Hydrated Magnesium Chloride Research Articles

Heavy metal removal from sewage sludge ash analyzed by thermogravimetry

A high temperature (1000 °C) thermochemical process for heavy metal removal from sewage sludge ash via the chloride pathway was investigated by thermogravimetry/differential thermal analysis (TG/DTA). TG and DTA measurements gave information about secession and evaporation of water, HCl, and heavy metal chlorides at different temperatures. Additionally, gaseous water and hydrochloric acid which occurred in the process were detected by an FT-IR detector that was coupled to the TG/DTA-system. Heavy metal chlorides which were also formed in the process cannot be detected by this technique. For that reason the outlet gas of the TG/DTA-system was discharged into washing flasks filled with water for absorption. The washing flasks were replaced in temperature steps of 50 °C and the heavy metal concentrations of the solutions were determined by ICP-OES. The temperature-dependent formation/evaporation of different heavy metal chlorides was analyzed and compared for two different thermochemical processes using magnesium chloride hydrate or calcium chloride hydrate as Cl-donors. In both cases evaporation of Cd, Cu, Pb, and Zn was observed from 600 °C, whereas As, Cr, and Ni remained in the solid state. The results were discussed against the background of thermodynamic calculations.

Magnesium chloride precipitation from mixed salt solution using 1,4-dioxan

This paper deals with the preparation of magnesium chloride hydrate from a mixed salt solution containing, besides MgCl 2, substantial quantities of undesired substances such as alkali metal chlorides and magnesium sulphate. Magnesium chloride extraction was done using dioxan. In particular, it was found that this salt precipitate as the ternary compound MgCl 2·6H 2O·C 4H 8O 2. Reaction equilibrium is reached after 40 min. It was shown that solid phase MgCl 2·6H 2O·C 4H 8O 2 conversion into MgCl 2·6H 2O is feasible by a drying carried out at constant temperature chosen in the range (70–110 °C). Physico-chemical properties of the final product are determined using XRD, complexometry, potentiometry, gravimetry and FAAS. Prepared MgCl 2·6H 2O purity is upper than 99%. Its X-ray diffractogram is impurity free.

Preparation of anhydrous magnesium chloride from ammonium magnesium chloride hexahydrate

Magnesium chloride hydrate can be dehydrated to some extent by heating. However, it is not possible to fully dehydrate magnesium chloride by heating in air because of hydrolytic decomposition. Accordingly, the dehydration should be carried out in hydrogen chloride gas atmosphere. However, this process causes many problems, including HCl gas storage and corrosive nature, consuming a large amount of HCl gas. Consequently, many alternative approaches have been tried for the production of anhydrous magnesium chloride. In this work, we proposed a process to prepare anhydrous magnesium chloride using ammonium magnesium chloride hexahydrate (NH 4MgCl 3·6H 2O). From this work, it was confirmed that anhydrous magnesium chloride can be produced by the dehydration of magnesium chloride hydrate in HCl gas atmosphere, and found that anhydrous magnesium chloride can be prepared from ammonium magnesium chloride hexahydrate at the reaction temperature range 50–400 °C and a reaction time of 30 min even in air atmosphere.

Solid-state hydrolysis of cellulose and methyl α- and β- d-glucopyranosides in presence of magnesium chloride

Solid-state hydrolysis proceeded with cellulose and methyl α- and β- d-glucopyranosides in the presence of hydrated magnesium chloride. This reaction was effective even at >100 °C since the hydrated water, which is held by MgCl 2 up to >200 °C, is utilized as a nucleophile. Excess water made this reaction ineffective due to the competition between water and sugar oxygen atoms in coordinating with Mg 2+, a Lewis acid. Consequently, this hydrolysis reaction is characteristic of solid-state reactions.

Ammoniation Technology for Dehydration of Hydrated Magnesium Chloride in China

Ammonination technique for dehydration of hydrated magnesium chloride is a special kind of method for preparation of high-pure anhydrous magnesium chloride, which is requisite for electrolytically manufacturing metal magnesium. The technique has been developing for decades in the west world. China has now been exploiting the technique for his magnesium ore, especially the magnesium resource in the west of China. We started investigation of the method for several years, and several new progresses were arrived for preparation of anhydrous magnesium chloride. From our study, ethanol, methanol and water solution can be used for the method, and each had an advantage over the others; the ammonia used in the technique for preparation of anhydrous magnesium chloride is less corrosive for the equipment, and friendly for environment. The method gives great potential application in industry of metal magnesium and magnesium matrix materials.

The reaction of MgCl 2·4H 2O with CCl 2F 2

A new reaction of MgCl 2·4H 2O with CCl 2F 2 is investigated by DTA and TG from room temperature to 350 °C. It is observed that MgF 2 was obtained between 252 and 350 °C, Below the temperature, MgCl 2·4H 2O dehydrates and hydrolyzes to MgCl 2 and Mg(OH)Cl, which are the real reactants of the reaction with CCl 2F 2. The formation of MgF 2 is ascribed to the reaction of MgCl 2 and Mg(OH)Cl with HF, which forms by decomposition of CCl 2F 2 with the taking part in of H 2O released from dehydration of hydrated magnesium chloride on the surface of MgCl 2 and Mg(OH)Cl, which catalyzes the decomposition of CCl 2F 2 in this case. Consequently, the reactions are tested in the fluid-bed condition. It is found that MgF 2 formed at temperatures down to 200 °C in a fluid-bed reactor. This reaction may be used as a method of disposing of the environmentally sensitive CCl 2F 2 (rather than release into the atmosphere). It is also a method for the preparation of MgF 2.

The Measurement of Hydration Heats for Magnesium Chloride with Low Water by Means of DSC

The heats of hydration reactions for MgCl2⋅4H2O and MgCl2⋅2H2O include two parts, reaction enthalpy and adsorption heat of aqueous vapor on the surfaces of magnesium chloride hydrates. The hydration heat for the reactions MgCl2⋅4H2O+2H2O→MgCl2⋅6H2O and MgCl2⋅2H2O+2H2O→MgCl2⋅4H2O, measured by DSC-111, is –30.36 and –133.94 kJ mol–1,respectively. The adsorption heat of these hydration processes, measured by head-on chromatography method, is –13.06 and –16.11 kJ mol–1, respectively. The molar enthalpy change for the above two reactions is –16.64 and –118.09 kJ mol–1, respectively. The comparison between the experimental data and the theoretical values for these hydration processes indicates that the results obtained in this study are quite reliable.

The effect of magnesium chloride hydrate on the fire retardation of cellulosic fibers

Thermal analysis was used to investigate the effect of the addition of magnesium chloride hexahydrate as a fire retardant to cellulosic fibers. The kinetics of the decomposition of the cellulosic material were first studied. The decomposition of the dry salt was also investigated and three steps disclosed. Then, the fabrics were impregnated into salt solutions of different concentrations and the loss in mass was followed by thermal analysis. The percent loss in mass was compared to that of pure cellulosic fabric at different temperatures. It was found that there is an appreciable improvement in fire retardation at a minimum percent add-on of the salt of 35%.

A Molecular Composite Containing Organic and Inorganic Components—A Complex from β‐Cyclodextrin and Hydrated Magnesium Chloride

Two interlocking substructures–infinite chains of β‐cyclodextrin monomers and [Mg(H2O)6]Cl2 building blocks–form the basis of a novel composite. The chains of inorganic components, comprising Mg(H2O)6 octahedra linked through Cl anions and water of crystallization, are threaded through the cavities of the cyclodextrins. The complete structure is stabilized by hydrogen bonds.

Supported titanium catalyst for propylene polymerization. Convenient synthesis of unsolvated anhydrous magnesium chloride from MgCl2 · 6 H2O

AbstractReaction of chlorosilanes (Me3SiCl, R2SiCl2, SiCl4; RMe, Ph) with MgCl2 · 6 H2O were investigated for the efficiency of removal of water. The nature of chlorosilane is found to govern the rate of dehydration. The treatment of hydrated magnesium chloride with dichlorodiphenylsilane gives unsolvated anhydrous magnesium chloride in high yields. Anhydrous MgCl2 is used as support for the preparation of titanium catalyst. The catalyst in conjunction with Et3Al and Ph2Si(OMe)2 as cocatalyst system shows high activity for propylene polymerization.

Magnesium – nucleotide interaction. Synthesis, structure, 1H, 13C nuclear magnetic resonance and Fourier transform infrared studies of Mg-inosine-5′-monophosphate complexes

The reaction of inosine-5′-monophosphate acid (IMPH2) with hydrated magnesium chloride MgCl2•6H2O gives complexes of the type Mg(IMP)•5H2O and Mg2(IMP)3•15H2O. The FT-IR spectra of Mg(IMP)•5H2O in the region 1800–400 cm−1 showed marked similarities with that of the structurally characterized N7-bound Ni(IMP)•5H2O and Co(IMP)•5H2O complexes, while Mg2(IMP)3•15H2O exhibited distinct spectral similarities with the known Cd2(IMP)3•12H2O and Ca(IMP)•6.5H2O compounds, where a direct metal–phosphate and metal–sugar binding as well as metal–N7-coordination has been shown crystallographically. The Mg(II) ion in Mg(IMP)•5H2O is N7-bound with an indirect metal–phosphate and metal–carbonyl interaction through a coordinated water molecule and in the Mg2(IMP)3•15H2O compound it binds directly to the phosphate and to the sugar moiety as well as to the N7-site of the purine ring system.

Thermoanalytical investigations on the decomposition of double salts

The melting and decomposition behaviour of carnallite was investigated in the closed system under dynamic heating conditions and in the open system under dynamic and quasi-isothermal and quasi-isobaric conditions in the temperature range between 20 and 300°. DTA heating and cooling cycles in the closed system illustrate the incongruent melting of carnallite and the occurrence of different magnesium chloride hydrate phases. The thermal decomposition under quasi-isothermal and quasi-isobaric conditions begins at a pressure of at least 100 kPa from the melt and under reduced pressure from the solid. In any case KCl · MgCl2 · 2 H2O is formed which is decomposed to a basic product KMgCl2.84–2.90(OH0.10–0.16.

Volatilization studies of magnesium compounds by a graphite furnace and flame combined atomic absorption method. The use ofa halogenating atmosphere

Separate vaporization of samples in a graphite furnace was combined to a flame atomic absorption spectrophotometer for metal specific detection of the evolved species. The internal temperature of the sample holder (graphite cup) was continuously monitored by a recording optical pyrometer in the 560–2400°C range, when solution and solid samples were heated at 7–16°C s −1 rate. A higher initial observation temperature of vaporization ( T f) of magnesium oxide was found with the present method than with the known electrothermal atomic absorption methods. This was explained by considering both the temperature dependence of the non-equilibrium oxygen partial pressure in the furnace and the difference of sensitivity of the detection methods. Calculations were performed to predict T i values for chemical systems of known thermodynamic data, and to determine vaporization heats on the theoretical base of the third-law method. An empirical approach was followed to specify vaporization characteristics of magnesium in the presence of aluminium and aluminium-calcium salt matrices using Ar and Ar + CCl 4 (chlorinating) atmospheres. The vaporization temperature of hydrated magnesium chloride altered significantly with the sample mass. The observations found with a relatively high mass of samples were used to explain certain interference and/or releasing effects involved in conventional electrothermal and flame atomization methods. The effect of excess CCl 4 vapor introduced into the flame, together with the sample aerosol was treated also theoretically in terms of dissociation equilibria. No aluminium interference on magnesium determination was found with the present combined method.

The polarographic reduction wave of magnesium ion(II) in a molten LiClKCl eutectic mixture

The polarographic reduction wave of magnesium ion was confirmed in the purified lithium chloride-potassium chloride eutectic + magnesium chloride (7.20 × 10 −2 mol/l) melt kept at 450°C. The half wave potential was −2.53V vs the PtPt 2+ reference electrode, which was very close to the equilibrium potential −2.580V of MgMg 2+ already reported. The limiting current increased proportionally with the increase of magnesium chloride concentration. The relation between the current and the potential in the reduction wave of magnesium cation was expressed by the Heyrovsky — Ilkovic equation. The residual current raised in two steps due to the reduction of water introduced in the purified lithium chloride-potassium chloride-magnesium chloride melt by the addition of unpurified magnesium chloride and hydrated magnesium chloride.

The polarographic reduction wave of magnesium ion(II) in a molten LiCl-KCl eutectic mixture

Abstract The polarographic reduction wave of magnesium ion was confirmed in the purified lithium chloride-potassium chloride eutectic + magnesium chloride (7.20 × 10 −2 mol/l) melt kept at 450°C. The half wave potential was −2.53V vs the PtPt 2+ reference electrode, which was very close to the equilibrium potential −2.580V of MgMg 2+ already reported. The limiting current increased proportionally with the increase of magnesium chloride concentration. The relation between the current and the potential in the reduction wave of magnesium cation was expressed by the Heyrovsky — Ilkovic equation. The residual current raised in two steps due to the reduction of water introduced in the purified lithium chloride-potassium chloride-magnesium chloride melt by the addition of unpurified magnesium chloride and hydrated magnesium chloride.

Electron beam effects on hydrated magnesium chloride revealed by XPS

Electron beam effects on hydrated magnesium chloride revealed by XPS

The reactions of dinitrogen tetroxide with lithium carbonate with a series of magnesium compounds, and with aluminium chloride

The reactions of liquid dinitrogen tetroxide with lithium carbonate, basic magnesium carbonate, magnesium oxide, magnesium hydrodixe, hydrated magnesium chloride, magnesium perchlorate and anhydrous aluminium chloride have been carried out. New methods for the preparation of anhydrous lithium nitrate and magnesium nitrate have been indicated. Evidence has been obtained for the formation of dinitrogen tetroxide adducts of magnesium nitrate and aluminium nitrate.