Buffer-free ozone-ferrate(VI) systems for enhanced oxidation of electron-deficient contaminants: Synergistic enhancement effects, systematic toxicity assessment, and practical applications.

The combination of ozone (O3) and ferrate (Fe(VI)) oxidation technology demonstrates substantial potential for practical applications, though it has been underreported, resulting in gaps in comprehensive activity assessments and thorough exploration of its mechanisms. This study reveals that the previous use of a borate buffer solution obscured certain synergistic reactions between O3 and Fe(VI), causing a reduction of activity by ∼40 % when oxidizing the electron-deficient pollutant atrazine. Consequently, we reassessed the activity and mechanisms using a buffer-salt-free O3/Fe(VI) system. Our findings showed that the hydroxyl radical (·OH) served as the predominant active species, responsible for an impressive 95.9 % of the oxidation activity against electron-deficient pollutants. Additional experiments demonstrated that the rapid production of neglected and really important superoxide radicals (·O2-) could facilitate the decomposition of O3 to generate ·OH and accelerate the reduction of Fe(VI) to Fe(V), reactivating O3 to produce ·OH anew. Intriguingly, as the reaction progressed, the initially depleted Fe(VI) was partially regenerated, stabilizing at over 50 %, highlighting the significant potential of this combined system. Moreover, this combined system could achieve a high mineralization efficiency of 80.4 % in treating actual coking wastewater, complemented by extensive toxicity assessments using Escherichia coli, wheat seeds, and zebrafish embryos, showcasing its robust application potential. This study revisits and amends previous research on the O3/Fe(VI) system, providing new insights into its activity and synergistic mechanisms. Such a combined technology has potential for the treatment of difficult-to-degrade industrial wastewater.

Direct Electron Transfer-Driven Nontoxic Oligomeric Deposition of Sulfonamide Antibiotics onto Carbon Materials for In Situ Water Remediation.

The rising in situ chemical oxidation (ISCO) technologies based on polymerization reactions have advanced the removal of emerging contaminants in the aquatic environment. However, despite their promise, uncertainties persist regarding their effectiveness in eliminating structurally complex contaminants, such as sulfonamide antibiotics (SAs). This study elucidated that oligomerization, rather than mineralization, predominantly governs the removal of SAs in the carbon materials/periodate system. The amine groups in SAs played a crucial role in forming organic radicals and subsequent coupling reactions due to their high f- index and low bond orders. Moreover, the study highlighted the robust adhesion of oligomers to the catalyst surface, facilitated by enhanced van der Waals forces and hydrophobic interactions. Importantly, plant and animal toxicity assessments confirmed the nontoxic nature of oligomers deposited on the carbon material surface, affirming the efficacy of carbon material-based ISCO in treating contaminated surface water and groundwater. Additionally, a novel classification approach, Δlog k, was proposed to differentiate SAs based on their kinetic control steps, providing deeper insights into the quantitative structure-activity relationship (QSAR) and facilitating the selection of optimal descriptors during the oligomerization processes. Overall, these insights significantly enhance our understanding of SAs removal via oligomerization and demonstrate the superiority of C-ISCO based on polymerization in water decontamination.

Embedding electronic perpetual motion into single-atom catalysts for persistent Fenton-like reactions.

In our quest to leverage the capabilities of the emerging single-atom catalysts (SACs) for wastewater purification, we confronted fundamental challenges related to electron scarcity and instability. Through meticulous theoretical calculations, we identified optimal placements for nitrogen vacancies (Nv) and iron (Fe) single-atom sites, uncovering a dual-site approach that significantly amplified visible-light absorption and charge transfer dynamics. Informed by these computational insights, we cleverly integrated Nv into the catalyst design to boost electron density around iron atoms, yielding a potent and flexible photoactivator for benign peracetic acid. This exceptional catalyst exhibited remarkable stability and effectively degraded various organic contaminants over 20 cycles with self-cleaning properties. Specifically, the Nv sites captured electrons, enabling their swift transfer to adjacent Fe sites under visible light irradiation. This mechanism accelerated the reduction of the formed "peracetic acid-catalyst" intermediate. Theoretical calculations were used to elucidate the synergistic interplay of dual mechanisms, illuminating increased adsorption and activation of reactive molecules. Furthermore, electron reduction pathways on the conduction band were elaborately explored, unveiling the production of reactive species that enhanced photocatalytic processes. A six-flux model and associated parameters were also applied to precisely optimize the photocatalytic process, providing invaluable insights for future photocatalyst design. Overall, this study offers a molecule-level insight into the rational design of robust SACs in a photo-Fenton-like system, with promising implications for wastewater treatment and other high-value applications.