Melting Alkali Research Articles

Tungsten Recovery from Tungsten Carbide by Alkali Melt followed by Water Leaching

Tungsten Recovery from Tungsten Carbide by Alkali Melt followed by Water Leaching

Inorganic vs Organic Cation Ionic Liquids and Their Solutions with Alkali Metal Containing Ionic Liquids

The burgeoning field of ionic liquids (in the current sense of low-melting liquids (Tm < 100°C) consisting only of ions), has been dominated by liquids containing organic molecular cations. Although a few cases of all-inorganic ionic liquids are known, the field is relatively unexplored. As in the case of the organic cation salts, the inorganic ionic liquids can have aprotic, protic, and solvate cases, and can also be mixed with low melting alkali salts to give mixed alkali-molecular inorganic ionic liquid systems. Here we explore the interesting properties of (i) a low-melting alkali bromoaluminate, NaAl2Br7, which exhibits huge alkali cation decoupling in the crystalline state (such that there is very little change in conductivity on fusion) and (ii) its mixture with the low-melting inorganic ionic liquid [PBr4+][Al2Br7−]. The structures and ionicities are confirmed by Walden plots and by 31P and 27Al NMR spectroscopy.

Recovery of Titanium Compounds from Ti-enriched Product of Alkali Melting Ti-bearing Blast Furnace Slag by Dilute Sulfuric Acid Leaching

The extraction of titanium from the Ti-enriched product which was prepared from Ti-bearing blast furnace slag by alkali roasting and water leaching, was investigated by dilute sulfuric acid leaching. The effects of sulfuric acid mass fraction, the ratio of acid to slag, reaction temperature and time on the extraction rate of titanium were studied in this paper. The results show that titanium recovery of 92.62 pct was obtained under the conditions of sulfuric acid mass fraction of 50 pct, ratio of acid to slag of 1.5:1, reaction temperature of 160°C and reaction time of 2.5hours. The kinetic study indicates that the acid leaching reaction was controlled by the rate of diffusion, and kinetics equation of drozdov can be described the acid leaching reaction.

Self-propagating high temperature synthesis of SiAlON

In this work, a new method of SHS process has been investigated for the synthesis of SiAlON under low nitrogen pressure. A gel mixture of silica and sodium oxide (sodium silicate) as a reactant and catalyst was produced by alkali melting of silica, solving the results in water and heating in auto clave. Al powder was also used as reactants. Urea and aluminum nitrate hydrate was used as igniting agents. The addition of Mg also was necessary for reaching the combustion. Sodium azide as a good reactant addition for preparing both combustion and nitrogen supply was tested. Beta-Si3N4 powder acted as diluting agent and by reducing the adiabatic temperature helped the nitrogen diffusion into the melted reactants which was not agglomerated. NH4Cl in some cases was used as a catalyst which showed good results for reaching SiAlON. For comparison possibility some experiments were made using silica powder instead of sodium silicate gel. These materials were mixed by pestle and mortar and laid into the combustion chamber cavity without pressing. The compound was heated by electrical element until the ignition happened by gases which were produced from urea and aluminum nitrate hydrate. The pressure of nitrogen in combustion chamber was kept constant near 0.1Mpa. The products of syntheses were of agglomerated one mostly O′-SiAlON & β and β′-SiAlON. Effects of NH4Cl were examined by XRD results. TGA and DTA graphs showed the thermodynamics of reaction which were analyzed in some parts by XRD spectroscopy. In some cases nano material of SiAlON was produced which is demonstrated by XRD and FTIR spectroscopy.

The Melting Reaction Mechanism of NaOH in Decomposing Ca2SiO4

The solid Ca2SiO4 is synthesized through solid-state reaction using analytical reagent CaSiO3 and CaO as raw materials. The conditions of melting reaction between Ca2SiO4 and NaOH are optimized through an orthogonal experimental method. The optimized experimental conditions are a reaction temperature of 873 K, a reaction time of 180 min, and an alkali to ore ratio of 6:1. Based on the optimized conditions, in situ detection for the melting reaction process between the Ca2SiO4 and NaOH is made by Raman spectroscopy analysis. Furthermore, an X-ray diffraction (XRD) and infrared spectrometer (IR) analysis are used to test the residue, which is separated from the post-reaction Ca2SiO4--NaOH melt after water leaching. The results show that the Si-O bond in the SiO44− is destroyed, and the Na+ inserts itself into the silicate lattice to produce an intermediate product, Na2CaSiO4, in the process of reaction. After the alkali melting reaction, Ca2+ can be fully separated from the SiO44− array structure and react with OH− in Ca2SiO4--NaOH melt to form Ca (OH)2.

Characterization of Ashes from Different Wood Parts of Norway Spruce Tree

Woody biomass from the forest sector is an abundant resource for renewable energy generation. Conventional woody biomass materials such as timber and stem are normally high quality solid fuels for combustion applications in terms of ash related operational problems. Recently, new raw woody materials such as forest residue are gaining interests for energy production purpose. Forest residue is the remaining fraction after harvest and outtake of the wood timber, including tree tops, branches and barks. Compared to conventional woody biomass, the forest residue has a wide variation of ash content and concentration of ash forming matters. The aim of this work was to characterize and investigate different parts from Norway spruce trees regarding ash content, ash composition and ash melting and slagging behaviors. Different parts from spruce tree were studied in present work including stem wood, bark, branch and twigs. The ash content and ash melting temperature of the four fuel samples were measured through following standard procedures. Concentrations of main ash forming elements were analyzed by an inductively coupled plasma optical emission spectroscopy (ICP-OES). The ashes from stem wood, bark and twigs were further investigated by a scanning electron microscopy equipped with energy dispersive X-Ray analysis (SEM- EDX) and X-Ray diffractometry (XRD). The results showed that the branches and twigs contain higher contents of ash forming matters than that of the stem wood. Chemical compositions of ashes from four parts of the spruce tree are dominated by Ca, K, and Si. The K and Na contents in the branches and twigs are significantly higher than that of stem wood and bark, indicating high tendency of ash melting and slagging. The melting points of ashes from branch and twigs were 100-200 °C lower than those of the ashes from stem wood and bark, respectively. SEM-EDX and XRD analysis, melting of ashes from branch and twigs are mainly attributed to formation and fusion of low temperature melting alkali silicates.

Influence of SiO2 and Al2O3 on the activity coefficients of alkalis in melts: An experimental study

The simultaneous saturation of silicate melts with variable Al2O3 and SiO2 contents in sodium, potassium, and rubidium was investigated at a total pressure of 1 atm and temperatures of 1300–1470°C using the crucible supported loop technique. It was shown that an increase in both SiO2 and Al2O3 contents in the melt results in a significant decrease in the activity coefficients of the alkalis, and the effect of Al2O3 is especially pronounced in silicic compositions. The extrapolation of the experimental data allowed us to estimate the influence of SiO2 and Al2O3 contents in the melt on the behavior of Li and Cs. Using a numerical experiment, it was shown how the inert and perfectly mobile behavior of alkalis in magmatic processes can be discriminated. A methodic investigation was performed on the loss of Na, K, and Rb from silicic glasses during microprobe analysis depending on beam diameter.

The extraction of gold from sulfide concentrates into molten lead

The results of investigation of the extraction of gold from mineral sulfide ore into molten lead at low temperatures (350–550°C) are given. The questions of solubility of Au in Pb in the mentioned temperature range and the kinetics of dissolution of metal are analyzed. The condition that determines extraction of gold is the presence of a processing medium, which provides the decomposition of carrier minerals of gold and prevents the anodic oxidation of the lead alloy. The alkali melt is suggested to be used as such a medium. The procedures of preparation of sulfide Au-containing concentrates to the extraction associated with obtaining the cakes and their charging into the extraction apparatus are considered. Extraction proceeds in the transient region. In this case, high characteristics of extraction are achieved. The reasons for collector dispersion, which conditions the losses of gold, are established.

Electrolytic production of metallic cadmium and cadmium–sodium alloys in alkali melts

Reprocessing of cadmium-containing wastes and used storage batteries produces cadmium oxide. Electrowinning of the metal from an alkali melt is proposed for processing of CdO and production of metallic cadmium or cadmium–sodium alloys. The design of a laboratory electrolyzer is discussed. Technological parameters of the electrolysis process are determined. Applied and engineering aspects of the electrowinning of cadmium and cadmium–sodium alloys are considered. Conditions of the electrolytic production of cadmium are optimized. Specific features of the electrochemical production of cadmium–sodium alloys are analyzed. Electrowinning of cadmium from an acid or chloride solution is considered. The comparison of the electrolysis of aqueous solutions and alkali melts is in favor of the latter.

Mineralogical Stabilization of Heavy Metals from Alkali Melting Furnace Fly Ash by Thermal Treatment with Adjustment of Its Chemical Composition

The potential of an inexpensive and simple method to control the solubilities of hazardous heavy metals such as Pb and Cr from CaO rich melting furnace fly ash (MFFA) by addition of silica and alumina with preceding heat-treatment was demonstrated. The addition of SiO2 and Al2O3 to melting furnace fly ash with preceding heat-treatment at 700°C resulted in a decrease in the pHs of the leachates from 12.4 to 11.2 and in a remarkable reduction of leachabilities of heavy metals although the leachability of Cd was below the ICP-AES detection limit (0.04 mg/l) even without the addition. In the CaO-SiO2-Al2O3 system the solubilities of Pb, Cr and Cu were much lower in the area where 3CaO·Al2O3, gehlenite, CaO·Al2O3 and anorthite deposit. The solubility of Zn was also much lower in the area where pseudowollastonite, rankinite and 3CaO·SiO2 as well as the above-mentioned minerals deposit. The leachabilities were fairly well correlated with practical parameters of CaO/(CaO + SiO2 + Al2O3) (or (SiO2 + Al2O3)/CaO) and Al2O3/(CaO + SiO2 + Al2O3) (or Al2O3/CaO) for Pb and CaO/(CaO + SiO2 + Al2O3) (or (SiO2 + Al2O3)/CaO) for Cu in the range of the present study. For Cr and Zn the leachabilities were very low in the range of the present study and no particular correlations were found. The significant reduction in their solubilities was confirmed not being caused by their volatilization during heat-treatment.

ANALYSIS OF MELTING FOR ALKALI EARTH AND ALKALI OXIDES BASED ON THE DIFFUSIONAL FORCE THEORY

An analysis of the melting alkali earth and alkali oxides is presented using the concept of diffusional force. The calculations are performed by developing an ionic model based on Harrison's quantum mechanical treatment of overlap repulsive potential which takes into account the interactions up to second neighbors. Van der Waals dipole–dipole and dipole–quadrupole interactions calculated by more accurate methods are also included in the model. Using the formula by Fang, derived on the basis of thermodynamic analysis, the values of interionic distances for 8 alkali earth and alkali oxides at melting have been obtained. A simple model for melting is developed based on the diffusional force models. The values of Tm thus obtained are found to show fairly good agreement with experimental values of melting temperatures.

The ash chemistry in fluidised bed gasification of biomass fuels. Part I: predicting the chemistry of melting ashes and ash–bed material interaction

This paper is part I in a series of two describing the modelling of the ash-chemistry of seven biomass fuels under reducing, pressurised conditions in fluidised bed gasification by means of thermodynamic multi-phase multi-component equilibrium (TPCE) calculations. The fuels considered were Salix, a Scandinavian forest residue, Miscanthus, Reed Canary Grass, Eucalyptus, Arundo Donax and Lucerne. The composition and amount of phases have been calculated for the gasification of the fuel as such and in presence of an excess amount of calcite, dolomite, magnesium olivine sand and sand by using TPCE calculations in a temperature interval of 600–900°C and a pressure of 10 bar. It was found that interaction of inorganic compounds released from the fuels with bed material is a prerequisite for the formation of bed agglomerates. The presence of an excess of dolomite decreased the amount of alkali components in the bed, thereby increasing the amount of alkali components volatilised. A silica bed, however, binds most alkali released from the fuel, retaining it in the bed as low melting alkali silicates. The chances of experiencing operating problems due to bed agglomeration may increase hereby significantly. Calculations at atmospheric pressure show that the amounts of melt present will be smaller when compared to pressurised conditions, thereby decreasing the chances of bed agglomeration. In a pressurised gasifier using calcite or dolomite as bed material a small amount of an alkali carbonate rich melt can be expected at temperatures above 620°C with each of the seven biomass fuels fired. In silica-rich cases such as when firing Miscanthus, Reed Canary Grass, Arundo Donax or using a Si-rich bed material a melt can be expected at temperatures above 770°C. The amount of melt is rather high, i.e. 12–100% of the original ash formed. In the case of a magnesium olivine sand bed an alkali melt can be expected at 620°C. At temperatures above 800°C, a silicate melt can form as well. The amount of melt was high, i.e. 60–300% of the original ash formed, showing a significant contribution of the bed material.

Deep sea explosive activity on the Mid-Atlantic Ridge near 34°50′N: Magma composition, vesicularity and volatile content

Submersible observations and sampling were carried out in the rift valley of the Mid-Atlantic Ridge (MAR) near 34°40′N–35°N. The 4-km-wide rift valley consists of a Neo Volcanic Zone (NVZ) (<1km wide) bounded at the west by a Median Ridge (MR) (5km wide and 20km long) and at the east by the first scarps of the eastern wall. The MR and the eastern wall are characterized by volcanic cones about 200–300m height culminating at depths of 1500–1900m which are made up of volcaniclastic deposits (pyroclasts and hyaloclasts) suggestive of explosive volcanism. Based on their surface morphology, degree of vesicularity, and composition, the erupted deposits are classified into four groups: (1) poorly vesicular (<15% vesicles) N- and T-MORBs (K/Ti <0.25, Na2O+K2O<2.9%) consisting of sheet flows and pillows formed during fissure eruptions in the NVZ at 2000–2300m depths; (2) vesicular (15–30% vesicles) E-MORBs (K/Ti=0.25−0.45,Na2O+K2O>2.8−3.2%) and alkali basalts (K/Ti=0.45−0.70,Na2O+K2O>3.3−4) made up mainly of pillows; (3) highly vesicular (>35% vesicles) pillow lava and pyroclastic (scoria-like) alkali basalts (K/Ti>0.45−0.80,Na2O+K2O>3−4%); and (4) hyaloclastites consisting of glassy shards of alkali basalt composition. The total water and carbon contents of the deposits increase with the incompatible element concentrations. The estimated initial H2O content for the N- and T-MORBs is less than 3500ppm, whereas for the E-MORBs and alkali basalts the H2O content is near 4000 and 7000ppm, respectively. While the H2O is mainly in the melt, the carbon is in the form of CO2 filling vesicles. The vesicles are formed from magma with an initial carbon content of 1000–3000 for the N- and T-MORBs, 3000–6500ppm for the E-MORBs and higher than 1wt% for the alkali basalts.The various lava types were derived from a heterogeneous mantle source composed of enriched and depleted components during sequential eruptions of N-, T- and E-MORBs and alkali basalts (K/Ti>0.7). The amount of CO2 and H2O in equilibrium with the dissolved species present in the vesicles indicates that CO2 (XCO2=1−0.84) was the main exsolved compound responsible for bubble nucleation. The increase in the degree of vesicularity and pressure of the volatile phases is mainly due to the early exsolution of CO2 from an alkali melt. The exsolution of significant amounts of dissolved water occurred only for the alkali basalt a few hundred meters beneath the seafloor and contributed to late bubble expansion. This subsequent addition of magmatic water to the vesicles increased the gas pressure and triggered explosions. An alternative hypothesis for the explosive volcanism is based on field observations. During crater collapsed, seawater could have been trapped in fractured volcanic conduits and later sealed by hydrothermal fluid circulation and precipitation. In such an environment, this seawater will be heated and vaporized during renewed magmatic upwelling. Both scenarios give rise to fragmented debris (hyaloclasts and pyroclasts) and the explosive events create turbulent flows followed by differential gravity settling of the particles (shards versus lapilli) through the seawater.

Na-K interdiffusion in alkali feldspar melts

Na-K chemical interdiffusion between albite and orthoclase melts has been measured at 1.0 GPa between 800 and 1600°C and at 2.0 GPa, 1400°C, in anhydrous melts and in hydrous, 5.5 wt% H 2O, melts at 1.0 GPa, 1200 and 1400°C. Anhydrous Na-K diffusivities at X or = 0.5 display Arrhenian behavior even through the inferred glass transition. After correction for diffusion occurring during heating Na-K interdiffusion can be described by D=2.39(+1.7,−0.98)×10 −5 exp(−145.8±6.8/ RT) where D is the diffusion coefficient in m 2s −1, 145.8 is the activation energy in kJ mol −1, R is the gas constant, and T is the temperature in kelvins. These diffusivities are four decades greater than estimated Si-Al diffusivities in the same melts due to the low alkali-oxygen bond valence, or cation field strength, and the abundance of appropriate charge-balanced locations for alkalis in alkali feldspar melts. Extrapolation of diffusion coefficients to 600–650°C for comparison with Na-K interdiffusion in alkali feldspar crystals demonstrates that melting increases diffusion by six orders of magnitude. The effect of pressure on Na-K diffusion at 1400°C is not measurable in this system and suggests that only minor dilation of the coordinating oxygen polyhedra which enclose alkalis in the melt is necessary for diffusion. A preliminary Arrhenius equation for alkali diffusion in silicic melts with 6 ± 0.5 wt% H 2O was calculated using results of this and previous studies D=4.97(+0.85,−0.73)×10 −6 exp(−115.8±1.8/ RT). The effect of H 2O only increases diffusivities by approximately a factor of four, distinctly different from the three orders of magnitude differences between Si-Al, Zr, and P diffusion in anhydrous and hydrous granitic melts. The differing behavior of alkalis and these other cations in hydrous silicic melts is associated with differences in the type and abundance of coordination polyhedra and the low bond valences and cation field strengths of alkalis.

Synthesis of Novel Oxide Pyrochlores, A2BB′O7 (A = La, Nd; BB′ = Pb, Sn, Bi), by Alkali Melt Route

Oxide pyrochlores of the formula A2BB′ O7 (A = La, Nd; BB′ = Pb, Sn, Bi) have been synthesized by a low-temperature ambient-pressure route employing KOH melts. All the compositions, including La2Bi2O7 and its strontium-substituted derivatives, La2-xSrxBi2O7-δ, are deeply colored insulators, confirming that a metallic ground state is not achieved for Pb(IV) and Bi(IV/V) oxides with the pyrochlore structure.

Some features of melting alkali borosilicate glass

Some features of melting alkali borosilicate glass

Effects of the ionization potential of the outer cations on the position of the charge-transfer bands for uranyl trinitrate compounds

The authors used the low-temperature spectra (T = 4.2 and 77 K) of uranyl trinitrate compounds to examine the effects of outer alkali-metal cations and ammonium on the position of the purely electronic transition band V00. The spectra for the compounds are shown; the data show that cation substitution in the sequence K, Rb, NH/sub 4/, Cs produces a monotone decrease in the pure electronic transition energy. The electronic transition frequency as a function of the ionization potential of the alkali melt are shown. The effect of the outer cation can be explained in terms of electron-density redistribution in the equitorial plane.

Influence of alkali on the carbonization process—III: Dependence on type of alkali and of alkali earth compounds

3,5-Dimethylphenol-formaldehyde resin was carbonized up to 1000°C with various kinds of alkali and alkali earth compounds added. The hydroxides of Li, Na, K, Sr and Ba reacted with the resin to produce large amounts of hydrogen and CO. The order of reactivity was, Li < K < Na and Ca, Mg ⪡ Sr < Ba. Carbonates evolve only a small amount of hydrogen, although evolution of CO was very large. Carbonates cannot react with reactive methylene groups or aromatic hydrogens, whereas hydroxides easily substitute these hydrogens with MO-, liberating hydrogen atoms. The reduction of carbonate with carbon takes place in a similar way as that with hydroxides. The lower the melting point of the alkali or alkali earth compounds is, the lower the temperature of evolution of hydrogen is. This may be due to the good wettability of lower melting alkali or alkali earth compounds.

Dehydrogenation of Triterpenoid Alcohols in Alkali Melt. A Short Synthesis of the So-Called Jasminol

Abstract Alkali fusion is a venerable method1 for the dehydrogenation of simple aliphatic alcohols to give carboxylic acids (Dumas-Stass reaction), and has been used in isolated cases for ketone synthesis from secondary alcohols as well. We report here the results of a study on alkali fusion reactions of some representative triterpenoid alcohols, and show that unique and preparatively useful reactions take place. Our results are summarised in the Table2.

Petrology of the Nandewar Volcano, N.S.W., Australia

The Nandewar Mountains, N.S.W., Australia, are the remains of a Miocene continental alkaline volcano whose products range from olivine basalts to comendites and alkali rhyolites. Intermediate hawaiites, mugearites and benmoreites predominate in the shield, in which olivine basalts are rare, and the trachytic rocks form many intrusions into the shield. The Nandewar alkaline series shows extreme fractionation of a relatively differentiated alkali olivine basalt magma, saturated with silica, to yield extremely oversaturated peralkaline comendites and peraluminous alkali rhyolites. The nature of the ferromagnesian phases forming was controlled by low oxygen fugacities. Throughout the series clinopyroxenes range from diopsidic augite, through sodic ferrohedenbergites to hedenbergite-acmite solid solutions. Riebeckite-arfvedsonite solid solutions appear in the trachytes and comendites, and aenigmatite appears in some of the peralkaline rocks. The feldspars in the series fractionate from calcic labradorite through potash oligoclase and calcic anothoclase towards the minimum melting alkali feldspar composition, Ab 65Or 35. The compositions of the alkali rhyolites approach the minimum in the system SiO 2-KAlSi 3O 8-NaAlSi 3O 8. All the mineralogical and chemical evidence points to the development of the Nandewar series by the processes of extreme crystallization differentiation of an alkali olivine basalt parent magma. No significant contamination occurred, xenoliths and xenocrysts are absent, and volatile transfer and metasomatism played a minor role.