Ammonium Carnallite Research Articles

From waste to wealth: Using MgO nanoparticles to transform ammonium into a valuable resource

In this contribution, a versatile approach to the crystallization of ammonium carnallite is discussed through a highly efficient process of ammonium removal from an aqueous solution on MgO(111) surface through a rapid one-pot route. In addition to effective ammonium removal from the reaction environment and recovering it in the form of ammonium carnallite, another dual-purpose application of this approach is the recovery of magnesium in the form of carnallite crystals as a valuable metal with wide application in the industry. The MgO nanoparticles (MgO-NPs) showed high adsorption potential due to the presence of high index surfaces of (111) in the nanoparticle lattice due to the unsaturated valley and edge locations. The phase purity and crystallinity of MgO-NPs were investigated by XRD, and the planes' lattice was confirmed using SAED patterns, and lattice fringes from HRTEM images, while their acidic active sites led to high NH4+ removal using NH3-TPD analysis. A mechanism of ammonium adsorption on the active sites of the MgO(111) surface is proposed for the crystallization phenomenon. FESEM, EDS, HRTEM, XRD, FTIR, and BET analyses were evaluated to confirm the synthesis of single-crystal carnallite. Subsequently, TGA tests displayed the ammonium carnallite weight loss through decomposition to NH3 and HCl and proved the formation of MgO. Therefore, the high recovery rate of 100 mg/L ammonium within 30 min at neutral pH with 125 mg/L of MgO-NPs through the adsorption/crystallization process was revealed. Ammonium recovery from wastewater reduces the costs, energy, and environmental footprints associated with its removal processes.

Stable phase equilibrium of the quaternary system NaCl-MgCl2-NH4Cl-H2O at 348.15 K and its application in industry

Based on the requirement of the new technology to achieve comprehensive utilization of sodium and magnesium resources by using the mother solution from the preparation of potassium salt as raw material, the phase equilibrium data of the quaternary system NH4Cl-MgCl2-NaCl-H2O as well as its ternary subsystems MgCl2-NH4Cl-H2O and NaCl-NH4Cl-H2O were investigated by an isothermal equilibrium method under atmospheric pressure at 348.15 K, and the dry-salt phase diagram and water-phase diagram were drawn. Two invariant points and four crystallization fields including two single salts NH4Cl and NaCl, one hydrate salt MgCl2·6H2O, and one double salt MgCl2·NH4Cl·6H2O were determined in this quaternary system. Combining our results with available experimental data in the literature, an optimized process to produce ammonium carnallite and NaCl was proposed. Using the Pitzer electrolyte solution model, the experimental results were regressed and calculated. The calculated values agree well with the experimental values.

Phase diagrams of the quaternary system NaCl-MgCl2-NH4Cl-H2O at 333.15 K and their application

Based on the requirement of the new technology for producing ammonium carnallite and NaCl via the solution left after the preparation of potassium salt as raw materials, the solubilities of the quaternary system NaCl-MgCl2-NH4Cl-H2O and ternary subsystem NaCl-MgCl2-H2O at 333.15 K were measured using the isothermal dissolution method, and the corresponding phase diagrams were plotted. The phase diagram of the ternary system consists of three fields of crystallization, which correspond to NaCl, MgCl2·6H2O and their co-existing fields respectively. There are four fields of crystallization in the quaternary system, which correspond to MgCl2·6H2O, NH4Cl, NaCl and the double salt MgCl2·NH4Cl·6H2O respectively. By analyzing and calculating the phase diagrams, a technological route was proposed, which indicated that the Na-Mg resources were fully utilized. The extended Pitzer model was applied to the phase equilibrium calculation and the results showed that the calculated data were consistent with experimental values well.

The dehydration of MgCl2·6H2O by inhibition of hydrolysis and conversion of hydrolysate

The hydrolysis of magnesium chloride hexahydrate and the countermeasures against hydrolysis were investigated. X-ray diffraction, TG-DSC analysis, and chemical analysis were employed to characterize the hydrolysis process, and then the hydrolysis reactions occurred at different temperatures were determined. After that, the combination of inhibition of hydrolysis and conversion of hydrolysate was adopted to cope with the different hydrolysis reactions. The hydrolysis process of MgCl2·6H2O includes the hydrolysis of dehydrated magnesium chloride below 300 °C with MgOHCl·xH2O as hydrolysate and the hydrolysis of anhydrous MgCl2 over 400 °C with MgO as hydrolysate. The inhibition of hydrolysis by forming dehydrated ammonium carnallite (below 300 °C) and the conversion of hydrolysate (above 400 °C) can effectively resolve the hydrolysis problem occurred at different stages. The dimension of the mixture of MgCl2·6H2O and NH4Cl influences the mass transfer and reaction process. When the ratio of height to diameter of the mixture was over 9:1, the magnesia content in anhydrous MgCl2 reached 0.1 wt.%.

Salt–Water Phase Equilibria in Ternary Systems K+(Mg2+), NH4+//Cl––H2O at T = 273 K

Phase equilibria for two ternary systems K+, NH4+//Cl––H2O, and Mg2+, NH4+//Cl––H2O at T = 273 K were investigated by means of the isothermal saturation dissolution method. The density of each equilibrium liquid phase was determined by using the weighting bottle method. The compositions of the solid phases were confirmed using Scherinemakers’ wet residue method. The phase diagrams and the figures of density versus composition were plotted in accordance with the experimental data. The ternary system Mg2+, NH4+//Cl––H2O is a type of complex with an incongruent type complex salt ammonium carnallite (NH4Cl·MgCl2·6H2O) formed at 273 K, which consists of two invariant points, three monovariant curves, and three solid phase crystallization fields. The ternary system of K+, NH4+//Cl––H2O consists of three invariant points, four monovariant curves, and five solid phase crystallization fields and is also a type of complex with two solid solutions [(K, NH4)Cl] and [(NH4, K)Cl] found at 273 K. The comparison of obtained phase diagrams at 273 K in this work and 298 K has been deliberated.

Phase Diagram of the Quaternary System KCl–MgCl2–NH4Cl–H2O at t = 60.00 °C and Their Application

Based on the requirement for the comprehensive exploitation and utilization of the salt lake resources magnesium chloride and potassium chloride, a new technology to produce KCl and ammonium carnallite (NH4Cl·MgCl2·6H2O) by using NH4Cl as salting-out agent to separate carnallite is proposed. The solubilities of quaternary system KCl–MgCl2–NH4Cl–H2O were measured by the isothermal method at t = 60.00 °C and the corresponding phase diagram was plotted and analyzed. The analysis of this phase diagram shows that there are seven saturation points and eight regions of crystallization. These eight regions of crystallization represent salts corresponding to KCl, NH4Cl, MgCl2·6H2O, (K1−n(NH4)n)Cl, ((NH4)nK1−n)Cl, (K1−n(NH4)n)Cl·MgCl2·6H2O, KCl·MgCl2·6H2O and NH4Cl·MgCl2·6H2O. According to the phase diagram analysis and calculations, ammonium carnallite (NH4Cl·MgCl2·6H2O) and KCl can be obtained using carnallite as raw materials and ammonium chloride as salting-out agent at t = 60.00 °C. The new technology shows the advantages of being easy to operate and having low energy consumption. The research on this quaternary phase diagram is the foundation for reasonable development of carnallite resources and comprehensive utilization of the salt lake brines.

Phase Diagrams of the Quaternary System NaCl–MgCl2–NH4Cl in Water at 0 and 25 °C and Their Application

On the basis of the comprehensive utilization of the Na–Mg salt deposit, a new process to produce NaCl and ammonium carnallite (MgCl2·NH4Cl·6H2O) by using NH4Cl and the solution left after the preparation of potassium salt as raw materials was proposed. For this, the phase equilibrium of the quaternary system NaCl–MgCl2–NH4Cl–H2O at 25 and 0 °C was studied. The solubilities of the quaternary system NaCl–MgCl2–NH4Cl–H2O were measured by an isothermal method, and the corresponding phase diagrams were drawn out. From the phase diagrams: there are four solid phase crystalline zones, which correspond to NaCl, MgCl2·6H2O, NH4Cl, and MgCl2·NH4Cl·6H2O respectively. NaCl and MgCl2·NH4Cl·6H2O have larger crystalline zones at 25 °C than at 0 °C, and NH4Cl has a smaller crystalline zone at 25 °C than at 0 °C. It indicates that NaCl and MgCl2·NH4Cl·6H2O are easy to crystallize out. On the basis of the analysis and calculation of the phase diagrams, the appropriate conditions for the process were identified. In the pro...

Preparation of Anhydrous Magnesium Chloride from Ammonium Carnallite

High-purity anhydrous magnesium chloride was prepared by using ammonium carnallite as starting material and alumina as covering agent. X-ray diffraction (XRD) analysis and thermogravimetric analysis and differential calorimetry analysis (TG-DSC) analysis were employed to characterize the process. The mechanism involved in the process was proposed and discussed. The factors affecting the purity of anhydrous magnesium chloride were investigated. The results reveal that the mass fraction of magnesia in anhydrous magnesium chloride could reach 0.08% under the optimum conditions: alumina with the thickness of 1.3 cm was put on top of dehydrated ammonium chloride (NH4Cl · MgCl2 · 1.2H2O), and then the sample was maintained at 450°C for 1.5 h. After that, the sample was calcined at 700°C for 1 h.

Preparation of Anhydrous Magnesium Chloride from Magnesium Chloride Hexahydrate

A method was proposed for the preparation of high-purity anhydrous magnesium chloride by using magnesium chloride hexahydrate and ammonium chloride as raw materials, and alumina as covering agent. X-ray diffraction was employed to investigate the process. The mechanism involved in the process was proposed. The factors affecting the purity of anhydrous magnesium chloride were investigated. Dehydrated ammonium carnallite was formed in the process to facilitate the dehydration process. Alumina as covering agent can guarantee that the formation of high-purity anhydrous magnesium chloride was obtained. The content of magnesia in anhydrous magnesium chloride was 0.02 pct under the optimum conditions: molar ratio of ammonium chloride to dehydrated magnesium chloride was 2:1, thickness of alumina 1.3 cm, reaction temperature 723 K (450 °C), reaction time 1 hour, and the number of crystallized water 0.6 to 2.2.

Production of amorphous hydrated impure magnesium carbonate through ex situ carbonation

The evaluation of the feasibility of ex situ carbonation in landfills utilizing raw natural substances (namely serpentinites as Mg-source and the CO2-rich fraction of biogas as C-source) was tested through a laboratory procedure comprising three steps. The first step is the acid attack of a serpentinite at 70 °C, by means of HCl 2 M, to get MgCl2-rich solutions. Attacks of different durations were performed to evaluate the time needed. The second step is the neutralization of the MgCl2-rich solution by addition of concentrated ammonia. The third (carbonation) step is mixing of the neutralized MgCl2-rich solution with a solution of ammonium carbonate. This was produced in a landfill by absorption of CO2 contained in biogas in a solution of ammonia. The neutralization of acid MgCl2-rich solutions caused the precipitation of ferrihydrite with secondary ammonium carnallite and salammoniac, whereas abundant precipitation of Amorphous Hydrated Impure Magnesium Carbonate (AHIMC), sometimes with minor nesquehonite, occurred in the third step. This solid carbonate acts as a stable CO2 sink up to 380 °C. The geochemical behavior of some minor elements was also investigated during the experimental processes revealing that Al, Cr and Ni were removed during neutralization (second step), in contrast to Ca which remained in the circumneutral MgCl2-rich solution and entered into the structure of AHIMC. During the carbonation step, precipitation of artinite, hydromagnesite, lansfordite, magnesite and nesquehonite was thermodynamically impossible as the aqueous phase was undersaturated with respect to these solid phases upon separation of AHIMC. The CO2 sequestered through this multi-step procedure is 0.34 ton for 1 ton of serpentinite utilized. However, despite that the use of Mg-rich silicates is a suitable approach to ex situ carbonation, due to their huge availability worldwide, the CO2 produced in making the chemicals and the overall energy balance of the process must be evaluated to assess its sustainability. Furthermore, this procedure could be of great interest in asbestos inertization and the AHIMC products could possibly be useful in industry.

Solid–Liquid Metastable Phase Equilibria in the Ternary Systems KCl + NH4Cl + H2O and NH4Cl + MgCl2 + H2O at 298.15 K

The metastable phase equilibria in the ternary systems KCl + NH4Cl + H2O and NH4Cl + MgCl2 + H2O were investigated at 298.15 K using an isothermal evaporation method. The metastable phase diagrams and the physicochemical properties versus composition diagrams were constructed on the basis of the experimental data. In the phase diagram of the ternary system KCl + NH4Cl + H2O, there are three invariant points and five crystallization fields, corresponding to potassium chloride (KCl), ammonium chloride (NH4Cl), a solid solution based on potassium chloride [(K, NH4)Cl], a solid solution based on ammonium chloride [(NH4, K)Cl], and a crystallization field of two kinds of solid solution [(K, NH4)Cl + (NH4, K)Cl] precipitation. Comparisons between the metastable and stable phase diagrams at 298.15 K show that the crystallization forms of salts are all the same, whereas the size of crystallization regions has slight changes. The ternary system NH4Cl + MgCl2 + H2O is a complex type system with a double salt ammonium carnallite (NH4Cl·MgCl2·6H2O) formed at 298.15 K. Comparisons between the metastable and the stable phase diagrams at 298.15 K and 323.15 K show that the crystallization forms have not changed, while the crystallization fields have slight changes. The density coefficient Ai and refractive index coefficient Bi of salts KCl, NH4Cl, and MgCl2 at 298.15 K were obtained by fitting. The calculated values of densities and refractive indices agree well with the experimental values, with a maximum relative error better than 0.010.

Study of Crystallization Kinetics of Ammonium Carnallite and Ammonium Chloride in the NH4Cl-MgCl2-H2O System

Crystallization kinetics of ammonium carnallite (NH4MgCl3·6H2O), a double salt formed in NH4Cl-MgCl2 solution, and ammonium chloride in the NH4Cl-MgCl2-H2O system were experimentally investigated w...

Preparation of anhydrous magnesium chloride in a gas-solid reaction with ammonium carnallite

Dehydrated ammonium carnallite was synthesized with bischofite from salt lake and ammonium chloride solution in a 1:1 molar ratio of MgCl2:NH4Cl, dehydrated at 160°C for about 4 h. The yield was above 85%. The product was then mixed with solid-state ammonium chloride with a 1:4 mass ratio for the further dehydration at 410°C. The decomposition of NH4Cl made a pressure of NH3 at 30.5 kPa to prevent the hydrolysis of ammonium carnallite. The anhydration of magnesium chloride was achieved at 700°C. The results showed that anhydrous magnesium chloride contains magnesium oxide in an amount that was less than 0.1% by weight. XRD pattern and SEM micrograph showed a good dispersion of ammonium carnallite and anhydrous magnesium chloride crystals with well-distributed big grains, just enough to meet the need for the production of magnesium metal in the electrolysis process.

Preparation and characteristic research of anhydrous magnesium chloride with dehydrated ammonium carnallite

Taking the saline lake bischofite and NH4Cl that was removed with the ammonia method and continuously followed by filtration as raw materials with a molar ratio of 1:1 of MgCl2 to NH4Cl, ammonium carnallite was synthesized. And then the ammonium carnallite was dehydrated to some extent at 160℃ for 4h. Ammonium carnallite reacted with ammonia at 240℃ for 150mm and the ammonation ammonium carnallite was produced. Finally, the ammonation ammonium carnallite was calcined at 750℃ into anhydrous magnesium chloride containing only 0.1%(mass fraction) of MgO. On the other hand, dehydrated ammonium carnallite was mixed with the solid ammonium chloride at mass ratio 1:4 at high temperature and with the differential pressure of NH3 above 30.5kPa. The dehydrated ammonium carnallite of mixture was dehydrated at 410℃, and then calcined at 700℃ into an- hydrous magnesium chloride with only 0.087% (mass fraction) of MgO. X-ray diffraction and electron microscopy analysis results prove that anhydrous magnesium chloride obtained by both methods hasn't mixed phases, the particle is large and even has good dispersion, which is suitable for preparation of metal magnesium in the electrolysis.

An unusual efflorescence on Greek ceramics

AbstractSalt efflorescences were found on four Greek ceramics on exhibition in cherrywood display cases at the Metropolitan Museum of Art. These salts were thought to be either a common archaeological salt, such as halite, or calclacite—a salt which results from the interaction of acetic acid vapors produced by the cherrywood with calcium and chloride ions already present in pores of the ceramic. X-ray diffraction, infrared spectroscopy and elemental analyses determined that one of the salts was, in fact, calclacite (CH3CO2CaCl·5H2O) while the other three were a relatively uncommon salt, ammonium carnallite (NH4MgC13·6H2O). It is suggested that this salt results from a two-step cleaning procedure which at times in the past has been employed for ceramics: hydrochloric acid followed by ammonia.

ChemInform Abstract: DEHYDRATION OF AMMONIUM MAGNESIUM CHLORIDE HEXAHYDRATE (AMMONIUM CARNALLITE)

AbstractDie Dehydratation von NH4MgCl3 ‐6 H2O wird im Temp.‐Bereich 373‐453 K und Wasserdampfpartialdrücken zwischen l‐10‐3 Nm‐2 und 2.7 kNm‐2 untersucht.

Dehydration of ammonium magnesium chloride hexahydrate (ammonium carnallite)

The dehydration of ammonium carnallite (NH4MgCl3·6H2O) has been studied in the temperature range 373–453 K under partial pressures of water vapour between 1 × 10–3 N m–2 and 2.7 kN m–2. At lower temperatures a dihydrate is formed by a phase-boundary controlled process, having an activation energy varying with water-vapour pressure between 65 and 125 kJ mol–1. At higher temperatures and low water-vapour pressures the anhydrous chloride is formed in a single stage following first-order kinetics with an activation energy close to 40 kJ mol–1. Intermediate temperatures and vapour pressures cause the reaction to proceed in two stages, both of which are controlled by phase-boundary processes; Arrhenius parameters have been derived for these also. Enthalpy data are given for the reactions as well as provisional X-ray diffraction data for the products.