Reduction Products Research Articles

Preparation of cementing material and recovery of iron resources using converter slag

This study aims to optimize the modification of blast furnace slag and converter slag using dust removal ash as a reducing agent, with the dual goals of enriching cementitious materials and recovering iron resources. The results show that the pulverization effect of the modified slag is optimized when the dust removal ash addition ratio is 14 wt%, the reduction temperature is 1450 °C, and the reduction time is 30 min. Under these conditions, the pulverization and iron recovery rates reached 65.23 % and 60.85 %, respectively. The composition of the reduction-modified product is influenced by the particle size of the reduction product, which in turn affects its phase composition. The main phases of small particles (particle size < 0.150 mm) identified were magnesium rose pyroxene (Ca3Mg(SiO4)2, C3MS2) and dicalcium silicate (γ-Ca2SiO4, γ-C2S). The main phases of large particles (particle size > 0.150 mm) identified were dicalcium silicate (β-Ca2SiO4, β-C2S) and Ca2Fe2O5. Iron primarily exists in the form of an alloy and cementite, while P is dispersed in the iron beads in the form of Fe3P, Fe2P, and Mn2P in a striped configuration.

Molecular Electrochemical Catalysis of CO-to-Formaldehyde Conversion with a Cobalt Complex.

Formox, a highly energy-intensive process, currently serves as the primary source of formaldehyde (HCHO), for which there is a crucial and steadily growing chemical demand. The alternative electrochemical production of HCHO from C1 carbon sources such as CO2 and CO is still in its early stages, with even the few identified cases lacking mechanistic rationalization. In this study, we demonstrate that cobalt phthalocyanine (CoPc) immobilized on multiwalled carbon nanotubes (MW-CNTs) constitutes an excellent electrocatalytic system for producing HCHO with productivity through the direct reduction of CO, the two-electron reduction product of CO2. By carefully adjusting both the pH and the applied potential, we identified conditions that enable the production of HCHO with a partial current density of 0.64 mA cm-2 (17.5% Faradaic efficiency, FE) and a total FE of 61.2% for the liquid products (formaldehyde and methanol). A reduction mechanism is proposed.

Metal–Organic Framework Supported Low‐Nuclearity Cluster Catalysts for Highly Selective Carbon Dioxide Electroreduction to Ethanol

AbstractIt is still a great challenge to achieve high selectivity of ethanol in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials and lower energy barrier of possible other C2+ products. Here, we report a MOF‐based supported low‐nuclearity cluster catalysts (LNCCs), synthesized by electrochemical reduction of three‐dimensional (3D) microporous Cu‐based MOF, that achieves a single‐product Faradaic efficiency (FE) of 82.5 % at −1.0 V (versus the reversible hydrogen electrode) corresponding to the effective current density is 8.66 mA cm−2. By investigating the relationship between the species of reduction products and the types of catalytic sites, it is confirmed that the multi‐site synergism of Cu LNCCs can increase the C−C coupling effect, and thus achieve high FE of CO2–to–ethanol. In addition, density functional theory (DFT) calculation and operando attenuated total reflectance surface‐enhanced infrared absorption spectroscopy further confirmed the reaction path and mechanism of CO2–to–EtOH.

Metal-Organic Framework Supported Low-Nuclearity Cluster Catalysts for Highly Selective Carbon Dioxide Electroreduction to Ethanol.

It is still a great challenge to achieve high selectivity of ethanol in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials and lower energy barrier of possible other C2+ products. Here, we report a MOF-based supported low-nuclearity cluster catalysts (LNCCs), synthesized by electrochemical reduction of three-dimensional (3D) microporous Cu-based MOF, that achieves a single-product Faradaic efficiency (FE) of 82.5 % at -1.0 V (versus the reversible hydrogen electrode) corresponding to the effective current density is 8.66 mA cm-2. By investigating the relationship between the species of reduction products and the types of catalytic sites, it is confirmed that the multi-site synergism of Cu LNCCs can increase the C-C coupling effect, and thus achieve high FE of CO2-to-ethanol. In addition, density functional theory (DFT) calculation and operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy further confirmed the reaction path and mechanism of CO2-to-EtOH.

Assessing the impact of carbon quota allocation in enhancing supply chain members emission reduction and advertising efforts

Carbon quota allocation, a precise implementation approach within the cap-and-trade policy, exerts an enduring impact on the production and economic activities of supply chain members. Recognizing the dynamic fluctuations in product goodwill, this study formulates differential game models involving both the manufacturer and retailer within the supply chain. Subsequently, differences in carbon emission reduction efforts, advertising expenditures, product goodwill, and profitability among supply chain members within each contractual framework are comprehensively compared and analyzed. Numerical illustrations are then utilized to validate the theoretical findings and strengthen the subsequent key insights. First, the implementation of carbon quotas allocation, especially those grounded in the benchmarking-based contract, enhances carbon reduction and advertising efforts by supply chain members. Second, both grandfathering-based and benchmarking-based regulations improve the product goodwill, with the latter yielding more substantial improvements. Third, the escalation in unit emission permit price positively impacts the dedication and profitability of supply chain members, although variations in profit enhancements between the manufacturer and retailer hinge on the specific carbon quota allocation methods employed. Lastly, the grandfathering-based total carbon quotas exclusively benefit the manufacturer's profitability, whereas the per-unit carbon quotas under benchmarking-based contract fosters enhanced individual efforts and profitability for all supply chain members.

Efficient reduction-oxidation coupling degradation of nitroaromatic compounds in continuous flow processes

Nitroaromatic compounds (NACs) with electron-withdrawing nitro (-NO2) groups are typical refractory pollutants. Despite advanced oxidation processes (AOPs) being appealing degradation technologies, inefficient ring-opening oxidation of NACs and practical large-scale applications remain challenges. Here we tackle these challenges by designing a reduction-oxidation coupling (ROC) degradation process in LaFe0.95Cu0.05O3@carbon fiber cloth (LFCO@CFC)/PMS/Vis continuous flow system. Cu doping enhances the photoelectron transfer, thus triggering the -NO2 photoreduction and breaking the barriers in the ring opening. Also, it modulates surface electronic configuration to generate radicals and non-radicals for subsequent oxidation of reduction products. Based on this, the ROC process can effectively remove and mineralize NACs under the environmental background. More importantly, the LFCO catalyst outperformed most of the recently reported catalysts with lower cost (13.72 CNY/ton) and higher processing capacity (3600 t/month). Furthermore, the high scalability, material durability, and catalytic activity of LFCO@CFC under various realistic environmental conditions prove the potential ability for large-scale applications.

Green Synthesis of Pure Superparamagnetic Fe3O4 Nanoparticles Using Shewanella sp. in a Non-Growth Medium

Conventional wet chemical methods for the synthesis of superparamagnetic magnetite nanoparticles (MNPs) are energy-intensive and environmentally unsustainable. Green synthesis using bacteria is a less-explored approach to MNP production. Large-scale biosynthesis of MNPs has heretofore been conducted using extremophilic bacteria that exhibit low growth rates and/or require strict temperature control. However, a decrease in material and energy costs would make such bioprocesses more sustainable. In this study, Shewanella putrefaciens CN-32, an iron-reducing bacterium, was employed to reduce amorphous iron oxyhydroxide and synthesize MNPs in a non-growth medium at ambient temperature and pressure. The synthesis was conducted using plain saline solution (0.85% NaCl) to avoid impurities in the products. X-ray diffraction and transmission electron microscopy indicated that the reduction products were MNPs with a pseudo-spherical shape and 6 ± 2 nm average size. Magnetometry showed that the particles were superparamagnetic with maximum saturation magnetization of 73.8 emu/g, which is comparable to that obtained via chemical synthesis methods. Using less than a quarter of the raw materials employed in a typical chemical co-precipitation method, we obtained a maximum yield of 3.473 g/L (&gt;5-fold increase). These findings demonstrate that our simple and ecofriendly process can help overcome the current barriers for large-scale synthesis of high-purity magnetic nanopowders.

Direct quantification of electrochemical CO2 reduction products with an improved DEMS setup

Direct quantification of electrochemical CO2 reduction products with an improved DEMS setup

High-purity ethylene production via indirect carbon dioxide electrochemical reduction

High-purity ethylene production from CO2 electroreduction (CO2RR) is a coveted, yet arduous feat because the product stream comprises a blend of unreacted CO2, H2, and other off-target CO2 reduction products. Here we present an indirect reduction strategy for CO2-to-ethylene conversion, one that employs 2-bromoethanol (Br-EO) as a mediator. Br-EO is initially generated from CO2RR and subsequently undergoes reduction to ethylene without the need for energy-intensive separation steps. The optimized AC-Ag/C catalyst with Cl incorporation reduces the energy barrier of the debromination step during Br-EO reduction, and accelerates the mass-transfer process, delivering a 4-fold decrease of the relaxation time constant. Resultantly, AC-Ag/C achieved a FEethylene of over 95.0 ± 0.36% at a low potential of −0.08 V versus reversible hydrogen electrode (RHE) in an H-type cell with 0.5 M KCl electrolyte, alongside a near 100% selectivity within the range of −0.38 to −0.58 V versus RHE. Through this indirect strategy, the average ethylene purity within 6-hour electrolysis was 98.00 ± 1.45 wt%, at −0.48 V (vs RHE) from the neutralized electrolyte after CO2 reduction over the Cu/Cu2O catalyst in a flow-cell.

Photoredox Cascade Catalysts for Solar Hydrogen Production from Sustainable Hydrogen Sources.

Visible-light-driven photocatalytic hydrogen (H2) production has been extensively studied as a clean and sustainable energy resource. Although sacrificial electron donors (SEDs) are commonly used to evaluate photocatalytic activity, their irreversible decomposition forces charge separation, which disrupts the inherent dual productivity of photocatalysis, that is, the formation of both the reduction and oxidation products. To achieve highly efficient photoinduced charge separation without SED decomposition, the layer-by-layer assembly of redox-active photosensitizing dyes and electron mediators through Zr4+-phosphonate bonds has been extensively studied as an artificial mimic of the electron transport chain in natural photosynthesis. This concept paper presents an overview of photoredox cascade catalytic (PRCC) systems comprising multiple Ru(II)-trisbipyridine-type dyes and mediator layers on Pt-loaded TiO2 nanoparticles for H2 production from redox reversible electron donors (RREDs). The PRCC structure-activity relationship for photocatalytic H2 production is briefly discussed in terms of layer thickness, surface structure and modification, and cooperativity with molecular oxidation catalysts. Finally, new insights into the design of efficient dual-production photocatalysts based on the PRCC structure are presented.

Kinetics study on the temperature-dependent reduction of aqueous U(VI) by natural pyrite

Previous studies have indicated that acid-washed pyrite is inert toward aqueous U(VI) under most pH conditions at ambient temperature, even though insoluble UO2 is the thermodynamically predicted product for the reduction of U(VI) by pyrite. Considering the exothermic nature of nuclear waste, the interaction between uranyl nitrate/acetate and natural pyrite was studied at temperatures ranging from 25 °C to 85 °C and at pH values between ∼4.0 and ∼9.5, to simulate the scenarios encountered in a high-level radioactive waste repository. The results revealed that the reactivity of pyrite toward aqueous U(VI) significantly increased with rising temperature, and the reaction could be described by a pseudo-first-order kinetic equation. Activation energies were calculated to be 79.4 ± 10.6 and 45.7 ± 3.8 kJ⋅mol−1 for the reduction of uranyl nitrate, and 78.2 ± 5.2 and 42.2 ± 5.8 kJ⋅mol−1 for the reduction of uranyl acetate, at pH values of ∼4.5 and ∼5.0, respectively. These values indicate that the reaction is controlled by the surface chemical processes. In addition, the complete reduction of aqueous U(VI) to UO2 product was first observed for the reactions at pH ∼4.0 to ∼5.5 when the temperature was ≥75 °C. Conversely, non-stoichiometric UO2+x(s) (0 < x ≤ 0.67) was found at lower temperatures within the same pH range, and also at 85 °C with a reaction pH of ∼9.5. Moreover, the ratio of reduced U(IV/V) on pyrite surfaces increased gradually over time, indicating that reaction time played a significant role in the reduction products. The findings are essential not only for the safety assessment of the high-level radioactive waste repository, but also for understanding the metallogenic mechanism of U(IV)-bearing ore deposits under the relevant anaerobic and hydrothermal conditions.

Efficient removal of U(VI) by graphene-based electrode modified with amidoxime: Performance and mechanism

The burgeoning interest in nuclear energy as a sustainable power source brings to the fore significant environmental and human health concerns associated with wastewater from uranium mining. This study presented the successful synthesis of amidoxime modified graphene-based electrode materials (PAO-N-rGO/CF) designed for treating uranium containing wastewater. The influencing factors of PAO-N-rGO/CF during the electrokinetic restoration process were systematically investigated, exploring the mechanisms of adsorption and electrochemical reduction from the perspectives of establishing adsorption theoretical models, evaluating electrochemical performance, and characterizing reduction products. According to the results, the optimal removal efficiency for U(VI) by PAO-N-rGO/CF reached 99.93 % under conditions of an applied voltage of 5 V, an electrification duration of 20 min, and a pH of 7. Compared to Ca2+, K+, and Mg2+, PAO-N-rGO/CF exhibited strong selectivity for UO22+. Whether dissolved oxygen was present or not, PAO-N-rGO/CF maintained its excellent electrochemical performance. After undergoing 10 cycles of reuse, the removal efficiency for U(VI) only decreased by 8.75 %. The establishment of the adsorption model demonstrated the presence of a chemical bond between uranium and amidoxime groups. The electrochemical performance tests evidenced that PAO-N-rGO/CF exhibited superior electron transfer capability. The reduction of (UO2)3(OH+)5 to UO2 in wastewater at a pH = 7 was verified by analysis of the reduction products. The successful development and mechanistic study of the novel and efficient electrode material provide theoretical support for the control of radioactive nuclide pollution and possess practical value for engineering applications in treating uranium containing wastewater.

The role of oxidants in the intensive cyanidation of gold. 1. Gold dissolution

In the intensive cyanidation of gravity gold concentrates, sodium m-nitrobenzene sulfonate (NBS) is often used to supplement dissolved oxygen as the oxidant in the process. This paper presents the results of a largely electrochemical study of the behaviour of NBS during cyanidation. The results have confirmed that NBS acts as an oxidant in the cyanidation of gold and that the mixed potential model can be applied to describe the mechanism of its action.The mixed potential is a good initial indicator of the rate of gold dissolution and, as expected, the anodic dissolution of pure gold in cyanide solutions is characterized by passivation at potentials above about −0.35 V.The reduction of oxygen under the conditions of the present study occurs in two 2-electron steps with peroxide as an intermediate. Dissolution of gold occurs at potentials in the diffusion-controlled region for the first step. The cathodic reduction of NBS occurs in the same potential region as the reduction of oxygen. The reaction is first order in the concentration of NBS and is largely independent of the pH. The stoichiometry of the reaction involves six moles of gold per mole of NBS confirming that the amine is the final product of reduction of NBS.Rates of gold dissolution in various solutions have been measured using a calibrated linear polarisation method. The rate increases approximately linearly with increasing NBS concentration and is independent of pH. The rate in 0.5 g/L NBS is approximately the same as in oxygenated solutions.A relatively simple titration has been adapted for use in determining NBS concentrations.

Thermodynamic modeling of silicon carbide formation during the Acheson process in non-stoichiometric mixtures

A brief review and critical evaluation of the literature related to the mechanism of carbothermic reduction of silicon oxide is presented. To resolve the contradictions in the literature data about the number of chemical reactions and key intermediate substances during the Acheson process, thermodynamic modeling of products of carbothermic reduction of silicon (IV) oxide at 1 bar total pressure was carried out. It was determined that CO2 and Si were absent among the intermediates at temperatures close to the silicon carbide formation temperature (from 1520 to ~2500 °С). Out of several dozen possible reactions, the two dominant reactions that result in the formation of silicon carbide in the Acheson process were identified. The effect of reagents temperature from 1000 to 3000 °С, bulk and local deviation from stoichiometry of the initial mixture on the composition of the reaction products was discovered. Obtained new data explains some empirical observations and greatly simplifies the physicochemical modeling of the Acheson process.

The excellent performance of oxygen evolution reaction on stainless steel electrodes by halogen oxyacid salts etching

Development of low-cost, efficient, and stable electrocatalysts for oxygen evolution reaction (OER) is the key issue for a large-scale hydrogen production. Recently, in-situ corrosion of stainless steel seems to be a feasible technique to obtain an efficient OER electrode, while a wide variety of corrosive agents often lead to significant difference in catalytic performance. Herein, we synthesized Ni-Fe based nanomaterials with OER activity through a facile one-step hydrothermal etching method of stainless steel mesh, and investigated the influence of three halogen oxyacid salts (KClO3, KBrO3, KIO3) on water oxidation performance. It was found that the reduction product of oxyacid salts has the pitting effect on the stainless steel, which plays an important role in regulating the morphology and composition of the nanomaterials. The KBrO3-derived electrode shows optimal OER performance, giving the small overpotential of 228 and 270 mV at 10 and 100 mA cm−2 respectively, a low Tafel slope of 36.2 mV dec−1, as well as durable stability in the long-time electrolysis. This work builds an internal relationship between the corrosive agents and the OER performance of the as-prepared electrodes, providing promising strategies and research foundations for further improving the OER performance and optimizing the structure of stainless steel electrodes.

Elucidating the effect of H2S on the syngas autotrophic fermentation: Focusing on functional microorganisms and metabolic pathway

As an impurity of syngas, hydrogen sulfide (H2S) has adverse effect of on syngas fermentation, but its inhibitory threshold and mechanism are still not clear. Here in, the present study systematically investigated the insight mechanism of H2S on syngas fermentation pathways via evaluating the key enzymatic activities, genes expression and functional microorganisms. Results showed that the inhibitory threshold of H2S on syngas fermentation was 200 ppm, reflected by a significant decrease of syngas consumption rate and volatile fatty acids (VFAs) production. However, low concentration of H2S (20–100 ppm) had a promotion effect on syngas fermentation and the highest of VFAs concentration of 2.8 g/L was observed at 50 ppm H2S. Low H2S concentrations improved the percent of lately apoptotic cells, but 200 ppm H2S led to most of cells at early apoptotic status. At the presence of H2S, the enzymatic activities (i.e., CODH and FDH) and functional genes (i.e., fhs and acsE) encoding the methyl branch were significantly decreased, while the expression of genes encoding the carbonyl branch (i.e., acsA) up-regulated. The down-regulated of genes encoding the acetogenic pathway (i.e., codh) proved the enhancement of reductive acetate production pathway. Moreover, the functional bacteria of Terrisporobacter and Acetobacter that involved in the methyl branch, showed significant decrease at the presence of H2S. Hence, H2S stress led to the changes of metabolic pathway from methyl branch to carbonyl branch. The proliferation of sulfur metabolizer (i.e., Mesotoga and SBR1031) explained the improvement of VFAs production at low H2S concentrations.

Dialumene‐Mediated Production of Phosphines through P4 Reduction

AbstractThe formation of phosphorus‐rich alanes featuring butterfly‐like geometries is achieved. The two‐electron reduction products feature a unique P42− structure and can act as a source of P3−. The treatment of these phosphorus containing products with electrophiles under mild conditions results in the formation of different phosphines. This approach eliminates the need for high temperatures and/or high pressures, which are commonly required in industrial processes for the preparation of useful phosphines.The activation and further functionalization of white phosphorus (P4) by main group complexes has become an increasingly studied topic in recent times. Herein, we report the controlled formation of phosphorus‐rich alanes featuring butterfly‐like geometries from the selective reaction of P4 with dialumenes, ([L(IiPr)Al]2) (1: L=Tripp=2,4,6‐iPr3C6H2; 2: L=tBu2MeSi; IiPr=[MeCN(iPr)]2C)). The two‐electron‐reduction product of P4 features a P42− structure and is shown to be able to act as a source of P3−. Treatments of different electrophiles (e.g., chlorotrimethylsilane (Me3SiCl), iodotrimethylsilane (Me3SiI), HCl, or acetyl chloride (CH3COCl)) with these alanes under mild conditions gave the corresponding phosphines (e.g., P(SiMe3)3, PH3, or P(COCH3)3).

Insight into the Selectivity-Determining Step of Various Photocatalytic CO2 Reduction Products by Inorganic Semiconductors

Insight into the Selectivity-Determining Step of Various Photocatalytic CO₂ Reduction Products by Inorganic Semiconductors

Synthesis of 5,5′-Dinitro- and 5,5′-Diaminobis(cyclopenta[&lt;i&gt;b&lt;/i&gt;]indoles) Bound at &lt;i&gt;N&lt;/i&gt;&lt;sup&gt;4&lt;/sup&gt;,&lt;i&gt;N&lt;/i&gt;&lt;sup&gt;4′&lt;/sup&gt; Atoms with a Dioxoalkane Spacer

Upon condensation of 2 equiv. of 3R*,3aR*,8bS*-3-iodo-7-methyl-1,2,3,3а,4,8b-hexahydrocyclopenta[b]indole with 1 equiv. of glutaric or decanedicarboxylic acid dichloranhydride [N4,N4′-di-(3R*,3aR*,8bS*,3′R*,3a′R*,8b′S*)- and N4,N4′-di-(3aR*,3aR*,8bS*,3′S*,3a′S*,8b′R*)-3-iodo-7-methyl-1,2,3,3а,4,8b-hexahydrocyclopenta[b]indolyl]alkanediamides were synthesized. Their didehydrohalogenation to 3aR*,8bR*,3a′R*,8b′R*- and 3aS*,8bS*,3a′R*,8b′R*-1,3a,4,8b-tetrahydroanalogues was carried out by boiling these diiodides in piperidine. The presence of rotamerism in the products of dehydrohalogenation was shown, which is manifested by doubling the signals in the NMR spectra in different ratios. Nitration with trifluoroacetyl nitrate in CH2Cl2 yielded their 5,5′-dinitro analogs, which, when reacted with freshly prepared Fe(OH)2, along with 5,5′-diamino derivatives, also formed 5-amino-5′-nitro-substituted products of incomplete reduction. When a nitro group or an amino group appears at the C5 and C5′ carbon atoms of the cyclopenta[b]indole fragments, the doubling of the signals in the NMR spectra disappears. The interaction of a 5,5′-diamino derivative (n = 8) with decanedicarboxylic acid dichloride yielded a compound with 30 atoms in the macrocyclic ring.

Agents of Different Origins for Reduction of Mycotoxins’ Level in Feed

Abstract Toxic secondary metabolites of some fungi (mainly representatives of Alternaria, Aspergillus, Fusarium and Penicillium genera) may contaminate agricultural products, representing serious health hazards to both humans and animals. Along with this, the economic losses due to the mycotoxins’ presence in feed production, including crop and animal feedstuff processing and distribution, motivated the plentiful research of detoxification strategies. Feed supplementation with mineral adsorbents (zeolites, hydrated sodium calcium aluminosilicate (HSCAS), bentonites, etc.) is the most prominent approach widely applied. Besides these, other products for mycotoxin level reduction based on the constituents of the yeast cell wall or Lactobacilli are often used. Recently, many investigations are directed toward plant-derived products that can efficiently adsorb mycotoxins in their native (biosorbents) or modified forms (e.g. activated carbon, biochar etc.). These renewable, easily accessible and readily prepared sorbents are economically viable and safe alternatives for mycotoxin decontamination of feed resources. Organic polymers (chitosan, cellulose, etc.) as well as synthetic polymers, such as polyvinyl pyrrolidine, also might reduce mycotoxins’ level in feed. Besides these conventional methods, new research trends are nanotechnologies, the promising, effective, low-cost way for mycotoxins’ removal. This overview systematically summarizes information on binding agents of different origins for the reduction of mycotoxins’ levels in feed. Furthermore, the knowledge of potential applications of binding agents in the feed industry is also reviewed and discussed.