under ambient conditions. With gas capture, cyclohexane was identified as a co-product with cyclohexanone and cyclohexanol, accounting for the previously “missing” carbon. The PtRu electrode exhibited a superior phenol conversion of 98.9% and a high faradaic efficiency (FE) of 59.5%, with product selectivity of ~32% cyclohexane, restoring the overall carbon balance to > 95%. In situ FT-IR spectroscopy revealed the dynamic changes of substances during the phenol hydrogenation process, including the attenuation of aromatic C=C and phenolic C–O bands, along with the growth of C=O/O–H features, which is consistent with stepwise hydrogenation. Density functional theory calculations indicated that the synergistic effect between Pt and Ru simultaneously enhanced the capture of phenol molecules and promoted electron transfer between electrode and surface-bound phenol, facilitating hydrogenation and subsequent C–O removal. This work reconciles the long-standing selectivity/carbon-balance gap in phenol ECH and provides a practical protocol for accurate product quantification and resource-oriented management of phenolic wastewater.

Spin-trapping agents-based electron paramagnetic resonance (EPR) is still widely used to detect hydroxyl radicals (•OH) in engineered environmental systems. Conventionally, the “four-line peak” of DMPO/•OH (1:2:2:1) was considered the gold standard for the presence of •OH, and signal intensity was occasionally applied to quantify •OH concentrations. Based on chemical reaction networks and reaction rate constants, we established a network dynamics model to quantitatively determine the concentrations of •OH and SO₄^•−. For example, when persulfate (S₂O₈^2–, 100 mmol/L, final pH = 3.33) was activated by FeS₂ (100 g/L), SO₄^•− concentration was 2.66 × 10⁻¹⁰ mol/L, 6 orders of magnitude higher than that of •OH (2.67 × 10⁻¹⁶ mol/L), while the concentration of DMPO/SO₄^•− (3.14 × 10⁻¹¹ mol/L) was 7 orders of magnitude lower than that of DMPO/•OH (2.34 × 10⁻⁴ mol/L). These results were validated by EPR. Our study revealed that 81.1%−81.5% of DMPO/•OH is derived from DMPO/SO₄^•− hydrolysis and only 18.5%−18.9% is from direct capture of •OH, questioning the reliability of detecting •OH based on the appearance of the “four-line peak”. Our study underscores the necessity of considering all the transformations among radicals and their adducts during EPR analysis, which also provides a direct and effective method for detecting other radicals with extremely short half-lives in other heterogeneous persulfate systems. The high sensitivity of SO₄^•− and •OH to pH also provides an avenue to regulate the generation of reactive species.

Arsenic (As) pollution in mining areas has become a critical global environmental issue. In particular, the excessive accumulation of As(V) in edible plants has raised significant concerns for food safety and human health. However, the mechanisms by which different concentrations of ferrous ion (Fe²⁺) influence phytotoxicity, As(V) uptake, and related metabolic processes remain unclear. In this study, we found that As(V) exposure significantly reduced biomass, root length, photosynthetic pigments and Fe content of Brassica chinensis L., inhibiting overall growth and development of the plant. As(V) triggered oxidative stress by generating excessive reactive oxygen species (ROS), which disrupted cellular homeostasis. Exogenous Fe²⁺ treatment, especially at 50 μmol/L, markedly enhanced the activities of key antioxidant enzymes, including SOD and POD, effectively mitigating oxidative damage. In addition, Fe²⁺ restricted As(V) uptake by promoting the formation of an adsorbed iron oxide film on the root surface and was associated with reduced expression of PHT1;4 in root tissues. Metabolomic analysis further demonstrated that Fe²⁺ treatment was associated with enhanced flavonoid biosynthesis pathways and increased accumulation of flavonoids under As(V) stress, which may contribute to improving plant tolerance. These findings underscore the protective role of Fe²⁺ against As(V) toxicity in Brassica chinensis L. and provide a potential strategy for mitigating risks to human food safety caused by As(V) contamination.

Organic aerosols (OA) are complex mixtures comprising thousands of compounds, posing challenges for molecular characterization. Liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) is a powerful tool for the analysis of OA. The selection of extraction solvents critically influences the molecular characterization of OA in LC-HRMS, yet selection biases are poorly understood. In this study, we systematically evaluated the extraction efficiencies of three commonly used solvents—methanol (MeOH), acetonitrile (ACN), and an ACN/H₂O mixture (8:2, v/v)—for diverse OA samples using HPLC-Orbitrap MS/MS. The sample set encompassed seasonal ambient PM_2.5 collected in a Chinese megacity, and aerosols emitted from cooking, coal combustion, and biomass burning. Generally, MeOH was the optimal solvent for non-targeted screening of ambient aerosols, yielding the broadest compound coverage and the highest signal intensities. However, ACN exhibited superior extraction efficiency for cooking and coal combustion aerosols, showing distinct selectivity towards compounds with higher carbon number (nC), higher DBE and lower OSc, particularly for aromatic and nitrophenolic compounds. ACN/H₂O extracted compounds with lower nC, DBE and higher OSc. It showed higher signal intensity for species containing hydrophilic functional groups, such as amines, pyridines, carbonyl compounds, polycarboxylic acids, and carbohydrates. This selectivity indicates that solvent selection may introduce relative quantification biases for specific compounds. The evaluation of procedural contamination revealed that ACN is most severely affected by procedural contaminants, particularly for long-chain fatty acid amides, aromatic and aliphatic amines from polypropylene plasticware. This study provided critical insights for optimizing solvent selection in non-targeted LC-HRMS analysis.

Starch wastewater (SW) has high organic loading (OL), rapid biodegradability, and strong oxygen demand, which often cause unstable treatment performance and excessive energy consumption in conventional aerobic processes. Magnetic field (MF) application was investigated as an auxiliary strategy to promote the magneto-bio-production of extracellular polymeric substances (EPS) during SW treatment, wherein a static MF served as a non-chemical stimulus for biological EPS generation in an aerobic sequencing batch reactor (SBR). The MF maintained chemical oxygen demand (COD) and soluble COD (SCOD) removal in the aerobic SBR at above 96.8% under low-to-medium OL conditions under six operational scenarios with varying OL and dissolved oxygen (DO) levels. Such stabilization could be attributed to MF-reinforced sludge structure with increased diameter of 247.7 µm and fractal dimension up to 0.41, which substantially reduced system sludge volume index and achieved high-quality effluent. Moreover, interfloc viscosity and aggregation were improved, with bound-EPS secretion of up to 80.22 mg/g mixed liquor suspended solids (MLSS). EPS flocculation rates reached 88.3%, thereby demonstrating potential for high-value applications. Mechanistically, MF enriches EPS-producing and magnetotactic bacteria (MTB), like Flavobacterium and Cloacibacterium. It also reorients intracellular metabolism by reinforcing the tricarboxylic acid (TCA) cycle and suppressing gluconeogenesis to accelerate glycolysis. The metabolic alteration expands α-ketoglutarate and succinate pools, thereby increasing the availability of amino acid and sugar precursors. Consequently, Kyoto Encyclopedia of Genes and Genomes (KEGG)-based functional redistribution may support the coordinated synthesis of proteinaceous EPS enriched in glutamate, histidine, valine, and polysaccharide EPS dominated by rhamnose, xylose, and fucoidan, whereas MTB-mediated spatial organization may further promote EPS retention and matrix stabilization. Comparative evaluation suggested that low-to-medium OL with medium DO was optimal for maximizing EPS production and sludge structural stability. Importantly, MF can enhance the stability and robustness of SW treatment through EPS-mediated sludge aggregation, community structure changes, and metabolic shifts, thereby enabling value-added EPS production.