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By W. E. Wallace

Rare earth elements combine with most, of the metallic elements. As early as 1971 over a thousand intermetallics had been identified and described(1) From a magnetics viewpoint, systems involving. the d-transition metals Fe, Co and Ni are particularly interesting. In these systems there are at least four significant interactions: R-R exchange (R - a rare earth), R-T exchange (T = a transition metal), R-R exchange and the crystal field interaction acting upon the. rare earth ion. There is complex interplay between these interactions leading to bewildering variety in their magnetic behavior., Because of this and in view of the commercial significance of some rare earth intermetallics, studies of these systems has been an unusually active area of inquiry for the past two or three decades. The large magnetic moment of many of the rare earths, viz., 10 µB per atom for Dy and Ho, 9 1B for Tb and Er, etc., attracted, attention many years ago to the rare earths as potential ingredients for alloys to be used in permanent magnet fabrication. The utility of a permanent magnet in high perform¬ance devices (travelling wave tubes, voice coil motors, brushless motors, etc.) is in large measure determined by its maximum energy product, (BH)max. [(BH)max is the maximum value of B (magnetic induction) and H in the 2nd quadrant of the hysteresis loop.] Enhanced atomic moment in princple can lead to increased B and a large maximum energy product. Until about 1970 the largest (BH)max value known was about 5 MGOe(mega-gauss Oersted). This was for A1NiCo - an alloy involving Al, Ni and Co. It was recognized that the rare-earths had the potential for much higher energy product; in the case of Dy the theoretical energy product is about 35.0 MGOe., 70 times that of Alnico. (Needless to say, this theoretical value has never been achieved.) Large-scale efforts began about 30 years ago to synthesize magnetic materials containing rare earths and which would be suitable for permanent magnet fabrication. It was recognized by Strnat(2) et al. that a material to, be useful in high energy magnet fabrication would have to satisfy three. criteria:

Jan 1, 1992

By Gavin K. W. Freeman

The efficient separation of cobalt from nickel is a fundamental objective in the refining of cobalt. Based on recent experience at the Corefco refinery in Fort Saskatchewan, the identification of a novel process for the selective precipitation of cobalt from aqueous ammonia leach liquors is described. The addition of calcium sulphate, CaSO4.2H2O (gypsum), to an aqueous solution containing cobalt(III) hexammine sulphate, [Co(NH3)6]2(SO4)3, will result in the precipitation of a sparingly soluble double salt having the stoichiometry, [Co(NH3)6]2(SO4)3.2CaSO4.xH2O, where x = 4 or 6. Leach residues, which may contain a significant quantity of cobalt associated with the cobalt calcium double salt, can be washed with process solutions that contain ammonium carbonate. After contact with ammonium carbonate, the cobalt is recovered into solution, while the calcium is re-precipitated as the insoluble carbonate. The simplicity of this elemental separation and its high selectivity for cobalt, as well as the demonstrated usefulness in improving cobalt recoveries, are the basis for the potential applications of this process.

Jan 1, 2003

By Gerardo Fuentes

The stoichiometry and kinetics of the hydrothermal reaction of enargite in copper sulphate solutions was investigated in the range 140–300 °C, and particle size under 15 and 50 μm. The stoichiometric experiment was performed at 300 °C, using one gram of sample (96% enargite, 4% tennantite) and 100 mL of copper sulphate solution (10 gpl) at 1.2 pH. Enargite reacted completely after 80 min. A solid product was obtained and characterized by XRD. The main product was chalcocite (M) and some traces of djurleite and chalcocite (Q). Tennantite did not react under these conditions. The kinetic experiments were conducted at 140 °C, 190 °C, 250 °C and 300 °C. From fitted data and Arrhenius equation the calculated activation energy (Ea) was 51 kJ/mol. According to the hydrothermal transformations studied, the reactivity of different phases found in the copper concentrates was bornite > chalcopyrite > covellite > sphalerite > pyrite > enargite > tennantite.

By Guo Xueyi

The electrochemical couple behavior of manganese dioxide with ferrous/ferric ions in acidic chloride medium was investigated, It was proven that the dissolution of Mn01 is due to the electrochemical couple reaction between MnO2/Mn2+ and Fe2+/lFe3+ in the solution, The driving force for the process originates from the rest potential difference of the two couples. The reduction of Mn02 is controlled by clectrochemical kinetics, whereas the conversion of F e2+ to Fe3+ is limited by diffusion, The factors such as the Mn2+, Fe2+, Fe3+, Cl concentration, pH of the solution and the temperature, have much influence on the kinetics of the couple process, This study will be useful to elucidate the mechanism for the leaching of manganese nodule from the deep ocean as well as manganese dioxide ores in land,

Jan 1, 2003

By Jitka Jandová

A laboratory process based on simple and environmental friendly operation, aimed at recycling of spent Li/MnO2 batteries, is described in this study. This process involves roasting Li/MnO2 batteries in a vacuum furnace at 650°C, followed by selective leaching Li2CO3 from calcined electrode material in distilled water at ambient temperature and controlled crystallization of pure Li2CO3.

Jan 1, 2006

By Rzyman Michal, Nakamura Takashi, Shibata Etsuro, Grabda Mariusz, Oleszek-Kudlak Sylwia

"Tetrabromobisphenol A (TBBPA) and many systems based on the synergistic effect of brominated organic compounds with Sb2O3 are extensively used as effective brominated flame retardants (BFRs) in many materials such as plastics and textiles. Thermal degradation of BFR containing plastics leads to the formation of hydrocarbons and gaseous compounds such as HBr and SbBr3. Our thermodynamic considerations indicate that these gases can act as bromination agents for metallic oxides such as ZnO, Cu2O, CuO, PbO and FeO. Moreover, these metallic oxides have the thermodynamic tendency to brominate easier than does Sb2O3. The aim of this study was to investigate experimentally the reactivity of ZnO with 1) HBr originating from the thermal decomposition of TBBPA and 2) SbBr3, which is formed during thermal degradation of brominated flame retardant plastics. The thermal treatments of the mixture of compounds of interest were investigated by thermogravimetry coupled with mass spectrometry.IntroductionTetrabromobisphenol A (TBBPA) and many systems based on the synergistic effect of brominated organic compounds with Sb2O3 are extensively used as effective brominated flame retardants (BFRs) in materials such as plastics and textiles. For instance, 4.5 million tons of flame retardant plastics containing BFRs are produced in Japan each year. Thus, in thermal treatments such as the incineration and melting of solid wastes, BFR containing plastics are intentionally or unintentionally included in the wastes. Thermal degradation of BFR-containing plastics leads to the formation of hydrocarbons and gaseous compounds such as HBr and SbBr3 [1-5]. Our thermodynamic considerations [6] indicate that heavy metal oxides such as ZnO, Cu2O, CuO, PbO and FeO should easily react with HBr prior to Sb2O3 and also with SbBr3, the main gaseous product in the thermal decomposition of TBBPA, forming low boiling point metallic bromides suitable for the volatile separation of heavy metals. The metal oxides are also expected to qualitatively and quantitatively affect debromination and decomposition of the flame retardant."

Jan 1, 2008

By Ibrahim Yusufoglu, Ahmet Orkun Kalpakli, Cem Kahruman, Sedat Ilhan

"The effects of oxalic acid concentration, temperature, stirring rate and particle size on the dissolution rate of synthetically prepared calcium molybdate were investigated. Dissolution of calcium molybdate in oxalic acid solutions takes place as a series - parallel type reaction. In the first reaction step, which proceeds according to the ""Langmuir - Hinshelwood Mechanism"", calcium aqua oxalato molybdate is formed as a complex chelate intermediate product. In the second reaction step, molybdic acid is formed during the slow hydrolysis of calcium aqua oxalato molybdate, and it reacts rapidly with oxalic acid to form the polymeric hydrogen oxalate dimolybdate chelate as an end product. Activation energies were calculated as 41.4 and 49.9 kJ mol-1 for the first and zero order reactions. The fractional conversion versus time relationship can be given by the following equation.IntroductionMolybdenum is used widely in electric-electronic, metal working, aerospace and aeronautic, nuclear, glass and petrochemical industries because of its high melting temperature and resistance against chemical effects. However, the largest molybdenum consumers are the iron-steel and super alloy industries where molybdenum is used as an alloying element. Industrially important molybdenum minerals are limited to molybdenite (M0S2), powellite (CaMo04) and wulfenite (PbMo04), which are considered as primary molybdenum resources. Secondary molybdenum resources are spent catalysts and scrap [1-4].Molybdenum has been produced by pyrometallurgical processes in the past. Since it is possible to process low grade molybdenum ores and industrial wastes by hydrometallurgical processes, which are more environmentally friendly than pyrometallurgical processes, the importance of the use of hydrometallurgical processes has increased in the molybdenum production industry."

Jan 1, 2012

By T. S. Montgomery

The performance of carbon-magnesia brick in electric arc furnaces (EAF) is interpreted in light of their observed optical microstructures. Features at the bricks' hot faces were protruding periclase grains, metal globules, graphite-metal contacts and linear void patterns. These features were com-pared to similar features previously seen from microstructures of basic oxygen furnace (BOF) refractories. Modes of formation were sought; an attempt was made to interpret their influence related to wear mechanisms.

Jan 1, 1982

By Zhao-Qun Ke, Wen-Feng Tan, Jiang Diao, Yu-Hao Liu, Bing Xie, Zhang Tao, Wang Zhou, Hong-Yi Li

An effective way to decrease the dephosphorization burden in the current vanadium extraction-steelmaking process is slagging with CaO in vanadium extraction step. The phase composition of vanadium slag with different basicity and the regularities distribution of elements have been investigated by X-ray diffraction analysis and scanning electron microscopy combining with energy disperse X-ray spectrometry, respectively. The results indicate that V mainly concentrates in the spinel phases; Ca and P are rich in the silicate phases. Fe2SiO4 transform to CaFeSiO4, while the basicity of vanadium slag is 1.3. With further increase of basicity, 2CaOSiO2 could form in the silicate phases. Moreover, the phosphorus-containing phase will transform from Ca3(PO4)2 to Ca3(PO4)2-nCa2SiO4. With the increase of P2O5 content, the crystallization rate of spinels decrease obviously. Furthermore, the peak temperature for crystallization of spinels decrease 5 K with the P2O5 content increasing 1 wt%.

Mar 1, 2017

By N. Kanarin

A thermodynamic study is reported on the chlorination of Fe(1-x.)O, Fe2O3, Cr2O3, MgO, Mg2SiO4 with chlorine in the presence or the absence of reducing atmospheres. The reactivities of these compounds as well as that of Mg3Si2O5(OH)4 using Cl2+N2, Cl2+air, and Cl2+CO gas mixtures were studied by non isothermal thermogravimetric analysis between 20 and 1000 °C. The same solids were chlorinated in a horizontal experimental set, during two hours between 350 and 1000 °C, in reducing and oxidizing atmospheres: The chlorination products were examined by XRD and SEM, and possible reaction paths were examined. Results indicate that the carbochlorination of these solids was better than their chlorination; Furthermore, the carbochlorination was performed at lower temperatures than those of the chlorination. Finally, the reaction extent was higher in the case of carbo-chlorination of these compounds. Based on these results, a process was suggested for the selective recovery of chromium compounds from the chromite concentrate.

Jan 1, 1995

By E. Morrice

Solubility of yttrium oxide (Y203) in fluoride melts was experimentally measured in the temperature range of 998 to 1273 K and, YF3 composition in LiF.YF3 melts varying from 20 to 50 mole pct using a graphite crucible in an argon atmosphere. Solubility of oxide in the melt was found to increase with increasing temperature and YF3 composition in the melt. An expression for in XY2O3 as a function of temperature for several melts was deduced. The calculated activity coefficients of Y2O3 in the melts exhibited a negative deviation from Raoult's law.

Jan 1, 1989

By Jianjun Wang, Jiaqing Peng, Lingen Luo, Zhenbang li, Yinghe Lin

Copper removal from ferronickel by FeS has been exploring studied. It is found that the decopperizing agent FeS makes the copper removal in ferronickel effectively. The effects of FeS addition amount, carbon content in ferronickel and experimental temperature were investigated. The results showed that the removal rate of copper in ferronickel increased with the amount of FeS increasing. When the dosage of FeS is 20% (mass percentage)，the removal rate of copper can reach higher than 11%. The rate of copper removal rises with the amount of carbon content increasing in ferronickel. When the amount of carbon content is 1.86%, the removal ratio of copper is 41.3%. Higher experimental temperature promotes the copper removal reaction in certain extent. The flux is acidity and weak oxidative can also promote the reaction of copper removal.

Jan 1, 2015

By John J. Mazza

Treatability studies were performed to determine the effectiveness of two commercially available treatment methods (solvent extraction and thermal desorption) for the removal of PCBs and PAHs from contaminated dredged riverbed sediments. The solvent extraction method evaluated was the B.E.S.T. process which extracts the contaminants with triethylamine. The thermal desorption method utilized was the ATP process which desorbs the contaminants at elevated temperature in an anaerobic atmosphere. A description of both methods and. an evaluation of the treatability study results is provided. Each treatment method was used to treat two separate samples (high and low concentration) from the site. Overall, both methods proved to be very effective with solvent extraction achieving 98% removal of both PCBs and PAHs and thermal desorption achieving better than 99% removal of both the PCBs and PAHs from the high concentration sample. Both solvent extraction and thermal desorption achieved greater than 99% removals of PCBs and PAHs from the low concentration sample. Vendor cost estimates for full scale treatment were roughly equivalent. The primary differences between the two methods lies in the realm of permitting, operational requirements, and emission concerns.

Jan 1, 1994

By Jean-Louis Dirion, Guy Depelsenaire, Patrick Sharrock, Souhila Kribi, Ange Nzihou, Jocelyn Ramaroson

"This study assesses the Novosol® process, an emerging technology developed by Solvay to treat heavy metals from dredged sediments using phosphoric acid. The main goal is to convert toxic metal ions, such as Pb2+, Cd2+, Zn2+ and Cu2+ to insoluble metallic phosphates. The effectiveness of the treatment was evaluated by performing the chemical reaction in a tubular reactor, followed by convective drying and maturation of the treated sediment at ambient temperature and finally thermal destruction of the organic matter by calcinations (500°C-700°C). Selected variables (acid concentration, volume fraction of solids, flow rate, drying and calcination temperature and time) were investigated. Laboratory scale experiments were carried out with various combinations of these parameters. The influence of the quantity of acid and the temperature of calcinations on physical properties of the sediment and stabilization of the heavy metals are discussed. Introduction The French territory counts 525 000 km of rivers which transport each year on average 6 million m3 of sediments. Their deposit causes the silting of channels, rivers and lakes. This completely natural phenomenon is exacerbated by the introduction of industrial and urban wastes into the erosion and sedimentation process. This silting leads to clogging of rivers, with a reduction in their flow rates. Consecutively, other problems appear, such as flooding risks, decrease of biological purification capacity and associated loss of the biodiversity. The presence of toxic compounds (from industrial, household or agricultural origins) in the sediments worsens the situation, and requires curing to restore the natural environment and its function. The dredged sediments are either spread on agricultural land, land tipped, confined or sent for chemical or physical treatment [12]. The first research programmes on toxic sediments appeared at the end of the Eighties in the United States, in Canada, in the Netherlands and in Germany. Several techniques of treatment were developed for the sediments; these techniques can be used alone or in combination. These techniques include extraction and concentration of the pollutants: the pollutants are isolated from the sedimentary matrix and the sediment is decontaminated. In some cases of organic contaminations, the pollutants are destroyed by chemical oxidation or biodegradation and in other cases, the contaminated material is either stabilized (mixed with hydraulic binders), or destroyed (incineration) [14,15]. Phytoremediation by afforestation has also been reported [19]."

Jan 1, 2008

By J. Méndez-Nonell

The thermodynamic and chemical properties of SrSO4 and SrS in a gaseous flow of CO and CO2 at high temperature are discussed. The thermodynamic analysis of the system was made using data from the literature. The results obtained from the thermodynamic analysis were experimentally verified using the thermogravimetric technique. The experimental results suggest the formation of a complex compound between SrO and SrSO4. It was also found a change in the chemical mechanism of the process between SrSO4 and CO-CO2 and in the chemical mechanism of the process between SrS and pure CO2.

Jan 1, 1995

By F. W. H. Dean

A very sensitive sensor for the detection and measurement of hydrogen in solid steel is described. This technique is non-invasive and uses a collector to sweep the hydrogen emanating from a steel surface and feed to it sensor. This method is particularly sensitive, resolving fluxes to < 2 pI cm?2 S?I, with a linear measurement up to 1000 pI cm&apos;2 S?I, The collector is held on the steel substrate by magnets and it is shown that emanation of hydrogen from the steel is controlled by bulk diffusion of the hydrogen through the steel. The technique is demonstrated to have an excellent response time and reproducibility.

Jan 1, 2001

By Wiraseranee. Chompunoot, Kazuki Morita, Toru H. Okabe

"Aiming at the development of more effective recycling processes, dissolution behavior of rhodium into molten slag was investigated. Using a pure rhodium crucible and Na2O-SiO2 slag system, equilibration experiments were carried out for 18 h at 1423-1623 K under various oxygen partial pressures of 0.005-1 atm with varied slag basicity. Rhodium solubility increased with increasing oxygen potential, slag basicity, and temperature. Rhodium dissolved into slag as rhodate ion ([RhO2]-) by the endothermic reaction: Rh(s) + 3/4O2(g) + 1/2O2-(in slag) = [RhO2]-(in slag). In the dissolution reaction, the “rhodate capacity” of slag is newly-defined. The correlation between rhodate capacity and optical basicity is reported.IntroductionDue to its high chemical resistance and outstanding catalytic properties, rhodium (Rh), one of the platinum group metals (PGMs), is utilized in various applications such as catalysts, molten glass vessels and containers, and electronic devices. Owing to the rarity of Rh resources in nature, recycled Rh from scraps such as spent automobile catalytic converters is currently considered as an important source of Rh supply [1]. According to the recycling practices, Rh is currently mainly recovered from scraps along with other PGMs such as platinum (Pt) and palladium (Pd) by a dry process (e.g., smelting), a wet process (e.g., leaching and subsequent separation of PGMs from aqueous solution), or a combination of both processes [2]-[4]. Among these processes, smelting is commonly applied because PGMs can be effectively separated from a relatively large amount of various impurities coexisting in scraps. In the smelting process, Rh and other PGMs are collected in the collector metal (e.g., iron and copper), and impurities in scraps are removed into slag [4]-[6]. The process may be carried out at a temperature range of 1573-1973 K, in either an oxidizing or reducing atmosphere. Due to the high oxidation resistance at high temperatures, Rh is expected to be collected efficiently in the metal collector rather than being oxidized and forming RhOx in a molten slag. However, Rh loss into slag does occur in this process [7]."

Jan 1, 2011

By G. S. Hanumanth

Sedimentation of particles during the liquid metal processing of particulate metal-matrix composites can affect the homogeneity, and thereby the properties, of the cast product. A novel electrical probe has been developed to measure the in-situ volume fraction of ceramic particles in molten metal baths. Using this probe, sedimentation rates for 90 pm silicon carbide particles dispersed in molten aluminum A356 alloy were measured over a wide range of particle volume fraction, 0.05 to 0.3. The sedimentation rate was found to depend strongly on particle volume fraction; the time to clarify a 0.15 m depth increased from approximately 60 to 500 seconds as the volume fraction increased from 0.05 to 0.3. Measured sedimentation rates agree well with the predictions of a sedimentation model based on one-dimensional, two-phase flow theory in which the inter-phase drag function is derived from the momentum equation, utilizing the Richardson-Zaki Equation for sedimentation in aqueous systems. The implications for solidification are discussed.

Jan 1, 1993

By Liwen Hu, Jianxun Song, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

The subchloride titanium was prepared by sponge titanium and titanium tetrachloride in the CaCl2 at 1173 K. The species were detected are mainly titanium dichloride, and the average valent in the melt are 2.05. The accurate equilibrium constants were obtained for the reaction 3Ti2+ = 2Ti3++Ti after the accurate activities of titanium chloride were evaluated with emf method, and the observed deviations from ideal behavior are discussed.

Jan 1, 2015

By Guozhu Ye, Mikael Larsson, Eric Burström, Sten Ångström

"Increased use of scrap in steelmaking including scrap use in BOF has a high economic and environmental potential in terms of increased productivity, energy saving and reduced emission of CO2. Preheating and surface cleaning of steel scrap is a concept developed by MEFOS in a four year research program funded by MISTRA, Swedish Foundation of Strategic Environmental Research. The process concept consists of four major steps: 1) Combustion of ASR or other waste fuel and composing of the gas composition. 2) Scrap heating and cleaning in a shaft where the coated zinc is removed as ZnCl2 and scrap is heated to about 600 ºC. 3) Dust separation for recovery of metal zinc. 4) Gas cleaning. This paper will describe the process concept and highlight the major results from preliminary trials around the scrap heating and cleaning shaft.IntroductionSteel is often coated to increase the corrosion resistance. Share of coated and galvanized steel in the world marked is steadily increasing. This results in increased amounts of scrap with different types of coatings. Use of galvanized scrap in EAF plant results in an EAF dust with high content of zinc ferrite and many other impurities like Pb, Hg, Cd and halide. EAF dust is classified as hazardous waste in most of the developed countries and the steel plant has to pay for external treatment for zinc recovery. For use in BOF plant this will result in a BOF dust containing typically 1-5%Zn making it impossible for recycling to the blast furnace.Different approaches for surface cleaning have been investigated in past. Dapper et al. [1] examined the possibility to evaporate Zn, Ni, Cr, Sn from coated materials using chlorine. Chlorinated rinsing of non iron oxides and metals using HCl from combustion of PVC was discussed by Fray [2]. Further studies by Tee and Fray [3-5] have been concentrated on the possibility to vaporize coatings with an air and chlorine gas mixture. The O2:Cl2 ratio in the gas mixture was found to have great importance for control of the process. To avoid the chlorination of iron, this ratio should be kept at a level of 10:1.Scrap pre-heating up to about 600 ºC is a well known method and this alone could save up to 100 kWh per ton steel. The technology has been established since many years and efficient processes were developed in the 90’s. However, no process has fully gained the expected energy savings as the large quantity of the exhaust gas has to be reheated to over 1000 ºC again to destroy the hazardous components like dioxins."

Jan 1, 2008