Aqueous Ammonium Sulfate Solutions Research Articles

Synchrotron small-angle X-ray scattering study of flame retardants based on ammonium sulfate and disubstituted ammonium phosphate

The use of wood in structural and finishing materials can significantly reduce the time of building construction, but the high flammability of wood limits its use in the building industry. To increase fire resistance, wooden structures are impregnated with flame retardants and the penetrating ability depends on their structure. We present the results of a small-angle X-ray scattering study of the structure of flame retardants based on ammonium sulfate and phosphate. The radii of inertia of hydrated complexes formed when flame retardants are dissolved in water, their shape and type of chains along which hydrated ions are located are determined. It is revealed that the presence of diffraction maxima indicates the presence of an ordering in the arrangement of hydrated ions. Aqueous solutions of ammonium sulfate and disubstituted ammonium phosphate contain two types of hydrated complexes of the same shape but different radius of inertia. At the same time, hydrated ions in complexes are located along persistent chains, and ordering revealed in the arrangement of ions, depended on their type. The results obtained can be used in developing flame retardants with a reduced radius of inertia, which will increase the penetrating capacity of the processing solution and increase the fire safety of wooden structures.

Direct recovery of electro-synthesized ammonia from low-concentration nitric oxide using pulse electrodeposited Cu/C catalyst in a catholyte-free system

Electrochemical production of ammonia (NH3) from nitric oxide (NO) offers a sustainable and environmentally friendly way to convert a nitrogenous pollutant into a valuable chemical feedstock and energy carrier. However, practical challenges in the electrochemical NO-to-NH3 conversion stem from mass transport limitations due to low NO concentrations in real-world streams and the need for post-purification of synthesized NH3. In this study, by synergistically developing an electrocatalyst (pulse-electrodeposited copper) and implementing a catholyte-free cell configuration with advantages of (i) facile NO transport, (ii) inhibited side reaction, and (iii) direct NH3 recovery in an external acid, we showcase an NH3 Faradaic efficiency of 85.6 % and a production rate of 53.4 μmol cm−2h−1 starting from 500 ppm NO. Crucially, the electro-synthesized NH3 was directly recovered as a high-purity aqueous ammonium sulfate solution comparable to industrial-grade quality. This approach opens the door to transforming waste into resources in a more energy-efficient and straightforward manner.

Extraction of phenolic compounds from walnut green husk (Juglans regia L.) by Salting-Out extraction method

Some factors in the salting-out extraction (SOE) method play a major role. The aim of this study was to investigate the interaction effects of the phase forming components and consequently select the best conditions to achieve a highly efficient recovery of phenolic compounds from walnut green husks (Juglans regia L.) using mixtures of ethanol and aqueous ammonium sulfate solutions. According to the results that were analyzed by response surface methodology, the optimal extraction conditions were obtained at ethanol: salt: water ratio of 34.8: 15.1: 54.4 (w/w) at a pH of 6–6.5 and 25 °C. At the optimal conditions, the overall phenolic and flavonoid content, and antioxidant activity were significantly higher than obtained by the conventional method. In addition, at a higher scale (i.e., 5 kg), similar results were obtained. Thus, it can be concluded that SOE has the potential to be scaled up for the simultaneous separation and purification of compounds from plant biomass. This paper is addressing extraction techniques, measurement, and characterization of new natural phenolic compounds from an agricultural by-product and valorization of waste.

Design of novel temperature-resistant and salt-tolerant acrylamide-based copolymers by aqueous dispersion polymerization

ABSTRACT Development of polymer-based flooding technology to improve oil recovery efficiency, water dispersion copolymerization of acrylamide, cationic monomer methacryloxyethyltrimethyl ammonium chloride (METAC), and anionic monomer acrylic acid (AA) were carried out in aqueous ammonium sulfate solution with polyvinyl pyrrolidone (PVP) as the stabilizer. The copolymers were characterized by 1H-NMR, FT-IR, TG, and SEM to confirm that they were prepared successfully and exhibited excellent salt-resistant property. Moreover, the effect of the aqueous solution of ammonium sulfate (AS) concentration, stabilizer concentration, and initiator concentration on the viscosity and size were systematically investigated. To further improve the thermal endurance properties of copolymer, hydrophobic monomers with different alkyl chain lengths were added to the above system. The acrylamide-based quadripolymer possessed prominent thermal and salt endurance properties by utilizing the advantages of zwitterionic structure and hydrophobic monomer. With the temperature rising, the viscosity retention could reach 70.2% in the water and 63.8% in the saline. This work had expected to provide a new strategy to design polymers with excellent salinity tolerance and thermal-resistance performances.

Low-temperature green synthesis of nanocrystalline La2O2S:Pr3+ powders and investigation of photoluminescence

Calcining an amorphous precursor in flowing hydrogen at 900 °C directly produced nanocrystalline La2O2S:Pr3+ powder (LOS:Pr3+; average size ∼35 nm) of a unimodal distribution of particle size (mean diameter ∼90 nm). The precursor, precipitated by titrating an aqueous solution of rare-earth nitrate and ammonium sulfate with ammonia water, was deduced to have an approximate composition of (La,Pr)2(OH)2.6(CO3)0.7SO4·2H2O. Aside from simplicity, the synthesis method reported herein has the obvious advantage of environmental friendliness, as it did not involve any harmful sulfidizing agent. The products were characterized in detail by XRD, FTIR, TG/DTA, and SEM/TEM to reveal the process of phase/morphology development and fine microstructure. Photoluminescence study found that the LOS:Pr3+ nanopowder exhibited strong luminescence at ∼508 nm (3P0,1 → 3H4 transition), with a fluorescence lifetime of ∼4.22 ± 0.03 μs, either through exciting the LOS host (∼263 nm, more efficient) or directly exciting the Pr3+ activator (∼304 nm), and retained ∼45% of its room-temperature intensity at 150 °C. Aside from phosphor application, the thus-synthesized powder would be useful for the fabrication of ceramic scintillators because of its nanosized crystallites and narrow distribution of particle size.

Screen-Printed Structures from a Highly Conductive Mildly Oxidized Graphene Suspension for Flexible Electronics.

In this study, the screen-printed flexible humidity sensor and supercapacitor structures from a suspension of mildly oxidized graphene (MOG) was obtained. MOG suspension with a low atomic oxygen content (~20%) was synthesized by electrochemical exfoliation of natural graphite in an aqueous solution of ammonium sulfate. MOG films (average thickness 5 μm) with a surface resistance of 102–103 kΩ/sq were obtained by screen printing on a flexible substrate. The thermal reduction of MOG films at 200 °C reduced the surface resistance to 1.5 kΩ/sq. The laser reduction with a 474 nm and 200 mW solid-state laser reduced the surface resistance to ~0.065 kΩ/sq. Various structures were screen-printed on a flexible substrate for a variety of flexible electronics applications. The structures representing a flat supercapacitor had an average specific capacitance of ~6 μF/cm2. The tensile deformations occurring during bending reduced the capacitance by 40% at a bending radius of 2 mm. Humidity sensing structures with sensitivity of 9% were obtained.

Simultaneous Infrared Spectroscopy, Raman Spectroscopy, and Luminescence Sensing: A Multispectroscopic Analytical Platform.

Scientific questions in fields such as catalysis, monitoring of biological processes, or environmental chemistry demand analytical technologies combining orthogonal spectroscopies. Combined spectroscopic concepts facilitate in situ online monitoring of dynamic processes providing a better understanding of the involved reaction pathways. In the present study, a low-liquid-volume multispectroscopic platform was developed based on infrared attenuated total reflection (IR-ATR) spectroscopy combined with Raman spectroscopy and luminescence sensing. To demonstrate the measurement capabilities, exemplary analyte systems including water/heavy water and aqueous solutions of ammonium sulfate were analyzed as proof-of-principle studies. It was successfully demonstrated that three optical techniques may be integrated into a single analytical platform without interference providing synchronized and complementary data sets by probing the same minute sample volume. In addition, the developed assembly provides a gastight lid sealing the headspace above the probed liquid for monitoring the concentration of molecular oxygen also in the gas phase via luminescence quenching. Hence, the entire assembly may be operated at inert conditions, as required, for example, during the analysis of photocatalytic processes.

Extraction sample preparation for chromatographic determination of residual quantities of acidic penicillins in milk

The distribution of six acid-type penicillins (penicillin G, penicillin V, oxacillin, cloxacillin, nafcillin, dicloxacillin) in the extraction systems of chloroform–aqueous solutions of ammonium sulfate was studied. The reported distribution coefficients values of penicillins demonstrated the effectiveness of using ammonium sulfate as a salting-out agent. Based on the data obtained, a procedure for milk sample preparation was developed for the quantification of the residual content of six acid-type penicillins.

Concentration-dependent structure of mixed (NH4)2SO4 and K2SO4 aqueous solutions using the X-ray diffraction, Raman spectroscopy and molecular dynamics simulations

In the production of potassium sulfate by ammonium sulfate, the purity of potassium sulfate product is relatively low due to the presence of potassium sulfate and ammonium sulfate solid solution. The microstructure of mixed aqueous solution of potassium sulfate and ammonium sulfate have been studied by X-ray diffraction, Raman spectroscopy and molecular dynamics simulation. And the molality of SO42− in the solution remained unchanged, and the molality of K+ and NH4+ were changed respectively. Reduced structure function [F(Q)], reduced pair distribution function [G(r)], excess Raman spectroscopy, radial distribution function (RDF), and structure of hydrogen bond network were obtained. With the decrease of K+ concentration and the increase of NH4+ concentration, a variety of new ion contact pairs were formed in the solution. The original hydrogen bond network is disrupted, and the cations would rebuild the hydrogen bond in the solution. When the NH4+ replaces the K+, the destruction to the hydrogen bond network is reduced. The addition of NH4+ might weaken the interaction between water molecules and anions, and exceed a certain critical concentration of 0.8 mol·L-1, NH4+ could promote the interaction between water molecules and anions. Moreover, the experimental results are in good agreement with the simulation results. This article provides certain theoretical guidance for its separation by studying the microstructure of its mixed solution.

Features of isothermal crystallization of ammonium sulphate

Soil fertility is rapidly decreasing due to irrational land use, erosion and soil pollution and adverse weather conditions. The use of composite granular organic-mineral fertilizers that contain mineral and organic components allows the soil fertility to be increased in the most effective and safe manner for the environment. In the production of granular composite fertilizers in a fluidized bed granulator, the process of isothermal mass crystallization is the main parameter that affects the quality.
 The effect of impurities on the morphological structure of ammonium sulfate microcrystals during mass crystallization on the surface was investigated by means of microscopic analysis. The influence of temperature and pH of the solution on the structure and shape of the microcrystal layer was studied.
 The process of mass crystallization depends on the presence of impurities, pH and temperature. Given the fact that there is no analytical or theoretical dependence describing the influence of impurities on the morphological structure, the influence is determined experimentally. The presence of even a small content of surfactants and other impurities in the ammonium sulfate solution has a significant effect on the morphological structure of ammonium sulfate microcrystals, which is revealed as reduction in the concentration of impurities in ammonium sulfate obtained by coke-chemical method. The pH level of the medium affects the structure and shape of microcrystals: smaller crystals with a layered structure are formed in the case of weakly alkaline medium with pH = 8 and smaller microcrystals with a granular structure are formed in the case of pH = 4. Therefore, it is important to maintain the required pH level of the medium during the mass crystallization of ammonium sulfate.
 In isothermal mass crystallization of saturated aqueous solutions of ammonium sulfate with humic compounds and bone meal proceeding on a surface with temperature 90 °C, small elongated crystals with microcrystal sizes from 10 to 100 μm are formed. Impurities of bone meal and humic compounds in the form of inclusions are placed between the crystals of ammonium sulfate: namely, the endosegregation of impurities in the microcrystalline framework is observed. As the concentration of organic matter in the solution increases, which crystallizes as droplets on the surface, rubble and dendrites are formed outside the initial droplet placement. This phenomenon is explained by the increase of diffusion resistance at the center of the drop; as a result, ammonium sulfate crystallizes in the zone with lower resistance.
 The process of isothermal mass crystallization of saturated aqueous solutions of ammonium sulfate with admixtures of humic compounds, bone meal and other target components in the specified ratios will create new highly effective fertilizers. The obtained results allow formulating theoretical bases for the formation of solid structures based on ammonium sulfate with admixtures of organic and mineral components.

CREATION OF GRANULAR COMPOSITE MATERIALS WITH MULTILAYER STRUCTURE

Granular products are widely used in many industries for the production of catalysts in oil refining and organic synthesis, drugs, food products, fertilizer production, etc. The main advantages of granular products are ease of operation and storage. Depending on the morphological structure, the granules obtained as a result of the technological process are divided into one-component, single-layer, composite-coated granule, multilayer granule, frame granule, and combinations thereof. In this paper, we consider, as an example, the technological basis of granulation of aqueous solutions of ammonium sulfate with impurities of humates, calcium carbonate and other substances with the formation of multilayer composite granules in a fluidized bed granulator. The processes of dehydration and mass crystallization during granulation, namely the influence of the drying rate and impurities on the kinetics of the evaporation process of the dispersed heterogeneous solution on solid particles have been studied. In the process of mass crystallization, when the saturation concentration is reached by removing the solvent, the processes of nucleation and crystal growth occur with the formation of a crystalline framework of ammonium sulfate crystals between, which impurities of organic matter and other components are evenly distributed in the volume of the formed micro layer. It was confirmed that the obtained granules of the composite granular fertilizer have a composite multilayer structure with a uniform distribution of suspended particles in the volume of the granule. Bibl. 14, Fig. 4.

Distribution constants and group increments of organic substances in the extraction systems of water saline–hexane

In the extraction systems of hexane–aqueous solutions of potassium carbonate, ammonium sulfate and sodium chloride, the distribution of a number of organic compounds (benzyl alcohol, tetrahydrofuran, phenol, aniline, pyridine, pyridazine, pyrimidine, n-butylamine, diethylamine, triethylamine, benzylamine) was studied. It was shown that sodium chloride, the most frequently used as a salting out agent, is noticeably inferior in salting ability to potassium carbonate, dipotassium phosphate and ammonium sulfate, since it contains singly charged ions with a relatively low charge density. Using the method of group increments on the example of aliphatic alcohols, the salting out ability of a number of mineral salts with singly charged ions was evaluated. By the value of this ability, the salts studied are arranged in the following order: NaNO2 > NaCl > KCl ~ NaBr > NaClO4 > KJ > NH4NO3 > NH4SCN. At the same time, the salting out effect of the last four salts from the above series is small. Based on the usage of the group increment method, the nature of the salting out effect is additionally confirmed, which consists, first of all, in strengthening the structure of the saline solution and increasing the increment of the methylene group (ICH2) with increasing the salt concentration.

The development of methods for the determination of residues of the insecticide pymetrozine in water, soil, cucumber and rape

Based on the literature data on the solubility of pymetrozine in water and organic solvents, as well as experimental data on the extraction of pymetrozine from water, soil and plant matrices, the optimal conditions for the extraction of pymetrozine from water; soil; cucumber; rape seeds, oil and green pods were selected. The conditions for cleaning extracts were selected as well. At the first stage, acetonitrile, a mixture of dichloromethane – isopropanol, or a mixture of dichloromethane – methanol in the presence or absence of inorganic salts were used for extraction of the pesticide. Pymetrozine was found to be a highly hydrophilic substance. For the purification of extracts of pymetrozine from plant matrices the extraction systems hexane – 0.02 mol/L aqueous solution of orthophosphoric acid, hexane or chloroform – aqueous solutions of ammonium sulfate were successfully used. The samples, obtained after this treatment, were pure enough to determine the residual amounts of pymetrozine in them at the maximum residue level (MRL), determined in Russia and the countries of the European Union, or lower using widespread liquid chromatography with diode-array (ultraviolet) detection.

Thermodynamic Modeling of CaSO4–(NH4)2SO4–NH3–H2O Quaternary System with Asymmetric E-NRTL Model

Ammonium sulfate [(NH4)2SO4], an undesired byproduct in the caprolactam process, can be converted into recyclable NH3 by the substitution reaction with lime milk to reduce the ammonia consumption and produce high-quality gypsum. However, the thermodynamic mechanism of this process has not been clarified, which results in the unpredictable crystal phase of calcium sulfate products. In this work, a thermodynamic model for the CaSO4–(NH4)2SO4–NH3–H2O quaternary system with the asymmetric E-NRTL activity coefficient model was developed to understand the thermodynamic behavior. The modeling works involved the data fitting of binary solubility, osmotic coefficient, enthalpy of solution, and heat capacity data as well as ternary solubility data. It was shown that the model could predict the solubility of ammonia and calcium sulfate in aqueous ammonium sulfate solution with temperature ranging from 0 to 160 °C and pressure up to 1.0 MPa. Furthermore, the constructed model for the quaternary system was proved to b...

Determination of protein crystallization kinetics by a through-flow small-angle X-ray scattering method

The kinetics of protein crystallization was analyzed using a modified Small-Angle X-ray Scattering (SAXS) setup that was operated in a flow-through mode. The model protein for the study was lysozyme, which was crystallized from supersaturated aqueous solutions of ammonium sulfate. A small amount of the protein solution was forced to recirculate within the SAXS setup. The SAXS intensity curves were measured at different time intervals and converted into kinetic profiles using a calibration factor. The diffraction images of the sample taken at the end of the kinetic experiments were recorded to confirm the presence of the crystalline phase. A population balance model was used to describe the course of the crystallization process. The results of the measurements and numerical simulations were compared to those obtained from a typical stirred-tank crystallizer (STC), where seeded and unseeded crystallization was performed. The kinetic data acquired from the SAXS and STC setups followed similar trends regarding kinetic dependencies on the salt concentration and the supersaturation degree. Moreover, the hydrodynamic conditions in the SAXS setup were determined, for which a quantitative agreement between the kinetic data acquired from both systems was achieved. Then, the same kinetic equations could be used to describe the course of crystallization in both systems. Hence, the modified SAXS technique can potentially substitute the STC-based method in quantification of crystallization kinetics.

Removal of ammonium ions from aqueous solutions using electrodialysis

We report results of investigating the processes of electrochemical oxidation of ammonium in a two-chamber electrolyzer depending on the composition of the original solutions ‒ anolyte and catholyte, current density, electrolysis duration. It is shown that the electrochemical oxidation of ammonia in aqueous solutions of ammonium sulfate proceeds at a rate of 14‒55 mg/(dm 3 ·hours) at a current density of 86.2‒172.4 A/m 2 and the starting concentrations of a given ion of 10‒120 mg/dm 3 . The rate of ammonium oxidation under these conditions increases with increasing starting concentrations of ammonium and with increasing current density. The output of oxidized ammonium for current and specific consumption of electricity for water purification from ammonium are defined based on ammonium concentrations and current density and increase with an increase in the concentration of a given ion and a decrease in current density. Ammonium oxidation rate increases by 1.66 times in solutions of ammonium sulfate ([NH 4 + ]=90 mg/dm 3 , j=172.4 A/m 3 ) in tap water, compared with distilled water. This is due to the presence of chlorides in tap water, which act as a catalyst during ammonium oxidation at the expense of the intermediate formation of active chlorine. Under these conditions, we observed complete oxidation of ammonia compared with solutions on distilled water where the residual ammonium concentrations reach 1‒3 mg/dm 3 . It is shown that the presence of chlorides in catholyte at a concentration of 30 mg/dm 3 almost does not accelerate the oxidation of ammonium. Our work demonstrated thatекек in all cases, during oxidation of ammonium, pH of solutions decreases to 6.1‒2.0, which is predetermined by the oxidation of ammonium to nitrates and the acidification of water by the formed nitric and sulphuric acids. Based on the reported results, it can be concluded that the electrochemical method is the most promising method for the extraction of ammonium ions from water. Its application makes it possible to achieve a 100 % water purification.

Forced Convection Evaporation for Bulk Protein Crystallization

Forced convection evaporation was adopted for bulk protein crystallization. As a model system ovalbumin in aqueous solutions of ammonium sulfate was used. The crystallization process was performed in a drying chamber, where the protein solution was contacted with a warm air stream at a temperature varied from 35 to 52 °C. The slow evaporation of water induced gradual crystallization of the protein. Heat and mass transfer in the water–air system during water evaporation caused the temperature of the protein solution to remain distinctly below the air temperature. This allowed processing the protein under mild conditions. The process design was guided by crystallization phase diagram and kinetic measurements. The supersaturation degree, which determines the nucleation and crystal growth rates, was adjusted by the rate of water evaporation. The latter was precisely controlled by matching the temperature in the chamber to the air humidity. The process could be accomplished in a single crystallization stage in...

Facile synthesis of graphene-phthalocyanine composites as oxygen reduction electrocatalysts in microbial fuel cells

In the path of direct energy conversion and wastewater disposal through microbial fuel cells (MFCs), the oxygen reduction reaction (ORR) plays a pivotal role. However, kinetic limitations hinders the spread of such technology requiring the use of a catalyst to develop efficient and cost effective devices. Herein we report a facile method for the preparation of iron-based catalyst supported on graphene oxide (GO) obtained by electrochemical exfoliation of graphite in aqueous solution of ammonium sulfate. Two different strategies to include nitrogen functionalities on/in GO matrix have been used, such as one-step nitrogen-doping in solution and post treatments based on annealing with ammonia gas. Iron (II) phthalocyanine (FePc) was used as iron source and deposited on GO by pyrolysis-free impregnation. Tuning the adjustable parameters governing the materials preparation allowed producing GO nanosheets with unique morphology and surface properties for enhancing the interaction with FePc. By combining the use of microscopy, electrochemical and spectroscopic techniques, a correlation between structure and surface chemistry of the prepared materials with catalytic activity towards ORR was established. The applicability of iron-based materials as ORR cathodes was evaluated by assembling single chamber air-cathodes MFCs, which power and voltage generation over time were acquired. The obtained results demonstrated that FePc/GO-based electrocatalysts can be used for electricity generation and waste treatment at the cathode side of MFCs.

Mildly oxidized graphene oxide suspension for printing technologies

The electrochemical exfoliation of graphite in an aqueous ammonium sulfate solution, in combination with ultrasound treatment, has been studied. It allows obtaining a high yield of mildly oxidized graphene oxide flakes during 15 min. The oxygen atomic content in mildly oxidized graphene oxide can be set by the ammonium sulfate concentration in the range from 20 to 28% (C/O ratio ∼3–5). The minimum of oxidation degree has been found to correspond to the electrolyte concentration of 0.15 M. The obtained mildly oxidized graphene oxide can be used to produce a water-based suspension of good time stability (without any visible temporal changes for one month). The films prepared from the mildly oxidized graphene oxide suspension by the drop casting method have sheet resistance 102–103 kΩ/sq, depending on film thickness. The thermal reduction at a relatively low temperature of 300 °C allows obtaining conductive films with a sheet resistance of about 1.5 kΩ/sq for a thickness of about 100 nm. The thin films (∼16–20 nm) obtained by inkjet printing or the use of spin-processor have their sheet resistance of 10–60 kΩ/sq and carrier mobility of 5–7 cm2 V−1 s. The mildly oxidized graphene oxide suspension is promising for preparing stable water-based inks to be used in conductive printed layers and flexible electronics.

Dispersion copolymerization of acrylamide and sodium 2-acrylamido-2-methylpropanesulfonate in aqueous salt solution stabilized with a macro-RAFT agent

Dispersion copolymerization of acrylamide (AM) and sodium 2-acrylamido-2-methylpropanesulfonate (AMPSNa) in aqueous ammonium sulfate (AS) solution was performed without mechanical stirring using a macro-RAFT agent sodium poly(2-acrylamido-2-methylpropanesulfonate) trithiocarbonate (PAMPSNa-TTC) as the stabilizer and 2,2′-azobis(2-methylpropionamide) dihydrochloride as the initiator. The effects of various polymerization parameters were systematically investigated regarding dispersion stability, particle size, molecular weight and apparent viscosity. A new mechanism for particle formation and the particle stability of aqueous dispersion polymerization was proposed.