Aqueous Solutions Of Manganese Nitrate Research Articles

Phase control of manganese sulfides during hydrothermal synthesis and their photocatalytic activity for H2 generation

We report a simple method to control phase formation in manganese sulfides during hydrothermal synthesis from aqueous solutions of manganese nitrate and thioacetamide without any additives or surfactants. In this work, MnS2, MnS or MnS2/MnS composites were obtained by adjusting the proportion of thioacetamide in the initial precursor mixture. The photocatalytic activities evaluated by H2 generation under ultraviolet light showed that MnS phase was found to be more active than the MnS2.

Water Activity and Freezing Points in Aqueous Solutions of Manganese Nitrate: Experimental and Modeling

The water activities of manganese nitrate solutions were measured using a humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic properties of the system were described by the Pitzer model and specific interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer model and SIT were carried out using experimental freezing points and osmotic coefficients of manganese nitrate aqueous solutions, collected from the open literature, and the water activity data measured in this work. A set of Pitzer and SIT parameters were estimated using a temperature dependency, that enables us to cover wider temperature ranges, and consequently calculate system properties to higher molalities. Both approaches represent very satisfactorily, and with similar accuracy, the experimental data and the calculated manganese nitrate molal activity coefficients are comparable to those already published for analogous systems. Additionally, the Pitzer model was also able to calculate the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt solution 6.5 mol·kg−1.

Catalytic Combustion of Ethyl Acetate over Manganese Oxides Deposited on Metallic Monoliths

AbstractMnOx/AISI 304 austenitic stainless‐steel monolithic catalysts were prepared by impregnation with aqueous solutions of manganese nitrate or acetate. The preparation method was satisfactory in terms of reproducibility and adherence of the deposited phase. The use of different precursors led to significantly dissimilar results. With manganese nitrate, the formation of Mn‐Cr‐O mixed phases on the surface was favored, whereas with manganese acetate, Mn2O3 was the predominant active phase. The Mn‐Cr‐O mixed phases would be highly dispersed but their catalytic activity was low. The major catalytic behavior was obtained with monoliths impregnated with manganese acetate.

Synthesis and Redox Behavior of Nanocrystalline Hausmannite (Mn3O4)

Hausmannite (Mn3O4) nanoparticles have been prepared by mixing aqueous solutions of manganese nitrate and hexamethylenetetramine from 20 to 80 °C. Activation energy for the particle formation increases from 0.5 to 0.8 kJ/mol with nitrate concentration. Nanoparticles (18−41 nm) with a faceted structure are prepared by this method. We describe synchrotron in-situ time-resolved XRD experiments in which Mn3O4 nanoparticles are reduced to MnO and subsequently reoxidized in ramping temperature conditions. The temperature of Mn3O4 to MnO reduction decreases as Mn3O4 particle size decreases. On oxidation, 18 nm and smaller MnO nanoparticles formed the intermediate phase Mn5O8 (MnO → Mn3O4 → Mn5O8 → Mn2O3), while larger MnO particles oxidized to Mn3O4 then directly to Mn2O3. Formation of Mn3O4 occurred at lower temperature for smaller MnO nanoparticles. Further oxidation to Mn2O3 required higher temperatures for the initially smaller MnO nanoparticles, indicating that the kinetics of forming the new oxide phases is not controlled by diffusion, where smaller distance favors faster reaction, but by nucleation barrier.

Studies of MnS cluster formation in laumontite zeolite

MnS clusters were prepared by treating laumontite zeolite with 0.1 N aqueous manganese nitrate solutions at 296 K (pH 5.8), using a solid/liquid ratio of 1/50, followed by a sulfidation process with H 2S, at 350 K, during 12 h. XRD and magnetic resonance measurements proved that the clusters are formed inside the zeolite channels. Examination of SEM revealed that no disintegration of zeolite framework had occurred during the synthesis. The 27Al MAS NMR spectra of the zeolite framework showed three main resonances in the 30–60 ppm region, which are attributed to distinct Al species. The NMR spectra indicate that structural changes occurred in the tetrahedral framework during the sulfidation process. EPR measurements performed at room temperature evidenced three different Mn species, which are affected by the sulfidation process. The local field effect is shown to be substantial for semiconductor clusters encapsulated in laumontite.

ChemInform Abstract: THERMAL DECOMPOSITION OF AQUEOUS MANGANESE NITRATE SOLUTIONS AND ANHYDROUS MANGANESE NITRATE. PART 1. MECHANISM. PART 2. HEATS OF REACTION. PART 3. ISOTHERMAL KINETICS. PART 4. NON‐ISOTHERMAL KINETICS

Chemischer InformationsdienstVolume 12, Issue 34 Physical Inorganic Chemistry ChemInform Abstract: THERMAL DECOMPOSITION OF AQUEOUS MANGANESE NITRATE SOLUTIONS AND ANHYDROUS MANGANESE NITRATE. PART 1. MECHANISM. PART 2. HEATS OF REACTION. PART 3. ISOTHERMAL KINETICS. PART 4. NON-ISOTHERMAL KINETICS T. J. W. DE BRUIJN, T. J. W. DE BRUIJNSearch for more papers by this authorW. A. DE JONG, W. A. DE JONGSearch for more papers by this authorP. J. VAN DEN BERG, P. J. VAN DEN BERGSearch for more papers by this author T. J. W. DE BRUIJN, T. J. W. DE BRUIJNSearch for more papers by this authorW. A. DE JONG, W. A. DE JONGSearch for more papers by this authorP. J. VAN DEN BERG, P. J. VAN DEN BERGSearch for more papers by this author First published: August 25, 1981 https://doi.org/10.1002/chin.198134028AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue34August 25, 1981 RelatedInformation

Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 1. Mechanism

The thermal decomposition of aqueous manganese nitrate solutions in air or nitrogen proceeds in three steps: 1. (i) partial evaporation of water to a concentrated solution containing equimolar amounts of water and Mn(NO 3) 2, 2. (ii) a first decomposition step in which the residual water evolves and part of the Mn(NO 3) 2 decomposes to MnO 2, and 3. (iii) a second decomposition step in which the remaining Mn(NO 3) 2 decomposes to MnO 2. Decomposition of part of the Mn(NO 3) 2 in the first step is caused by the presence of water (vapour) which accelerates the decomposition of anhydrous Mn(NO 3) 2 and lowers the temperature at which this reaction starts. Without water [anhydrous Mn(NO 3) 2] only one decomposition step occurs. Off-gas analysis with mass spectrometry, IR spectroscopy and chemiluminescence showed NO 2 to be the main gaseous product, NO being formed in much smaller amounts. amounts.

Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 2. Heats of reaction

Differential thermal analysis of the thermal decomposition of aqueous manganese nitrate solutions in air and nitrogen shows three distinct endothermic heat effects. The first effect results from partial evaporation of water to a solution containing equimolar amounts of H 2O and Mn(NO 3) 2. The two subsequent decomposition steps produce MnO 2. The heat effect of each of the latter two steps depends on the sample weight but their sum remains constant at about 170 ± 14 kJ mole −1. Decomposition under vacuum of anhydrous Mn(NO 3) 2 shows only one heat effect of 155 ± 12 kJ mole −1. DTA and X-ray analysis indicate that decomposition of a Mn(NO 3) 2 solution results in γ-MnO 2 and decomposition under vacuum of anhydrous Mn(NO 3) 2 results in γ-MnO 2 with large amounts of Mn(NO 3) 2. A comparison between measured and calculated heats of reaction shows fair agreement.

Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 3. Isothermal kinetics

The kinetics of the thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate in air were established from isothermal experiments. By heating the solution, first most of the water evaporates to a composition of equimolar amounts of water and manganese nitrate; this concentrated solution then decomposes to γ-Mn(NO 2, NO 2 and water, usually in two steps. The first step can be described best by the model [−ln(1 − α)] 1 2 = 8.9 × 10 11 exp(−121000/ RT) t, whereas the second step is described equally well by several models. The kinetic parameters of these models are quite similar, the average activation energy being 141 kJ mole −1. The decomposition of anhydrous Mn(NO 3) 2, which proceeds in a single step, can also be described with several similar models. In this case the average activation energy is about 92 kJ mole −1.

Thermal decomposition of aqueous manganese nitrate solutions and anhydrous manganese nitrate. Part 4. Non-isothermal kinetics

Kinetic parameters for the decomposition of aqueous manganese nitrate solutions were derived from non-isothermal experiments in air. First, most of the water evaporates to a solution containing approximately equimolar quantities of water and manganese nitrate which then decomposes in two steps to MnO 2. The first step can be described by a model valid for two-dimensional growth of a constant number of nuclei, viz. g(α) = [−ln-(1 − α)] 1 2 , and the second by a model based on a surface reaction, viz. g(α) = 1 − (1 − α) 1 3 . The decomposition of anhydrous manganese nitrate most probably occurs via nuclei formation with a decreasing rate and one-dimensional growth of the nuclei formed. The model g(α) = [ −ln(1 − α)] 0.6 described the measurements satisfactorily. The parameters in the above models closely agree with results from isothermal experiments.

Electron paramagnetic relaxation in aqueous solutions of manganese (II) ions

The processes of the electron paramagnetic relaxation, molecular motions and structural changes in aqueous solutions of manganese nitrate have been investigated by direct measurement of spin-lattice (T 1) and spin-spin (T 2) relaxation times for a wide range of concentrations, temperatures and viscosities. T 1 and T 2 were measured by a non-resonance absorption method. It was discovered that some structural regions exist at the different concentrations of Mn(II) ions in solution. So, the structure of highly concentrated solutions may be considered as one of the corresponding crystallohydrate. The structural microinhomogeneities were observed also in the intermediate concentration range at definite temperatures. It is shown that the relaxation mechanism proposed by Bloembergen and Morgan is not effective in the concentration range studied by us. The analysis of relaxation times and E.P.R. spectra has shown the formation of ‘liquid microphases’ at the freezing point of the solution. Such microphases can exist at temperatures a few tenths of a degree below the solvent freezing point, and its composition considerably differs from the initial solution. The correlation times for intramolecular and intermolecular electron relaxation mechanisms are evaluated and their nature is discussed.