Search Results (17)

As a type of sustainable and renewable natural source, biomass-derived 5-hydroxymethyl furfural (HMF) can be converted into high-value chemicals. This study investigated the interactions between silver (Ag) and oxide supports with varied reducibility and their contributions to tuning catalytic performance in the selective oxidation of HMF. Three representatives of manganese dioxide (MnO₂), zirconium dioxide (ZrO₂), and silicon dioxide (SiO₂) were selected to support the Ag active sites. The catalysts were characterized by techniques such as STEM (TEM), Raman, XPS, H₂-TPR, and FT-IR spectroscopy to explore the morphology, Ag dispersion, surface properties, and electronic states. The catalytic results demonstrated that MnO₂ with the highest reducibility exhibited superior catalytic performance, achieving 75.4% of HMF conversion and 41.6% of selectivity for 2,5-furandicarboxylic acid (FDCA) at 120 °C. In contrast, ZrO₂ and SiO₂ exhibited limited oxidation capabilities, mainly producing intermediate products like FFCA and/or HMFCA. The oxidation ability of these catalysts was governed by support reducibility, because it determined the density of oxygen vacancies (Ov) and surface hydroxyl groups (O_OH), and eventually influenced the catalytic activity, as demonstrated by the reaction rate: Ag/MnO₂ (3214.5 mol_HMF·g_Ag⁻¹·h⁻¹), Ag/ZrO₂ (2062.3 mol_HMF·g_Ag⁻¹·h⁻¹), and Ag/SiO₂ (1394.4 mol_HMF·g_Ag⁻¹·h⁻¹). These findings provide valuable insights into the rational design of high-performance catalysts for biomass-derived chemical conversion. Full article

Chlorine plays an essential role in various industries, such as wastewater treatment, disinfection, plastics, and pharmaceuticals, contributing to a significant global demand. Traditional methods of chlorine production, including chemical reactions involving manganese dioxide, potassium chlorate, and potassium permanganate, as well as the electrolysis of saturated salt solutions, are associated with safety and efficiency concerns. This study introduces a novel approach for the photoelectrocatalytic production of chlorine gas through the oxidation of chloride ions in potassium chloride solutions using a dual semiconductor photoelectrode system composed of TiO₂ and Cu₂O. By harnessing solar energy, this system enables the concurrent, safe, and efficient production of both chlorine and hydrogen gases. The TiO₂ photoelectrode is employed for chlorine production, while Cu₂O is used for hydrogen generation. The dual photoelectrode system mimics the process of electrolytic seawater electrolysis, offering a promising alternative to conventional methods. Through linear sweep voltammetry, current–time tests, and electrochemical impedance spectroscopy, we demonstrate the effectiveness of this approach, supported by a detailed analysis of the energy band structure. Additionally, the material’s characteristics were verified using X-ray diffraction (XRD) and scanning electron microscopy (SEM). This work not only provides a safer and more efficient method for chlorine production but also highlights the potential of solar-powered photoelectrocatalysis in large-scale applications. These findings point toward a sustainable and environmentally friendly direction for chlorine production under simulated seawater conditions, with significant implications for renewable energy-driven industrial processes. Full article

Indirect combustion with the chemical looping combustion (CLC) of solid oxygen carriers is one of the most promising technologies for capturing carbon dioxide (CO₂) in energy production from fossil fuels since the separation of the generated CO₂ is inherent to the process itself. Therefore, the cost associated with capturing this gas will be significantly reduced. This technology transfers oxygen from air to fuel through a metal oxide that acts as an oxygen carrier, avoiding direct contact between air and fuel. This oxygen carrier circulates in a fluidized bed reactor called a reduction reactor and an oxidation reactor. (1) This research work has focused on evaluating the behavior of oxygen carriers based on the original and improved manganese mineral (copper-impregnated mineral) named for this study, OXMN009 and OXMN009P, respectively. (2) Equilibrium experiments were carried out on a thermogravimetric balance (TGA) to evaluate the kinetic behavior of these oxygen transporters OXMN009 and OXMN009P, using the gases methane (CH₄), carbon monoxide (CO), and hydrogen (H₂). (3) The enhanced solid oxygen carrier OXMN009P exhibited good performance for the CLC process with gaseous fuels in terms of reactivity and combustion efficiency, having high reactivity and oxygen transfer properties due to copper impregnation. (4) The results show that OXMN009P has comparable reactivity to other manganese-based materials reported in the literature. It may be an effective option for carbon dioxide capture, as it uses metal oxides as the oxygen transporters (TO). (5) These oxygen transporters, OXMN009 and OXMN009P, are used in a cyclic process that prevents the formation of nitrogen oxides by keeping the air and fuel separate. (6) Thermogravimetric balance (TGA) experiments were conducted to evaluate the kinetic behavior of these copper-modified oxygen transporters. (7) It was found that OXMN009P improved the reactivity and oxygen transfer properties due to copper impregnation. The kinetic parameters obtained in the TGA indicate that the reaction is non-thermal and requires less energy to initiate. (8) The results show that OXMN009P has reactivity comparable to other manganese-based materials reported in the literature and can be an effective option for carbon dioxide capture. Full article

Metal oxide nanoparticles (MONP/s) induce DNA damage, which is influenced by their physicochemical properties. In this study, the high-throughput CometChip and micronucleus (MicroFlow) assays were used to investigate DNA and chromosomal damage in mouse lung epithelial cells induced by nano and bulk sizes of zinc oxide, copper oxide, manganese oxide, nickel oxide, aluminum oxide, cerium oxide, titanium dioxide, and iron oxide. Ionic forms of MONPs were also included. The study evaluated the impact of solubility, surface coating, and particle size on response. Correlation analysis showed that solubility in the cell culture medium was positively associated with response in both assays, with the nano form showing the same or higher response than larger particles. A subtle reduction in DNA damage response was observed post-exposure to some surface-coated MONPs. The observed difference in genotoxicity highlighted the mechanistic differences in the MONP-induced response, possibly influenced by both particle stability and chemical composition. The results highlight that combinations of properties influence response to MONPs and that solubility alone, while playing an important role, is not enough to explain the observed toxicity. The results have implications on the potential application of read-across strategies in support of human health risk assessment of MONPs. Full article

We investigated the reducing rate of manganese oxides (MnOs) and organic matter in water by using pre-oxidation and coagulation/sedimentation methods with different chemicals. The reduction rate using NaOCl for organic matter was about 11%, while that of manganese was 12%. The reduction rate using chlorine dioxide (ClO₂) was only 7% for organic matter. However, the rate of manganese was 29% when using ClO₂. Potassium permanganate (KMnO₄) removed organic matter and MnOs more effectively, with a rate of 18 and 71%. Moreover, aluminum sulfate (Al₂(SO₄)₃), ferric chloride (FeCl₃), and polysilicate iron (PSI) worked more effectively, with a reduction rate of 99% and 55% for turbidity and organic matter. Full article

A manganese oxide-coated cylindrical graphite cathode with a zinc anode was developed to treat wastewater containing selenite in a dual-chambered microbial fuel cell. COD and selenite removal in the anodic chamber by Bacillus cereus with energy generation were evaluated in batch mode. A manganese dioxide-coated graphite cathode was tested for its surface morphology and chemical composition using scanning electron microscopy and dispersive energy analysis of X-rays. Compared to the non-coated graphite electrode, up to 69% enhancement was observed in the manganese dioxide-coated electrode voltage generation with 150 ppm selenite concentration. The fuel cell achieved a maximum power density of 1.29 W/m² with 91% selenite reduction and up to 74% COD (initial COD of 120 mg/L) removal for an initial selenite concentration from 100 to 150 ppm. The current study demonstrated the possibility of a modified cathode in enhancing energy generation and the use of microbial fuel cell technology to treat wastewater containing selenite. Full article

Heterogenized metalloporphyrin catalysts for oxidation reactions are extensively explored to improve chemical production. In this work, manganese meso-tetraarylporphyrins were immobilized on hydrated mesoporous titanium dioxide (S_BET = 705 m² g⁻¹) through carboxylate or phosphonate anchoring groups separated from the macrocycle by the 2-arylimidazole linker fused across one of the pyrrolic rings of the macrocycle. The element composition of two mesoporous hybrid materials thus obtained were investigated and the integrity of the immobilized complexes was shown by different physicochemical methods. Finally, the catalytic efficiency of the more stable material Mn(TMPIP)/TiO₂ with the phosphonate anchor was evaluated in the selective oxidation of sulfides to sulfoxides by molecular oxygen in the presence of isobutyraldehyde (IBA). The heterogenized complex has shown excellent catalytic activity exhibiting a turnover (TON) of ~1100 in a single catalytic run of the sulfoxidation of thioanisole. The catalyst was successfully reused in seven consecutive catalytic cycles. Full article

In this paper, the yeast wastewater secondary treatment effluent using catalytic odor oxidation treatment, using an orthogonal reaction experiment to determine the best reaction conditions, and the online monitoring of the pH, oxidation-reduction potential (ORP), and liquid ozone concentration monitoring, to the catalytic odor oxidation reaction, chemical oxygen demand (COD), and color removal effect were analyzed. The results showed that the optimal reaction condition for the advanced treatment of yeast wastewater by catalytic ozonation was accomplished with manganese dioxide used as the catalyst and a catalyst dose of 6 g·L⁻¹, pH of 12, and catalytic ozonation reaction time of 20 min. The COD was effectively reduced from 880 mg·L⁻¹ to 387 mg·L⁻¹ under this condition, the chroma was reduced from 700 times to 40 times, and these two parameters of the effluent could meet the standard of GB25462-2010. The real-time monitoring system showed that the whole reaction can be divided into two processes. The first 14 min was the indirect reaction of ozone and then the direct oxidation reaction of ozone. This process was further verified by the change trend of COD and the amount of ozone depletion by COD removal. The average ozone consumption levels of the two stages were 1.97 and 4.91 mgO₃·mgCOD⁻¹. This system can effectively monitor the reaction of the catalytic odor oxidation in the complex system to guide the effective use of ozone in practical engineering applications. Full article

Formaldehyde is an important downstream chemical of syngas. Furniture and household products synthesized from formaldehyde will slowly decompose and release formaldehyde again during use, which seriously affects indoor air quality. In order to solve the indoor formaldehyde pollution problem, this paper took the catalytic oxidation of formaldehyde as the research object; prepared a series of low-cost, acid-treated manganese dioxide nanorod catalysts; and investigated the effect of the acid-treatment conditions on the catalysts’ activity. It was found that the MnNR-0.3ac-6h catalyst with 0.3 mol/L sulfuric acid for 6 h had the best activity. The conversion rate of formaldehyde reached 98% at 150 °C and 90% at 25 °C at room temperature. During the reaction time of 144 h, the conversion rate of formaldehyde was about 90%, and the catalyst maintained a high activity. It was found that acid treatment could increase the number of oxygen vacancies on the surface of the catalysts and promote the production of reactive oxygen species. The amount of surface reactive oxygen species of the MnNR-0.3ac-6h catalyst was about 13% higher than that of the catalyst without acid treatment. Full article

Chemical warfare agents (CWAs) have inflicted monumental damage to human lives from World War I to modern warfare in the form of armed conflict, terrorist attacks, and civil wars. Is it possible to detect the CWAs early and prevent the loss of human lives? To answer this research question, we synthesized hybrid composite materials to sense CWAs using hydrothermal and thermal reduction processes. The synthesized hybrid composite materials were evaluated with quartz crystal microbalance (QCM) and surface acoustic wave (SAW) sensors as detectors. The main findings from this study are: (1) For a low dimethyl methyl phosphonate (DMMP) concentration of 25 ppm, manganese dioxide nitrogen-doped graphene oxide (NGO@MnO₂) and NGO@MnO₂/Polypyrrole (PPy) showed the sensitivities of 7 and 51 Hz for the QCM sensor and 146 and 98 Hz for the SAW sensor. (2) NGO@MnO₂ and NGO@MnO₂/PPy showed sensitivities of more than 50-fold in the QCM sensor and 100-fold in the SAW sensor between DMMP and potential interferences. (3) NGO@MnO₂ and NGO@MnO₂/PPy showed coefficients of determination (R²) of 0.992 and 0.975 for the QCM sensor and 0.979 and 0.989 for the SAW sensor. (4) NGO@MnO₂ and NGO@MnO₂/PPy showed repeatability of 7.00 ± 0.55 and 47.29 ± 2.69 Hz in the QCM sensor and 656.37 ± 73.96 and 665.83 ± 77.50 Hz in the SAW sensor. Based on these unique findings, we propose NGO@MnO₂ and NGO@MnO₂/PPy as potential candidate materials that could be used to detect CWAs. Full article

Persulfate (PS) is widely used to degrade emerging organic contaminants in groundwater and soil systems, and various PS activation methods (e.g., energy or chemical inputs) have been considered to increase oxidation strength. This study investigates PS activation through manganese amendment in the form of potassium permanganate (KMnO₄) and manganese dioxide (MnO₂) to subsequently degrade the emerging and recalcitrant groundwater contaminant 1,4-dioxane (1,4-D). The activation of PS by MnO₂ was confirmed by radical trap and by product formation. The degradation kinetics of 1,4-D by PS was also compared with varying amendments of KMnO₄ and MnO₂. The results showed that MnO₂ activated PS, which increased the degradation rate constant of 1,4-D. KMnO₄ activation of PS was not observed even though the binary oxidant mixture did enhance the degradation of 1,4-D. These results have implications for applying in situ chemical oxidation in subsurface systems, especially for conditions wherein manganese exists naturally in groundwater or aquifer minerals to support possible PS activation. Full article

2-Methylisoborneol (2-MIB) is one of the most commonly observed taste and odor (T&O) compounds present in drinking water sources. As it is biodegradable, a preservation agent, typically mercury chloride, is needed if the water is not analyzed right after sampling. Since mercury is a toxic metal, an alternative chemical that is cheaper and less toxic is desirable. In this study, two chemicals commonly used in water treatment processes, chlorine (as sodium hypochlorite) and KMnO₄ (potassium permanganate), are studied to determine their feasibility as preservation agents for 2-MIB in water. Preservation experiments were first conducted in deionized water spiked with 2-MIB and with chlorine or permanganate at 4 and 25 °C. The results indicate that 2-MIB concentrations in the water samples spiked with both chemicals remained almost constant within 14 days for all the tested conditions, suggesting that oxidation and volatilization did not cause the loss of 2-MIB in the system. The experiments were further conducted for three different reservoir water samples with 30–60 ng/L of indulgent 2-MIB. The experimental results demonstrated that preservation with permanganate may have underestimated the 2-MIB concentration in the samples as a result of the formation of manganese dioxide particles in natural water and adsorption of 2-MIB onto the particles. Chlorine was demonstrated to be a good preservation agent for all three tested natural waters since oxidation of 2-MIB was negligible and biodegradation was inhibited. When the residual chlorine concentrations were controlled to be higher than 0.5 mg/L on the final day (day 14) of the experiments, the concentration reduction of 2-MIB became lower than 13% at both of the tested temperatures. The results demonstrated that sodium hypochlorite can be used as an alternative preservation agent for 2-MIB in water before analysis. Full article

The residue from desulfurization and denitrification of exhaust gas treatment process with pyrolusite ore as absorbent is regarded as a potential source of iron and manganese. In this study, an extraction process is proposed for recovery of iron and manganese with ammonium sulphate roasting followed by sulphuric acid leaching. Firstly, the conversion mechanism was analyzed through mineral phase analysis of roasting products at different roasting temperature by means of X-ray diffraction (XRD) technology. Then, the parameters of the roasting procedure such as roasting temperature and time, ammonium sulphate dosage, leaching temperature, leaching time, and sulphuric acid concentration are examined. The results implicate that the iron oxide and manganese dioxide in the residue are firstly converted into the water-soluble ${\left({\mathrm{NH}}_4\right)}_3\mathrm{Fe}{\left({\mathrm{SO}}_4\right)}_3$ and ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Mn}}_2{\left({\mathrm{SO}}_4\right)}_3$ at 200–350 °C, and then the more stable ${\mathrm{NH}}_4\mathrm{Fe}{\left({\mathrm{SO}}_4\right)}_2$ and ${\mathrm{MnSO}}_4$ are formed, at temperature higher than 350 °C. Under optimum conditions, 95.2% Fe and 97.0% Mn can be extracted. Reactant diffusion through inert layer of silicon dioxide was considered as the rate-limiting step for iron extraction with an activation energy of 20.56 kJ/mol, while, the recovery process of Mn was controlled by both reactant diffusion and chemical reaction with an activation energy of 29.52 kJ/mol. Full article

This paper presents research on Fe and Mn removal from groundwater. In treatment systems of aeration followed by rapid filtration (no chemical dosage), manganese removal is possible due to the manganese dioxide catalyst present on the grains of filtration material. The goal of the presented research was to find a correlation between the catalyst layer’s composition as well as its internal porosity and the effectiveness and stability of manganese removal in the filtration process. In order to establish the influence of catalyst characteristics on manganese removal effectiveness, the filtration experiment was conducted using filtration materials with catalytic contact layers of different origin. Oxide coated auto-activated silica sand and Gabon manganese ore were tested. Inactive silica sand was used as reference. The results of filtration experiments were combined with analyses of chemical composition, internal porosity, and crystalline parameters of catalyst contact layers of grains. For the determination catalyst contact layer parameters, the following methods were used: Raman spectroscopy, X-ray powder diffractometry (XRD), Scanning Electron Microscope – Energy dispersive spectroscopy (SEM-EDAX), nitrogen adsorption. Pilot scale research on the filtration process demonstrated that auto-activated filtration material was characterized by the highest efficiency of manganese removal and stability of effects during the whole research. The effectiveness of Gabon manganese ore dropped from 90% and stabilized on the level of ca. 60% within 15 days of the experiment. Full article

In this work, we present the electrochemical deposition of manganese dioxide (MnO₂) thin films on carbon-coated TiN/Si micro-pillars. The carbon buffer layer, grown by plasma enhanced chemical vapor deposition (PECVD), is used as a protective coating for the underlying TiN current collector from oxidation, during the film deposition, while improving the electrical conductivity of the stack. A conformal electrolytic MnO₂ (EMD) coating is successfully achieved on high aspect ratio C/TiN/Si pillar arrays by tailoring the deposition process. Lithiation/Delithiation cycling tests have been performed. Reversible insertion and extraction of Li⁺ through EMD structure are observed. The fabricated stack is thus considered as a good candidate not only for 3D micorbatteries but also for other energy storage applications. Full article