Mackinawite (FeS) nanoparticles have been extensively tested for reducing contaminants under anoxic conditions, while the oxidizing impact induced by FeS oxic conditions has largely underestimated. In light of previous findings that hydroxyl radicals (·OH) can be produced from oxygenation sediment Fe(II), herein we revealed ·OH efficiently at circumneutral yielding 84.7 μmol per g FeS. Much more was compared with siderite, pyrite, and zerovalent iron same conditions. The oxidation a...

Reactive oxygen species (ROS) production in O2-perturbed subsurface environments has been increasingly documented recent years. However, the constraining conditions under which abiotic and/or biotic mechanisms predominate for ROS remain ambiguous. Here, we demonstrate that mechanism, and abiotic, is determined by sediment redox properties compositions. Upon oxygenation of 10 field sediments, cumulative H2O2 concentrations reached up to 554 μmol/kg within 2 h. The autoclaving sterilization...

Hydroxyl radical (•OH) production by electron transfer from Fe(II)-bearing clay minerals to oxygen has been increasingly reported. However, the influence of ubiquitous coexisting humic acid (HA) on this process is poorly understood. Here, we investigated effect different HA •OH during oxygenation reduced nontronite NAu-2 (rNAu-2), montmorillonite, and sediment. Results showed that could enhance production, enhancement was related content reactive Fe(II) in rNAu-2 electron-accepting capacity...

Dark formation of hydroxyl radicals (•OH) from soil/sediment oxygenation has been increasingly reported, and solid Fe(II) is considered as the main electron donor for O2 activation. However, role organic matter (SOM) in •OH production not clear, although it represents an important pool subsurface. In this study, reduced humic acid (HAred) was investigated at pH 7.0. linearly correlated with electrons released HAred suspension. Solid transferred rapidly to via surface-reduced moieties...

The continuous electron supply for oxidant decomposition-induced reactive oxygen species (ROS) generation is the main contributor long-standing micropollutant oxidation in iron-based advanced processes (AOPs). Herein, as a new class of co-catalysts, metal borides with dual active sites and preeminent conductive performance can effectively overcome inherent drawback Fenton-like reactions by steadily donating electrons to inactive Fe(III). Among borides, tungsten boride (WB) exhibits...

Fe-bearing clay minerals are widely distributed in soils, sediments, and rocks, representing a significant Fe pool the Earth's crust. The electron transfer (ET) from/to structural is crucial energy flux natural environment, which drives numerous biogeochemical processes contaminant transformation. Depending on types properties of both exogenous reactants as well aqueous chemistry, ET could involve interfacial through edge/basal planes interior inside minerals. This paper reviews important...

In subsurface environments, Fe(II)-bearing clay minerals can serve as crucial electron sources for O2 activation, leading to the sequential production of O2•–, H2O2, and •OH. However, observed •OH yields are notably low, underlying mechanism remains unclear. this study, we investigated oxidants from oxygenation reduced Fe-rich nontronite NAu-2 Fe-poor montmorillonite SWy-3. Our results indicated that dependent on mineral Fe(II) species, with edge-surface exhibiting significantly lower...

Iron electrocoagulation (Fe EC) is normally considered as a separation process. Here, we found that Fe(II)–O2 interactions in Fe EC systems could produce reactive oxidants, mainly hydroxyl radicals (•OH), for refractory organic contaminant transformation. Production of probed by benzoate conversion to p-hydroxybenzoic acid (p-HBA), depended on dissolved oxygen (DO) concentration and Fe(II) speciation. Measurable levels DO were required significant p-HBA production. precipitates evolved from...

The potential of oxygenating Fe(II)-bearing sediments for hydroxyl radical (·OH) production and contaminant degradation has been proposed recently. Here, we further show that specific ligands can largely enhance during sediment oxygenation due to increased utilization efficiency electrons. With the addition 0–2 mM sodium ethylene diamine tetraacetate (EDTA) or tripolyphosphate (TPP) in suspension (50 g/L, pH 7.0), trichloroethylene (TCE, 15 μM) from 13% without ligand a maximum 80% with 2...

Hydrogen peroxide (H2O2) and hydroxyl radical (•OH) production during oxygenation of reduced iron (Fe(II)) natural organic matter (NOM) in the subsurface has been increasingly discovered, whereas effect C/Fe molar ratio Fe(II) NOM coexisting systems remains poorly understood. In this study, aqueous humic acid (HAred) mixture at different ratios (0-20) were oxygenated. Results show that both H2O2 •OH accumulation increased almost linearly with increase ratio, a more prominent high ratios. At...

Electron transfer (ET) is the essence of most biogeochemical processes related to element cycling and contaminant attenuation, whereas ET between different minerals controlling mechanism remain elusive. Here, we used surface-associated Fe(II) as a proxy explore reduced nontronite NAu-2 (rNAu-2) Fe (hydr)oxides in their coexisting systems. Results showed that could occur from rNAu-2 ferrihydrite but not goethite, amount was determined by number reactive sites reduction potential difference...

Electron transfer (ET) is the fundamental redox process of life and element cycling. The ET distance normally as short nanometers or micrometers in subsurface. However, gradient subsurface long centimeters even meters. This gap triggers an intriguing question whether directional long-distance from reduced to oxidized zones exists along gradient. By using electron-donating capacity variation a proxy ET, we show that can last over 10 cm sediment columns, through chain constituted by series...

Mobilization of Arsenic in groundwater is primarily induced by reductive dissolution As-rich Fe(III) oxyhydroxides under anoxic conditions. Creating a well-controlled artificial environment that favors oxidative precipitation Fe(II) and subsequent oxidation uptake aqueous As can serve as remediation strategy. We reported proof concept study novel iron-based dual anode system for As(III) removal synthetic groundwater. An iron was used to produce iron-deficient conditions, another inert...

Electrochemical cathodes are often used to reduce contaminants or produce oxidizing substances (i.e., H2O2). Alkaline conditions develop automatically around the cathode in electrochemical processes, and O2 diffuses onto easily. However, limited attention is paid contaminant transformation by reactive species produced on under oxic alkaline due inapplicability of pH for Fenton reaction. In this study, a new oxidation mechanism presented developed conditions. an sand column, 6.67 μM As(III)...