MnO2 Particles Research Articles

The effect of hydrothermal aging on Mn2O3/Cu-SSZ-39 composite catalysts for selective catalytic reduction of NOx by NH3

The latest generation of fuel-efficient engines produces exhaust at cooler temperatures, highlighting a need for enhancement in the low-temperature effectiveness of Cu-zeolite catalysts. The metal oxide/Cu-zeolite composite catalysts have demonstrated superior deNOx performance at lower temperatures compared to Cu-zeolite alone. However, the hydrothermal stability of these composite catalysts remains unexplored. In this study, we focus on the Mn2O3/Cu-SSZ-39 catalyst, chosen for its exceptional activity at low temperatures. The synergy between the nitrate groups on Mn2O3 and NH4+ ions on the Brønsted acid sites of Cu-SSZ-39 enhances NOx conversion efficiency. Nonetheless, the efficiency of Mn2O3/Cu-SSZ-39 diminishes following exposure to hydrothermal conditions at various temperatures (700 °C, 750 °C, and 800 °C), with the degradation degree intensifying at higher temperatures. Characterization studies revealed that hydrothermal treatment leads to the recrystallization of Mn2O3 particles, which reduces the content of active adsorbed oxygen. This reduction impedes the formation of active bridged nitrates in the aged catalysts and disrupts the SCR pathway through the interaction between bridged nitrates and NH4+ on the composite catalysts. Despite these challenges, some adsorbed oxygen remains on the Mn2O3/Cu-SSZ-39 after aging, ensuring that the aged composite catalyst still exhibits higher activity than the fresh Cu-SSZ-39 catalyst. This observation suggests that there is potential for the application of Mn2O3/Cu-SSZ-39 in practical scenarios.

Characterization and Cellular Toxicity Studies of Commercial Manganese Oxide Nanoparticles.

Manganese oxide nanoparticles (MnOx NPs) are finding applications in several environmentally important areas such as farming and energy storage. MnOx NPs span a range of metal oxidation states that open up a wide range of applications in catalysis as well. As a result, it is important to understand how such materials can impact human health through incidental exposure. In this study, we examined a range of commercially available Mn2O3 NPs and compared our characterization data to those supplied by manufacturers. Discrepancies were noted and then measured values were used to assess the biological impact of these materials on three mammalian cell lines-A549, HepG2 and J774A.1 cells. Cell toxicity assays showed that all Mn2O3 particles exhibited cytotoxic effects that may be correlated, at least in part, to the production of reactive oxygen species. All eight nanoforms also activated caspase 3 but not caspase 1, although the magnitude of these changes varied greatly between materials.

Catkin-derived carbon microtubes for hybrid anode materials of high-performance lithium ion batteries

As a common biological waste, catkin shows negligible economic value and is hazardous to the environment and human respiratory health. To turn waste into treasure, in this work, a hybrid anode is successfully prepared by using the catkin-derived 1D hollow carbon microtube as dispersing agents to well disperse the MnO particles via a simple one-step pyrolysis method. Benefiting from the high electrical conductivity and hollow microtubule structure of the catkin-derived carbon, as well as the evenly dispersion of the MnO particles and the interfacial energy storage of Mn0/Li2O interfaces, the lithium ion battery based on the resultant MnO/C hybrid anode exhibits outstanding rate performance (high reversible specific capacity of 1365 mAh g−1 at a current density of 0.1 A g−1 and maintains 451 mAh g−1 even at a high current density of 6.4 A g−1) and superior cycling stability (retains ∼100 % after 1000 cycles at a current density of 0.8 A g−1). This work conforms to the development concept of green environmental protection and realizes the unity of economic and social benefits.

Dispersed MnO2 nanoparticles/sugarcane bagasse-derived carbon composite as an anode material for lithium-ion batteries.

Bagasse-derived carbon electrodes were developed by doping with nitrogen functional groups and compositing with high-capacity MnO2 nanoparticles (MnO2/NBGC). The bagasse-derived biochar was N-doped by refluxing in urea, followed by the deposition of MnO2 nanoparticles onto its porous surface via the hydrothermal reduction of KMnO4. Different initial KMnO4 loading concentrations (i.e. 5, 10, 40, and 100 mM) were applied to optimize the composite morphology and the corresponding electrochemical performance. Material characterization confirmed that the carbon composite has a mesoporous structure along with the dispersion of MnO2 nano-particles on the N-containing carbon surface. It was found that the 5-MnO2/NBGC sample exhibited the highest electrochemical performance with a reversible capacity of 760 mA h g-1 at a current density of 186 mA g-1. It delivered reversible capacities of 488 and 390 mA h g-1 in cycle tests at 372 and 744 mA g-1, respectively, for 150 cycles and presented good reversibility with nearly 100% coulombic efficiency. In addition, it could exert high capacities up to 388 and 301 mA h g-1 even under high current densities of 1860 and 3720 mA g-1, respectively. Moreover, most of the prepared composite products showed high rate capability with great reversibility up to more than 90% after testing at a high current density of 3720 mA g-1. The great electrochemical performance of the MnO2/NBGC nanocomposite electrode can be attributed to the synergistic impact of the hierarchical architecture of the MnO2 nanocrystals deposited on porous carbon and the capacitive effect of the N-containing defects within the carbon material. The nanostructure of the MnO2 particles deposited on porous carbon limits its large volume change during cycling and promotes good adhesion of MnO2 nanoparticles with the substrate. Meanwhile, the capacitive effect of the exposed N-functional groups enables fast ionic conduction and reduces interfacial resistance at the electrode interface.

2D carbon-supported MnO@C nanoparticles for high capacity and long life lithium-ion battery anode enabled by a relatively green and facile method

MnO is regarded as a promising alternative anode for lithium-ion batteries (LIBs) due to its large specific capacity. Nonetheless, low intrinsical conductivity and large volumetric change of the MnO anode cause fast capacity fading during cycle, and hence its practical use in LIBs is hindered. In spite of many effective solutions for above problems, most of them involve requirement of harmful chemicals or special equipments, are not conducive to development of MnO anode. Herein, a relatively green and facile method is demonstrated to prepare a two dimensional (2D) MnO/C composite (MnO NPs@C Ps), consisting of carbon-coated MnO nanoparticles anchored on 2D carbon plates. The results confirm outstanding electrochemical performances of the MnO NPs@C Ps anode in terms of high capacities and ultra-long lifespan, with 1046.8 mA h g−1 after 500 cycles at 200 mA g−1 as well as 463 mA h g−1 after even 1500 cycles at 1000 mA g−1. The combination of the materials and electrochemical characterizations demonstrates that the rational synergistic effects of nano-sized MnO particles and 2D carbon support contribute to thus outstanding electrochemical performances of the MnO NPs@C Ps anode. It is believed that this work may provide a meaningful insight into development of other advanced metal oxides/carbon composite anodes.

Synthesis of Multifunctional Mn3O4-Ag2S Janus Nanoparticles for Enhanced T1-Magnetic Resonance Imaging and Photo-Induced Tumor Therapy.

The global burden of cancer is increasing rapidly, and nanomedicine offers promising prospects for enhancing the life expectancy of cancer patients. Janus nanoparticles (JNPs) have garnered considerable attention due to their asymmetric geometry, enabling multifunctionality in drug delivery and theranostics. However, achieving precise control over the self-assembly of JNPs in solution at the nanoscale level poses significant challenges. Herein, a low-temperature reversed-phase microemulsion system was used to obtain homogenous Mn3O4-Ag2S JNPs, which showed significant potential in cancer theranostics. Structural characterization revealed that the Ag2S (5-10 nm) part was uniformly deposited on a specific surface of Mn3O4 to form a Mn3O4-Ag2S Janus morphology. Compared to the single-component Mn3O4 and Ag2S particles, the fabricated Mn3O4-Ag2S JNPs exhibited satisfactory biocompatibility and therapeutic performance. Novel diagnostic and therapeutic nanoplatforms can be guided using the magnetic component in JNPs, which is revealed as an excellent T1 contrast enhancement agent in magnetic resonance imaging (MRI) with multiple functions, such as photo-induced regulation of the tumor microenvironment via producing reactive oxygen species and second near-infrared region (NIR-II) photothermal excitation for in vitro tumor-killing effects. The prime antibacterial and promising theranostics results demonstrate the extensive potential of the designed photo-responsive Mn3O4-Ag2S JNPs for biomedical applications.

Efficient separation of Li and Mn from spent LiMn2O4 cathode materials by NH4HSO4 reduction roasting-selective ammonia leaching

With the imminent peak in the retirement of rechargeable lithium-ion batteries worldwide, the development of efficient methods for recycling valuable elements from LIBs has attracted considerable attention. In this work, a novel method of NH4HSO4 reduction roasting-selective ammonia leaching was proposed to thoroughly separate Li and Mn from the spent LiMn2O4 cathode materials. Using the TG-DSC-FTIR, XRD, SEM-EDS and ICP methods, the detailed mechanism of reduction roasting process was revealed, showing that the Mn4+ and Mn3+ in the spinel structure of LiMn2O4 were reduced by the NH4+ from the molten ammonium salt, and transformed into water-soluble MnSO4 and Li2Mn2(SO4)3. According to the water-leaching performance of the roasting products, the sulfation conversion rate of Mn reaches 98.1 %, while Li is almost completely transformed under the optimal roasting conditions (475 ℃, 60 min). Using the NH3·H2O-air leaching-system, complete separation of Li and Mn can be achieved. It was shown that the introduction of air into the ammonia solution at a rate of 0.2 L/min under the optimal leaching condition leads to Mn precipitation in the form of nanoscale Mn3O4 particles with a precipitation rate of over 99.99 %, while Li still remains completely leached. Based on the in situ detection of the oxidation reduction potential and pH during the selective leaching, the key mechanism of efficient Mn precipitation was revealed. that is, the increasing potential accelerates the oxidation of Mn(OH)2, and the rapid consumption of Mn(OH)2 promotes the hydrolysis of Mn2+, thereby achieving a significant improvement in the separation efficiency of Li and Mn.

Reversible MnO to Mn3 O4 Oxidation in Manganese Oxide Nanoparticles.

Manganese is an attractive element for sustainable solutions. It is largely available in the earth's crust, making it ideal for cost-effective and large-scale applications. Especially MnO nanoparticles have recently received attention for applications in battery technology. However, manganese has many oxidation states that are energetically very similar, indicating that they may easily transform from one to the other. Herein, the reversible oxidation of MnO nanoparticles to Mn3 O4 studied with in situ transmission electron microscopy is shown. The oxygen sublattices of MnO and Mn3 O4 are found to be perfectly aligned, and an atomic mechanism where the transformation is facilitated by the migration of Mn cations on the shared O sublattice is proposed. Even when protected with an amorphous carbon layer, MnO particles are highly unstable and oxidize to Mn3 O4 in ethanol. The poor stability of MnO lacks discussion in many battery-related works, and strategies aimed at avoiding this should be developed.

Robust iron-doped manganese oxide nanoparticles from facile fabrication to photo-catalytic degradation application of binary dyes mixture

The manganese oxide (MnO2 and iron-doped manganese oxide (Fe–MnO2) nanoparticles (NPs) with reduced band gap (Eg) were fabricated through the co-precipitation process. They used to degrade Indigo Carmine (IC) and Rhodamine B (RB) binary mixture in an aqueous medium under solar light irradiation. From FT-IR, the twisting modes of the Mn–O bond and the stretching vibrations of the Fe–Mn–O2 bond were confirmed from the peaks observed at 480 cm−1,584 cm−1,675 cm−1, and 900 cm−1, 1150 cm−1, and 1200 cm−1 respectively. The MnO2 has an optical band gap of 3.2 eV, which was decreased to 3 eV in Fe–MnO2. The zero charge (PZC) point was 8 for Fe–MnO2 and 7 for MnO2. The BET surface area for Fe–MnO2 was 398 m2/g, relatively higher than MnO2 particles, having a surface area of 384 m2/g. The average crystallite sizes calculated from Scherer formulae were 37 nm for MnO2 and 31 nm for Fe–MnO2 NPs. SEM confirmed the irregular morphology of the prepared particles. It was analyzed that agglomeration occurs in MnO2 than the Fe–MnO2. The maximum degradation of IC dye was 99%, and that of RB was 98% at the optimum conditions. The data were best fitted to second-order kinetics.

Thermal stability of AlCrO antireflection layer for high-temperature cermet-based solar selective absorber applications

Highly stabled antireflection layers play a crucial role in enhancing the optical and thermal performance of cermet-based solar selective absorbing coatings. Few state-of-the-art antireflection layers are qualified for high-temperature (>873 K) utilizations due to the insufficient thermal stability and increased infrared emissivity. Herein, a highly stable multilayer cermet-based absorber with an AlCrO antireflection layer is developed using cathode arc ion plating. The deposited coating exhibits a solar absorptivity of 0.908 ± 0.005 and a thermal emissivity of 0.144 ± 0.004 even after annealing at 923 K for 2000 h in air, compared to the pristine coating with a spectral selectivity of 0.898 ± 0.002/0.186 ± 0.003. After undergoing the extensive annealing treatments, abundant particles with an average size of approximately 8 μm have been detected on the coating surface. However, the AlCrO layer exhibits a remarkably flawless and dense surface topography devoid of any cracks or voids. Based on the GI-XRD and TEM evaluations, the particles have been identified as Mn2O3 nanocrystals. The formation of Mn2O3 particles originates from the diffusion of Mn atoms from the stainless-steel substrate to the surface of the AlCrO layer, where they undergo oxidation. The presence of Mn2O3 can enhance the solar absorptivity by increasing transmittance in the visible light spectrum and reduce the emittance by enhancing reflection of infrared radiation. Then, the impact of Mn2O3 on spectra selectivity and thermal stability is discussed. These results indicate that the AlCrO layer exhibits remarkable durability when subjected to high-temperature annealing in an air environment, thereby significantly enhancing the thermal stability and optical performance of cermet-based solar selective absorbing coatings. These findings suggest that the AlCrO layer exhibits exceptional durability under high-temperature annealing in an air environment, thereby significantly enhancing the thermal stability and optical performance of cermet-based solar selective absorbing coatings.

Energy storage investigation on regenerated graphite-metal oxide composites from end-of-life LIBs and promising for a closed-loop approach

Different metal oxide/graphite composite materials (TiO2/regenerated graphite (RG) and MnO2/RG) were prepared with use of RG from fatigued lithium-ion batteries. The regeneration of spent graphite was done via acetic acid treatment, and the graphite/metal oxide composite was prepared by an ultrasonication route. The structural properties of the as-prepared composite materials are effectively influenced by the introduction of TiO2 and MnO2 particles as evidenced by the variation in the intensity of the diffraction peaks and the appearance of new peaks. The decoration of graphite flakes with metal oxide particles is demonstrated by morphological and mapping analysis. The optimum concentration of MnO2 particles is found to be 10 wt% in a graphite framework and results in good functional properties when compared with RG and a TiO2/RG composite. Finally, the optimized 10 wt% MnO2/RG composite displays excellent charge storage of 184 F/g in 1 M KOH electrolyte, which is greater than for the other graphite composite samples. The impact of MnO2 productively contributes to the excellent capacitance of graphite, which is due to greater grain conductivity, thus reducing the charge transfer resistance and providing a large contact area for storage of ions. As a result of this, a 10 wt% MnO2/RG-based symmetric supercapacitor shows the greatest electrochemical storage, which is 36.78 F/g. Therefore, as-prepared MnO2/RG composite has great prospects for upcoming advanced charge storage devices and supports the re-fabrication of waste material as well as a closed-loop approach.

A Kinetic Study on the Preparation of Al-Mn Alloys by Aluminothermic Reduction of Mn3O4 and MnO Powders

The study of aluminothermic reduction in manganese compounds is a complex challenge in preparing Al-Mn alloys. The primary objective of this study was to ascertain the activation energy values for the aluminothermic reduction of MnO and Mn3O4 oxides derived from alkaline batteries. The study melted aluminum found in beverage cans and utilized the technique of powder addition with mechanical agitation. The kinetics of the reaction were studied under the effects of temperature (750, 800, and 850 °C), degree of agitation (200, 250, and 300 rpm), and the initial concentration of magnesium in molten aluminum (1, 2, 3, and 4% by weight). Kinetic measurements for Mn3O4 particles suggest a reaction mechanism that occurs in stages, where manganese undergoes oxidation states [Mn+3] to [Mn+2] until it reaches the oxidation state Mn0, which allows it to dissolve in the molten aluminum, forming alloys with up to 1.5 wt.% of Mn. Therefore, the kinetic of the aluminothermic reduction of MnO is described by the geometric contraction model, while the mechanism of Mn3O4 reduction occurs in two stages: geometric contraction, followed by an additional stage involving the diffusion of chemical species to the boundary layer. In addition, this stage can be considered a competition between the formation of MnO and the chemical reaction itself.

Effect of Mn addition on the tellurium embrittlement resistance of GH3535 alloy

The effect of Mn addition on the tellurium (Te) corrosion and Te embrittlement resistance have been systematically investigated by comparing the standard GH3535 alloy and high-Mn one. After corroded in Te vapor at 700 °C, the more MnTe and (Cr, Mn)3O4 particles are formed on the surface in the high-Mn alloy than that in standard one. The high-Mn alloy possesses more MnTe particles at the grain boundaries near the surface. In the standard alloy, the Te mainly exist in the form of segregation at grain boundaries, and the distribution depth is more than that of MnTe in high-Mn alloy. The tensile tests indicated that the high-Mn alloy exhibits the higher ultimate tensile strength and elongation than the standard one in the corroded state. The deeper intergranular cracks can be observed from the gauge of tensile speicmens of standard alloy. These facts proved that the high-Mn alloy is more resistant to Te embrittlement. By connecting the corrosion and embrittlement behaviors, it can be concluded that Te embrittlement can be significantly improved by transforming the Te segregation into the intergranular MnTe tellurides. Our study provides one new protection strategy for the tellurium embrittlement of alloys, which seems to be more applicable to the harsh service environment.

Alleviating Manganese – Vanadium Redox Flow Batteries for Energy Storage and Subsequent Hydrogen Generation

Dual-circuit redox flow batteries (RFBs) consist of two discharging modes which has the potential to store energy beyond the capacity of the electrolytes in the form of hydrogen generation [1-3]. Inspired from the recent exploratory study by Reynard and Girault et al., this work focuses on utilizing Mn3+/Mn2+ (RFB catholyte ~ 1.51 V vs. SHE) in conjunction with V3+/V2+ (RFB anolyte ~ −0.26 V vs. SHE) as indirect redox mediators to drive mediated electrolysis of water in spatially separated external catalytic reactors [3]. The advantage of an additional layer to existing RFB is that a fully charged battery could potentially be chemically discharged particularly when green electricity is available in abundance to provide a secondary resource for energy such as hydrogen gas or other value-added commodity chemicals. However, Mn3+ is prone to rapid chemical disproportionation yielding Mn4+ which precipitates as MnO2(s) particles in acidic media, responsible for severe capacity fade during cycling. Studies in the literature suggest that oxygen scavenging additives such as V5+ is possibly the best defense mechanism to prevent MnO2 formation [4].In this study, the electrochemical behavior of Mn3+/Mn2+ couple in the favorable presence of V5+ is elucidated using cyclic voltammetry and ionic speciation diagrams. The voltammograms obtained under systematically varied conditions provide direct experimental evidence for competing redox reactions at the electrode surface. Nonetheless, the response measured from a macroelectrode mainly describes the quasi reversibility of the redox couple and gives little insight on electrode-electrolyte interface phenomenon. To obtain a more detailed picture of the diffusion layer, we employ carbon disk ultramicroelectrode (UME) for in-depth qualitative analysis. We anticipate that any deviation from the sigmoidal shape is an indication of a growing diffusion layer due to MnO2 passivation on the surface of electrode. Lastly, galvanostatic charge discharge profiles are obtained for Mn-V based redox flow battery with an aim to reveal the optimum state of charge because there exists a trade-off between the extent of Mn disproportionation within RFB during energy storage mode and volume of hydrogen gas produced during secondary mode. The knowledge obtained throughout the study will provide a fundamental understanding required for the rational design and development of aqueous electrochemical flow systems using Mn as the redox active species. Peljo, P., et al., All-vanadium dual circuit redox flow battery for renewable hydrogen generation and desulfurisation. Green Chemistry, 2016. 18(6): p. 1785-1797. Piwek, J., et al., Vanadium-oxygen cell for positive electrolyte discharge in dual-circuit vanadium redox flow battery. Journal of Power Sources, 2019. 439: p. 227075. Reynard, D. and H. Girault, Combined hydrogen production and electricity storage using a vanadium-manganese redox dual-flow battery. Cell Reports Physical Science, 2021: p. 100556. Reynard, D., et al., Vanadium-Manganese Redox Flow Battery: Study of MnIII Disproportionation in the Presence of Other Metallic Ions. Chemistry - A European Journal, 2020. 26.

Application of sawdust particles modified by in situ surface polymerization of m-phenylenediamine and its by-product: Batch and continuous removal of Cr(VI)

The primary objective of this research was to synthesize an adsorbent for Cr(VI) removal using a simple synthesis method that involved the use of KMnO4 for the surface activation of sawdust in which the polymerization of m-Phenylenediamine (mPD) can take place directly on the surface of the adsorbent. The adsorbent's surface morphology was assessed using various techniques including FESEM, EDS, FT-IR, and XRD. The optimal adsorbent was prepared by synthesizing different adsorbents under various KMnO4/sawdust and PmPD/sawdust mass ratios and the best performance was obtained at ratios of 1 and 0.6 respectively. Batch experiments were conducted at optimal conditions (pH = 2, adsorbent dosage of 2 g L−1, contact time of 50 min) and removal efficiency of 90.28% was achieved at a Cr(VI) concentration of 100 mg L−1. The Langmuir isotherm model provided the most accurate fitting to the experimental data, resulting in the maximum adsorption capacity of 62.11 mg g−1. The interparticle diffusion model presented the most precise fitting to the experimental values. The positive value ΔH° and negative values ΔG° prove that the adsorption reactions are endothermic and spontaneous. To assess the effectiveness of PmPD/MnO2/sawdust in removing Cr(VI) at dynamic scales, column experiments were carried out at various flow rates and initial Cr(VI) concentrations. Also, the MnO2 particles obtained after the oxidation of sawdust were functionalized using the mentioned process, and the value of adsorption capacity was determined as 270.27 mg g−1. The easy separation, and full-scale applicability showed a promising application of sawdust/MnO2/PmPD for Cr(VI) removal from aquatic environments.

The Analysis of Lithium Diffusion in the Cathode Material Particles of Primary Lithium-Manganese Cells by Measuring Electrochemical Noise and Magnetoresistance Relaxation.

The process of lithium diffusion in the cathode material of lithium-manganese chemical power sources (CPS) after a short-term discharge are analyzed by an analyzing of the relaxation parameters of electrochemical noise and the magnitude of the magnetoresistance of the layer of injected lithium. It is shown that fluctuations in the diffusion flow of lithium are the source of electrochemical noise in such CPS. The data obtained also confirm the assumption made in the literature about the formation of a poorly conducting phase with a spinel crystal structure during the discharge of an element in the surface layer of MnO2 particles, which inhibits the diffusion process.

Orthorhombic (Ru, Mn)2O3: A superior electrocatalyst for acidic oxygen evolution reaction

The development of efficient oxygen evolution reaction (OER) electrocatalysts is of vital importance for acidic water decomposition. Currently, the rutile structured RuO2 is considered to be the best candidate and has been studied widely. However, the state-of-the-art rutile RuO2 still suffers from unsatisfactory activity and stability, while other crystalline structures of Ru-based oxides are seldom reported as OER electrocatalysts. The present work, for the first time, successfully synthesizes orthorhombic (Ru, Mn)2O3 electrocatalyst through cation exchange. The orthorhombic (Ru, Mn)2O3 particles exhibit the outstanding electrocatalysis performance as OER electrocatalyst, showing an ultralow overpotential of 168 mV at 10 mA cm−2 in acidic water and good stability in 40 h of OER. The outstanding electrocatalysis performance is attributed to the distinct Ru d-band structure together with the larger surface density of Ru active site, which reduces the free energy of the rate-limiting step during OER.

First-principles molecular dynamics simulation study on Ti/Mn ions in aqueous sulfuric acid for use in redox flow battery

The effect of the Ti4+ ion on the structural and chemical features of the Mn3+ ion in aqueous sulfuric acid was investigated using first-principles molecular dynamics (FPMD) simulation and second-order perturbation theory (CASPT2) with a complete active space self-consistent field (CASSCF) reference function. The focus was on the role of the Ti ion in the MnO2 formation reaction from the Mn3+ ion. The simulations showed that Mn3+ forms two types of complexes, [Mn(H2O)4(SO4)2]1− and [Mn(H2O)6]3+ in aqueous sulfuric acid with Ti ions where the population of the former was found to be higher than that of the latter. We found that when the HSO4− ion was coordinated to a Ti4+ ion, it released one proton, which increases proton concentration in the solution. Detailed quantum chemical calculations on the isolated Mn complexes show that if the Mn complexes interact with a hydronium ion, the stability of Mn3+ ion is increased to a large extent. Such a result implies that the increased local proton concentration due to Ti4+ ions hinders formation of MnO2 particle.

Preparation of a Novel Formaldehyde-Free Impregnated Decorative Paper Containing MnO2 Nanoparticles for Highly Efficient Formaldehyde Removal.

The loading of catalytic manganese dioxide (MnO2) nanoparticles onto an impregnated decorative paper has been an effective method for the removal of indoor formaldehyde (HCHO) pollutants. However, its preparation can present numerous challenges, including instability in dipping emulsions and leaching. In this investigation, a novel and stable formaldehyde-free polyacrylate dipping emulsion containing MnO2 particles was prepared and then back-coated on a decorative paper. To improve the dispersion and fixation, the MnO2 was modified with silane. HCHO can undergo physical adsorption on the cellulosic fibers present in the paper, while it can also undergo chemical degradation into CO2 within the MnO2 groups. The silane not only enhanced the interfacial adhesion to a polyacrylate resin but also increased the interlayer distance, thereby creating a larger space for HCHO absorption. The impregnated decorative paper back-coated with 10 wt % of silane-modified MnO2 exhibited a removal efficiency of approximately 90% for HCHO at 20 °C. The removal rate further improved to approximately 100% when the temperature was increased to 60 °C. Moreover, it is worth noting that the release of volatile organic compounds was exceptionally minimal. Additionally, the particleboard bonded with this impregnated decorative paper exhibited an extremely low emission of HCHO, with a value that approached 0 mg·L-1. Furthermore, the bonding strength of the surface remained unaffected. Therefore, this study provides a simple and eco-friendly method for effectively removing HCHO, which can enhance indoor air quality.

Effect of Oxide Presence in Activated Carbon on Arsenic Removal

This study investigated the effect of oxides on the removal of As when present in simple mixtures with granular activated carbon (GAC) particles. The performance of these mixtures was compared with other reported GAC-based adsorbents. A standard curve for ultraviolet adsorption vs. As concentration was obtained using the silver diethyldithiocarbamate (SDDC) method to evaluate various samples. A preliminary study was carried out to find the optimal conditions for experiments. For 50 mL samples with 2.35 ppm As, the optimal values of pH, adsorption time, and amount of adsorbent were pH 7, 30 min, and 50 mg, respectively. The ratio between the amount of adsorbent and well water in this study showed a superior As adsorption capacity (1 g/L, 2.1 mg/g) compared to similar adsorbents reported previously (12.5 g/L, 1.0-1.4 mg/g). Among the adsorbents, KOH-treated AC-Mn3O4 exhibited the best performance in As removal with an efficiency of ~95%. The oxide particles had a synergistic effect with GAC on As removal. This was primarily due to the change in the potential of partially agglomerated nano Mn3O4 particles on the ACK surface. The influence of the surface area of the adsorbents was not pronounced. All results were explained in terms of microstructure, specific surface area, and zeta potential. This finding could be extended to other activated carbons (AC) obtained from different sources.