Thermal suppression of charge disproportionation accelerates interface electron transfer of water electrolysis.

The sluggish electron transfer kinetics in electrode polarization driven oxygen evolution reaction (OER) result in big energy barriers of water electrolysis. Accelerating the electron transfer at the electrolyte/catalytic layer/catalyst bulk interfaces is an efficient way to improve electricity-to-hydrogen efficiency. Herein, the electron transfer at the Sr3Fe2O7@SrFeOOH bulk/catalytic layer interface is accelerated by heating to eliminate charge disproportionation from Fe4+ to Fe3+ and Fe5+ in Sr3Fe2O7, a physical effect to thermally stabilize high-spin Fe4+ (t2g3eg1), providing available orbitals as electron transfer channels without pairing energy. As a result of thermal-induced changes in electronic states via thermal comproportionation, a sudden increase in OER performances was achieved as heating to completely suppress charge disproportionation, breaking a linear Arrhenius relationship. The strategy of regulating electronic states by thermal field opens a broad avenue to overcome the electron transfer barriers in water splitting.

An active site mutation induces oxygen reactivity in D-arginine dehydrogenase: A case of superoxide diverting protons.

Enzymes are potent catalysts that increase biochemical reaction rates by several orders of magnitude. Flavoproteins are a class of enzymes whose classification relies on their ability to react with molecular oxygen (O2) during catalysis using ionizable active site residues. Pseudomonas aeruginosa D-arginine dehydrogenase (PaDADH) is a flavoprotein that oxidizes D-arginine for P. aeruginosa survival and biofilm formation. The crystal structure of PaDADH reveals the interaction of the glutamate 246 (E246) side chain with the substrate and at least three other active site residues, establishing a hydrogen bond network in the active site. Additionally, E246 likely ionizes to facilitate substrate binding during PaDADH catalysis. This study aimed to investigate how replacing the E246 residue with leucine affects PaDADH catalysis and its ability to react with O2 using steady-state kinetics coupled with pH profile studies. The data reveal a gain of O2 reactivity in the E246L variant, resulting in a reduced flavin semiquinone species and superoxide (O2•-) during substrate oxidation. The O2•- reacts with active site protons, resulting in an observed nonstoichiometric slope of 1.5 in the enzyme's log (kcat/Km) pH profile with D-arginine. Adding superoxide dismutase results in an observed correction of the slope to 1.0. This study demonstrates how O2•- can alter the slopes of limbs in the pH profiles of flavin-dependent enzymes and serves as a model for correcting nonstoichiometric slopes in elucidating reaction mechanisms of flavoproteins.

The DsrD functional marker protein is an allosteric activator of the DsrAB dissimilatory sulfite reductase.

Dissimilatory sulfur metabolism was recently shown to be much more widespread among bacteria and archaea than previously believed. One of the key pathways involved is the dsr pathway that is responsible for sulfite reduction in sulfate-, sulfur-, thiosulfate-, and sulfite-reducing organisms, sulfur disproportionators and organosulfonate degraders, or for the production of sulfite in many photo- and chemotrophic sulfur-oxidizing prokaryotes. The key enzyme is DsrAB, the dissimilatory sulfite reductase, but a range of other Dsr proteins is involved, with different gene sets being present in organisms with a reductive or oxidative metabolism. The dsrD gene codes for a small protein of unknown function and has been widely used as a functional marker for reductive or disproportionating sulfur metabolism, although in some cases this has been disputed. Here, we present in vivo and in vitro studies showing that DsrD is a physiological partner of DsrAB and acts as an activator of its sulfite reduction activity. DsrD is expressed in respiratory but not in fermentative conditions and a ΔdsrD deletion strain could be obtained, indicating that its function is not essential. This strain grew less efficiently during sulfate and sulfite reduction. Organisms with the earliest forms of dsrAB lack the dsrD gene, revealing that its activating role arose later in evolution relative to dsrAB.

Shielding Mn3+ Disproportionation with Graphitic Carbon-Interlayered Manganese Oxide Cathodes for Enhanced Aqueous Energy Storage System.

Manganese dioxide (MnO2) materials have recently garnered attention as prospective high-capacity cathodes, owing to their theoretical two-electron redox reaction in charge storage processes. However, their practical application in aqueous energy storage systems faces a formidable challenge: the disproportionation of Mn3+ ions, leading to a significant reduction in their capacity. To address this limitation, the study presents a novel graphitic carbon interlayer-engineered manganese oxide (CI-MnOx) characterized by an open structure and abundant defects. This innovative material serves several essential functions for efficient aqueous energy storage. First, a graphitic carbon layer coats the MnOx molecular interlayer, effectively inhibiting Mn3+ disproportionation and substantially enhancing electrode conductivity. Second, the phase variation within MnOx generates numerous crystal defects, vacancies, and active sites, optimizing electron-transfer capability. Third, the flexible carbon layer acts as a buffer, mitigating the volume expansion of MnOx during extended cycling. The synergistic effects of these features result in the CI-MnOx exhibiting an impressive high capacity of 272 mAh g-1 (1224 F g-1) at 0.25 A g-1. Notably, the CI-MnOx demonstrates zero capacity loss after 90 000 cycles (≈3011 h), an uncommon longevity for manganese oxide materials. Spectral characterizations reveal reversible cation intercalation and conversion reactions with multielectron transfer in a LiCl electrolyte.

14-Membered Macrocyclic ß-Diiminato Gold(II) - A New Member for the Gold(II) Complex Family?

The chemistry of molecular gold compounds is dominated by the oxidation states +I and +III. For the intermediate oxidation state +II with 5d9 electron configuration, dimerization or disproportionation of the gold(II) radicals is favored, so that only a few mononuclear gold(II) complexes have been isolated to date. The present study addresses the one-electron reduction of the macrocyclic gold(III) complex [AuIIIL]+ of the innocent ß-diiminato ligand L2- with a 14-membered macrocycle (L2-=5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-5,7,12,14-tetraenato). Electrochemistry, spectroelectrochemistry and chemical reduction of [AuIIIL]+ monitored by UV/Vis, NMR and EPR spectroscopy together with density functional theory calculations reveal disproportionation of the initially generated but elusive gold(II) complex AuIIL and provide guidelines for prospective stable mononuclear tetraazamacrocyclic gold(II) complexes.

Cerium Oxide Catalyzed Disproportionation of Hydrogen Peroxide: A Closer Look at the Reaction Intermediate.

Cerium oxide nanoparticles (CNPs) have recently gained increasing interest as redox enzyme-mimetics to scavenge the intracellular excess of reactive oxygen species, including hydrogen peroxide (H2 O2 ). Despite the extensive exploration, there remains a notable discrepancy regarding the interpretation of observed redshift of UV-Visible spectroscopy due to H2 O2 addition and the catalase-mimicking mechanism of CNPs. To address this question, we investigated the reaction mechanism by taking a closer look at the reaction intermediate during the catalase mimicking reaction. In this study, we present evidence demonstrating that in aqueous solutions, H2 O2 adsorption at CNP surface triggers the formation of stable intermediates known as cerium-peroxo (Ce-O2 2- ) and/or cerium-hydroperoxo (Ce-OOH- ) complexes as resolved by Raman scattering and UV-Visible spectroscopy. Polymer coating presents steric hinderance for H2 O2 accessibility to the solid-liquid interface limiting further intermediate formation. We demonstrate in depth that the catalytic reactivity of CNPs in the H2 O2 disproportionation reaction increases with the Ce(III)-fraction and decreases in the presence of polymer coatings. The developed approach using UV-Visible spectroscopy for the characterization of the surface peroxide species can potentially serve as a foundation for determining the catalytic reactivity of CNPs in the disproportionation of H2 O2 .

Integrative Salt Selection and Formulation Optimization: Perspectives of Disproportionation and Microenvironmental pH Modulation.

We report a novel utilization of a pH modifier as a disproportionation retardant in a tablet formulation. The drug molecule of interest has significant bioavailability challenges that require solubility enhancement. In addition to limited salt/cocrystal options, disproportionation of the potential salt(s) was identified as a substantial risk. Using a combination of Raman spectroscopy with chemometrics and quantitative X-ray diffraction in specially designed stress testing, we investigated the disproportionation phenomena. The learnings and insight drawn from crystallography drove the selection of the maleate form as the target API. Inspired by the fumarate form's unique stability and solubility characteristics, we used fumaric acid as the microenvironmental pH modulator. Proof-of-concept experiments with high-risk (HCl) and moderate-risk (maleate) scenarios confirmed the synergistic advantage of fumaric acid, which interacts with the freebase released by disproportionation to form a more soluble species. The resultant hemifumarate helps maintain the solubility at an elevated level. This work demonstrates an innovative technique to mediate the solubility drop during the "parachute" phase of drug absorption using compendial excipients, and this approach can potentially serve as an effective risk-mitigating strategy for salt disproportionation.

Transformation of Mercurous [Hg(I)] Species during Laboratory Standard Preparation and Analysis: Implication for Environmental Analysis.

Hg(I) may control Hg redox kinetics; however, its metastable nature hinders analysis. Herein, the stability of Hg(I) during standard preparation and analysis was studied. Gravimetric analysis showed that Hg(I) was stable in its stock solution (1000 mg L-1), yet completely disproportionated when its dilute solution (10 µg L-1) was analyzed using liquid chromatography (LC)-ICPMS. The Hg(I) dimer can form through an energetically favorable comproportionation between Hg(0) and Hg(II), as supported by density functional theory calculation and traced by the rapid isotope exchange between 199Hg(0)aq and 202Hg(II). However, the separation of Hg(0) and Hg(II) (e.g., LC process) triggered its further disproportionation. Polypropylene container, increasing headspace, decreasing pH, and increasing dissolved oxygen significantly enhanced the disproportionation or redox transformations of Hg(I). Thus, using a glass container without headspace and maintaining a slightly alkaline solution are recommended for the dilute Hg(I) stabilization. Notably, we detected elevated concentrations of Hg(I) (4.4-6.1 µg L-1) in creek waters from a heavily Hg-polluted area, accounting for 54-70% of total dissolved Hg. We also verified the reductive formation of Hg(I) in Hg(II)-spiked environmental water samples, where Hg(I) can stably exist in aquatic environments for at least 24 h, especially in seawater. These findings provide mechanistic insights into the transformation of Hg(I), which are indicative of its further environmental identification.

Thermodynamic Inhibition of Microbial Sulfur Disproportionation in a Multisubunit Designed Sulfur-Siderite Packed Bioreactor.

Sulfur disproportionation (S0DP) poses a challenge to the robust application of sulfur autotrophic denitrification due to unpredictable sulfide production, which risks the safety of downstream ecosystems. This study explored the S0DP occurrence boundaries with nitrate loading and temperature effects. The boundary values increased with the increase in temperature, exhibiting below 0.15 and 0.53 kg-N/m3/d of nitrate loading at 20 and 30 °C, respectively. A pilot-scale sulfur-siderite packed bioreactor (150 m3/d treatment capacity) was optimally designed with multiple subunits to dynamically distribute the loading of sulfur-heterologous electron acceptors. Operating two active and one standby subunit achieved an effective denitrification rate of 0.31 kg-N/m3/d at 20 °C. For the standby subunit, involving oxygen by aeration effectively transformed the facultative S0DP functional community from S0DP metabolism to aerobic respiration, but with enormous sulfur consumption resulting in ongoing sulfate production of over 3000 mg/L. Meanwhile, acidification by the sulfur oxidation process could reduce the pH to as low as 2.5, which evaluated the Gibbs free energy (ΔG) of the S0DP reaction to +2.56 kJ, thermodynamically suppressing the S0DP occurrence. Therefore, a multisubunit design along with S0DP inhibition strategies of short-term aeration and long-term acidification is suggested for managing S0DP in various practical sulfur-packed bioreactors.

In situ small-angle X-ray scattering reveals solution phase discharge of Li-O2 batteries with weakly solvating electrolytes.

Electrodepositing insulating lithium peroxide (Li2O2) is the key process during discharge of aprotic Li-O2 batteries and determines rate, capacity, and reversibility. Current understanding states that the partition between surface adsorbed and dissolved lithium superoxide governs whether Li2O2 grows as a conformal surface film or larger particles, leading to low or high capacities, respectively. However, better understanding governing factors for Li2O2 packing density and capacity requires structural sensitive in situ metrologies. Here, we establish in situ small- and wide-angle X-ray scattering (SAXS/WAXS) as a suitable method to record the Li2O2 phase evolution with atomic to submicrometer resolution during cycling a custom-built in situ Li-O2 cell. Combined with sophisticated data analysis, SAXS allows retrieving rich quantitative structural information from complex multiphase systems. Surprisingly, we find that features are absent that would point at a Li2O2 surface film formed via two consecutive electron transfers, even in poorly solvating electrolytes thought to be prototypical for surface growth. All scattering data can be modeled by stacks of thin Li2O2 platelets potentially forming large toroidal particles. Li2O2 solution growth is further justified by rotating ring-disk electrode measurements and electron microscopy. Higher discharge overpotentials lead to smaller Li2O2 particles, but there is no transition to an electronically passivating, conformal Li2O2 coating. Hence, mass transport of reactive species rather than electronic transport through a Li2O2 film limits the discharge capacity. Provided that species mobilities and carbon surface areas are high, this allows for high discharge capacities even in weakly solvating electrolytes. The currently accepted Li-O2 reaction mechanism ought to be reconsidered.

Scandium Ion-Promoted Electron-Transfer Disproportionation of 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide (PTIO•) in Acetonitrile and Its Regeneration Induced by Water.

2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO•), a persistent nitronyl nitroxide radical, has been used for the detection and trapping of nitric oxide, as a redox mediator for batteries, for the activity estimation of antioxidants, and so on. However, there is no report on the reactivity of PTIO• in the presence of redox-inactive metal ions. In this study, it is demonstrated that the addition of scandium triflate, Sc(OTf)3 (OTf = OSO2CF3), to an acetonitrile (MeCN) solution of PTIO• resulted in an electron-transfer disproportionation to generate the corresponding cation (PTIO+) and anion (PTIO-), the latter of which is suggested to be stabilized by Sc3+ to form [(PTIO)Sc]2+. The decay of the absorption band at 361 nm due to PTIO•, monitored using a stopped-flow technique, obeyed second-order kinetics. The second-order rate constant for the disproportionation, thus determined, increased with increasing the Sc(OTf)3 concentration to reach a constant value. A drastic change in the cyclic voltammogram recorded for PTIO• in deaerated MeCN containing 0.10 M Bu4NClO4 was also observed upon addition of Sc(OTf)3, suggesting that the large positive shift of the one-electron reduction potential of PTIO• (equivalent to the one-electron oxidation potential of PTIO-) in the presence of Sc(OTf)3 may result in the disproportionation. When H2O was added to the PTIO•-Sc(OTf)3 system in deaerated MeCN, PTIO• was completely regenerated. It is suggested that the complex formation of Sc3+ with H2O may weaken the interaction between PTIO- and Sc3+, leading to electron-transfer comproportionation to regenerate PTIO•. The reversible disproportionation of PTIO• was also confirmed by electron paramagnetic resonance (EPR) spectroscopy.

Disproportionation of Co2+ in the Topochemically Reduced Oxide LaSrCoRuO5.

Complex transition-metal oxides exhibit a wide variety of chemical and physical properties which are a strong function the local electronic states of the transition-metal centres, as determined by a combination of metal oxidation state and local coordination environment. Topochemical reduction of the double perovskite oxide, LaSrCoRuO6 , using Zr, yields LaSrCoRuO5 . This reduced phase contains an ordered array of apex-linked square-based pyramidal Ru3+ O5 , square-planar Co1+ O4 and octahedral Co3+ O6 units, consistent with the coordination-geometry driven disproportionation of Co2+ . Coordination-geometry driven disproportionation of d7 transition-metal cations (e.g. Rh2+ , Pd3+ , Pt3+ ) is common in complex oxides containing 4d and 5d metals. However, the weak ligand field experienced by a 3d transition-metal such as cobalt leads to the expectation that d7+ Co2+ should be stable to disproportionation in oxide environments, so the presence of Co1+ O4 and Co3+ O6 units in LaSrCoRuO5 is surprising. Low-temperature measurements indicate LaSrCoRuO5 adopts a ferromagnetically ordered state below 120 K due to couplings between S=1 /2 Ru3+ and S=1 Co1+ .

New Reaction Pathway of Superoxide Disproportionation Induced by a Soluble Catalyst in Li-O2 Batteries.

Aprotic Li-O2 battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O2 - ) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O2 - disproportionation and its kinetics in both the discharge and charge processes. RB captures O2 - dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol-1 . This facilitates the discharge and charge processes and simultaneously mitigates O2 - and singlet oxygen related side reactions. These endow the Li-O2 battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO2 catalyst. This work highlights the vital role of superoxide disproportionation for Li-O2 battery.

Photo-Induced Disproportionation-Mediated Photodynamic Therapy: Simultaneous Oxidation of Tetrahydrobiopterin and Generation of Superoxide Radicals.

We herein present an approach of photo-induced disproportionation for preparation of Type-I photodynamic agents. As a proof of concept, BODIPY-based photosensitizers were rationally designed and prepared. The photo-induced intermolecular electron transfer between homotypic chromophores leads to the disproportionation reaction, resulting in the formation of charged intermediates, cationic and anionic radicals. The cationic radicals efficiently oxidize the cellularimportant coenzyme, tetrahydrobiopterin (BH4 ), and the anionic radicals transfer electrons to oxygen to produce superoxide radicals (O2 - ⋅). One of our Type-I photodynamic agents not only self-assembles in water but also effectively targets the endoplasmic reticulum. It displayed excellent photocytotoxicity even in highly hypoxic environments (2 % O2 ), with a half-maximal inhibitory concentration (IC50 ) of 0.96 µM, and demonstrated outstanding antitumor efficacy in murine models bearing HeLa tumors.

General Synthesis of Single-Crystal Spinel Cathodes with the Tailored Orientation of Exposed Crystal Planes for Advanced Lithium-Ion Batteries.

The spinel Mn-based cathodes with 3D Li+ diffusion channels, high voltage, and low-cost show promise for developing high-power lithium-ion batteries (LIBs). But the disproportionation and Jahn-Teller distortion lead to structural degeneration and capacity decay, especially at high working temperatures. Herein, considering the merits of single crystals and orientation of exposed crystal planes, single-crystal truncated octahedral LiMn2 O4 (TO-LMO) with exposed {111}, {100} and {110} facets is rationally designed, in which the mainly exposed {111} facets are truncated by a small portion of {100} and {110} facets. The Li-deficient intermediate phase is innovatively proposed to prepare the single-crystal TO-LMO. The synergistic effects of single crystals and the orientation of exposed crystal planes significantly reduce the disproportionation of Mn3+ ions and thereby improve their structural stability. Consequently, the cycling stability of the single-crystal TO-LMO is remarkably enhanced, obtaining outstanding capacity retention of 84.3% after 2000 cycles, much better than that of 61.2% for octahedral LiMn2 O4 . The feasibility of preparing single-crystal truncated octahedral LiNi0.5 Mn1.5 O4 with exposed {111}, {100}, and {110} facets via the Li-deficient intermediate phase is further demonstrated. These findings offer new insight into regulating the orientation of exposed crystal planes and improving the reversibility of Mn-based redox couples in LIBs.

Constructing Biomass-Based Ultrahigh-Rate Performance SnOy @C/SiOx Anode for LIBs via Disproportionation Effect.

To break the stereotype that silica can only be reduced via a magnesiothermic and aluminothermic method at low-temperature condition, the novel strategy for converting silica to SiOx using disproportionation effect of SnO generated via low-temperature pyrolysis coreduction reaction between SnO2 and rice husk is proposed, without any raw materials waste and environmental hazards. After the low-temperature pyrolysis reaction, SnOy @C/SiOx composites with unique structure (Sn/SnO2 dispersed on the surface and within pores of biochar as well as SiOx residing in the interior) are obtained due to the exclusive biological properties of rice husk. Such unique structural features render SnOy @C/SiOx composites with an excellent talent for repairing the damaged structure and the highly electrochemical storage ability (530.8 mAh g-1 at 10 A g-1 after 7500 cycles). Furthermore, assembled LiFePO4 ||SnOy -50@C/SiOx full cell displays a high discharge capacity of 463.7 mAh g-1 after 100 cycles at 0.2 A g-1 . The Li+ transport mechanism is revealed by density functional theory calculations. This work provides references and ideas for green, efficient, and high-value to reduce SiO2 , especially in biomass, which also avoids the waste of raw materials in the production process, and becomes an essential step in sustainable development.

Kinetic Barriers to Disproportionation of Salts of Weakly Basic Drugs.

Disproportionation is a major issue in formulations containing salts of weakly basic drugs. Despite considerable interest in risk assessment approaches for disproportionation, the prediction of salt-to-base conversion remains challenging. Recent studies have highlighted several confounding factors other than pHmax that appear to play an important role in salt disproportionation and have suggested that kinetic barriers need to be considered in addition to the thermodynamic driving force when assessing the risk of a salt to undergo conversion to parent free base. Herein, we describe the concurrent application of in situ Raman spectroscopy and pH monitoring to investigate the disproportionation kinetics of three model salts, pioglitazone hydrochloride, sorafenib tosylate, and atazanavir sulfate, in aqueous slurries. We found that even for favorable thermodynamic conditions (i.e., pH ≫ pHmax), disproportionation kinetics of the salts were very different despite each system having a similar pHmax. The importance of free base nucleation kinetics was highlighted by the observation that the disproportionation conversion time in the slurries showed the same trend as the free base nucleation induction time. Pioglitazone hydrochloride, with a free base induction time of <1 min, rapidly converted to the free base in slurry experiments. In contrast, atazanavir sulfate, where the free base induction time was much longer, took several hours to undergo disproportionation in the slurry for pH ≫ pHmax. Additionally, we altered an established thermodynamically based modeling framework to account for kinetic effects (representing the nucleation kinetic barrier) to estimate the solid-state stability of salt formulations. In conclusion, a solution-based thermodynamic model is mechanistically appropriate to predict salt disproportionation in a solid-state formulation, when kinetic barriers are also taken into consideration.

The Effect of In-Situ-Generated Moisture on Disproportionation of Pharmaceutical Salt.

Pharmaceutical salts are ubiquitously present in the market given their benefits in optimizing the critical properties of an active pharmaceutical ingredient (API). Achieving these benefits requires careful selection and understanding of the salt form of choice. Stability is especially critical here, as salts are susceptible to disproportionation. Several studies have shown the impact of moisture on disproportionation, with more focus on external humidity (moisture coming from outside the system). This work, on the other hand, is systematically designed to study the impact of moisture generated in situ (moisture produced within the system). To that end, an in-house developed compound 1 was selected as our salt API, and its disproportionation was studied in blends (binary and prototype) with hydrated model excipient─trisodium phosphate dodecahydrate (TSPD). TSPD possesses 12 water molecules, which could get released when triggered with enough energy (confirmed by thermogravimetric analysis and humidity studies). As a control for this study, similar blends were prepared with anhydrous trisodium phosphate (TSP), which has comparable properties to TSPD but lacks water. Overall, significant disproportionation was observed in TSPD blends exposed to 40 °C or 70 °C in a closed system; while no disproportionation was observed when the system was left open due to the escape of the moisture generated in situ. The API also remained intact for the blends with anhydrous TSP, as expected. Meanwhile, stressing at 40 °C/75%RH condition resulted in significant disproportionation for both TSPD and TSP blends due to the exposure to external humidity. Hydrated excipients are normally used in drug development, and this work stresses the need for probing the impact from within the system when such excipients are utilized with salt API. This will help fully unravel the overall effect of moisture on the drug, which is relevant downstream when selecting processing conditions, packaging, and so forth.

Effect of hydraulic regime on sulfur-packed bed performance: Denitrification and disproportionation.

Sulfur-packed beds (SPBs) have been increasingly incorporated into constructed wetland systems to overcome limitations in achieving satisfactory nitrate removal efficiency. However, the underlying impact of hydraulic regimes on SPB performance remains understudied. This study investigated the performance of a pilot-scale SPB, encompassing sulfur autotrophic denitrification (SAD) and sulfur disproportionation (SDP) processes, under various horizontal flow (HF) and vertical flow (VF) regimes. The HF regime exhibited superior SAD efficiency, achieving 3.1-4.4 mg-N/L of nitrate removal compared to 0.9-2.8 mg-N/L under VF regimes. However, greater sulfide production of 3.8-5.6 mg/L was observed, in contrast to only 1.5-2.3 mg/L under VF regimes when SDP occurred. Employing current computational fluid dynamics simulations could predict general regimes but lacked precision in detailing sulfur layer dynamics. In contrast, determining the spatial distribution of SAD substrates and SDP products offered a viable solution, revealing stagnate, short-circuit, and back flows. Moreover, the feasibility of an aeration approach to reduce sulfide emissions below 0.5 mg/L in case of accidental SDP occurrence was confirmed. This study offers a method for assessing detailed hydraulic regimes within SPBs. Additionally, it provides guidance on optimizing the packing of sulfur-based materials when implementing SPBs in constructed wetland systems and presents a strategy for mitigating excessive sulfide emissions.

Bifunctional Silica-Supported Ionic Liquid Phase (SILP) Catalysts in Silane Production: Their Synthesis, Characterization and Catalytic Activity.

A mesoporous silica support was synthesized using the sol-gel method from trichlorosilane. There is a tendency for the specific surface area and the proportion of silica particles mesopores to increase during all stages of sol-gel synthesis. It has been shown that the insertion of hexane and toluene, as additional solvents, into the structure-forming polyethylene glycol, makes it possible to regulate the pore size and specific surface area of silica. Silica functionalization was carried out using SILP technology. The activities of the catalytic systems based on polymer and inorganic supports immobilized by imidazole-based ionic liquids during the trichlorosilane disproportionation reaction were compared. There is a tendency for the monosilane yield for catalytic systems based on an inorganic support to increase. We identified the most promising catalyst in terms of monosilane yield and proposed a bifunctional catalyst that exhibited activity in two parallel reactions: trichlorosilane disproportionation and silicon tetrachloride hydrogenation.