Triplet-Excited Riboflavin Promotes Labile Fe(III) Accumulation and Changes Mineralization Pathways in Fe(II)-Catalyzed Ferrihydrite Transformation.

Flavins are well-known endogenous electron shuttles that facilitate long-distance extracellular electron transfer in dissimilatory iron reduction (DIR), but the effects of their photosensitivity on DIR and the transformation of metastable iron (oxyhydr)oxides like ferrihydrite (Fh) remain underexplored. This study compared the kinetics, pathways, and products of Fh transformation catalyzed by aqueous Fe(II) (Fe(II)) in the presence of oxidized riboflavin (RF) at pH 7 under both dark and light conditions. While RF has a negligible impact on Fe(II)-catalyzed Fh transformation in the dark, its photoexcited triplet state (RF*) can significantly accelerate interfacial electron transfer (IET) from Fe(II) to Fh, increasing the reductive dissolution rate of Fh and boosting the accumulation rate of the key intermediate labile Fe(III) (Fe(III)) from 14.

Numerical modeling and parametric analysis of temperature distribution in soil based on water content variation under radio frequency heating for in-situ thermal remediation.

Radio frequency heating (RFH) is recognized as an efficient and economical method for volatilizing organic pollutants from contaminated soils. Although some numerical simulations have been conducted to predict temperature changes during RFH, models that account for effects of water content (WC) variation on dielectric properties and temperature evolution in soil were rarely reported. To address this, a three-dimensional numerical model integrating electromagnetic-thermal conversion, heat transfer, and mass transfer was developed with coupling dynamic changes in WC and corresponding impacts on soil properties.

Contribution assessment and accumulation prediction of heavy metals in wheat grain in a smelting-affected area using machine learning methods.

Due to the diverse controlling factors and their uneven spatial distribution, especially atmospheric deposition from smelters, assessing and predicting the accumulation of heavy metals (HM) in crops across smelting-affected areas becomes challenging. In this study, integrating HM influx from atmospheric deposition, a boosted regression tree model with an average R > 0.8 was obtained to predict accumulation of Pb, As, and Cd in wheat grain across a smelting region.

Time-varying contributions of Fe and Fe to As immobilization under anoxic/oxic conditions: The impacts of biochar and dissolved organic carbon.

Engineering black carbon (e.g. biochar) has been widely found in natural environments due to natural processes and extensive applications in engineering systems, and could influence the geochemical processes of coexisting arsenic (As) and Fe, especially when they are exposed to oxic conditions.

Evaluation on leachability of heavy metals from tailings: risk factor identification and cumulative influence.

The leachability of heavy metals (HMs) in tailings is significantly affected by multivariate factors associated with environmental conditions. However, the leaching patterns of HMs in molybdenum (Mo) tailings due to environmental change and cumulative influences of multi-leaching factors remain unclear. The leaching behaviors of HMs in Mo tailings were studied through static leaching tests.

Understanding the Importance of Labile Fe(III) during Fe(II)-Catalyzed Transformation of Metastable Iron Oxyhydroxides.

Transformation of metastable Fe(III) oxyhydroxides is a prominent process in natural environments and can be significantly accelerated by the coexisting aqueous Fe(II) (Fe(II)). Recent evidence points to the solution mass transfer of labile Fe(III) (Fe(III)) as the primary intermediate species of general importance. However, a mechanistic aspect that remains unclear is the dependence of phase outcomes on the identity of the metastable Fe(III) oxyhydroxide precursor.

Adsorption kinetics, conformational change, and enzymatic activity of β-glucosidase on hematite (α-FeO) surfaces.

Substantial fractions of extracellular enzymes are intimately associated with soil minerals, which may protect enzymes from denaturation, precipitation, proteolysis, or microbial consumption in soil environments. However, how mineral surface properties affect enzyme-mineral interactions and enzymatic activity of enzymes associated to mineral surface is still unclear. In the present study, adsorption behavior, conformational change, and enzymatic activity of β-glucosidase (BG) on hematite (001) face and (104) face, respectively, were investigated using in situ attenuated total reflectance FTIR spectroscopy and batch experiments.

Citrate Controls Fe(II)-Catalyzed Transformation of Ferrihydrite by Complexation of the Labile Fe(III) Intermediate.

Ferrihydrite (Fh) is generally associated with dissolved organic matter (DOM) in natural environments due to a strong sorption affinity at circumneutral pH and its high specific surface area. In suboxic conditions, aqueous Fe(II) (Fe(II)) can catalyze transformation of Fh into more stable crystalline Fe(III) phases, but how DOM influences the transformation kinetics and pathway is still unclear. Using citrate as a surrogate, we have examined Fh transformation with 1 mM Fe(II) and 0-60 μM citrate at pH 7.

Kinetics and Mechanisms of Protein Adsorption and Conformational Change on Hematite Particles.

Adsorption kinetics and conformational changes of a model protein, bovine serum albumin (BSA, 0.1, 0.5, or 1.

Dissolution Behavior of Isolated and Aggregated Hematite Particles Revealed by in Situ Liquid Cell Transmission Electron Microscopy.

Dissolution behavior of isolated and aggregated hematite particles in 10, 36, and 103 nm, respectively, was investigated using in situ liquid cell transmission microscopy (LCTEM). The high spatial and temporal resolution of LCTEM enables us to differentiate the respective effects of primary particle size, crystal defects, and aggregation state on particle dissolution. At similar electron-beam irradiation parameters, the initial surface-area normalized dissolution rates ( R) of isolated 10, 36, and 103 nm particles are 4.

Aggregation Kinetics of Hematite Particles in the Presence of Outer Membrane Cytochrome OmcA of Shewanella oneidenesis MR-1.

The aggregation behavior of 9, 36, and 112 nm hematite particles was studied in the presence of OmcA, a bacterial extracellular protein, in aqueous dispersions at pH 5.7 through time-resolved dynamic light scattering, electrophoretic mobility, and circular dichroism spectra, respectively. At low salt concentration, the attachment efficiencies of hematite particles in all sizes first increased, then decreased, and finally remained stable with the increase of OmcA concentration, indicating the dominant interparticle interaction changed along with the increase in the protein-to-particle ratio.

In Situ Observation of Hematite Nanoparticle Aggregates Using Liquid Cell Transmission Electron Microscopy.

Aggregation of nanoparticles impacts their reactivity, stability, transport, and fate in aqueous environments, but limited methods are available to characterize structural features and movement of aggregates in liquid. Here, liquid cell transmission electron microscopy (LCTEM) was utilized to directly observe the size, morphology, and motion of aggregates that were composed of 9 and 36 nm hematite nanoparticles, respectively, in water or NaCl solution. When mass concentrations were same, the aggregates of 9 nm nanoparticles were statistically more compact and slightly larger than those of 36 nm nanoparticles.