Mn Loading Research Articles

Effect of Mn loading onto hydroxyapatite supported Mn catalysts for toluene removal: Contribution of PCA assisted ToF-SIMS

A series of hydroxyapatite (Hap; of ideal formula: Ca10(PO4)6(OH)2) supported MnOx materials (MnxHap; x=Mn wt.%:2.5, 5.0, 10, 20, and 30 based on MnO2) has been tested prepared by wet impregnation using manganese (II) nitrate tetrahydrate as metal precursor followed by calcination at 400°C in toluene total oxidation (800 ppmv in dry air) at 220°C for 40h. It was shown that the fresh catalysts can be ranked as follow by decreasing activity: Mn5Hap > Mn2.5Hap > Mn10Hap > Mn20Hap > Mn30Hap and that Mn10Hap exhibited the best resistance to deactivation. Investigation of the surface state of the fresh and used MnxHap catalysts has been performed using X-ray photoelectron spectroscopy (XPS) and principal component analysis (PCA) assisted static time-of-flight secondary-ion mass spectrometry (ToF-SIMS). Based on the XPS results a Mn speciation scheme can be proposed: initial incorporation of Mn2+ into Hap (2.5wt% Mn) followed by additional well dispersed oxidized manganese species on Hap (5–10wt% Mn) to end up with the formation Mn2O3/ε-MnO2 particles detected by XRD (20–30wt% Mn). Principal components analysis (PCA) has been applied to the (+) ToF-SIMS spectra taking into account of all the detected significant manganese containing secondary ions. PC1 (75% of the variance) discriminates well the fresh and used samples in a similar way and was related to the surface manganese content. The resulting volcano plot obtained by plotting PC2 (12% of the variance) as a function of the resistance to deactivation discriminates the catalysts in the same way as depicted in the PC2 score plot. Consequently also taking into account of the PC2 loading plot it was suggested that a redispersion of Mnn+/Ca2+ takes place with time on stream preferentially for MnxHap (x=5–10wt%) improving their catalyst stability.

Indoor Dust Metal Loadings: A Human Health Risk Assessment

In order to characterize the influence of environmental factors in dust metal loadings inside homes in an urban environment and to evaluate the associated potential health risks, samples of settled indoor dust from 10 apartments in the urban area of Madrid (Spain) were collected with wet wipes. Cd, Cr, Cu, Pb, Zn, Ni, and Mn loads were determined by Atomic Absorption Spectroscopy (AAS) after a HNO3 + H2O2 digestion. The environmental factors evaluated were load distribution between rooms, number of residents, presence of smokers, traffic intensity, apartment elevation, and frequency of house cleaning. Tukey’s range test and stepwise multiple linear regression analysis revealed that metal dust loadings present two prevailing origins: (1) They present higher loadings in the entry hall, which suggest that dust is tracked indoors adhered to footwear and clothing and (2) they arise from tobacco smoking. Significant correlations were also observed between metal loadings and traffic intensity (Cr), number of residents (Cr, Pb, and Cu), number of days between cleaning (Ni), and flat height (Mn). A human health risk assessment considering a mechanistic hand-to-mouth model for dust ingestion and dermal absorption revealed that urban children are not expected to develop adverse health effects from exposure to trace elements in household dust. The contribution of this exposure scenario to the overall received dose should be included when assessing the background exposure of children to trace elements. A more precise assessment should attempt to reduce the significant uncertainty of the risk model output associated with estimates of exposure variables, deposition rates, and metal bioaccessibility.

Effect of annealing and process parameters on microstructure and properties of DC Magnetron Sputtered Ni-Zr alloy thin films

Ni-Zr alloy thin films were processed by DC magnetron sputtering of high purity Ni and Zr targets in ultrahigh vacuum at ambient temperature, with the substrate being subjected to either 0 V or -60 V bias. Some of the as-deposited films were annealed in vacuum at 700°C for 1 h. Surface profilometer and atomic force microscope were used to measure the film thickness and surface roughness, respectively. X-ray diffraction and cross-sectional TEM analysis have shown dispersion of nano-sized Ni3Zr dispersed in nanocrystalline Ni matrix. Nano-indentation and scratch tests conducted at 2 mN load have shown variation of hardness, Young’s modulus, scratch resistance, and coefficient of friction with substrate bias and annealing due to changes in grain size and surface roughness.

Manganese-rich MnSAPO-34 molecular sieves as an efficient catalyst for the selective catalytic reduction of NO x with NH3: one-pot synthesis, catalytic performance, and characterization.

Manganese-rich MnSAPO-34 molecular sieves were prepared by one-pot synthesis method for NO x abatement using the ammonia-selective catalytic reduction (NH3-SCR) technology and characterized using ICP, BET, XRD, FE-SEM, H2-TPR, NH3-TPD, XPS, and DR UV-Vis analyses. The experimental results indicate that the Mn content and chemical state, as well as the surface acidity, of the MnSAPO-34 molecular sieves significantly enhance their DeNO x efficiency at low temperatures (ca. 200-300°C). The manganese-rich MnSAPO-34 was synthesized using a combination of triethylamine and diisopropylamine as the structural directing agents and high Mn loading (n(MnO)/n(P2O5)=0.4). The resulting catalyst exhibits the highest activity among all of the samples with a NO x conversion value of nearly 95% and a N2 selectivity that is higher than 90% at 220-400°C. In addition, this catalyst presents higher NO x conversion than the conventional V2O5-WO3/TiO2 catalysts and other SAPO-based catalysts below 300°C. Furthermore, the analytical results indicate that the manganese species in the catalyst are mainly in the form of a framework Mn(IV), which could play a significant role in the NH3-SCR process as the specific active species. The results suggest that controlling the types and content of the organic amine templates and variations in the surface acidity of the catalysts may significantly enhance the SCR activity at lower temperatures.

Removal of NOx in the presence of oxygen over Mn/BaO/Al2O3 catalysts.

In this study, the influence of Mn content on the NOx decomposition in the presence of oxygen over xMn/BaO/Al2O3 catalysts (x is molar ratio of Mn/Ba) was investigated. Samples were characterized by N2 adsorption, XRD and SEM-EDX. The Mn loading, the dispersion of Ba on the surface and the BET surface area are the key factors affecting the NOx removal activity of the catalysts. The maximum conversion of NOx was obtained with 0.5 MnBa/Al sample. Lower and higher Mn loading resulted in a significant loss of the overall efficiency of NOx conversion. The lower NOx conversion at lower Mn loading (x=0.1) demonstrated that oxide manganese is the catalyst active site. The loss in efficiency observed at higher Mn loading is attributed to the lower dispersion of Ba on the surface, which could decrease the NOx storage ability, and the lower BET surface. There is no NOx conversion on support γ-Al2O3 or Ba/γ-Al2O3.

Removal of phenol from oil/gas produced water using supercritical water treatment with TiO2 supported MnO2 ctalyst

MnO2 catalyst supported on TiO2 was synthesized and evaluated for removal of phenol in supercritical water. Synthesized catalysts were characterized using temperature programmed reduction, pulse chemisorption, and X-ray powder diffraction. Catalyst activity for phenol conversion was evaluated in a continuous packed bed reactor at supercritical water conditions by analyzing gaseous and liquid products. Process variables evaluated include O2 stream concentration and Mn catalyst loading. Both variables had positive effects on phenol conversion. The process achieved complete conversion of phenol at oxygen ratio of 5 based on complete phenol combustion stoichiometry. Increasing catalyst Mn loading increased its active site concentration, enhancing the contribution of heterogeneous reaction kinetics for supercritical water oxidation (SCWO) of the phenol. A phenol conversion of 70% was reached at 12% (w/w) Mn in the catalyst with oxygen ratio of 1.

РАЗРАБОТКА МАТЕМАТИЧЕСКОЙ МОДЕЛИ СИСТЕМЫ УПРАВЛЕНИЯ ЗВЕНЬЯМИ ЗМЕЕПОДОБНОГО РОБОТА

The mathematical model of a modular control system of links of the snake like robot for realization of the wave movement considering the moments of the external forces created by adjacent links and external indignations is given in work. As model of the electric drive of a direct current the differential equation of the second order connecting tension of u(t) given on the electric motor, the moment of loading of Mn (t) and an output angle of rotation of a shaft θ(t) is used. Transfer functions of separate links are calculated, and transfer function of a control system in general is received.

Modeling and optimization of NH3-SCR performance of MnOx/γ-alumina nanocatalysts by response surface methodology

To model and optimize the NH3-SCR performance of MnOx/γ-alumina nanocatalysts, the response surface methodology (RSM) based on a central composite design (CCD) was employed. The MnOx/γ-alumina nanocatalysts were prepared by homogeneous deposition precipitation and characterized by XRD, H2-TPR, N2 adsorption and TEM. The effect of process variables, including Mn loading, calcination temperature, concentration of O2, NH3/NO ratio and reaction temperature on NOx conversion and N2 selectivity was studied. Analysis of variance confirmed the accuracy and precision of generating quadratic models. The calcination temperature and reaction temperature had the most pronounced effects on NOx conversion and N2 selectivity, respectively. The maximum NH3-SCR performance (94.6% NOx conversion and 93.7% N2 selectivity) was predicted and experimentally validated at the optimum conditions: Mn loading 6.7wt. %, calcination temperature 507.5°C, concentration of O2 4.5 (vol. %), NH3/NO ratio 0.94 and reaction temperature 269.8°C.

Manganese‐Promoted Oxidative Cyclization of Unsaturated Oximes Using Molecular Oxygen in Air under Ambient Conditions

A highly efficient manganese‐promoted oxidative cyclization of unsaturated oximes to afford the corresponding 4,5‐dihydroisoxazoline alcohols was developed. A very low loading (generally 0.1–0.2 mol‐%) of Mn(acac)3 (acac = acetylacetonate) promoted the oxidative cyclization through the direct incorporation of molecular oxygen present in air (open flask) at room temperature.

Impact Energy Absorption Analysis of Spark Plasma Sintered Al2O3Reinforced Bulk Multiwalled Carbon Nanotube Compacts Using Nanoindentation

For utilizing the outstanding energy absorbing capacity of highly elastic carbon nanotube (CNT), bulk multiwalled CNT (MWCNT) structure containing 15 wt% alumina (Al2O3) was fabricated using spark plasma sintering at 1600°C for 10 min under 50 MPa. The compacted mass was ~85% dense having morphologically stable MWCNTs. Microindentation studies up to 9.81 N indicated outstanding elastic recovery of the bulk structure leaving only a diffused indentation mark at indenter-specimen interaction zone. Quantitative estimation of elastic response behavior of the fabricated structure using instrumented nanoindentation in 10–300 mN load range indicated promising applicability of Al2O3/MWCNT compact structure as energy absorbing material.

Local Mechanical Properties of SiC - TiNbC Composite and its Constituents

SiC based composite with 50 % of additives (Ti and NbC with ratio of 9:16) has been prepared. The microstructure, porosity, and chemical composition were studied using SEM equipped with EDS analyser. Local mechanical properties such a hardness and elastic modulus of individual components of the composite were investigated by nanoindentation using Berkovich indenter tip. Hardness and fracture toughness of studied material as a whole was evaluated by means of classic Vickers macroindentation. Indentation cracks were observed and their propagation was analyzed. It was shown that the present phases were distributed uniformly. Moreover, final density was satisfactory with porosity lower than 1 %. The individual constituents shown similar elasticity modulus (550 - 590 GPa). Hardness (HIT) exhibited very pronounced load-size effect. At 10 mN load, hardness was 42.33 GPa ± 1.1 GPa for SiC and 35.73 GPa ± 0.9 GPa for TiNbC, while at 500 mN the composite hardness was 27.61 GPa ± 0.505 GPa. It is in good agreement with macrohardness values, when 27.6 GPa and 25 GPa has been measured for 1 and 10 kg loads, respectively. Indentation fracture toughness was 3.3 MPa.m1/2 ± 0.22 MPa.m1/2. Electrical conductivity was measured by four point probes method and its value was 8.8×104 ± 0.3×104 Sm-1.

Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2

A catalyst composed of manganese oxides supported on titania (MnOx/TiO2) synthesized by a sol–gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, etc. The effects of Mn loading, reaction temperature and individual flue gas components on denitration and Hg0 removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240°C for NO conversion. O2 and a proper ratio of [NH3]/[NO] are essential for the denitration reaction. Both NO conversion and Hg0 removal efficiency could reach more than 80% when NO and Hg0 were removed simultaneously using Mn0.8Ti at 240°C. Hg0 removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg0 removal efficiency. O2 and HCl had a promotional effect on Hg0 removal. SO2 and NH3 were observed to weaken Hg0 removal because of competitive adsorption. NO first facilitated Hg0 removal and then had an inhibiting effect as NO concentration increased without O2, and it exhibited weak inhibition of Hg0 removal efficiency in the presence of O2. The oxidation of Hg0 on MnOx/TiO2 follows the Mars–Maessen and Langmuir–Hinshelwood mechanisms.

Photochemical Water Oxidation by Manganese Oxides Supported on Zeolite Surfaces

Photocatalytic properties of disordered birnessite-like Mn oxides deposited on the zeolite Y surface is investigated. Synthesis was carried out by ion-exchanging Mn2+ along with M2+=Ba2+, Sr2+, Ca2+, Mg2+ into zeolite, followed by precipitation of nanosized Mn oxides on the zeolite surface after reaction with KMnO4. These samples are labeled M2+MnOx-Y, and they were treated with K+ to prepare KMnOx-Y(M2+). XRD, XPS, Raman, and electron microscopy provided information on the comparative structural features for M2+MnOx-Y and KMnOx-Y(M2+). Photocatalytic water oxidation using these samples was evaluated using Ru(bpy)32+-S2O82− system. The catalytic activity of KMnOx-Y(M2+) is higher than M2+MnOx-Y, for comparable Mn loadings, and forms the interesting observation in this paper. For M2+MnOx-Y, the catalytic activity normalized to the Mn content followed the order: Ba2+> Sr2+> Ca2+> Mg2+ and is possibly reflection of the lower Mn loadings, which leads to smaller MnOx crystallites.

Manganese and lead in dust fall accumulation in elementary schools near a ferromanganese alloy plant

Previous studies have shown elevated airborne manganese (Mn) in villages adjacent to a Mn alloy production plant in Brazil and negative associations between biomarkers of Mn and children's cognition and behavior. Since small Mn particles may be carried for long distances, we measured manganese (Mn) and lead (Pb) dust fall accumulation in 15 elementary schools, located between 1.25 and 6.48km from the plant in the municipality of Simões Filho, Bahia, Brazil. Passive samplers (polyethylene Petri dishes) were set in interior and exterior environments. After 30 days, the samplers’ content was solubilized with diluted nitric acid and Mn and Pb levels were analyzed by electrothermal absorption spectrometry. The overall geometric mean and range of Mn and Pb accumulation in dust fall (loading rates) were 1582μg Mn/m2/30 days (37–37,967) and 43.2μg Pb/m2/30 days (2.9–210.4). A logarithmic decrease in interior and exterior Mn loading rates was observed with distance from the ferro-manganese alloy plant. Multiple regression analyses of log-transformed Mn loading rate within the schools showed a positive association with Mn levels in outdoor dust, a negative association with distance from the plant; as well, wind direction (downwind>upwind) and school location (urban>rural) entered significantly into the model. For the interior school environments, located within a 2-km radius from the plant, loading rate was, on average, 190 times higher than the Mn levels reported by Gulson et al., (2014) in daycare centers in Sydney, Australia, using a similar method. Pb loading rates were not associated with distance from the plant and were lower than the rates observed in the same daycare centers in Sydney. Our findings suggest that a significant portion of the children in this town in Brazil may be exposed to airborne Mn at concentrations that may affect their neurodevelopment.

Catalytic oxidation and capture of elemental mercury from simulated flue gas using Mn-doped titanium dioxide

Titanium dioxide (TiO2) and Mn-doped TiO2 (Mn(x)-TiO2) were synthesized in a sol-gel method and characterized by BET surface area analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Gasphase elemental mercury (Hg0) oxidation and capture by the Mn-doped TiO2 catalyst was studied in the simulated flue gas in a fixed-bed reactor. The investigation of the influence of Mn loading, flue gas components (SO2, NO, O2, and H2O) showed that the Hg0 capture capability of Mn(x)-TiO2 was much higher than that of pure TiO2. The addition of Mn inhibits the grain growth of TiO2 and improves the porous structure parameters of Mn(x)-TiO2. Excellent Hg0 oxidation performance was observed with the catalyst with 10% of Mn loading ratio and 97% of Hg0 oxidation was achieved under the test condition (120 °C, N2/6%O2). The presence of O2 and NO had positive effect on the Hg0 removal efficiency, while mercury capture capacity was reduced in the presence of SO2 and H2O. XPS spectra results reveal that the mercury is mainly present in its oxidized form (HgO) in the spent catalyst and Mn4+ doped on the surface of TiO2 is partially converted into Mn3+ which indicates Mn and the lattice oxygen are involved in Hg0 oxidation reactions.

Weathering steel as a potential source for metal contamination: Metal dissolution during 3-year of field exposure in a urban coastal site

Surface and building runoff can significantly contribute to the total metal loading in urban runoff waters, with potential adverse effects on the receiving ecosystems. The present paper analyses the corrosion-induced metal dissolution (Fe, Mn, Cr, Ni, Cu) from weathering steel (Cor-Ten A) with or without artificial patinas, exposed for 3 years in unsheltered conditions at a marine urban site (Rimini, Italy). The influence of environmental parameters, atmospheric pollutants and surface finish on the release of dissolved metals in rain was evaluated, also by means of multivariate analysis (two-way and three-way Principal Component Analysis). In addition, surface and cross-section investigations were performed so as to monitor the patina evolution. The contribution provided by weathering steel runoff to the dissolved Fe, Mn and Ni loading at local level is not negligible and pre-patination treatments seem to worsen the performance of weathering steel in term of metal release. Metal dissolution is strongly affected by extreme events and shows seasonal variations, with different influence of seasonal parameters on the behaviour of bare or artificially patinated steel, suggesting that climate changes could significantly influence metal release from this alloy. Therefore, it is essential to perform a long-term monitoring of the performance, the durability and the environmental impact of weathering steel.

Airborne toluene degradation by using manganese oxide supported on a modified natural diatomite

The catalytic combustion of toluene over manganese oxide supported on natural diatomite has been investigated in the paper. The catalyst was prepared by the wet impregnation method and characterized by using the Brunauer Emmett Teller, field emission scanning electron microscopy, X-ray diffraction, X-ray fluorescence and temperature-programmed reduction analysis. The higher activity of the catalyst supported on diatomite for toluene oxidation was obtained at 12 wt% Mn loading. It was able to convert 90 % of toluene (T 90) at 380 °C. The results indicated that the selectivity towards CO2 was almost 100 % and no intermediates, such as CO or other hydrocarbons, were detected.

Geochemistry and background concentration of major ions in spring waters in a high-mountain area of the Hamedan (Iran)

Little is known about the natural phenomena that govern the chemical composition of spring waters in Alvand mountain ecosystem. A total of 50 spring water samples of the Avand mountains, Hamadan, western Iran were collected and analyzed for the main components in an effort to both identify ion chemistry and establish background concentrations of major ions and some trace elements (Cd, Fe, Mn, Ni, Zn).The order of relative abundance of major cations in the spring waters was Ca, Mg, Na, K, while that of anions was HCO3, Cl, SO4, NO3. Most spring water samples were undersaturated with respect to calcite. The major water types in spring waters were Ca–HCO3 (group 1), CaHCO3–Cl, CaMg–HCO3Cl, and CaMg–Cl–HCO3 (group 2), which were mainly due to the dissolution of carbonate minerals and silicate weathering and partly due to the ion exchange. Activity diagrams showed that spring waters fall into the kaolinite field due to the short interaction with silicate minerals. In general, mineralization, pH, mean concentrations of Ca, Mg, HCO3, TDS, saturation indices of calcite, dolomite and PCO2 were greater in water samples from the group 1 than in water samples from group 2. Spring waters were mainly soft water (84%) in group 2 and hard water (16%) in group 1. The factor analysis performed on spring water samples identified four factors controlling their variability in spring water samples. Four extracted factors explained 84.7% of data set variance. Factor 1 had the highest factor loadings of EC, HCO3, SO4, Cl, Ca, Mg, Na, Mn, Cd, Ni, and Fe, while factor 2 had the highest factor loadings of Zn. Factors 3 and 4 had the highest factor loading for NO3, P and K, respectively. Factors 1, 2 and 4 together may be related to the dissolution of carbonate minerals (group 1) and silicate weathering, while factor 3 may be due to the anthropogenic input. Different statistical methods were used in the evaluation of background values of the spring waters. Trace element concentration in spring waters was low and associated with local mineralogy.

Assessment of Elasticity, Plasticity and Resistance to Machining-induced Damage of Porous Pre-sintered Zirconia Using Nanoindentation Techniques

Porous pre-sintered zirconia is subject to white machining during which its elasticity, plasticity and resistance to machining-induced damage determine its machinability and final quality. This study used nanoindentation techniques and the Sakai's series elastic and plastic deformation model to extract the resistance to plastic deformation from the plane strain modulus and the contact hardness for pre-sintered zirconia. The modulus and the resistance to plasticity were used to calculate the relative amount of elasticity and plasticity. The fracture energy and the normalized indentation absorbed energy were used to deconvolute the resistance to machining-induced cracking based on the Sakai–Nowak model. All properties were extracted at a 10 mN peak load and loading rates of 0.1–2 mN/s to determine the loading rate effects on these properties. We found that the resistance to plasticity and the resistance to machining-induced cracking were independent of the loading rate (ANOVA, p > 0.05). The elastic and plastic displacements depended on the loading rate through power laws. This loading rate-dependent deformation behaviour was explained by the maximum shear stress generated underneath the indenter and the indentation energy. The plastic deformation components and the indentation absorbed energy at all loading rates were higher than the elastic deformation components and the elastic strain energy, respectively. Finally, we established the linkage among the pore structure, indentation behaviour and machinability of pre-sintered zirconia.

Exploring Quaternary paleolake evolution and climate change in the western Qaidam Basin based on the bulk carbonate geochemistry of lake sediments

This study focuses on the concentration of major and trace elements in the diluted acetic acid-soluble fraction of SG-1 core lacustrine sediments from the western Qaidam Basin (Tibetan Plateau) in order to explore the potential of applying bulk carbonate analysis to tracing paleolake evolution and climate change. The SG-1 core sediments are considered highly suited to the exploration of the paleoenvironmental significance of bulk carbonate geochemistry, because most carbonates in the core are authigenic in origin. Based on a principal component analysis of the elemental composition of diluted acetic acid leachate, four major components with distinct characteristics have been extracted, accounting for ~80% of the total variance. The first and most important component is associated with a high positive loading of Mn, P, Y, Sc and rare earth elements (REE); the second component is characterized by a high positive loading of Ca, Sr, and U; the third component displays a high negative loading of Mg, Li, and B; and the fourth component is associated with a relatively high positive loading of Fe, V and Cr. After considering the geochemical behavior of these element assemblies during acid leaching, we have concluded that these four components contain information indicative of watershed climate conditions, carbonate precipitation, lake water salinity and iron oxide content, respectively. Reconstructions of watershed climate change and paleolake evolution using the component scores are comparable to those reconstructed from other independent proxy records, indicating a long-term trend of lake shrinkage and climatic drying since ~2.7Ma with abrupt drying events at ~2.5Ma, ~1.8Ma, ~1.2Ma and ~0.6Ma. Our results suggest that lake carbonates bear more information about watershed climate and lake evolution than expected, and that occurrences of some elements, in particular trace elements, in the diluted acetic acid leachate are not solely and necessarily linked to carbonate minerals.