NH4Cl System Research Articles

Expermintal Research of Electrochemical Behaviour of Zinc in Ammonium Chloride Solutions

A present study was investigated “Experimental Research of Electrochemical Behaviour of Zinc in Ammonium Chloride Solutions.” The study was investigated by the electrochemical corrosion of sine is a problem of high significance both in the fundamental and applied fields of electrochemistry. Hence investigations were undertaken to study the corrosion of zinc in storage systems, the electrodeposition and characterisation of sine and the electrodeposition and characterisation of Siti nickel alloy. Results was shows that Potential-pH diagram for zinc in ZnClg/ NH₄Cl electrolyte, as used in Laclanche’s cell. When the surface composition of polished zinc. A freshly polished Zn surface was immersed in 0.5M NH₄Cl for 45 seconds and then analysed for energy measurements by ESCA. The composition of the modified zinc surface is summarised in table-1, When the binding energy was scanned in a narrow range of 1021 to 1010 eV, the participation of Zn 2PI electrons in the bond formation was confirmed. The investigations on the zinc- NH₄Cl system were hence carried out with the following specific objectives: IC4 find out the structure and nature of the species formed un the surface of sine when introduced in NH₄Cl solutions.

The Cathodic Reduction of Zn (II) on the Zn and Au Electrode in the Zinc(II)–NH4Cl System

The Cathodic Reduction of Zn (II) on the Zn and Au Electrode in the Zinc(II)–NH4Cl System

Removal of Metallic Iron from Reduced Ilmenite by Aeration Leaching

Aeration leaching was used to obtain synthetic rutile from a reduced ilmenite. The reduced ilmenite, obtained from the carbothermic reduction of ilmenite concentrate in a rotary kiln at about 1100 °C, contained 62.88% TiO2 and 28.93% Metallic iron. The particle size was about 200 μm and the size distribution was uniform. The effects of NH4Cl and HCl concentrations, stirring speed, and aeration leaching time on the extent of removal of metallic iron from the reduced ilmenite were studied at room temperature. The results revealed that aeration leaching is feasible at room temperature. When using the NH4Cl system, the metallic iron content was reduced to 1.98% in synthetic rutile, but the TiO2 content only reached 69.16%. Higher NH4Cl concentration did not improve the leaching. Using 2% NH4Cl with 3% HCl, we were able to upgrade the synthetic rutile to 75%, with a metallic iron content as low as 0.14% and a total iron content of about 4%. Synthetic rutile could be upgraded to about 90% using HCl solution alone. HCl and NH4Cl are both effective on the aeration leaching process. However, within the scope of this experiment, hydrochloric acid is more efficient in aeration leaching.

Kinetics of carbon steel dissolution in ammonium chloride solution containing sodium thiosulfate

AbstractThe dissolution behavior of carbon steel in ammonium chloride (NH4Cl) solution containing sodium thiosulfate (Na2S2O3) of various concentrations (0.01 and 0.1 M) was investigated using electrochemical impedance spectroscopy (EIS) and other nonelectrochemical techniques. The weight loss and polarization measurements indicate a significant increase in the NH4Cl corrosion rate of carbon steel on addition of Na2S2O3. The EIS measurements exhibited two capacitive loops at multiple direct current (dc) potentials for both the concentrations. Electrical equivalent circuit (EEC) and reaction mechanism analysis (RMA) were employed to analyze the impedance data. A four‐step mechanism with two intermediate adsorbate species of same charge was proposed to explain the dissolution behavior of carbon steel in the given system. The surface coverage values enumerated that the surface was entirely covered with adsorbed species unlike in the pure NH4Cl system. Charge transfer resistance and polarization resistance values estimated from RMA parameters indicate the increase in a dissolution rate with dc potential. The surface morphology was inspected via field emission scanning electron microscopy, and the corrosion products including surface state of carbon steel electrode were analyzed using energy dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy.

Electrochemical Processes at the Bi0–Bi3+ Interface in Chloride Melts

For rational design of technological schemes for production of high-grade bismuth and to improve electrochemical bismuth refining, knowledge of physicochemical properties of low-valent bismuth compounds and the mechanisms underlying processes occurring at the Bi0–Bi3+ interface in molten salts is necessary. For this purpose, the kinetics and mechanism of formation of low-valent bismuth compounds in the Bi0–BiCl3–ZnCl2–NH4Cl system by UV–Vis spectroscopy was studied. Chemical interactions between metallic bismuth and Bi3+ species in the melt give rise to Bi+ intermediates and [Bi5]3+ clusters, which are registered by their characteristic absorption bands at approximately 18000 and 14000 cm–1. The kinetic parameters for the Bi+ and [Bi5]3+ formations are estimated from the dependence of intensities of these absorption bands on the time of contact between metallic bismuth and Bi3+ species in the melt. The rate constants characterizing the Bi+ and [Bi5]3+ formations are estimated to be 3.33 × 10–3 and 2.31 × 10–3 s–1, respectively. The mechanism of anodic bismuth dissolution is proposed, and the cathodic and anodic current efficiencies for bismuth are determined.

Cadmium Refining in Chloride Melts Using a Bipolar-Electrode Electrolyzer

The kinetics and mechanism of the formation of subvalent cadmium complexes in the Cdo – CdCl2 – ZnCl2 – NH4Cl system were studied spectroscopicaly. The results indicate that metallic cadmium reacts with Cd2 2+ and Cd2 3+ complex cations. The formation of Cd2 2+ and Cd2 3+ is evidenced by the absorption bands around 270 and 335 nm, respectively, in the electronic spectrum of the melt. The variation of the intensity of absorption bands during the reaction between Cd2+ and metallic cadmium was used to evaluate the kinetics of Cd2 2+ and Cd2 3+ formation. The rate constants for the formation of Cd2 2+ and Cd2 3+ complex cations evaluated from the slop of plot of lg(Ao - A∞) versus time are 4.22∙10-3 and 3.50∙10-3 s-1 , respectively. The effect of the electrolysis conditions on the rate of cadmium exchange between the electrodes was examined. The anode current efficiency of cadmium dissolution was found to increase with current density and temperature and to exceed the theoretically predicted value, which was attributed to the formation of subvalent cadmium compounds. The present results may be helpful in assessing parameters of cadmium electrorefining. A method was proposed for electrolytic Cd refining in which electrolysis is performed in molten cadmium chloride containing Cd in lower oxidation states. The technique for the preparation of the electrolyte was described. To prevent impurity transfer from the anode to cathode, bipolar Cd electrodes were used. The distribution ratios evaluated for typical metallic impurities in Cd show that high-purity Cd can be obtained in a single electrolysis cycle.

Self-assembly properties of ultra-long-chain gemini surfactants bearing multiple amide groups with high performance in fracturing fluid application

In this work, a series of cationic gemini surfactants (C25-alkyl-C25, C25-ester-C25 and C25-amide-C25), which possessed a special structure consisting of ultra-long hydrophobic chains and cleavable groups, were synthesized using a main feedstock source obtained from rapeseed and applied as viscoelastic surfactant (VES) fracturing fluids in high temperature formations. Surface activities, rheological behavior analysis, scanning electron microscope (SEM) and cryogenic transmission electron microscopy (cryo-TEM) observations, and fracturing fluid performance were performed to determine the solution properties of gemini surfactants in the presence of ammonium chloride (NH4Cl). The results showed that the order of the critical micelle concentration (CMC) value was C25-alkyl-C25<C25-ester-C25<C25-amide-C25. And their ΔGmic0 values were found to have negative values, indicating that their self-assembly processes were spontaneous. The three surfactant/NH4Cl fluids exhibit high viscoelasticity and three-dimensional (3D) network structure. The 20mmolL−1 C25-ester-C25 fluid containing 0.19molL−1 NH4Cl meets the demands of a fracturing operation under 100°C, so do C25-alkyl-C25/NH4Cl and C25-amide-C25/NH4Cl fluids. In particular, the highest applicable temperature of the C25-amide-C25/NH4Cl system can reach to 150°C. Hence, C25-amide-C25 is a very promising candidate material for VES fracturing fluids.

The dehydration of MgCl2·6H2O in MgCl2·6H2O–KCl–NH4Cl system

The dehydration of MgCl2·6H2O in MgCl2·6H2O–NH4Cl–KCl system was investigated. The dehydration process was characterized by X-ray diffraction and chemical analysis. The dehydration effects of MgCl2·6H2O in different systems were compared. The dehydration mechanism of MgCl2·6H2O in MgCl2·6H2O–NH4Cl–KCl system was proposed and discussed. The formation of NH4Cl·MgCl2·nH2O (6>n≥0) below 300°C can effectively suppress hydrolysis. The anhydrous KMgCl3 formed above 400°C is more stable than anhydrous MgCl2 at elevated temperature, which can effectively protect the dehydration product from hydrolyzing at high temperature. The content of MgO in anhydrous MgCl2 was 0.02wt.% when dehydrating MgCl2·6H2O in MgCl2·6H2O–KCl–NH4Cl system with the molar ratio of MgCl2·6H2O:KCl:NH4Cl was 1:2.87:1.

Effect of La3+ on Dehydrogenation Capacity of the LiAlH4− NH4Cl System

Abstract The effect of the catalysts LaCl 3 and La 2 O 3 on the dehydrogenation properties of the LiAlH 4 -NH 4 Cl system was analyzed. The results show that La 2 O 3 doping shortens the starting time of hydrogen release, and improves the rate of hydrogen release. While, LaCl 3 doping induces an obvious decrease of the rate of hydrogen release. Furthermore, the study shows that with the increase of the amounts of LaCl 3 and La 2 O 3 , the hydrogen release amounts of the samples present a gradual decrease within 180 min except for the sample doped with 3 mol% LaCl 3 . However, the maximum hydrogen release amount of the sample doped with La 2 O 3 is obviously higher than that of the sample doped with LaCl 3 . In addition, the analysis of the SEM images of the undoped sample and the doped samples indicates that the microstructure of all the samples seems to be similar and obvious differences are not found.

Vacuum membrane distillation–crystallization process of high ammonium salt solutions

The batch mode of vacuum membrane distillation–crystallization (VMDC) process was carried out in the ammonium salt solutions. Vacuum membrane distillation (VMD) was used to permeate water to a desired concentration and the crystallizer was applied for the precipitation of crystals. The influence of concentration time on the permeate flux was investigated and the transfer resistances were estimated. Membrane fouling resistance increased gradually when the solution was concentrated up to the critical point of supersaturation factor. Beyond this critical point, the NH4Cl system revealed an irreversible membrane fouling, whereas the (NH4)2SO4 system revealed a reversible membrane fouling. By analyzing the transfer resistances, the determining concentration in the VMD process could be obtained, which would provide a way of avoiding membrane fouling problem. The permeated total nitrogen (TN) increased significantly from 4.7 to 59.8 mg/L with the NH4Cl solution. However, low level permeated TN (TN < 3 mg/L) with (NH4)2SO4 solution was maintained during the whole concentration process. The NH4Cl crystals with dendritic structure and (NH4)2SO4 crystals of lamellar form were obtained by the crystallizer with the production of 125.7 and 58.4 kg/m3, respectively.

Thermodynamics of leaching roasted jarosite residue from zinc hydrometallurgy in NH4Cl system

The thermal decomposition process of jarosite residue and the solubility of various oxides presented in the decomposed residue in NH4Cl-H2O system were studied. The results of heat decomposition of jarosite residue show that the insoluble ZnFe2O4 phase in the residue can be decomposed at temperatures ranging from 500 °C to 650 °C for 1 h. The OLI Systems software was used to study the thermodynamics of the solubility of various metal oxides existing in the decomposed residue in NH4Cl-H2O system. The results show that the solubility of ZnO, PbO, CdO, CuO and Ag2O is high, while the solubility of Fe2O3 is less than 10−4 mol/L in the pH range from 4.0 to 9.0. The calculated data are in accordance with the experimental results.

Study on dehydrogenation properties of the LiAlH4–NH4Cl system

In this work, the dehydrogenation properties of the LiAlH4–NH4Cl system and the LiAlH4–NH4Cl doped with CeO2 were analyzed by PCT (pressure–composition–temperature) equipment and SEM (Scanning Electron Microscope) analysis method. The result showed that the LiAlH4–NH4Cl system presented the fastest rate and the earliest starting time of hydrogen release when the molar ratio of LiAlH4 to NH4Cl was 1:1, and the dehydrogenation amount of the sample which the molar ratio of LiAlH4 to NH4Cl is 1:1 was very high and reached to 6.6wt%. The study on doping with CeO2 showed that doping with CeO2 had further raised the rate and the amount of hydrogen release of the LiAlH4–NH4Cl system and shortened the starting time of hydrogen release. Furthermore, the result showed that doping with CeO2 made the flocculent microstructure of the LiAlH4–NH4Cl system more obvious and looser.

Thermodynamic Analysis and Single Crystal Growth of ZnSe from ZnSe−N−H−Cl System

The thermodynamic properties of the transporting reactions in the closed-tube ZnSe−N−H−Cl system are analyzed by solving a set of equations with numerical methods, where NH4Cl serves as the transport agent. The results show that ZnSe−NH4Cl system has the properties of high total pressure and low transporting reaction equilibrium constant. The decomposition of hydrogen selenide determines the difference between the partial pressures of ZnCl2 and H2Se, which slows down the growth rate. This difference can be adjusted by adding extra Se and the hydrogen (H2) produced through decomposition of NH3. The ZnCl2 and a little extra Se should be added into the ZnSe−NH4Cl system to improve the utilizing efficiency of H2 and the concentration of practical transporting components of ZnCl2 and H2Se. A ZnSe single crystal as large as 20 × 15 × 8 mm3 was obtained by using ZnCl2·2NH4Cl as the transport agent with a little extra Se at about 1300 K. The experimental results about the diffusion-limited transport rate are well coincided to the thermodynamical analysis.

Electrorefining zinc dross in ammoniacal ammonium chloride system

A zinc dross was cast into anodes and electrorefined in an ammoniacal ammonium chloride electrolyte (NH 3–NH 4Cl) to produce high purity zinc. The influence of several factors, such as zinc concentration, current density and temperature, on cathodic current efficiency and power consumption were investigated. The results indicated that increasing Zn concentration increased the current efficiency, but, very high Zn concentrations affected the progress of the electrolysis of zinc dross. The power consumption can be decreased effectively by increasing the temperature of electrolyte. High current density adversely affected the quality of the cathodes and increased the power consumption. The morphology of cathodic zinc can be improved by increasing Zn concentration at an appropriate current density and its purity was very acceptable. All the experimental results obtained showed a technical feasibility of the NH 3–NH 4Cl system as an electrolyte system for electrorefining of zinc dross.

Study on the dissolution process of zinc anode in ammoniacal ammonium chloride system

To evaluate the feasibility of ammoniacal ammonium chloride system (NH3–NH4Cl) served as the electrolyte for the electrorefining process of zinc slag. The zinc anode's dissolution process in the NH3–NH4Cl solution was studied through electrochemical test, meanwhile, the effects of each component concentration of the NH3–NH4Cl electrolyte on the dissolution potential of zinc anode were investigated. The results suggested that zinc anode mainly took place active dissolution in the NH3–NH4Cl system, the apparent activation energy was 14.46 kJ mol−1 and the exchange current density 1.48×10−4 A cm−2. The increment of the NH4Cl concentration made a little contribution on decreasing the dissolution potential of zinc anode. However, the increment of NH3 concentration exhibited a notable effect on decreasing the dissolution potential of zinc anode. The anodic dissolution potential moved to positive-direction with the increase of Zn2+ concentration in the NH3–NH4Cl system.

Efficient Transition‐Metal‐Free Oxidation of Benzylic and Secondary Alcohols to the Carbonyl Compounds Using an N‐Bromosuccinimide/NH4Cl System

The oxidation of a variety of benzylic and secondary alcohols was achieved in excellent yields using an NBS/NH4Cl system in aqueous acetonitrile (CH3CN‐H2O; 7/3 v/v) at 80°C under very mild conditions.

Solid-phase reactions of alkanedicarboxylic acids with the Pb(OAc) 4–NH 4Cl system

The title reactions of HOOC(CH2)nCOOH acids afford α,ω-dichloroalkanes (n = 3, 4, 6) and lactones (n = 3, 4) as the main products.

Transition from rod- to disk-like micelles in APFO/D 2O/NH 4Cl systems studied by SANS and SAXS

The structures of the micelles in the APFO/0.5 molal NH 4Cl system have been studied. It is found that with increasing weight fraction w of APFO a gradual change from rod- to disk-like micelles occurs. At 4 w ⩽ 0.05, all APFO is present in rod-like micelles with radius 1.6 nm and length in excess of 30 nm. Whilst at w = 0.25 only disk-like micelles occur with thickness 3.2 nm and radius 2.6 nm.

The λ-phase transitions in NH4Cl

Abstract We show here the correlations between the volume changes and the vibrational frequencies of the disorder-induced Raman modes of NH4Cl near the λ-phase transitions of first order (P=0), tricritical (P⋍1.6 kbar) and second order (P⋍2.8 kbar). We obtain the values of the mode Gruneisen parameter for each phonon across the λ-phase transitions and use them to predict the Raman frequencies for the phonon modes studied as functions of temperature in the λ-phase change regions. Our calculated frequencies for the M-point phonons of v7 (93 cm−1) and v5 (144 cm−1) of NH4Cl are in good agreement with our observed Raman frequencies. This shows that the method employed here is satisfactory for predicting the Raman frequencies from the volume changes near the λ-phase transitions in the NH4Cl system.

General thermodynamic treatment of ammonium chloride system close to phase transitions

In ammonium halides the optical and acoustical phonons may be represented by the Einstein and Debye models. Close to the λ-phase-transition, the model for the lattice vibrations in these crystals requires an extra component which can be described by an Ising model. In this study we have developed an Ising model superimposed on an Einstein and/or Debye model and have applied it to the NH 4Cl system. In this application we have used the Raman frequency of the ν 5(174cm −1) phonon of NH 4Cl to characterize the corresponding Einstein and Debye frequency for this crystal system. Thus from our observed frequencies for the 174cm −1 (TO) mode we have obtained an approximation for the lattice vibrational contribution to the specific heat C y of NH 4Cl. The critical behaviour of the specific heat has been obtained for the Ising model, since the Einstein or Debye model is considered to show no anomaly in C v near the phase transition. The predicted values are close to observed C p data but differ significantly from the only observed C v data available, (Sakamoto, 1954) It is suggested that the observed C y data is unreliable in the vicinity of the λ-transition. The present model, or modifications of it should be capable of giving quite precise descriptions of the thermodynamic properties of solids close to second-order (or nearly second-order) phase transitions.