Alkaline Nitrates Research Articles

One-step synthesis of ZnO and Ag/ZnO heterostructures and their photocatalytic activity

By following a one-step, novel methodology, ZnO and Ag/ZnO heterostructures were successfully synthesized at room-temperature. This route is simple, effective, high yield (91%), environmentally friendly (green synthesis) and consists of a mechanically assisted metathesis reaction. The metathesis reaction used in this investigation showed two results: the in-situ generation of alkaline nitrates, LiNO3/NaNO3, and the direct crystallization of the desired Zn-based compounds in milling media; revealing a true mechanochemical synthesis of ZnO and Ag/ZnO (1.25, 2.50 and 4.50mol% of Ag) heterostructures. Particles showed spherical-like morphologies and sizes smaller than 20nm. The Ag/ZnO heterostructures exhibited higher photocatalytic activity than ZnO for degrading methylene blue (MB) dye. It was also shown that the presence of Ag (up to 1.25mol%) nanoparticles (NPs) in ZnO accelerates the photodegradation reaction and then slows down with further increases in Ag contents. The 1.25-Ag/ZnO sample (10mg) showed the highest photocatalytic activity (96%) for degrading MB (100ml, 10mgL−1) within 100min under UV–Vis light irradiation (λ = 310nm).

Neoformations on stony materials of modern building works

Stony materials applied in the built environment interact with diverse pollutants and can originate INORGANIC neoformations that can contribute to depreciation of these materials.Microscopy studies help to characterize the chemical and textural features of these neoformations hence contributing to the understanding of the decay processes. In a study of diverse modern constructions in towns of Northern and Central Portugal were identified diverse neoformation substances in stony materials that were sampled and subjected to scanning electron microscopy (SEM) studies. While, in a strict perspective, implying destructive procedures that require the removal of a sample, microscopy techniques require minute amounts and can study occurrences of neoformations that can be detected at the macroscopic level. Products clearly resulting of metals corrosion were not considered in this study.The dominant inorganic coatings and stains in the studied constructions are carbonate-rich whitish ones that can present diverse morphological features. Some of these carbonate-rich coatings have showed textural features defining a kind of urban travertine and the existence of several layers suggesting diverse episodes of solutions circulation and crystals precipitation, indicating the recurrence of the neoformation processes. Phosphates aggregates were also detected in several built surfaces, including indoor areas (Figure 1a,b). Another relatively common occurrence are efflorescences of more soluble salts, dominated by alkaline sulphates and carbonates (especially sodium sulphate) but were other salts such as alkaline nitrates (Figure 1c,d) and chlorides and magnesium sulphates have also been occasionally found. In some buildings it was possible to observe black crusts resulting from the fixation of atmospheric particles by gypsum aggregates. A very rare neoformation are silica-rich stains that in the situation presented in Figure 1e,f occur associate with calcium carbonate stains and metal corrosion products. The observed neoformations show a great geochemical and textural diversity in the surfaces of stony materials of modern built works, being evidences of diverse possible pollution sources that can interact under variable environmental conditions. Besides an important role that seems to be attributable to mortars materials (namely in relation to calcium carbonates and alkaline sulphates but that might also be the case for the phosphates in inside portions), there are also possible contributions from atmospheric pollutions (in the case of the black crusts) and the presence of alkaline nitrates could be indicative of organic sources as this connection is well established in older works. It has been admitted that alkaline nitrates in these modern works could either represent the persistence of contamination conditions from the past in the soils or the recurrence of the same polluting conditions. Also of particular interest are the textural informations indicating recurrence of neoformation episodes (relevant for possible cleaning interventions) and the chemical associations observed even in some very small samples.The author acknowledges the support of the Fundação para a Ciência e Tecnologia (PEST-OE/CTE/UI0697/2011, funding by the national budget of the Portuguese Republic).

Preparation and characterisation of calcined Mg/Al hydrotalcites impregnated with alkaline nitrate and their activities in the combustion of particulate matter

The effect of incorporating alkaline nitrates in hydrotalcites for use in the combustion of particulate matter from diesel emissions has been studied. The catalysts were characterised by X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), elemental analysis (EA), atomic absorption spectrophotometry (AAS) temperature programmed reduction (TPR) and Fourier transform infrared spectroscopy (FTIR). Activity measurements were carried out using a thermobalance in air and using a fixed-bed reactor with a NO/O2 flow. The observed activities decreased in the following order: HTMgAlcCs>HTMgAlcK>HTMgAlcLi>HTMgAlc.

Perovskite-Type Metal Oxides Exhibiting Negligible Grain Boundary Resistance to Total Electrical Conductivity

In this paper, we report the synthesis, structure and electrical properties of the perovskite-type AZn0.33+xNb0.67-xO3-δ (A = Sr or Ba; 0 ≤ x ≤ 0.08). The investigated compounds were prepared by employing the solid-state (ceramic) reaction using alkaline nitrates, zinc oxide, and niobium oxide at elevated temperatures in air. Powder X-ray diffraction (PXRD) showed the formation of disordered Zn and Nb at the B-sites of space group Pm3̅m with cubic structure and a lattice constant comparable to that of the literature. The AC impedance study showed mainly bulk contribution to the total electrical conductivity over the investigated frequency range of 0.01 Hz to 1 MHz in all the investigated atmospheres even at low temperatures, which is significantly different from that of the well-known perovskite-type B-site ordered BaCa0.33+xNb0.67-xO3-δ and the disordered acceptor-doped BaCeO3. The bulk dielectric constant determined at 500 and 700 °C in air was found to be in the range of 35-100. In air, the isothermal bulk dielectric constant seems to increase with an increasing Zn content, and a similar trend was observed for total electrical conductivity. In dry and wet H2, the electrical conductivity decreases with an increasing Zn content in AZn0.33+xNb0.67-xO3-δ, and the x = 0 member of the Ba compound exhibits the highest total conductivity of 7.2 × 10(-3) S cm(-1) in dry H2 at 800 °C. Both Sr and Ba compounds were found to be stable against the reaction with pure CO2 at 700 °C and H2O at 100 °C for a long period of time. SrZn0.33+xNb0.67-xO3-δ was found to be stable in 30 ppm H2S at 800 °C, while the corresponding Ba compound formed reaction products such as BaS (JCPDS Card 01-0757), BaS2 (JCPDS Card 21-0087), and BaS3 (JCPDS Card 03-0824).

Determination of the selectivity coefficient of the CMX cationic membrane at various ionic strengths

Equilibrium between CMX cationic membrane and solutions of cations at various ionic strengths were studied and the affinity order for different counter-ions was made. Membrane water content and ion exchange capacity were determined. The equilibrating solutions were equimolar mixtures of alkaline nitrates of potassium, sodium and calcium and the ionic strength (I) was varied from 0.1 to 1.5 mol.L-1. All experiments were maintained at constant temperature (25°C). Adsorption isotherms for the five binary systems: Na+/K+, Li+/K+, Li+/Na+, Na+/Ca2+ and K+/Ca2+ were studied. The affinity order observed was: K+ > Ca2+ > Na+ > Li+. Selectivity coefficients KK+Na+, KK+Li+,KNa+Li+, KCa2+2Na+ and KCa2+2K+ were determined at 25°C. The selectivity coefficients decreases with increasing ionic strength for low values of I and tended asymptotically to the unity for high values of I.

Solubility of Aqueous Mixtures of Alkaline Nitrates and Nitrites Determined by Differential Scanning Calorimetry

The solubility of aqueous electrolyte solutions is a critical property for absorption refrigeration and heat pump working fluids. In this paper, we report a systematic study on the solubility of 21 alkaline nitrate and nitrite mixtures determined by a visual polythermal method. The solubility of the mixtures (LiNO3 + NaNO3 + KNO3) + H2O with salt mass ratios of 53:19:28 and 53:05:42 and (LiNO3 + KNO3 + NaNO2) + H2O with salt mass ratios of 53:35:12 and 60:36:04 was further determined accurately by differential scanning calorimetry. Saturation temperature data of these mixtures were correlated with the total salt mass fraction using empirical polynomial equations. The mixtures of LiNO3 + NaNO3 + KNO3 (53:05:42) and LiNO3 + KNO3 + NaNO2 (53:35:12) showed the highest solubility in water.

Molecular design of macrocyclic extractants for extraction and separation of alkali and alkaline-earth metals

The distribution coefficients of the alkaline and alkali-earth metal nitrates are determined for the processes of extraction from nitric acid solutions with crown ethers, which differ in sizes of their cycles (from 18 to 22 atoms) and in side phenyl and cyclohexyl substituents, but have unchanged number of the O atoms in a cycle. The phenyl and cyclohexyl derivatives of 18-crown-6 are found to be more efficient extractants of alkali metals as compared with unsubstituted crown ethers. However, the selectivity of separation of a pair Cs-Na remains low. The 18-crown-6 derivatives with one and two cyclohexyl fragments selectively extract Sr, which can be used to separate it from the remaining alkali and alkaline-earth metals. An increase in the size of a macrocycle from 18 to 20 and 22 atoms leads to a reduction in the extraction efficiency for all alkali and alkaline-earth metals, insignificantly improves separation of a pair Cs-Na, but noticeably deteriorates Sr-Na separation.

Cleaving of muscovite powder by molten lithium nitrate

Muscovite powder was cleaved along the (0 0 1) planes in molten lithium nitrate. The condition for optimal cleavage was 1 g muscovite with 17 g lithium nitrate at 350 °C for 12 h. The specific surface area of muscovite increased from 3.5 to 170 m2/g. IR spectroscopy and XRD confirmed that the structure of muscovite did not change. Reaction with some other alkaline nitrates did not markedly increase the specific surface area.

Catalytic combustion of particulate matter: Catalysts of alkaline nitrates supported on hydrous zirconium

In order to explore a method to remove particulate matter, catalysts of different alkaline nitrates (Li, K and Cs) supported on hydrous zirconium were prepared by the method of incipient humidity and tested as catalysts for particulate matter combustion. The catalytic activity was determined by using the temperature programmed oxidation technique (TPO), utilizing two equipments, a thermogravimetric reactor and other of fixed bed. In the first case the particulate matter/catalyst mixture was milled carefully in a mortar (tight contact) while in the second case more realistic operative conditions were used, particulate matter/catalyst mixture was made with a spatula (loose contact). All prepared catalysts showed good activity for the particulate matter combustion. The cesium catalyst was the one that presented higher activity, decreasing the combustion temperature between 200 and 250 °C with respect to the combustion without catalyst. The catalyst with lithium nitrate became active at higher temperature than its melting point and the same occurred with the potassium catalyst. This did not occur for the catalyst containing cesium nitrate that melts at 407 °C and became active from 350 °C.

Catalytic combustion of particulate matterCatalysts of alkaline nitrates supported on hydrous zirconium

In order to explore a method to remove particulate matter, catalysts of different alkaline nitrates (Li, K and Cs) supported on hydrous zirconium were prepared by the method of incipient humidity and tested as catalysts for particulate matter combustion. The catalytic activity was determined by using the temperature programmed oxidation technique (TPO), utilizing two equipments, a thermogravimetric reactor and other of fixed bed. In the first case the particulate matter/catalyst mixture was milled carefully in a mortar (tight contact) while in the second case more realistic operative conditions were used, particulate matter/catalyst mixture was made with a spatula (loose contact). All prepared catalysts showed good activity for the particulate matter combustion. The cesium catalyst was the one that presented higher activity, decreasing the combustion temperature between 200 and 250 °C with respect to the combustion without catalyst. The catalyst with lithium nitrate became active at higher temperature than its melting point and the same occurred with the potassium catalyst. This did not occur for the catalyst containing cesium nitrate that melts at 407 °C and became active from 350 °C.

Drift study of the products formed by radiolysis and photolysis of alkaline nitrates

The products of the radiolysis and photolysis of crystalline sodium, potassium, rubidium, cesium nitrates have been investigated by the diffuse reflectance infrared Fourier transform spectroscopy. The bands in the 1260-1220 and 804-809 cm−1 regions observed after the n -irradiation and photolysis by a light with the wave length 253.7 nm of crystalline alkali nitrates were identified as the vibrational modes of NO− 2 x 3 and x 2, respectively. The frequency of the x 3 oscillation of nitrite ions decreases from 1260 cm−1 up to 1220 cm−1 with the increase of the atomic weight or polarizability of a cation. The detection limit of the nitrite ions (1 ‐ 10−7 mol g−1) for the diffuse reflection method has been determined. The bands observed in KNO3, RbNO3 and CsNO3 spectra in the 947-940 and 722-737 cm−1 regions appearing only after photolysis are due to stretch oscillations of the peroxide bond O-O and wagging oscillations of the -ON=O group of peroxynitrite accordingly.

The phase diagrams of LiNO 3-NaNO 3 and LiNO 3-KNO 3: the behaviour of liquid mixtures

The binary phase diagrams of LiNO 3-NaNO 3 and LiNO 3-KNO 3 are studied by means of differential scanning calorimetry (DSC). For each phase diagram, the temperatures for solids and liquids have been determined and tabulated. Two models, based on regular solution theory, are employed to reproduce the phase diagrams. The first uses the values of the temperatures and enthalpies of fusion of the nitrates and the change in the heat capacity on melting, all of which are determined by differential scanning calorimetry. In the second model, we assume a variation of interaction energy with temperature to preserve regular solution treatment for the mixtures of alkaline nitrates.

Kinetic determination of trace amounts of nitrite based on its inhibitory effect on the photochemical reaction between iodine and ethylenediaminetetraacetic acid

A kinetic method for the determination of trace amounts of nitrite based on its inhibitory effect on the photochemical reaction between l2 and EDTA (6 × 10–5M l2, 2 × 10–4M EDTA, pH 5, 40 °C and 2000 lux) is reported. The reaction is monitored amperometrically (Pt-SCE, 100 mV) by measuring the time required for the current due to iodine to decrease to zero. Nitrite can be determined at concentrations between 3 and 100 ng ml–1. The proposed method has been applied to the determination of nitrite in waste waters and alkaline nitrates.

Thermoanlytical investigation of latent heat thermal energy storage materials

For solar energy utilization, waste heat recovery and load levelling, latent thermal energy storage is a useful tool, and the thermophysical properties, such as latent heat and specific heat capacity, of the materials are very important as well as thermal stability. DSC and TG have been applied for the purpose to the materials, such as polyethylene, urea, pentaerythritol and eutectic mixtures of alkaline hydroxides with alkaline nitrates or nitrites. Performance of polyethylene latent thermal energy storage equipment is also described.

Kinetics of the cathodic decomposition of silver iodide in molten alkaline nitrates

The cathodic decomposition of AgI was studied using a single pulse galvanostatic technique. The working electrode was an AgI-rotating disc immersed in the molten KNO 3-NaNO 3 eutectic. Linear overpotential-log (current density) plots were obtained for varying concentrations of I −. Evidence was found for the existence of two different control steps, depending on the iodide concentration. At lower I − concentrations a chemical reaction forming an adsorbed AgI − 2 complex ion is postulated as the rate-determining step. At higher I − concentrations the rds is related to the electrochemical reaction AgI + e = Ag° + I −. An alternative charge transfer process is suggested corresponding to the transfer of an I − ion between the two ionic media.

Potentiodynamic behaviour of graphite and platinum electrodes in molten sodium nitrate-potassium nitrate eutectic

The electrochemical behaviour of graphite and platinum electrodes has been studied in molten alkaline nitrates using cyclic voltammetry. The voltammograms obtained with graphite exhibit two current peaks not observed on platinum under similar conditions. An electrochemical reaction involving O 2 − ion and NO has been shown to proceed via an oxide on the graphite electrode surface which can be electrochemically reduced. It was assumed the formation of the NO 3 intermediate is mainly responsible of the corrosion of the graphite in this melt. The thermal and electrochemical properties of graphite in the molten alkaline nitrate have been correlated.

Gamma radiolysis of ionic liquids—II the free volume factor

It has been shown that the free volume is the decisive factor affecting the radiation decomposition yield for molten alkaline nitrates. The temperature dependence for liquids may be connected, therefore, with the temperature change of their free volumes. A general equation for the decomposition yield has been derived: G( prod) −1 = a+b exp ( γV c V f ) , where V f is the free volume, and the other quantities are constants for the same type of liquid.

Melting and pre-melting effects in the alkaline earth halides

Abstract : Heats and entropies of fusion, and heat content data for CaBr2, SrCl2, BaCl2 and BaBr2, determined by the method of phase-transition drop calorimetry, are reported. Solid-state transitions were confirmed for SrCl2 and BaCl2, and the possible nature and extent of these transitions are examined. An assessment of the phase-transition properties for the alkaline earth halides and nitrates is developed and the results are discussed relative to pre-melting effects and the process of fusion for these salts. For SrCl2, the relatively small value of the melting and pre-melting effects is note-worthy. (Author)

Eine Neue Methode Zur Massanalytischen Bestimmung Von Nitraten

Alkaline nitrates can be transformed quantitatively into alkaline carbonates by evaporating with conc. formic acid and heating the residue to about 550°. This procedure, by titration of the formed carbonate, permits an accurate determination of nitrate. Alkaline nitrites behave in the same way. Alkaline sulphates have no influence on the procedure, whereas in the presence of chlorides it is necessary to precipitate first the chlorine ions.

LXXIV. On a supposed analogy in atomic constitution between the earthy carbonates and alkaline nitrates

LXXIV. <i>On a supposed analogy in atomic constitution between the earthy carbonates and alkaline nitrates</i>