Unveiling the dual role of calcium peroxide in enhancing green rust-catalyzed arsenite oxidation and stabilization.

Iron oxyhydroxide redox processes coupled with reactive oxygen species (ROS) generation play a critical role in the transformation of arsenic (As). However, low ROS generation limits the detoxification and stabilization of As(III). In this study, we propose a novel strategy by integrating Fe(II) rich green rust (GR) with calcium peroxide (CaO) for the efficient transformation of As(III) under oxic conditions.

Cadmium Immobilization on Fe Oxyhydroxides Enhanced by DOM Using Single-Molecule Determinations.

The groups from dissolved organic matter (DOM) enhance cadmium (Cd) immobilization on Fe oxyhydroxide, while it is difficult to evaluate the contributions of different groups on the binding configurations and strength between Cd and Fe oxyhydroxides because of DOM's complex composition and lack of in situ methods. Here, we selected organic small molecules with representative functional groups to investigate the molecular mechanisms of Cd immobilization on goethite using batch experiments, solid characterization, theoretical calculations, and single-molecule force spectroscopy (SMFS) combined with K-means analysis. These organic molecules increase Cd adsorption on goethite, with carboxyl groups showing the most substantial enhancement (increased by 81.

Biogeochemical mechanisms of zero-valent iron and biochar for synergistically mitigating antimony uptake in rice.

Antimony (Sb) contamination in paddy fields can lead to its accumulation in rice grains, posing a threat to food safety. To address this issue, the combined use of zero-valent iron (ZVI) and biochar (BC) were applied to decrease the uptake of Sb in Sb-polluted soils, and their effects on Sb uptake from soil to rice grains were investigated. Our results showed that the combination treatment of 0.

Dual-Ligand-Driven Dark Reactive Oxygen Species Generation on Iron Oxyhydroxides: Implications for Environmental Remediation.

The dark generation of reactive oxygen species (ROS), particularly hydroxyl radicals (·OH), is crucial in the oxidative transformation of various pollutants. However, the mechanisms behind this process are predominantly linked to direct O activation by reduced substances such as Fe(II) and natural organic matter. In this study, we introduce a previously overlooked dual-ligand mechanism that significantly amplifies ·OH generation on iron oxyhydroxides, facilitated by cysteine and pyrophosphate.

Aluminum substitution stabilizes organic matter in ferrihydrite transforming into hematite: A molecular analysis.

The association of soil organic matter (SOM) with iron (Fe) oxyhydroxides, particularly ferrihydrite, plays a pivotal role in the biogeochemical cycling of carbon (C) in both terrestrial and aquatic environment. The aging of ferrihydrite to more crystalline phases can impact the stability of associated organic C, a process potentially influenced by aluminum (Al) substitution due to its abundance. However, the molecular mechanisms governing the temporal and spatial distribution of SOM during the aging process of Al-substituted Fe oxyhydroxides remain unclear.

The synergistic effect of multiple organic macromolecules on the formation of calcium oxalate raphides of Musa spp.

Needle-like calcium oxalate crystals called raphides are unique structures in the plant kingdom. Multiple biomacromolecules work together in the regulatory and transportation pathways to form raphides; however, the mechanism by which this occurs remains unknown. Using banana (Musa spp.

Direct observations of nanoscale brushite dissolution by the concentration-dependent adsorption of phosphate or phytate.

With the development of agricultural intensification, phosphorus (P) accumulation in croplands and sediments has resulted in the increasingly widespread interaction between inorganic and organic P species, which has been, previously, underestimated or even ignored. We quantified the nanoscale dissolution kinetics of sparingly soluble brushite (CaHPO·2HO, DCPD) over a broad range of phosphate and/or phytate concentrations by using in situ atomic force microscopy (AFM). Compared to water, we found that low concentrations of phosphate (1-1000 µM) or phytate (1-100 µM) inhibited brushite dissolution by slowing single step retraction.

Cooperative roles of phosphate and dissolved organic matter in inhibiting ferrihydrite transformation and their distinct fates.

Phosphate and dissolved organic matter (DOM) mediate the crystalline transformation of ferrihydrite catalyzed by Fe(II) in subsurface environments such as soils and groundwater. However, the cooperative mechanisms underlying the mediation of phosphate and DOM in crystalline transformation of ferrihydrite and the feedback effects on their own distribution and speciation remain unresolved. In this study, solid characterization indicates that phosphate and DOM can collectively inhibit the crystalline transformation of ferrihydrite to lepidocrocite and thus goethite, via synergetic effects of inhibiting recrystallization and electron transfer.

Facet-dependent electron transfer induces distinct arsenic reallocations on hematite.

The interfacial electron transfer (ET) between electron shuttling compounds and iron (Fe) oxyhydroxides plays a crucial role in the reductive dissolution of Fe minerals and the fate of surface-bound arsenic (As). However, the impact of exposed facets of highly crystalline hematite on reductive dissolution and As immobilization is poorly understood. In this study, we systematically investigated the interfacial processes of the electron shuttling compound cysteine (Cys) on various facets of hematite and the reallocations of surface-bound As(III) or As(V) on the respective surfaces.

Adsorption effects and mechanisms of phosphorus by nanosized laponite.

Phosphorus (P), an important macroelement for crops, may be lost into water systems by human activities and subsequently cause serious environmental problems such as eutrophication. Thus, the recovery of P from wastewater is essential. P can be adsorbed and recovered from wastewater using many natural, environmentally friendly clay minerals, however the adsorption ability is limited.

Controlled Deformation of Soft Nanogel Particles Generates Artificial Biominerals with Ordered Internal Structure.

Biominerals can exhibit exceptional mechanical properties owing to their hierarchically-ordered organic/inorganic nanocomposite structure. However, synthetic routes to oriented artificial biominerals of comparable complexity remain a formidable technical challenge. Herein we design a series of soft, deformable nanogels that are employed as particulate additives to prepare nanogel@calcite nanocomposite crystals.

The nature of metal atoms incorporated in hematite determines oxygen activation by surface-bound Fe(II) for As(III) oxidation.

The incorporation of secondary metal atoms into iron oxyhydroxides may regulate the surface chemistry of mediating electron transfer (ET) and, therefore, the biogeochemical pollutant processes such as arsenic (As) in the subsurface and soils. The influence of incorporating two typical metals (Cu and Zn) into a specific {001} hematite facet on O activation by surface-bound Fe(II) was addressed. The results showed that Cu-incorporated hematite enhances As(III) oxidation in the presence of Fe(II) under oxic conditions and increases with increasing Cu content.

Direct Observations of the Occlusion of Soil Organic Matter within Calcite.

Global soil carbon cycling plays a key role in regulating and stabilizing the earth's climate change because of soils with amounts of carbon at least three times greater than those of other ecological systems. Soil minerals have also been shown to underlie the persistence of soil organic matter (SOM) through both adsorption and occlusion, but the microscopic mechanisms that control the latter process are poorly understood. Here, using time-resolved in situ atomic force microscopy (AFM) to observe how calcite, a representative mineral in alkaline soils, interacts with humic substances, we show that following adsorption, humic substances are gradually occluded by the advancing steps of spirals on the calcite (1014) face grown in relatively high supersaturated solutions, through the embedment, compression, and closure of humic substance particles into cavities.