Aqueous Ammonium Chloride Solution Research Articles

Anode plasma electrolytic carburizing of commercial pure titanium

Abstract The study investigates the influence of electrolyte compositions with acetone, glycerol, sucrose, ethylene glycol and ammonium chloride on the properties and structure of commercial pure titanium (CP-Ti) in the process of anode plasma electrolytic carburizing (PEC). The wear of the samples was measured using pin-disk friction in lubricated testing conditions. The effects of electrolyte composition on corrosion resistance of the PEC samples were examined by means of potentiodynamic polarization in a solution of sodium sulfate. It is shown that anode PEC of CP-Ti samples leads to formation of solid solution of carbon in titanium and external oxide layer in all studied electrolytes. The mechanism of carbon transfer from electrolytes containing sucrose, ethylene glycol and acetone to treated CP-Ti is found. The anode PEC of CP-Ti samples at 850 °C during 5 min was established to result in decrease in their surface roughness Ra from 1.13 ± 0.01 μm to 0.04 ± 0.01 μm and friction coefficient from 0.29 ± 0.01 to 0.10 ± 0.01. The treatment in the aqueous solution of ammonium chloride (10 wt.%) and sucrose (10 wt.%) resulted in the decrease in the wear rate by 3–3 orders. The base-sucrose electrolyte conditioned a decrease in the corrosion current density by a factor 18 due to passivating effect of the oxide layer.

Bubble explosion in pool boiling around a heated wire in surfactant solution

This paper reports a new pool boiling phenomenon of bubble explosion in a surfactant solution. The working fluid was an aqueous solution of cetyltrimethyl ammonium chloride (CTAC) with addition of sodium salicylate (NaSal) at the same mass concentration. A platinum wire was horizontally placed in the fluid for heating. The boiling heat transfer performances of the tested fluid at fluid temperature (288.15K) and different concentrations of CTAC/NaSal solution (0–400ppm) have been presented. It’s found that the tested surfactant solution significantly augmented boiling heat transfer as compared with water, and the best heat transfer performance was found at the concentration ranging from 5 to 100ppm. With a high-speed camera and an inverted microscope, the nucleation boiling process on the heated wire was recorded. For the first time, we observed a new bubble explosion phenomenon around the heated wire in CTAC/NaSal solutions (at concentration beyond 0.1ppm), which is apparently different from the previously reported boiling explosion due to homogeneous nucleation. Together with the observed strong jet-flow behaviors, bubble explosion strengthened the local disturbance and enhanced the boiling heat transfer. It was conjectured that the strong jet-flow phenomenon is essentially the traces of small bubbles and bubble explosion is a failed coalescence of unstable bubbles, which leads to the disturbance and boiling heat transfer enhancement.

Increase in Corrosion Resistance of Commercial Pure Titanium by Anode Plasma Electrolytic Nitriding

Features of the anode electrolytic plasma processing of commercial pure titanium and its alloys in aqueous solutions of ammonium chloride and ammonia additives are studied. It is identified that structure of modified layer contains an external TiO2 or TiO layer with micropores of up to 100 nm and a diffusion sub-layer after nitriding in the solution with the ammonia addition. Some increase in the surface microhardness is found. The plasma electrolytic treatment of titanium makes it possible to enhance its corrosion resistance by short-term (5 min) saturation with nitrogen at 750 °C in an electrolyte containing 5% ammonia and 10% ammonium chloride. The oxide coating formed during the anodic treatment has a positive effect on the corrosion resistance of titanium and results in reduce of the corrosion rate by two orders under continuous tests. Saturation of titanium samples with nitrogen leads to an increase in their strength properties after corrosion tests with a slight decrease in ductility. An additional advantage of this coating is to reduce of leaching of alloying elements from samples in corrosive environments.

Selective Synthesis of Trimethylamine by Catalytic N‐Methylation of Ammonia and Ammonium Chloride by utilizing Carbon Dioxide and Molecular Hydrogen

AbstractThe synthesis of trimethylamine (TMA) through a multicomponent combination of ammonia with carbon dioxide and molecular hydrogen by using a homogeneous ruthenium catalyst was explored. The use of [Ru(triphos)(tmm)] [triphos: 1,1,1‐tris(diphenylphosphinomethyl)ethane, tmm: trimethylene methane] together with aluminum trifluoromethanesulfonate as a co‐catalyst resulted in high ammonia conversion and excellent selectivity for TMA in organic solvents. Aqueous solutions of ammonium chloride were methylated almost quantitatively to the corresponding hydrochloride salt (i.e., TMA⋅HCl) in a biphasic solvent system by using the same Ru complex without the need for any co‐catalyst.

Solubility of Calcium Carbonate in Ammonium Chloride Aqueous Solution at T = (298.15, 323.15, and 348.15) K

Solubility and physicochemical properties (viscosity, density, and pH value) of calcium carbonate in ammonium chloride aqueous solution at (298.15, 323.15, and 348.15) K were investigated by using isothermal dissolution method. The solubility of calcium carbonate is 0.1521 mmol·kg–1 in water, but the solubility up to 10.5899 mmol·kg–1 when the molality of ammonium chloride aqueous solution is 1.5946 mol·kg–1 at 323.15 K, and the solubility increases with an increase on temperature and on molality of ammonium chloride. The reason for this result is interpreted by hydrolysis theory that hydrolysis of ammonium cause pH to decrease. The behavior about physicochemical properties is also analyzed, and the viscosity of the solution was predicted by the exponential model and extended Jones–Dole model. The solubility and physicochemical properties in this work is basically required for studying of calcium carbonate, which would provide a basis to optimize the process of calcium carbonate in the industrial production.

Heatline Visualization During Solidification of a Eutectic Solution in a Rectangular Cavity

The present work is focused on the visualization of heatline during solidification. The investigation considers a rectangular cavity filled with eutectic aqueous ammonium chloride solution. In order to develop Rayleigh-Bennard convection in the cavity, the temperatures of the top and bottom walls are maintained below and above eutectic temperature of the solution, respectively, whereas the vertical walls are assumed to be adiabatic. The solidification process is modelled by a set of mass, momentum and energy conservation equations coupled with boundary conditions. The governing differential equations are solved using semi-implicit finite volume method according to SIMPLER algorithm with the help of line-by-line TDMA solver. The evolution of heatline pattern during solidification is presented. From the evolution of solid–liquid interface, it is found that the solidified layer undergoes remelting at the solid–liquid interface during later stages of solidification as a consequence of thermal superheat. In the present work, the cause of the remelting phenomenon during solidification is investigated in details using energy flux vectors. It is observed that convection loop pattern i.e. energy flow below the remelted interface changes at the time of remelting.

Removal of ammonia nitrogen from leachate of Muribeca municipal solid waste landfill, Pernambuco, Brazil, using natural zeolite as part of a biochemical system

The inadequate disposal of leachate is one of the key factors in the environmental impact of urban solid waste landfills in Brazil. Among the compounds present in the leachates from Brazilian landfills, ammonia nitrogen is notable for its high concentrations. The purpose of this study was to assess the efficiency of a permeable reactive barrier filled with a natural zeolite, which is part of a biochemical system for the tertiary treatment of the leachate from Muribeca Municipal Solid Waste Landfill in Pernambuco, Brazil, to reduce its ammonia nitrogen concentration. This investigation initially consisted of kinetic studies and batch equilibrium tests on the natural zeolite to construct the sorption isotherms, which showed a high sorption capacity, with an average of 12.4 mg NH4+.L−1, a value close to the sorption rates found for the aqueous ammonium chloride solution. A permeable reactive barrier consisting of natural zeolite, as simulated by the column test, was efficient in removing the ammonia nitrogen present in the leachate pretreated with calcium hydroxide. Nevertheless, the regenerated zeolite did not satisfactorily maintain the sorption properties of the natural zeolite, and an analysis of their cation-exchange properties showed a reduced capacity of 54 meq per 100 g for the regenerated zeolite compared to 150 meq per 100 g for the natural zeolite.

Interaction between quaternary ammonium surfactants with coal pitch and analysis surfactants effects on preparing coal pitch water slurry

The wetting behavior, adsorption amount and Zeta potential of aqueous solutions of the octadearyl dimethyl ammonium chloride (OTAC), cetyl trimethyl ammonium chloride (CTAC) and benzyl hexadecyl dimethyl ammonium chloride (HDBAC) on coal pitch surface were investigated. When the content of surfactant was constant, along with the growing of slurry concentration, the apparent viscosity of coal pitch water slurry (CPWS) increased. On the other side, it declined when shear rate grew. There was a liner relationship between contact angle and surface tension, so Zisman theory was well agreed with this wetting system. The adsorption amount of dispersants on coal pitch surface increased with the growing of solution concentration. The Zeta potential grew at first, and then stayed the constant.

Plasma electrolytic modification of the VT1-0 titanium alloy surface

The features of the anodic plasma electrolytic treatment of commercial titanium in an aqueous ammonium chloride solution with ammonia and glycerol additions are investigated. It is revealed that the modified layer comprises an external TiO2 or TiO layer with micropores of up to 100 nm and a diffusion sublayer after nitriding in the solution with the ammonia addition. It is ascertained that the anodic dissolution of the titanium alloy dominates over its oxidation at treatment voltages reaching 210 V and an ammonium chloride concentration of 100 g/L. This effect is accompanied by a decrease in the sample mass. The sample mass grows due to an increase in the oxide layer exceeding the dissolution losses at higher voltages and ammonium chloride concentrations. It is shown that the corrosion current density in Ringer’s solution can be decreased after commercial titanium is treated in the ammonium chloride and glycerol solution.

Specific ion effects on membrane potential and the permselectivity of ion exchange membranes.

Membrane potential and permselectivity are critical parameters for a variety of electrochemically-driven separation and energy technologies. An electric potential is developed when a membrane separates electrolyte solutions of different concentrations, and a permselective membrane allows specific species to be transported while restricting the passage of other species. Ion exchange membranes are commonly used in applications that require advanced ionic electrolytes and span technologies such as alkaline batteries to ammonium bicarbonate reverse electrodialysis, but membranes are often only characterized in sodium chloride solutions. Our goal in this work was to better understand membrane behaviour in aqueous ammonium bicarbonate, which is of interest for closed-loop energy generation processes. Here we characterized the permselectivity of four commercial ion exchange membranes in aqueous solutions of sodium chloride, ammonium chloride, sodium bicarbonate, and ammonium bicarbonate. This stepwise approach, using four different ions in aqueous solution, was used to better understand how these specific ions affect ion transport in ion exchange membranes. Characterization of cation and anion exchange membrane permselectivity, using these ions, is discussed from the perspective of the difference in the physical chemistry of the hydrated ions, along with an accompanying re-derivation and examination of the basic equations that describe membrane potential. In general, permselectivity was highest in sodium chloride and lowest in ammonium bicarbonate solutions, and the nature of both the counter- and co-ions appeared to influence measured permselectivity. The counter-ion type influences the binding affinity between counter-ions and polymer fixed charge groups, and higher binding affinity between fixed charge sites and counter-ions within the membrane decreases the effective membrane charge density. As a result permselectivity decreases. The charge density and polarizability of the co-ions also appeared to influence permselectivity leading to ion-specific effects; co-ions that are charge dense and have low polarizability tended to result in high membrane permselectivity.

H2O-NH4Cl system: Thermodynamics and structure of supersaturated (8÷28m) solutions at 298.15 K

Thermodynamic characteristics are determined for supersaturated (8÷28m) aqueous ammonium chloride solutions at 298.15 K: activity as well as partial molar enthalpy, volume, and excess entropy of water, osmotic coefficients, density, and salt hydration numbers. The relative humidity above the solution decreases from 75.6% (8m solution) to 44.7% (28m solution). A directly proportional dependence is found between the enthalpy and entropy characteristics. The negative values of the nonideal portion of the Gibbs energy are due to structural effects (excess entropy). The excess entropy of water has the same value 1.8 J/(mol·K) in supersaturated 12m NaCl and 28m NH4Cl. The ratio 12/28 = 3/7 is also valid for other “isoentropic” molalities of the said salts.

Remelting and interface dynamics during solidification of a eutectic solution in a top-cooled rectangular cavity: A numerical study

The present work is a numerical investigation on the occurrence of remelting phenomenon during solidification of a eutectic aqueous ammonium chloride solution in a top-cooled rectangular cavity. The analysis is performed following a fixed-grid single-domain approach. Accordingly, the solidification process is represented by a set of mass, momentum and energy conservation equations, where the enthalpy update scheme is used to trace the solid–liquid interface during solidification. The set of governing differential equations is solved using semi-implicit finite volume method, based on SIMPLER algorithm, applying line-by-line TDMA solver. The present simulation predicts the distribution of temperature and streamline along with fraction of solid in the computational domain, and evolution of the solidified layer during solidification. The simulation shows remelting of solidified layer at the solid–liquid interface during later stages of solidification due to irregular superheat of the bulk solution convected towards the solid–liquid interface. Hence, the occurrence of the remelting phenomenon during solidification is studied by evaluating the interface growth history as a function of the process parameters, namely, cavity height and thermal gradient imposed across the cavity. It is found that there is a small increase in the solidification growth rate with increase in cavity height, where the possibility of remelting is high. With the increase in imposed thermal gradient, the solidification growth rate increases significantly and the occurrence of remelting disappears.

Surface behavior of hydrated guanidinium and ammonium ions: a comparative study by photoelectron spectroscopy and molecular dynamics.

Through the combination of surface sensitive photoelectron spectroscopy and molecular dynamics simulation, the relative surface propensities of guanidinium and ammonium ions in aqueous solution are characterized. The fact that the N 1s binding energies differ between these two species was exploited to monitor their relative surface concentration through their respective photoemission intensities. Aqueous solutions of ammonium and guanidinium chloride, and mixtures of these salts, have been studied in a wide concentration range, and it is found that the guanidinium ion has a greater propensity to reside at the aqueous surface than the ammonium ion. A large portion of the relative excess of guanidinium ions in the surface region of the mixed solutions can be explained by replacement of ammonium ions by guanidinium ions in the surface region in combination with a strong salting-out effect of guanidinium by ammonium ions at increased concentrations. This interpretation is supported by molecular dynamics simulations, which reproduce the experimental trends very well. The simulations suggest that the relatively higher surface propensity of guanidinium compared with ammonium ions is due to the ease of dehydration of the faces of the almost planar guanidinium ion, which allows it to approach the water-vapor interface oriented parallel to it.

Reduced Limestone Consumption in Steel Manufacturing Using a Pseudo-catalytic Calcium Lixiviant

A mineral carbonation method for using anthropogenic carbon dioxide emissions is discussed. In this method, steel manufacturing slags are carbonated with gaseous carbon dioxide at atmospheric pressure and temperature using an aqueous ammonium chloride solution. This lixiviant extracts calcium selectively from the slag material, after which the dissolved calcium is precipitated as calcium carbonate. A flue gas stream can be used as a CO2 source without pre-separation. The reactions occur pseudo-catalytically in one vessel, resulting in considerable savings regarding process capital costs and reagent usage compared to a previously developed two-step carbonation method (Slag2PCC). The one-step method uses steel slag more efficiently, potentially reducing the amount of landfilled slag while capturing significantly more carbon dioxide in the same amount of slag. The two-step method produces >95% pure calcium carbonate, which can be used, e.g., in papermaking, while the one-step method is capable of manufacturi...

Ni/La2O3 catalyst containing low content platinum–rhodium for the dehydrogenation of N2H4·H2O at room temperature

Ni/La2O3 nanocatalyst with Pt and Rh content as low as 5 mol%, respectively, is successfully synthesized by a facile co-reduction method in the presence of hexadecyl trimethyl ammonium chloride aqueous solution under ambient atmosphere. Interestingly, the resulted Ni/La2O3 catalyst with low cost exhibits excellent catalytic activity to dehydrogenation of hydrous hydrazine (N2H4·H2O), producing hydrogen with 100% selectivity at room temperature (298 K), which represents a promising step toward the practical application for N2H4·H2O system on fuel cells.

Influence of oxide layer on carbon diffusion during anode plasma electrolytic carburizing

This study is devoted to the effect of the oxide layer formed upon anodic plasma-electrolytic carburization on the rate of carbon diffusion in low carbon steels upon application of an aqueous solution of ammonium chloride with glycerol as a working electrolyte. Approximate determinations of carbon distribution in the surface layer of low carbon steels after their anodic plasma-electrolytic carburizing confirmed the hypothesis that there is deceleration of carbon diffusion by the oxide layer. Different structures of the oxide layer were revealed that depend on the method of sample cooling after their saturation with carbon in an anodic vapor-gas envelope. A possibility of controlling the thickness of the oxide layer was shown, as well as clarification of the surface by the choice of an electrolyte and treatment mode, was shown. A reduction in the roughness of the carburized surface from 0.62 ± 0.02 to 0.22 ± 0.02 μm was revealed.

Filling-box process during solidification of a liquid hypoeutectic binary solution

Solidification of binary solutions often occurs in many industrial applications, including the casting of binary alloys. In this study we consider the effect of a side cooling wall on the development of double-diffusive convection during solidification of a hypoeutectic aqueous ammonium chloride (NH4Cl–H2O) solution. To study flow development during solidification of this solution, we used the shadowgraph technique, particle image velocimetry, and a thermochromic-liquid-crystal slurry. In addition, the transient temperature distribution within the test cell was measured by type-T thermocouples. The results of these experiments revealed that the filling-box process originated from the bottom of the test cell to the top. This process induced several double-diffusive layers and counterclockwise roll cells in the melt, mainly caused by double-diffusive convection. Consequently, the filling-box process may cause serious V-segregates and material defects in solidified ingots.

小型水样氨氮自动光学检测装置

A compact optical sensor for the automatic detection of ammonia nitrogen in water was developed based on a combination of liquid-gas separation and gas-phase reversible colorimetry.The sensor consists of a sample chamber,a test chamber,aprogram-controlled sampling unit and a data-processing circuit module.The sensor performance was investigated by using a series of aqueous ammonium chloride solutions with different concentrations as the ammonia nitrogen samples.The linear relationship between the measured absorbance and the ammonia-nitrogen concentration was obtained and the high reliability of sensor was demonstrated by comparing the measured and given concentrations of standard ammonia nitrogen samples.The experimental results indicate that the sensor works continuously and automatically for a long time at a room temperature and has good repeatability.The detection limit is 0.04mg/L(NH3-N).The sensor is characterized by its smaller volume,light-weight,lower cost and power consumption,high-level automation,and it is suitable for on-site rapid detectionof ammonia nitrogen in a practical water environment.

Aqueous ammonia and ammonium chloride hydrates: Principal infrared spectra

The infrared (IR) spectra of aqueous ammonia (NH3) and aqueous ammonium chloride (NH4Cl) were recorded by attenuated total reflectance to obtain their molecular organizations. Factor analysis (FA) of the spectra revealed two hydrates for each species: (NH3)2⋅H2O and NH3⋅3H2O; NH4+,Cl-2·H2O; and (NH4+,Cl-)·3H2O, respectively. The hydrate spectra and species abundances were obtained as a function of total concentrations. From this the equilibrium equation between the two ammonia hydrates was determined: 2[(NH3)2·H2O]+5(H2O)2⇌4[NH3·3H2O] with its equilibrium constant Kα=(2.3±0.6)×10−5L3mol−3. Similarly, for the two ammonium chloride hydrates the equation is 2[(NH4Cl)2·H2O]+5(H2O)2⇌4[NH4Cl·3H2O] with its equilibrium constant: Kβ=(4±1)×10−7L3mol−3. Band simulations of the hydrate spectra were compared to that of pure liquid water and parent molecules. For aqueous ammonium chloride solutions the water and all ammonium hydrate bands are slightly displaced from that of pure water and pure ammonium chloride, respectively. However, for ammonia hydrates the situation is different: compared to the gas situation the hydrate water bands have similar displacements as that of pure liquid water; the ammonia deformation bands are also little displaced but the stretching bands are strongly red shifted. These shifts, which are even greater than that in pure liquid water, are attributed to strong hydrogen bonding situations: water–H with N–ammonia and ammonia–H with O–water. This explains the high solubility of ammonia in water. The comparison between the spectra of aqueous ammonium chloride and ammonia hydrates indicates that ammonium ion is not present in aqueous ammonia from 11.3M down to at least our detection limit of 3mM NH3.

Photoelectrochemical properties of oxide films formed by anode plasma electrolytic oxidation on titanium in water solutions

It is shown that films of titanium dioxide obtained by anodic plasma electrolytic processing of commercial titanium in an aqueous solution of ammonium chloride are photosensitive. Incident photon to charge carrier efficiency (IPCE) in the near ultraviolet (366 nm) reached 8.5%. Magnitude of the photocurrent generated by the films obtained under optimum processing conditions decreases no more than 20% at the transition from the ultraviolet to the mixed light.