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TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of Ti02 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the Ti02 film in H2S or CS2 gas at 1273 K for 1 hour, the surface atomic structure was changed. Furthermore, the Ti/TiO2 film was successfully prepared by the subsequent ablation of Ti and TiO2 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By Berndt Moeller

Mercury-cell chlor-alkali production plants generate mercury contaminated wastewater streams from which mercury must be precipitated and filtered, resulting in a sludge containing 2% mercury (designated KI06) that cannot be landfilled in the United States without treatment. REMERC is a chemical treatment process used to recover 99% of the mercury from wastewater sludge generated at these plants. The process uses leaching to oxidize mercury compounds to mercuric chloride, washing and filtration to separate mercuric chloride from the treated sludge, and cementation to reduce the mercuric chloride to metallic mercury. Mercury not recovered in cementation is recycled to the wastewater process for precipitation and filtration. Treated sludge contains less than 260 ppm total mercury and 0.2 ppm TCLP, meeting the USEPA low mercury subcategory specifications that allow landfill disposal. REMERC uses readily available chemicals, is straightforward to control and inexpensive to operate, has no mercury emissions to air, and recovers metallic mercury. REMERC enabled significant cost savings including lower solids disposal costs, recovery and reuse of metallic mercury in the chlor-alkali process, and ability to treat non-wastewater sludge. No new EPA permits were required. REMERC was shown to be a viable process for recovery of metallic mercury from K106 designated sludge.

Jan 1, 2003

By Wenbo Luo, Jilai Xue, Tiepeng Li, Jun Zhu

Sodium silicate solutions for producing silica have been ultrasound treated to enhance the precipitation process in laboratory scale. Higher precipitation rate was found with ultrasound treated solutions than those without ultrasound. The obtained SiO2 powder products were characterized using XRD, SEM, BET and laser particle size analyzer. The particle size distribution and the specific surface area of the powder products varied with the power input level and the processing time of the ultrasonic treatment. The results indicate that the efficiency of the precipitation process can be improved optimally when the ultrasound is conducted into the solutions before the nucleation stage.

Jan 1, 2015

By Takahiro Miki

Soldering material widely used is Sn-Pb alloy, which have low melting point and excellent electrical, strength properties and wettability. However, Pb is one of the toxic elements, which is undesirable due to environmental and safety reasons, thus Pb-free alternative alloy is preferred for new soldering materiaL Sn-Ag and Sn-Zn based alloys have been viewed as very promising candidates, among many potential substitutes. Addition of third element to these alloys will decrease melting point of the alloys. Hence, Sn-Ag-In and Sn-Zn-Mg alloys are expected to be suitable for replacing Sn-Pb solder alloy. In order to dcsign new Pb-free soldering materials, it is crucial to understand precise thermodynamic properties and phase diagrams of alloy systems. In the present work, ion current ratios of Ag to In and Mg to Zn were measured for Sn-Ag-In and Sn-Zn-Mg alloys by mass spectrometry, respectively. Also, the authors reviewed the thermodynamic properties of terminal binary alloys determined by other researchers and evaluated a thermodynamic functions to express the excess Gibbs free energy of each binary alloy. Thermodynamic functions to express the excess Gibbs free energy of liquid Sn-Ag-In and Sn-Zn-Mg ternary alloys were determined, utilizing the assessed Gibbs free energy of terminal binary alloys with the measured ion current ratios using mass speetrometer.

Jan 1, 2003

By R. L. Nyirenda

The use of ammoniacal ammonium carbonate (AAC) leaching for the treatment of carbon steelmaking EAF dust has been investigated on a laboratory scale. The experiments have been conducted on dust samples obtained from three European steelmaking companies. As received, the dusts were found to be toxic when tested according to current EPA toxicity testing procedures. Toxicity was on account of the leachability of one or more of the following elements: Ag, Hg, Pb, and Cd. Leaching experiments with concentrated AAC solution at 40 " C showed that zinc oxide present in the three dust samples, 60-80% of the total contained zinc, was rapidly solubilized. Data on the dissolution characteristics of Cd, Fe, Pb, Mg, and Mn are also presented. Toxicity tests conducted on residues of the leaching experiments found these to have leachates below past and current EPA toxicity threshold limits.

Jan 1, 1993

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4T13O12 (BIT) which has a positive temperature coefficient of dielectric constant (TE) can be used to modify the negative of typical microwave dielectric ceramic BaNd2Ti4O12(BMT). However, BaNd2Ti4O12/Bi4Ti3O12/BaNd1Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C was much higher than that of Bi4Ti3O12 ceramic (around /1100°C). in this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated divided proposed to prepare ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second mop, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti1O12 ceramic pellets and spark plasma sintered at 900'C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe mircoanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/B1T/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.8, a low dielectric loss of 0.0068 and a small temperature coefficient of dielectric constant v/35 ppm/C at 1 MHz.

Jan 1, 2003

By J. E. Wey

Extraction of cobalt from cobalt sulfide and cobaltite flotation concentrate from the Blackbird Mine, Idaho, was investigated using an adapted strain of Thiobacillus ferrooxidans. Cobalt extractions as high as 100% were realized in the inoculated experiments, whereas only 4% extraction was obtained in the sterile run. The influence of pulp density on the rate and extent of cobalt extraction was also determined. It was found that the extraction of cobalt followed predominantly the indirect mode of bacterial activity. In this process, ferric iron oxidizes cobaltite to cobalt sulfate and ferric arsenate while being reduced to its ferrous state; the bacteria continuously re-oxidize ferrous to ferric iron. Electrochemical measurements using cyclic voltammetry suggested that cobaltite oxidation involved a number of intermediate reactions.

Jan 1, 1993

By W. G. Davenport

Chapters 7,8and 9 calculated three combinations of: blast composition (mass% O2, mass% N2) oil quantity per tonne of concentrate blast temperature that will steadily produce molten 65% Cu matte from pure chalcopyrite-concentrate. The combinations are:

Jan 1, 2001

By Q. G. Liu

New solid-state electrochemical sensors 1;.1sing Li2SO4-Ag2SO4 electrolytes have been developed to measure SO2 and/or SO3 in gas mixtures. Silver embedded in part of the electrolyte is used as the reference electrode. Although single-phase electrolyte sensors yield accurate results for one to two days, a two-phase electrolyte cell exhibits excellent long-term chemical stability. For example, stable and accurate potent iometric responses have been obtained over a six mo.nth period. The. advantages of the two-phase electrolyte ( 23 mol% Ay 2SO4 ) cell include excellent mechanical strength on temperature cycling and an insensitivity to compositional variations in the electrolyte and to temperature fluctuations. Experimental tests have shown excell.ent results in SO2-air. mixtures with the SO2 concentration ranging from 3 to 10,000 ppm (vol). However, the SO2 concentration range was limited by a lack of standard gas mixtures, and our sensor cells can be used to measure S02 concentrations significantly less than or larger than our experimental range. Results also indicate that the presence of significant concentrations of CO2 and H2O in the gas mixture has no effect on the sensor response. Thus the two-phase electrolyte ( 23 mol% Ag2S04) sensor has exceptional selectivity, reliability and long-term chemical and mechanical stability.

Jan 1, 1985

By Sadegh Safarzadeh, Anne-Marie Suriano, Stanley Howard

The electrodeposition of metal ions from aqueous electrolyte solutions has been a well-known process for the last half century. With numerous industrial applications such as electroplating, electrowinning and electrorefining, the kinetics of electrochemical reactions involved in the process has been extensively researched. Arrhenius-type rate equations, the Butler-Volmer equation, and the empirical Tafel equation are among the most important models to explain the rate of electrochemical reactions. The study of the kinetics of metal deposition is critical to understanding the underlying mechanisms through which a certain morphology of metal deposit is formed on the cathode. The purpose of this paper is to elucidate the influence of experimental parameters such as pH and additives on the rate and the reaction mechanism determining the rate limiting step of the electrodeposition reactions.

Jan 1, 2015

By Yong .. Jun Wu

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4Ti3O12 (BIT) which has a positive temperature coefficient of dielectric constant (,E) can be used to modify the negative tE of typical microwave dielectric ceramic BaNd2Ti4O12(BNT), However, BaNd2Ti4O12/Bi4TiO12/Bi4Ti3O12/BaNd2Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C) was much higher than that of Bi4Ti3O12 ceramic (around 1100°C). In this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second step, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti4O12 ceramic pellets and spark plasma sintered at 900°C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/BIT/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.85, a low dielectric loss of 01068 and a small temperature coefficient of dielectric constant of 35 ppm/°C at MHz.

Jan 1, 2003

By Hideki Yamamoto

A new technology to convert fluoride gas (C2H2F4 : R-134a) contained in the exhaust gases from semiconductor manufacturing plants and refrigerators directly into a harmless substance have been established, thus, presenting a new concept for the disposal of fluoride gases such as CFCs that are associated with the global warming. Experimental results verify that chemical reactions with metal compounds can take place at substantially lower temperatures of 700- 800K as compared with combustion treatment temperatures of 1200-1500K. The reaction product is mainly metal fluoride, which chemically is a harmless material. Furthermore, this process is compact, easily controlled, safe and has low running costs. This paper deals with a new chemical reaction method for the harmless disposal of gases effecting the global warming.

Jan 1, 2003

By R. W. Smith

The flotation response and electrokinetic behavior of Chlorella vulgaris and Chlamydomonas sp . when using dodecylamine hydrochloride as collector were studied in the absence and presence of Pb(I1). Also, an electron microscopy study was made of the algae after Pb accumulation. The flotation behavior of the organisms after Pb accumulation appears at least partially related to the location of the abstracted Pb onto or into the organisms.

Jan 1, 1991

By Marcelo B. Mourão

An experimental investigation was carried out to -study the rates of reduction of pellets containing iron oxides by carbon dissolved in liquid iron, at temperatures ranging from 1720 K to 1973 K. Several different pellet types were employed; the materials used in the pellet's manufacture were pure hematite, two kinds of commercial iron ores, and mixtures hematite/silica and hematite/lime: Reaction times were determined employing the constant volume pressure increase technique (CVPI). It has been observed that the reaction rate increases as the temperature and the pellet's specific surface area increases. The reaction rate is also affected by the oxide type: pellets made from commercial ores or from mixtures hematite/silica or hematite/lime show reaction rates lower than those made from pure hematite.

Jan 1, 1996

By W. D. Cho

Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking -ladle and tundish - to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-A12O3 and CaO-A12O3-SiO2 slags at the temperatures between 1450 and 1550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopies. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al2O3, Siq, CaF2 and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase has been observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.

Jan 1, 2002

By Roberto Parra

The wear and corrosion phenomena in the furnace lining of the ferrous and non ferrous pyrometallurgical processes are complex problems where chemical, interfacial and mechanical phenomena are presents. The characteristics of the processes determine the conditions to which these materials are submitted, where the thermal conditions reached during the operation is one of the most important parameter. Assuming that all the degradation phenomena are thermal activated, the rate of the different steps of the wear mechanism will depend on the thermal field in the lining. In view to apply the independent physicochemical knowledge of degradation mechanisms to the analysis and design of furnace lining the methodology of the Nodal Wear Model (NWM) was done. It combines the mathematical modelling of the heat transfer in the lining with the physicochemical control equation for the wear-corrosion phenomena. The NWM has been applied to different examples: theoretical analysis, laboratory scale test and industrial applications. We present in this paper the theoretical background of the model and two examples of applications: the sole of an electric furnace and the earth of a blast furnace.

Jan 1, 2006

By Gerald Onyedika, Tochi Onwumere, Martin Ogwuegbu

"The kinetic study for the leaching of iron from cassiterite ore in KOH solution was studied. The effects of KOH concentration, particle size and reaction temperature on the leaching rate of iron were also examined. The results of leaching studies showed that the leaching of iron from cassiterite ore in KOH solution is significantly influenced by the reaction temperature, KOH concentration, and decrease in particle size. The study showed that 90.62% of iron ore was leached in 8M KOH solution at 80°C within 120 minutes. The experimental data were well evaluated using the shrinking model for surface chemical reaction and diffusion control through the product layer. The activation energies for the iron ore dissolution using the two models were calculated to be 32.06KJmor1 and 97.97 KJmor' respectively.IntroductionIn recent times, there has been increasing attention on the kinetic study of mineral dissolution. In most of these studies, the experimental results were analyzed with a suitable shrinking core model under the assumption that the ore is a homogeneous spherical solid phase [1-4]. A study of the dissolution kinetics of a Nigerian cassiterite ore by hydrochloric acid showed that increase in the hydrochloric acid concentration is accompanied with increase in the amount of cassiterite ore dissolved at various times [4]. The optimal concentration was found to be 4.0M HCl, after which there was a decline in the amount of the ore dissolved, which showed that the concentration of the reagent has a significant effect on the leaching rate of the ore. Also in studying the effect of stirring speed on the rate of cassiterite ore dissolution while keeping other conditions constant for 120 minutes, the result showed that the rate of cassiterite ore dissolution was dependent on the stirring speed over a range of 0 to 630 rpm. Above 360 rpm, the stirring speed no longer had any effect on the solid dissolution. The dissolution rates of cassiterite were analyzed using a suitable shrinking model. The results showed that the reaction was controlled by the diffusion of tin through the porous product layer, a reaction order with respect to hydrogen ion concentration of 0.92 M and activation energy of 50.05KJmor'. In another kinetic study on the leaching of a low grade niobium-tantalum ore with concentrated KOH solution the effect ofreaction temperature, KOH concentration, agitation speed, particle size and alkali-to-ore mass ratio on the dissolution rate of niobium were examined [5]. The result of niobium leaching from low grade niobium-tantalum ore with concentrated KOH, solution at different agitation speeds showed that the dissolution rate increased with increase in agitation rate. In the case of particle size effect, the results show that small particles require much shorter time for complete dissolution than the large ones."

Jan 1, 2013

By T. J. White

Xtaltite is the trade name for a generic technology which exploits the well known insolubility of some minerals, which naturally incorporate toxic waste elements, to consolidate and immobilise a range of inorganic waste products. It is a specific case of synthetic mineral immobilisation technology (SMITE) which is already used to immobilise high level nuclear wastes (HLW. Although HLW is highly toxic, it exists in relatively small volumes, occurs in central facilities and may be stabilised at low waste loading (< 10 wt%). In contrast, heavy metal wastes are of considerable volume, therefore Xtalitite waste forms must routinely accommodate high waste loadings (usually in excess of 30 wt% for a particular toxic oxide or combination of oxides) and be suitable for fabrication in remote locations using relatively simple technology. This paper details the methodology underlying Xtaltite, with particular emphasis given to the interplay between solid state chemistry, durability and economic considerations. Specific reference is made to the treatment of arsenious and mercurial wastes.

Jan 1, 1994

By Fatbardha Osmani, Skender Osmani

"A system analysis of the resource and environment management (water, energy etc) starts from its definition. Unfortunately, there is not a unique semantics of the mentioned concept. On these circumstances, in this paper the following issues are presented: 1.A short view on the existing concepts of management. 2.A new definition on the concept of management. It is considered as a complex and rational activity on human and natural resources ,environment etc, which starts from a analysis of infrastructure ,technology , etc, mission , alternatives , project etc. and ends to an optimal output. Basing on this definition, the management has two principal components: strategy and policy. The strategy is referred as a blue print program (the same definition as in Game Theory), which contains all the contingency alternatives. , while the policy is referred as a strategy applied into practice. The strategy is the first , while the policy is the second one. The best alternative of a policy is the project, Each strategy has one and only one project. The mentioned definition erases the differences between concept of policy and politics. Each strategy has its alternatives ,the next has its sub strategy and so on, i.e. whatever are going to be the strategy, there are a hierarchy composed by sub strategies up to the simplest strategies applied by a single individual (human beings or robots). The strategy objectives are necessary and sufficient conditions for its realization i.e . the strategy is an optimal activity, in which all resources are integrated and processed . Several strategies could be joined into one( for example the surface water strategies of the Balkan countries) . In this view, the strategy could be globalized into optimal way basing on different criteria’s as social, economic, environmental, their risks and effectiveness etc. etc An example from the water management illustrates the mentioned concepts."

Jan 1, 2008

By H. Roberts, C. Hassall

The opening years of the new millennium will be characterised by the closure of many lead and zinc mines because of reserve depletion. However, weak commodity prices through the second half of the 1990s have slowed project evaluation and have made it difficult to raise finances for the development of new mines required to replace lost output and to meet increasing demand for metal in the future. Growth of lead and zinc demand will be determined by the pace of global economic activity, especially in the emerging economies. How rapidly demand grows will have a key bearing on the possible shortfall in mine output and the response of prices to the implied tightening of metal supplies early in the new millennium. These issues are the focus of a discussion of the critical lead and zinc supply developments which will unfold post 2000, taking into account project lead times and the role that recycled metal plays in meeting market demand.

Jan 1, 2000