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By Filiz Sahin

This paper presents a synthesis of TiB2 via carbothermal reduction method using a mixture of TiO2, B4C and C prepared in molar ratio of 2:1:3. Reduction experiments were carried out in a high temperature graphite furnace in a graphite crucible under argon atmosphere at different time (0, 15, 30 and 60 min.) and temperatures (1400, 1500 and 1600 °C). The products obtained were investigated using XRD technique.

Jan 1, 2008

By Agnes Y. Lee

he U.S. Bureau of Mines developed a method to treat lead-contaminated soil and ebonite battery casing wastes to produce a nonhazardous material. The cleanup procedure involves wet screening to separate a minus 18-mesh soil fraction; removal of metal1ic lead, rocks, wood, etc. ; carbonation to change lead sulfate to acid-soluble lead carbonate; size reduction; acid leaching; and rinsing. The casing wastes undergo size reduction and washing to remove the lead sulfate sludge before carbonation. Similarly, the minus 18-mesh soil is carbonated, then acid leached and rinsed. In leaching, fluosilicic acid (H SiF,) and hydrogen peroxide (H20,) are used to dissolve lead compounds. An electrowinning method is employed to strip lead from the lead-rich leachate. The acid content in the leachate is replenished with fresh H,SiF, acid prior to recycling. Treated casing wastes and soils pass the Toxicity Characteristic Leaching Procedure (TCLP) test and can be reclassified as nonhazardous materia1s. Based on this process, a conceptual pilot plant has been designed which will be demonstrated on wastes from two Superfund sites.

Jan 1, 1993

By Arpad E. Tonna

Recycling of materials from lithium-oxyhalide batteries is a complex task, since the dismantling of batteries is associated with many hazards. The electrolyte and the lithium anode metal are extremely reactive in the presence of water or water vapor. Therefore, the dismantling process is a complex task. In this process, the lithium battery is electrically discharged, then frozen in liquid argon, and cut into small size pieces. These are fed into an incinerator, where the unreacted portion of lithium metal, thionyl chloride, plastic separators and carbon paste are decomposed and burned to gaseous products. The aluminum, iron (steel) and nickel pieces are recovered as saleable scrap metals. The off-gases are scrubbed with an alkaline sodium carbonate containing solution. The clean gases are released to the environment. The particulate mater recovered from the scrub-suspension would be available as additive to the cement industry . The recycling of battery decomposition products improves the economic viability of the disposal processes. Work is in progress to develop safe handling, processing and recycling large size lithium batteries.

Jan 1, 1995

By Albert F. S. Seboukens

A 5;6 MVA pyrometallurgical demonstration-scale pilot plant was commissioned at Mintek, South Africa, in 1994, using lead blast-furnace slag and coke as raw materials. The plant included a.d.c. power. supply, two plasma-arc furnaces' and an ISP lead-splash condenser. Slags containing typically 12 per cent zinc oxide and 3 per cent lead oxide are produced as a waste during the smelting of lead in a blast furnace. These slags are a potential: resource for the recovery of lead and zinc. During 1994, about 600 t of lead blast-furnace, slag was proceced through the pilot plant using the Enviroplas process. Zinc and lead oxides were reduced to their respective metals, volatilized, and collected in an. ISP lead splash condenser. Prime Western grade zinc and slags disposable in accordance with current US legislation, were produced. Zinc condensation efficiencies of about 80 per cent were achieved.

Jan 1, 1995

By Brajendra Mishra

Molten Salt electrolytic processes offer unique opportunities to extract and refine metals where gaseous or metallothermic reduction, hydro metallurgical extraction and aqueous electrolytic methods are thermodynamically constrained. Production of aluminum and magnesium by molten salt electrolysis are well known commercial processes. Several other reactive metals, such as lanthanides and actinides, as well as beryllium and calcium, make use of molten salt processing for extraction and refining. This presentation describes the science of molten salt chemistry and electrochemistry for winning and refining of several metals. In addition, recovery of metals from waste process salts by molten salt reduction as well as oxidation have been discussed. Material issues in design of molten salt reactors have been included. Various applications have been presented through case studies. Experimental data have been included to justify the suitability as well as limitations of these specific processes.

Jan 1, 2003

By Murali Thirukkonda, Rahul Shah, Srinivas Tangrila, Shankar Rachakonda, Jan Kajuch, Arthur Gurson

"High-temperature superconductors have potential for a variety of applications such as power generators, superconducting magnets for mine sweepers or ship propulsion motors, and magnetic levitation transportation systems. Interest in the use of superconducting wires and tapes increased dramatically after the discovery of high-critical-temperature (high-Tc) oxide superconducting compounds, which offer operating temperatures above that of liquid nitrogen. Several techniques have been proposed to produce commercially viable high-Tc oxide based superconducting wires. One of the promising methods involves multi-pass powder-in-tube (PIT) wire drawing followed by rolling and heat treatment. This work focuses on the development of a numerical model to simulate the PIT drawing process for fabrication of long lengths of silver sheathed Bi-2212 superconducting wires. The finite element based model was used to predict densification of the oxide powder, wire drawing forces, and silver sheath thickness during drawing. A cap-type pressure dependent constitutive equation was implemented in the model to simulate the powder behavior. The model incorporated experimentally obtained material data for the silver and powder. Results indicate that powder densification is increased by decreasing the initial silver thickness and increasing the silver strength. Data from wire drawing experiments were used to verify model predictions. IntroductionSuperconducting wires and tapes can be used to carry large dc currents with no measurable loss due to resistivity. When used in superconducting magnets for power generators, motors, levitation devices, magnetic detectors, or energy storage devices, they could potentially result in significantly reduced energy losses. In the past, most prototypes were tested in liquid helium at 4.2K [1]. However, the necessity to provide liquid-helium cooling systems proved to be a serious limitation in commercialization. In 1986 high-critical-temperature (high-Tc) oxide superconductors were discovered [2], which could allow for higher operating temperatures above liquid nitrogen (77 K). Since then, both academia and industry have concentrated their efforts on the development of high-Tc oxide superconducting wires, tapes and coils. As yet, large scale fabrication of long lengths of these wires with the required current carrying capacity and mechanical properties remains an enormous challenge."

Jan 1, 1994

By Gernot Schenker

With the shut-down in the mid-1970s of the last shaft furnaces in the Harz Smelter Plant the long tradition of the Primary Lead Smelter in Oker came to an end. A continuation of the concern was nevertheless possible as a result of the timely commencement with the development and construction of lead production from secondary raw materials. Then as today, the most essential secondary raw material is lead accumulator scrap with over 80 % of the raw material pallet. Already in the 1960?s a method of reclamation lead battery scrap was developed and successfully carr.ied out by Preussag. In 1983 this process was fundamentally modified, also for environmental protection reasons within the framework of a rehabilitation programme of the existing plant. Today Metaleurop's HarzMetall GmbH in Oker is equipped with a modern secondary lead smelter which includes all environmental protection installations required by law. Besides processing battery scrap, the. smelter is in a position to process a ?multitude of other lead bearing residues in an economically useful way, whose waste disposal would otherwise be impossible due to the ever-increasing environmental protection laws or only be achieved at great expense.

Jan 1, 1990

By Zhang Hanbo, Niu Liping, Zhang Zhiqi, He Jicheng, Dou Zhihe

"Rutile, ilmenite and Al-Ca complex reducer were used to prepare high titanium ferrous alloy by enhanced reduction-SHS method. The effects of the complex reducer compositions and slag types on the enhanced reduction-SHS process were investigated. The high titanium ferrous alloys were characterized by XRD and SEM. The results indicate that the high titanium ferrous alloys consist mainly of TiFe2, AlTi3 and Al2O3. The oxide inclusions exist resulting in directly the high oxygen content and micro-structural defects in the alloys. The titanium and oxygen contents decrease, but the aluminum content in the alloy increases while the mass ratio of calcium in the Al-Ca complex reducers increases. When the mass ratio of Al/Ca in the Al-Ca complex reducer is 6:1, titanium, oxygen and aluminum contents are 63.75%, 3.01% and 10.72% respectively. When the mass ratio of Al/Ca is 5:1 titanium content is 55.00% nearly and aluminum content is higher than 14.00%, but oxygen content is lower than 2.0%.1. IntroductionThe high titanium ferroalloys with 65%~75% titanium have the advantages of low melting point and high titanium content. They are widely used in special steel refining, while they are also a kind of very important quality orientation alloys in the rage of aviation and aerospace. At present, the methods of preparing high titanium ferroalloy include vacuum remelting and thermit reduction. The alloys prepared by the vacuum remelting method have good qualities and low oxygen content, so it is widely used in Russia, Western Europe and other developed countries. In China, there are abundant rutile resources, but waste titanium is lack, therefore, the preparation method is the thermit reduction. But there are many quality defects in the high ferrotitanium alloy, including high oxygen content, unstable quality and so on. In order to improve the qualities of the high titanium ferroalloy, especially to reduce oxygen content, the domestic and overseas have done a lot of further researches. For example, Sichuan E-mei ferroalloy plant and Beijing Nonferrous Metal Research Institute have prepared high titanium ferrous with 73.77% titanium with natural rutile, but the oxygen content is high. Through controlling the quality of raw material, they obtained the better qualities, but the oxygen content is still very high. South Africa Mintek company have prepared high titanium ferrous alloy with low nitrate by plasma heating under the isolation air conditions, but they couldn’t also remove effectively oxygen in the alloy. The oxygen exists in the form of Al2O3 and titanium protoxide. So it can be speculated that except TiO2 not being fully reduced, the no-sufficient alloy-slag separation is the direct reason resulting in high oxygen and poor microstructure. In view of present technical difficulties during preparing high titanium ferroalloy by thermit reduction, this paper proposed a new method of preparing high titanium ferrous with low oxygen by enhanced reduction-SHS with Al-Ca complex reducer. Ca in Al-Ca complex reducer has stronger reductive ability, it can effectively strengthen the reductive degree of TiO2. The slagging agent CaO CaF2 and MgO can effectively reduce the viscosity of Al2O3 slag to improve its liquidities to strengthen alloy-slag separation effects so that to remove inclusions and oxygen. In this paper, effects of slagging agent type on the reduction and the qualities of high-titanium ferroalloy were studied."

Jan 1, 2012

By Nobuaki Sato, Tetsuo Fukasawa, Akira Kirishima

To apply the fluoride volatility process for the treatment of fuel debris formed in the damaged nuclear reactors, study on the fluorination behavior of main constituents, such as fuel and cladding is essential. The mixture of uranium and zirconium oxides is formed under severe conditions such as high temperature and oxidizing atmospheres. In this paper, fluorination and volatilization behavior of uranium and zirconium oxides have been studied by TG-DTA method in the presence of fluorine. From the TG-DTA result of UO2 in F2 atmosphere, the weight gradually increased up to 7% at 350 oC followed by rapid weight decrease with exothermic peak showing the vaporization of uranium as UF6. ZrO2 showed similar fluorination behavior to that of UO2. However, fluorination of UO2-ZrO2 seemed to be suppressed with increasing ZrO2 amount. This may be caused by the formation of solid solution.

Jan 1, 2016

By Pandey H. D.

The paper describes a fluidised bed ion exchange method for simultaneous removal of phenols and cyanide from the effluent. Use of an eluant enables regeneration of the resin in the continuous operation mode. The breakthrough experiments conducted both on the laboratory scale and on a pilot plant scale have shown that while the level of phenol can be brought down from 462 ppm to about 6 ppm, the free cyanide is almost totally removed. An examination of data indicates that the method can serve the twin objectives of pollution control and phenolic compounds recovery.

Jan 1, 1992

By Jennifer Murphy, Brad S. Schake, Karol Holmes, John R. FitzPatrick, Mike H. West

"The separation and purification of uranium from either nitric acid or hydrochloric acid media can be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps.We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (1 DO-gram) flow experiments, using depleted uranium, were done after the small-scale evaluation of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos.Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process.Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail."

Jan 1, 1996

By Takashi Araki

In this work, we have elucidated the two-step oxidative reaction mechanism of 2,4,5-trichlorophenol by adsorbing oxygen atom for oxidative decomposition reaction of 2,4,5-trichlorophenol on oxide catalyst surface using ab initio molecular orbital calculation. In the first oxidation, total energies of reaction products have been shown extremely stabilized at all oxidation positions. This reaction occurs due to charge transfer from benzene ring to adsorbing oxygen atom. As a result, ? bonding of benzene ring are weakened. However, the benzene ring of 2,4,5-trichlorophenol does not perform cleavage reaction. In the second oxidation, the benzene ring of 2,4,5-trichlorophenol can perform cleavage reaction, since the second oxidation obtains larger stabilized energies than the first oxidation.

Jan 1, 2003

By D. Doungdeethaveeratana

The extraction kinetics in a novel solvent extraction process have been investigated. In this process, the liquid-liquid emulsion is generated by bottom gas injection into countercurrently flowing aqueous and organic phases. This process has a number of advantages over the mixer-settler unit or the spray column in terms of simple equipment configuration, without any mechanical moving parts, and the ease of cleaning and process control, while providing a sufficiently large interfacial area for rapid mass transfer. The overall rate increased with increasing gas injection rate and height of the aqueous phase but decreased with increasing injector diameter at the same gas injection rate. The variation of the overall rate constant was correlated against a set of dimensionless numbers, representing the operating conditions. Extraction rates and efficiencies comparable to those in a mechanically generated emulsion were attained in this new process.

Jan 1, 1998

By Akira Yazawa

The similarities and differences in copper, nickel and lead smelting processes are discussed based on the sulfur-oxygen chemical potential diagrams and the free energy minimization assessments using a thermodynamic software. The prominent features of copper smelting are ascribable to the fact that copper has a strong affinity for sulfur but weak for oxygen and the liquid phase immiscibility between Cu and Cu2S. During the oxidation of sulfides, nickel metal is not stable except at temperatures higher than 1500°C, well miscible with its sulfide, and is oxidized more easily than copper. Metallic lead looks as stable as copper during the oxidation of the concentrate but Pb and PbS. are much more miscible with each other and the vaporization loss is considerable. In the reductive smelting of oxides, the effects of oxygen potential and temperature on the copper contents in slag are not significant due to the monovalent character of copper and the reduction of copper content in slag is not easy in practice. The effect of the slag compositions on the oxidic metal contents of slag is much more significant for lead than either copper or nickel. Due to the immiscible nature between Pb and Fe, high grade lead bullion is easily obtained and lead is more tolerant to impurities.

Jan 1, 1998

By José D. T. Capocchi

Viscosity of liquid lead, tin, and Pb-Sn alloys has been measured by the rotational viscometer method in the temperature range from 50 K above their respective liquidus temperature to 823 K. The results are accurate to within ±1.0 %. The variation of viscosity with temperature followed the Arrhenius-type equation µ = µo.exp(Q/RT). The composition dependence of the isothermal viscosity and the activation energy for viscous flow have not shown anomalous changes at the eutectic composition of the Pb-Sn system.

Jan 1, 2000

By J. Y. Hwang

Microwave heating is an attractive alternative to conventional heating methods because heat is generated directly within the microwave absorbing materials. It has potential to be utilized for selective heating and removal of specified components from a materials mixture. This investigation was undertaken to explore the potential of selective heating and burning of binders for foundry sand reclamation. Selected raw materials and binders used in foundry operations were tested to determine their receptivity to microwave heating. Time needed to reach 600°C and/or the maximum temperature achieved for samples irradiated by microwaves for twenty minutes under 800 W microwave power are reported. The microwave heating characteristics of the selected materials are summarized and discussed. The interactions between microwaves and the raw materials used in a foundry. such as silica sand. chromite sand and bentonite (clay) binder were studied. The results showed that chromite sand coupled well with microwave energy at ambient temperature while silica sand did not. This was expected because the major component of chromite sand. iron chromite (FeCr2O4). is a good microwave absorber. while quartz, which is the major component of silica sand, is a microwave transparent material at ambient temperature. Bentonite absorbs microwaves well because it contains a hydroxyl functional group and water molecules in its structure. It was found that the structure of bentonite was changed through microwave irradiation. Microwave heating characteristics of silica sand mixed with different amounts of bentonite binders were investigated. The presence of bentonite in the mixture improved the microwave heating of silica sand significantly. and bentonite was deactivated by the microwave processing.

Jan 1, 1995

By Hong Yong Sohn, Miguel Olivas-Martinez

"Different approaches are used for calculating the ‘energy requirement’ of a process. The determination of energy requirement becomes confusing for a process in which a fuel is also a reactant. The key issue is which heat of chemical reaction should be included in the ‘energy requirement’ value. We will use the example of ironmaking processes to illustrate the problem. The different approaches essentially boil down to the question: does one include the combustion heat of the reductant used in the reduction reaction or just the heat of the reduction reaction? Depending on the viewpoint, either approach can be accepted; it is a matter of convention. There is a need, however, to select a standard approach because the absolute value of ‘energy requirement’ of a process depends on the choice. The energy requirement of a novel flash ironmaking process will be compared with that of an average blast furnace operation.IntroductionDifferent approaches are used for performing energy balance calculations and perhaps more significantly in presenting the ‘energy requirement’ of a process. The question becomes more involved for a process in which one or more reactants are also used to generate the process heat by combustion. Often the key issue is which heat of chemical reaction to include in presenting the ‘energy requirement’ of the process.It is worthwhile to note at the outset that the difference in energy requirements between different processes for converting similar raw materials to the same desired product is largely unaffected by the choice of chemical reactions to be included. However, the absolute value presented as the ‘energy requirement’ of a process can be different by a large amount depending on the approach. We use the example of ironmaking processes to illustrate the problem. In these processes, as currently practiced or under development, carbon and/or hydrocarbons (including hydrogen) are used as the fuel as well as the reactant for reducing the iron oxide mineral.The different approaches in this case essentially boil down to the following question: does one include the combustion heat of the reductant used in the reduction reaction or treat the reductant portion as just a reactant? Depending on the viewpoint, either approach can be considered acceptable. It is a matter of convention. There is a need, however, to select a standard approach because the absolute value of ‘energy requirement’ of an ironmaking process (e.g., the currently dominant blast furnace process) depends on such a choice. It is particularly important to clearly state the specific approach used when the energy requirement of ironmaking is compared with those of other industrial processes such as petrochemicals production."

Jan 1, 2014

By Yuanbo Zhang, Zhixiong You, Daoxian Duan, Guanghui Li, Tao Jiang

"Manganese is mainly consumed by steel and battery industries. In recent years, it is essential to utilize the low-grade manganese oxide ores with total manganese grade below 25%, as the high quality manganese ore resources are becoming scarce with the rapid development of the steel industry. Conventional pyro-metallurgical processes for utilizing manganese oxide ores are characterized by high production cost and energy consumption, low productivity, serious environmental pollution, etc. In this study, reduction thermodynamic of MnO2 reduced by sulfur was firstly carried out. Then, a novel process of reduction roasting with sulfur followed by acid leaching was developed to recover manganese from the very low-grade manganese oxide ores. Effects of main factors, including temperature, reduction time and S/Mn mole ratio, were investigated, and a high leaching efficiency of Mn above 95% was obtained under optimal conditions.IntroductionHigh/middle-grade manganese oxide ores are generally used in the metallurgical industries, particularly in steel plants and ferro-alloy units. The consumption of metal manganese in the ferro-alloy industry accounts for 85- 90% of the total Mn demanded [1]. Therefore, high quality manganese ore resources are becoming scarce with the rapid development of steel industry. It is essential to make good use of large quantity of low-grade manganese ores (TMn < 25%) presently available."

Jan 1, 2012

By M. L. Apel

A conceptual approach to the bioremediation of uranium mill tailings (UMT) is presented., This approach focuses on, biosorption to remediate the. effluent solution and bioleaching remediate the. solid fraction. Comparative biosorption studies were performed with synthetic single metal solutions using a commercially available biopolymer. The maximum rate of metal sorption by calcium alginate was found to be 5.43, 6,39, 6.48, and 9.74 mg dm-3 min-1 for U022*, Ba2+, Cd2+ and Zn2+, respectively. Activation energy (AEa) for barium uptake by calcium alginate beads was determined to be 11.5 kJ, indicating a diffusion controlled reaction mechanism. Thermodynamic values (AG+ AH+ and ASt) of the metal-alginate activated complex, as reported in the literature, were found to be in agreement with those calculated from this research. Results show that this biopolymer can be effectively applied in the removal of select metals prevalent in uranium mill tailing effluents and associated waste streams.

Jan 1, 1991

By Jorge Alberto Soares Tenório, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Franco Alves Lavacchini Ramunno

"The traditional process for recovery of metals from waste electric and electronic equipment (WEEE) usually involves pyrometallurgical processing. However, the application of this technology to processing waste printed circuit boards (WPCBs) might lead to the formation of dioxins and furans, due to thermal degradation of flame-retardants and polymeric resins present in the board substrate. Therefore, this paper proposes a hydrometallurgical route for the recovery of copper. The acid leaching behavior of copper has been investigated at three different temperatures (25°C, 50°C and 75°C) with and without the addition of an oxidizing agent (hydrogen peroxide - H202). The dissolution kinetics for acid copper leaching was calculated based on chemical analysis by ICP-OES (Inductively Coupled Plasma - Optical Emission Spectroscopy). At 50°C with 1 mol/L H2S04 added 10 mL H202 (30%) each half hour under pulp density of 1 g I 10 mL, 100% of copper was extracted after 3 hours. The dissolution kinetics of copper with H2SO4-H2O 2 followed 1 - (1 - X)113 =Ket, i.e. chemically controlled reaction model.IntroductionThe information regarding the generation of waste electric and electronic equipment (WEEE) are still difficult to obtain because the estimates should take into consideration the historical production and sale of various products and the rate at which they reach the end of their life cycle, whose duration depends on the behavior of consumers [1]. Thus, the estimated overall WEEE generation varies between 25 and 50 million tons each year, which corresponds to more than 5% of all municipal waste generated [2], and this amount will increase at a rate of 3 to 5% per year, approximately three times faster than other individual types of waste [3].Printed circuit boards (PCBs) are essential parts of electric and electronic equipment (EEE), being found in virtually all electronic products, as well as in weapons systems [4]. A PCB is a basic component, which consists of a board where copper tracks are deposited. While the board behaves as an electrical insulator, the tracks connect electrically the various components attached to the board [ 5]. In addition to glass fibers, paper and resins, the PCBs contain significant amounts of metals, such as copper, iron, nickel, lead, stain, silver, gold and palladium [6]. In general, the weight fraction of metal is around 28% and the remainder of the boards is composed of plastic (19%), bromine (as flame retardant - 4%) and ceramic material (49%) [7]."

Jan 1, 2014