7,042 research outputs found
Mn/carbon sphere catalyst for heterogeneous activation of peroxymonosulfate for methylen blue removal
No full textOne of the latest innovations in textile waste treatment is advanced oxidation processes (AOPs) methods using an oxidizing agent capable of producing sulfate radicals (SO4•). This study aims to determine the activity of the Mn/Carbon sphere catalyst in the oxidation process, reduce the dye content by using a combination of peroxymonosulfate (PMS) and Mn/Carbon sphere catalyst as an oxidizing agent, and determine the optimum conditions in the process of reducing dye levels in the water. A hydrothermal process carried out the catalyst synthesis process to produce black carbon from D-glucose solution, then impregnated with variations of 3% and 5% of Mn metal. The degradation of methylene blue (artificial waste) of 25mg/L (1:10 dilution) was carried out for 120 minutes with variations in the catalyst mass of 0.001, 0.002, 0.003, and 0.004g and the mass of PMS 0.01, 0.02, 0.03, and 0, 04g in 100ml sample. Mn/Carbon sphere catalyst was able to activate PMS and was able to degrade methylene blue by 88.16%. The optimum condition for reducing the methylene blue levels in the water is at a concentration of 1g/L PMS and a Mn/Carbon sphere catalyst (5% Mn metal) 0.5g/L with an efficiency of 88.16%
Nonlinear influence of excess Mn on the magnetoelastic transition in (Mn,Cr)<sub>2</sub>Sb
No full textThe influence of excess Mn on the magnetoelastic ferromagnetic-to-antiferromagnetic transition Tt in the magnetocaloric compound (Mn,Cr)2Sb has been studied. With increasing excess Mn the magnetoelastic transition temperature for (Mn,Cr)2Sb initially increases and then decreases. This trend is accompanied by a strong reduction of the (Mn,Cr)Sb secondary phase. With increasing excess Mn a higher Cr content was found in the (Mn,Cr)Sb secondary phase in comparison to the matrix phase. This competition for Cr leads to a nonlinear dependence of Tt with increasing excess Mn at a fixed nominal Cr content. However, we observed that Tt depends linear on the c/a ratio for a wide range of temperatures from 170 to 350 K. A compositional diagram of the c/a ratio was constructed to assist the selection of (Mn,Cr)2Sb alloys with a desired transition temperature.RST/Fundamental Aspects of Materials and Energ
Characteristics of Fe and Mn bearing precipitates generated by Fe(II) and Mn(II) co-oxidation with O2, MnO4 and HOCl in the presence of groundwater ions
No full textIn this work, we combined macroscopic measurements of precipitate aggregation and chemical composition (Mn/Fe solids ratio) with Fe and Mn K-edge X-ray absorption spectroscopy to investigate the solids formed by co-oxidation of Fe(II) and Mn(II) with O2, MnO4, and HOCl in the presence of groundwater ions. In the absence of the strongly sorbing oxyanions, phosphate (P) and silicate (Si), and calcium (Ca), O2 and HOCl produced suspensions that aggregated rapidly, whereas co-oxidation of Fe(II) and Mn(II) by MnO4 generated colloidally stable suspensions. The aggregation of all suspensions decreased in P and Si solutions, but Ca counteracted these oxyanion effects. The speciation of oxidized Fe and Mn in the absence of P and Si also depended on the oxidant, with O2 producing Mn(III)-incorporated lepidocrocite (Mn/Fe = 0.01–0.02 mol/mol), HOCl producing Mn(III)-incorporated hydrous ferric oxide (HFO) (Mn/Fe = 0.08 mol/mol), and MnO4 producing poorly-ordered MnO2 and HFO (Mn/Fe > 0.5 mol/mol). In general, the presence of P and Si decreased the crystallinity of the Fe(III) phase and increased the Mn/Fe solids ratio, which was found by Mn K-edge XAS analysis to be due to an increase in surface-bound Mn(II). By contrast, Ca decreased the Mn/Fe solids ratio and decreased the fraction of Mn(II) associated with the solids, suggesting that Ca and Mn(II) compete for sorption sites. Based on these results, we discuss strategies to optimize the design (i.e. filter bed operation and chemical dosing) of water treatment plants that aim to remove Fe(II) and Mn(II) by co-oxidation
Effective Treatment of Industrial Wastewater Contaminated with Mn and Pb using Mesoporous Silica from Yogyakarta Beach
No full textThe research was investigated using Yogyakarta beach sand as the main material to synthesize mesoporous silica (MS). The MS usage in the environmental field is mainly to overcome water pollution, contaminated from chemical waste used in industrial productions. In the sol-gel method, the silica from beach sand was extracted and synthesized into MS using a dodecyl amine (DDA) template. MS is used as an adsorbent for manganese (Mn) and lead (Pb) printing liquid waste. MS produced was analyzed with FTIR and surface area analyzer (SAA). The process of waste adsorption used MS weight variables of 1 gr, 2 gr, and 3 gr. The MS was mixed in the waste and stirred with a rotation speed of 120 rpm for 2 hours. The solution was left for 24 hours until separated from the adsorbent. AAS analyzed the resulting liquid, and the adsorbent was dried at 100 °C for 24 hours and analyzed by SEM-EDX. The synthesized MS was characterized. It has a surface area of 122.78 m2/gr and a pore diameter of 4.65 nm. The AAS analysis results showed that the wastewater contains Ni <0.076 mg/L and Pb <0.415 mg/L. The SEM-EDX analysis showed that the adsorbent used contains 0.01% Mn, 0.01% Pb, and 0.39% Cu. The research showed that the liquid printing waste analyzed contains nickel, lead, and copper
Nano-Mn-[3-Nitrophenyl-Salicylaldimine-Methyl Pyranopyrazole] Cl<sub>2</sub> as a New Schiff Base Complex and Catalyst
No full textBy the reaction of 3-nitrobenzaldehyde with ethyl acetoacetate, malononitrile and hydrazine hydrate, pyranopyrazole derivative as an active biological compound was prepared and then reacted with salicylaldehyde and MnCl2·4H2O to give nano-Mn-[3-nitrophenyl-salicylaldimine-methylpyranopyrazole]Cl2 (nano-[Mn-3NSMP]Cl2). The presented nano-Schiff base complex was fully characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), scanning electron microscope (SEM), and energy dispersive X-ray analysis (EDX) and applied as an efficient and new catalyst for the synthesis of 1,2,4,5-tetrasubstituted-imidazoles. </p
Surface Oxidation and Wettability of Fe–Mn and Fe–Mn–Si-Alloyed Steel After Annealing
No full textThe surface oxidation and wettability of Mn and Si-alloyed steel after annealing at different conditions are studied with scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and a so-called de-wetting method. After exposure at 950 °C for 1 hour in an Ar + 5 vol pct H2 gas atmosphere with dew points (DP) ranging from – 40 °C to 10 °C, oxides were observed along the grain boundaries or dispersed on the surface for the Fe–1.8 Mn steels while a continuous oxides layer was formed on Fe–1.9 Mn–0.94 Si steels (composition in weight fractions). The oxides formed at different DPs were predicted based on thermodynamic calculations. (Fe,Mn)O was formed on Fe–1.8 Mn steel at the whole range of DPs, while the oxide phase on Fe–1.9 Mn–0.94 Si steel depends on the DP. At low-DP SiO2 were formed and with increasing the DP (Fe,Mn)SiO3 or (Fe,Mn)SiO3 + (Fe,Mn)2SiO4 were formed and finally (Fe,Mn)2SiO4 were formed. An increase of the fraction of Fe in the oxide with increasing DP for both steels was observed with XPS analysis. As a measure for the surface wettability, the contact angle of Pb droplets on the annealed steels surfaces was determined with SEM and image analysis software. Also, the contact angle of Pb on pure Fe and on the Mn and Si alloyed steels free of surface oxides was measured for comparison. The results show that the contact angle of Pb on the steel surfaces after annealing decreases with increasing DP. This improved wettability with increasing dew point is related to the Fe fraction of the oxides formed on the surface.Team Kevin RossiTeam Maria Santofimia NavarroTeam Marcel Herman
Temperature-Dependent Microstructural Evolution of Al-Rich Medium-Mn Steel During Intercritical Annealing
No full textMedium-Mn automotive sheet steels require optimized heat-treatment processes to obtain benefits caused by strain-induced martensitic transformation of retained austenite (RA) during sheet metal forming or crash events. The intercritical annealing (IA) approach at different temperatures in a range of 640 °C to 800 °C is proposed in the study for a 5Mn hot-rolled medium-Mn sheet steel. The experiments were performed in terms of dilatometry. The analysis of the cooling curves allowed development of a new method for calculating the high-temperature phase equilibrium. The calculations were validated by modeling with JMatPro and experimentally verified by X-ray diffraction (XRD). The microstructure evolution was characterized using light optical microscopy and scanning electron microscopy (SEM), including electron backscatter diffraction (EBSD). The quantitative determination of the fraction, morphology, chemical composition, and stability of the RA was done. Mechanical properties were determined by hardness measurements. The research showed a substantial influence of the IA temperature on the RA fraction and chemical stability and properties of medium-Mn Al-alloyed steel. At temperatures of 680 °C and 700 °C, the largest fraction of over 35 pct of stable RA was obtained, which does not transform to martensite during cooling.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Kevin Ross
Mn/Ca ratios of Ammonia tepida as a proxy for seasonal coastal hypoxia
No full text Climate variability has major implications for marine geochemical cycles and biogenic carbonate production. Therefore, past climate-driven changes in marine environments are often inferred from geochemical data of the marine carbonate archive. Proxy calibration studies are essential for the reconstruction of such past environmental changes. Here, we use the geochemical composition of living specimens of the benthic foraminifer Ammonia tepida at three sites in a seasonally hypoxic (oxygen concentration < 63 μmol/L) marine coastal system (Lake Grevelingen, the Netherlands) to explore the use of Mn/Ca as a proxy for coastal hypoxia. The study is based on samples from three stations along a depth transect, that show contrasts in the seasonal cycle of Mn 2+ concentrations in the pore water of the surface sediment. In general, the sediment and pore water geochemistry of the three stations in Lake Grevelingen show increased Mn 2+ concentrations in late winter/spring, combined with increased Mn refluxing in summer, which are due to cable bacteria activity and bottom water hypoxia/anoxia, respectively. Laser Ablation-ICP-MS (LA-ICP-MS) allowed a comparison of Mn/Ca ratios of different parts of the benthic foraminiferal test. Our results show that higher Mn/Ca ratios are registered at the deepest station, which experiences the longest and most severe seasonal periods of hypoxia/anoxia. Additionally, the signal preserved in the central part of the benthic foraminiferal tests, which is thought to reflect the entire calcification history of the analysed specimen, appears to be driven by high pore water Mn 2+ concentrations due to cable bacteria activity in late winter/spring. Conversely, high Mn/Ca ratios in the last chambers reflect increased Mn refluxing in the surface sediment due to summer hypoxia/anoxia. Thus, Mn/Ca ratios of A. tepida give insight into the complex spatial and temporal variability of pore water manganese. Accepted Author ManuscriptBT/Environmental Biotechnolog
Investigation on high Mn austenitic lightweight steels weldability via GTAW overlay welding and butt-welding operations
No full textLightweight steels are currently under development for potential applications in the transportation sector. These alloys are characterized by high manganese (Mn) and aluminium (Al) content, exceptional mechanical properties (yield strength up to 800 MPa and elongation at break up to 55 %), and reduced density (approximately 16 % lower than conventional stainless steel). Due to the demands of the application sector, a thorough assessment of the alloy's weldability is crucial. The high concentration of chemical elements in these steels leads to critical phenomena, notably Mn evaporation and κ-carbide precipitation, both of which can significantly influence the microstructure. Mn evaporation may result in an inhomogeneous chemical composition, leading to variations in microstructure and mechanical properties. κ-carbide precipitation, while typically utilized as a strengthening mechanism, may cause an undesirable reduction in ductility. A lightweight austenitic steel alloy with high Mn content was evaluated using Gas Tungsten Arc Welding (GTAW) under various configurations and material conditions. The microstructure and mechanical properties of the welded joints were analysed. Sound welded joints free from porosity and hot cracking were achieved. In the fusion zone, a duplex structure with dendritic morphology was observed, while the heat-affected zone (HAZ) exhibited coarse grains. The fusion zone demonstrated low hardness values, and no hardness peaks associated with κ-carbides were detected in the HAZ. Despite similarities in microstructure and welding parameters, mechanical testing revealed that direct current (DC) samples exhibited superior ductility compared to alternating current (AC) samples
Assessment of zn, fe mn and ni pollution around agriculture area by using mosses as biomonitor / Nur Amalina Ahmad
No full textThe aim of this study was to determine the concentration of Zn, Fe, Mn and Ni in the moss samples around Felda Mawar Jengka 10 plantation area, Bandar Pusat Jengka, Pahang. Eight samples were collected from two locations where each of the location has four different sites with different distances from the main road; 25m, 50m, 75m, and 100m. The concentration of atmospheric heavy metal was estimated by using mosses as bioindicator and the metal concentration in mosses were analysed by Flame Atomic Absorption Spectrometer (FAAS). The mean concentration of heavy metal in moss samples were; Zn with 21.39 mg/kg, 351.92 mg/kg for Fe, 55.68 mg/kg for Mn and 8.56 mg/kg for Ni and were ranked as: Fe> Mn > Zn > Ni. Two different parameters were used to describe the contamination level of these metals around the studied area: Enrichment Factor (EF) and Pollution Load Index (PLI). The EF values clearly indicate that, only 10% of the overall metal contents were strongly related to the anthropogenic sources. Most of the metals were originated from natural sources. With the PU values were obtained below one, its strongly suggest that the study area has not been contaminated with the studied element
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