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By Robert Mensah-Biney

The loading characteristics of gold-tetrabromide species onto a weak-base resin, PAZ-4, were evaluated using a completely mixed batch reaction system. The time. to attain equilibrium loading was substantial, on the order of several days. However, abnormally high loading capacity values of 15 to 20 meq Au/g dry resin (1000 to 1300 kgAu/tonne) were attainable in 24 hours. The loading of gold-bromo species by P AZ-4 was visualized as consisting of two processes: (i) the rapid adsorption of [AuBr4r species by simple ion exchange mechanisms and (ii) reduction of [AuBr4r to metallic gold by an electron exchange mechanism. Elution of gold from loaded resin was feasible provided the resin had not been loaded to high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the loaded resin. For the high loading capacities observed this option would appear to be cost effective.

Jan 1, 1991

By Sergey Shabala

Green leaf tissues convert solar energy into the energy of chemical bonds of sugar molecules during the process of photosynthesis. The efficiency of this conversion can be much higher than efficiency of any of the currently known silicon-based solar panels. Importantly, vast amounts of CO2 are assimilated during this process. The efficiency of photosynthesis is critically dependent on the availability of a large number of nutrients, among which metal cations such as K, Ca, Mg, Cu, Zn, Fe, Mn, and Ni play a key role. In this paper I summarize basic requirements and major functions for each of these essential nutrients in plant photosynthesis, both at the whole-plant and molecular level. I will talk about how these requirements may be affected by the global climate trends and discuss the prospects of creating artificial photosynthetic “bioreactors” for efficient energy conversion and CO2 assimilation.

Jan 1, 2009

By James P. Bennett

The U.S. Bureau of Mines, Tuscaloosa Research Center, is conducting a review of the usage of different types of refractories, the current industrial practices to recycle/dispose of spent refractories, and the concerns associated with these practices. This information will serve as the technical basis for initiating a research program to recycle or find alternate uses for spent refractory materials. Approximately 1.6 million metric tons of clay based and 1.2 million metric tons of non-clay based refractory materials were manufactured in the United States in 1992 alone, representing a value of almost 2 billion dollars. Landfill has been and remains the disposal means of choice. Issues such as environmental regulations, concerns over landfill disposal, future liability, and product stewardship programs have brought about increased emphasis for recycling or alternate material use. Information on refractory consumption and the issues associated with recycling or disposing of used materials will be discussed, including current recycling practices.

Jan 1, 1995

By P. E. Donaldson

Since 1992, Falconbridge has made available to the international copper industry, Kidd Creek's licensed refinery process technology under the name of the Kidd Process. This has resulted in the supply and installation of permanent cathodes and associated product handling equipment to refineries in Canada, the United States, South Korea, Chile and Mexico. These installations accommodate both electrorefining and electrowinning processes. The growth and industrial acceptance of the Kidd Process has generated technical advancements in the areas of product random sampling, corrugation, marking, labeling, product tracking and data acquisition. In a different area, the expanded development of custom materials processing at Kidd created a need to advance technologically. The process-related problem of high nickel concentrations in refinery electrolyte compromised an increase in current density to >300 A/m2. The need for nickel removal resulted in Kidd Creek's newly developed Nickel Recovery System. The effective and economical extraction of nickel, along with reduced antimony and bismuth levels, reduces bleed stream volumes and/or neutralization costs and simultaneously produces a marketable nickel carbonate product.

Jan 1, 1999

By J. Kevin Cotchen

The results of "submerged arc" electric furnace processing of a variety of materials is discussed with respect to the process and products, including the characteristics of the products (e.g. TCLP or Toxicity Characteristics Leaching Procedure). The materials melted include slags and wastes containing various metal oxides including copper, tin, lead, zinc, chrome, nickel and other associated elements. The findings of these tests are compared to those reported in the literature for other operations treating similar "wastes".

Jan 1, 1992

By M. Moinpour, E. Liao, C. Y. Aw, D. J. Brown, P. W. Cheung

"Currently, silicon-based insulated-gate field-effect devices are being widely developed as the basic structural elements in a new generation of chemical microsensors. In this paper, we discuss some of the process considerations related to the fabrication of the Chemically Sensitive Field-Effect Transistor (CHEMFET). This ion-sensitive CHEMFET (or ISFET as it is often called) can be used for pH measurements (i.e., as a pH sensor) when the gate insulator of the electrolyte/insulator interface is made of Si3N4 obtained by the LPCVD method. Effects of processing parameters such as the Si3N4 deposition rate, gas composition, total flow rate, annealing treatment, etc. on Si/Si02, Si/Si3N4 and Si/Si02/Si3N4 structures are discussed in relation to the CHEMFET fabrication. Their effects on the electrical characteristics and chemical response of the sensor are also examined. Capacitance-Voltage (C-V) measurements and ESCA analysis have been used to interpret the results. The Si3N4/Si02 double dialectric layer provides improved ion blocking for the gate insulator in electrolyte solutions with enhanced pH sensitivity over time. The stability and performance of the fabricated CHEMFET sensors were tested by measuring the pH sensitivity in various storage conditions. The SEM analysis was used to evaluate the hydration effect at the ISFET's gate insulator with respect to different storage conditions.IntroductionThere has been a continuous interest in the development and fabrication of various chemical microsensors for chemical and biomedical applications over the last fifteen years. The application of semiconductor (particularly silicon) technology to the area of sensor fabrication has led to an emergence of a new generation of miniaturized, microelectronic, solid-state chemical sensors. There are numerous clinical situations where continuous monitoring of body electrolytes concentrations such as Na+, K+, Ca+2 , etc. and blood gases (pH, Po2 , and PC02) would be essential for the effective diagnosis and management of patients under critical conditions. Solid- state microsensors can be used for direct and continuous in vivo measurement of the above parameters in most instances."

Jan 1, 1988

By F. Garcia-Carcedo

This research aimed to develop a clean technology for the production of ZnO from residues generated by the steel making industry. Scientific and technologic parameters were both investigated in order to define an industrial methodology allowing the integral recycling of EAF dusts. A reengineering of the Waelz process was perform,~d, aiming to produce a clean fraction of ZnO, fluorine free, as well as a slag enriched in metallic iron, which can be recycled in electric arc furnaces. The technical conditions used to produce the ultra pure fraction of ZnO are described. The magnetic separation of the EAF dust allowing the production of a phase high in iron and recyclable to the electric arc furnace is also discussed. Thermodynamic of the volatilization of all the elements contained in the EAF dust was performed in order to better control the thermal process in the rotary kiln. Tests were run using different reducing agents, weakly or highly reactive, aiming to determine their specific efficiency.

Jan 1, 2000

By Behrouz Abedian, Livia M. Racz

"We address dynamic interactions between high-energy, reactive surfaces of polymer-matrix composites and solid surfaces. A common characteristic of these interfaces is that bonding occurs readily upon contact. In many industrial and biomedical applications, it is desirable to suppress this bonding phenomenon. This interfacial effect is discussed in light of the development of our new method of handling polymer-matrix composites in dental applications. This method involves vibration of the solid-polymer interface at different frequencies. For each material, there is a critical frequency at which the sum of the viscoelastic and inertial energies of the fluid at the surface exceeds the energy available for bonding. When the polymer is vibrated at or beyond this frequency, it does not adhere to solid surfaces. An important aspect of the developed process is that it can be used to characterize surface and interfacial properties of polymers under dynamic conditions, whereas existing techniques are restricted to the study of bulk dynamic properties.IntroductionThe purpose of this paper is to report on the development of a new method for manipulating polymer-matrix composite materials used in dental applications, and the potential of this process for use in materials characterization. The materials under discussion have polymer matrices of a combination of bisphenol A-glycidyl methacrylate (BIS-GMA) and triethylene glycol dimethacrylate (TEGDMA), and contain filler particles of silica and/or zirconia glasses. These materials are called direct aesthetic restorative materials, and are used for filling of cavities, repairing chipped teeth, and for other restorations in which appearance is of importance. They have the appearance of natural tooth material, and are therefore in great demand for use in the anterior portion of the mouth(l,2)."

Jan 1, 1998

By Yoshifumi Abe, Akinori Toraiwa

"Nippon Mining & Metals started a new copper anode slime treatment plant that processes slimes in a chloride media. The basic plan of the process was proposed by Mr. James E. Hoffmann and Nippon Mining & Metals modified and advanced to produce precious metals in acceptable qualities for the company. The process has a wet chlorination stage of decopperized slimes, a solvent extraction and a reduction stages of gold, a silver chloride reduction stage and separative reduction stage of its gold extraction raffinate. The new plant of this process started in 1997 and has been operated in good condition.IntroductionThe old anode slime treatment plant of Nippon Mining & Metals, located in it's Hitachi Refinery, processed anode slimes through a combination of pyrometarllurgical processing and electrorefining. There was a need to plan a future of the plant because the maintenance cost increased year by year and a new selenium registration was going to be applied to the plant. Some plans were discussed and the result was that the process proposed by Mr. Hoffmann was superior among them.Nippon Mining & Metals started 'to examine the process and the experimental result showed that the process had an ability to be its new process but further research should be necessary to produce precious metals in acceptable qualities. The final process flow has some modified and additional stages to be suitable for its requirement. Silver processing stage is quite changed. Gold extraction stage has a new step to polish gold loading DBC. Gold extraction raffinate treatment stage is advanced to be able to recover precious metals, selenium and tellurium, separately. Aeration under atmospheric pressure is employed in decopperizing stage.The basic design of the new plant started in 1995 and finished in 1997. The construction of the new plant began in April 1997 and finished in October. The plant has been operating well after the four months test operation."

Jan 1, 2000

By K. Twite, K. Mujinga, J-M. Dereydt, P. Louis

"GECAMINES is a large mining concern and the world's leading cobalt producer having some of the richest cobalt deposits in the world. Cobalt is associated in the ore with copper as sulphides and oxides and in some locations with nickel too. Specific hydrometallurgical processes have been developed by GECAMINES which had done an important contribution to the development of the cobalt hydrometallurgy.In the Shituru plant, cobalt is obtained from an unique in-pulp electrolysis process, while in Lullu, cobalt is electrolyzed in a clear acidic solution giving a purer deposit. In the beginning of 1996 Shituru started the treatment of mixed Cu-Co-Ni Shinkolobwe hydrates obtained as by-product of an uranium solvent extraction plant. A typical analysis of this feedstock is: 2% Cu, 8% Co and 4% Ni.The nickel sulfide depolarized cementation process developed previously by GECAMINES was inefficient to treat such a high level of nickel contamination and it was decided to produce alloyed Cobalt-Nickel cathodes in the Shituru tankhouse.As anticipated from laboratory tests as previous studies and publications, a lower Ni/Co in the deposit was obtained compared to the Ni/Co ratio solution, despite the nickel reversible electrochemical potential is somewhat higher than the one of cobalt (-0.25 V vs -0.28 V).In this paper, the process flow-sheet and production data are given. Cobalt alloy with 5 - 20 % Ni was obtained at a production level of 300 t per month. The process developed is a new contribution to cobalt hydrometallurgy."

Jan 1, 1997

By A. McLean, S. Dawson, N. D. G. Mountford

"IntroductionIn order to predict the accepted industrial practice for the year 2000, it may be helpful to first consider the rate of development of scientific knowledge. If the speed with which man can travel on commercial vehicles is taken as a criterion for determining the rate of progression, then it can be seen from Figure 1 that advancement in our present century is very rapid. Likewise, if computer technology is used as a criterion for the measurement of scientific advancement, it becomes evident that technological evolution can be highly exponential. These two examples are sufficient to demonstrate that engineers and managers cannot afford to regard scientific development as being linear with respect to time if they are to avoid underestimating the needs of society.Within this framework of overall development, the time required for individual ideas to progress from inception to regular application has decreased considerably. For example, X-rays first discovered by Roentgen in the 1890's and now used widely in medicine and engineering, required a developmental period of some eighty years. The motorcar evolved from early beginnings at the turn of the century to a position of great social impact in sixty years. Rectifier materials used in high frequency radar to the present explosion in communications, required forty years. As illustrated in Figure 2, the period is shortening rapidly.The use of sound waves appears to be following a similar path. There is now a considerable body of knowledge concerning their behaviour and exceptional advances have been made. In medicine and engineering the sonic approach to examination is well established, and acoustic testing forms the basis of several diagnostic and quality control applications. With respect to metals engineering, ultrasonic testing has contributed to the understanding of the relationship between the size and number of internal defects and the probability of premature failure. This has allowed the designer to incorporate appropriate safety factors in his designs; but more importantly, the realization of the deleterious effect of inclusions on the performance of the final product has resulted in a continuous pressure on the material suppliers to reduce the number of defects in their products.It is not only the designer who is demanding defect free material but also the fabricator, as material breakdown during manufacture can be prohibitively expensive. Examples of this can be found in both the aluminum and steel industries where ultra clean sheet is required to ensure that rejections are minimized during beverage can manufacture and other deep drawing operations."

Jan 1, 1988

By Baozhong Ma, Yonglu Zhang, Yongqiang Yang, Chengyan Wang, Yongqiang Chen

During the past decades, slurry electrolysis (SE) has been implemented commercially for the processing of bismuthinite and complex Pb-Cu bearing gold concentrates. Recently, SE was proven effective for the treatment of As-rich antimonic gold concentrates. Laboratory test results suggest over 98% of the antimony was extracted, while the extraction of arsenic and gold was less than 0.5%, and that of iron was less than 6%. Moreover, the cathode antimony contained over 98% antimony and less than 0.3% arsenic. Considering the disadvantages of traditional 3 kA slurry electrolysis baths, such as smaller electrode area, reduced capacity, and greater electrode deterioration, the authors have developed an innovative 12 kA slurry electrolysis bath equipped with mesh and fence type titanium alloy electrodes. Furthermore, the technique was successfully used within a pilot scale plant yielding results similar to those observed in the laboratory. The technique yielded ametallic antimony ingot of 99.9% purity after arsenic removal via the addition of Na2CO3.

Jan 1, 2014

By Chao Zhang, Jian Guo, Chaoquan Yao, Leige Xia, Xinyu Li, Jianliang Zhang

In this research, analytical reagents were used for the sintering experiments. And the sinters were using X-ray diffraction, scanning electron microscope and mineralogical microscope analysis to study the effect mechanism of manganese on the silico-ferrite of calcium and aluminum (SFCA) bonding phase formation during the sintering process. The results indicated that the increasing content of manganese would greatly reduce the content of SFCA, and promote the formation of calcium aluminum silicate and the amount of pores and cracks. The existence of manganese inhibited the silicon form into the SFCA and a great deal of Fe2O3 was participated in the crystal transition to Fe3O4. When the ratio of the added manganese was less than 3% in the mixing, the calcium ferrite was in substantially interleaving corrosion with hematite and magnetite. Both the porosity and silicate glass phase content were low simultaneously, which contributed to the sintering production.

Jan 1, 2015

By Faustino G. Prado

In the, quest for an economical and environmentally friendly reclamation of metallurgical dusts generated during pyrometallurgical operations, our goal has been the separation and recovery of most of the components, as well as the complete recycle of all the reagents. Effluents have been avoided, within acceptable economic parameters. This presentation, which can be applied to a large spectrum of dusts and other residual-materials-, has focused on the dusts generated by the operation of Secondary Copper Smelters. Those dusts show a wide range of components, including zinc, lead-, copper, cadmium, tin, chlorine and-alkalies. Our present work deals with the use of ammonium salts in the separation and recovery of-the above mentioned elements in a marketable form. Most of the chemistry and techniques involved have teen already confirmed in commercial scale operations. Others have gone through pilot scale tests or bench scale tests. The recycle of reagents has also been- confirmed at the same operating levels. A preliminary evaluation indicates that the chosen route, in addition to a viable economy, offers a complete and safe reclamation within the most strict environmental regulations.

Jan 1, 1995

By Julian Johnson

The effect of changing redox potential (Eh) on the high temperature sulfuric acid leaching of Western Australian dry-land nickel laterite ores has been investigated. In particular, the effect of added reductant (sulfur, sodium sulfite) or oxidant (potassium chromate) on Eh, leaching kinetics, metal extractions, acid utilisation and leach residues has been determined. Three separate ores - nonhonitic ores from Murrin Mumn and Bulong, and limonitic ore from Cawse - were used in the study. Sulfur addition varied from 0 to 7.8 kg/t ore. The total acid loading was kept constant at 430 kg/t (Murrin Murrin ore) and 330 kglt (Cawse ore), whilst acid loading for Bulong ore was varied according to the presence of either reductant or oxidant. The extraction of both nickel and cobalt from limonite ore remained unaffected when small amounts of sulfkr were added, but addition of even small amounts of reductant to nontronitic ore decreased both nickel and cobalt extraction. Increased manganese and iron dissolution were observed as the levels of reductant increased, accompanied by a decrease in chromium dissolution. As the iron dissolution increased, free acidity decreased, with a subsequent decrease in nickel extraction. In contrast, addition of oxidant lead to reduced iron and manganese dissolution and slower extraction of nickel and cobalt. Keywords: Limonite, Nonhonite, Eh, Nickel Extraction

Jan 1, 2004

By Mohamed Ahmed, A. Kawy

"Smelting of scrap copper and residual anodes and cathodes carried out in a reverberatory type furnace. In this, deoxidation process is carried out by wood, which acts as a resource of reduction gases such carbon monoxide, hydrogen and methane. Use of wood causes the formation of soot pollutants and efficiency of oxygen removal from copper is low leading to added costs in removing contaminants. This expensive problem was solved by using of reformed natural gas as a source of reduction gases (CO+ H2).IntroductionThree reverberatory furnaces were used for smelting of scrap copper and residual anodes and cathodes. Each furnace had a 7tpd capacity and was operated at 1183 °C.In this furnace, Step1-compressed air supplied by tubes from the side of the furnace to remove sulfur from copper matte by oxidation .The copper is also oxidized to copper oxide .[1]Step 2- copper from matte is deoxidized by a reductant. Typically deoxidation process is carried out using wood as a resource of carbon monoxide, hydrogen and methane which are the reduction gases. Use of wood causes the following:1- Forms soot pollutants2- Oxygen removal efficiency from copper is low; more contamination in copper matte increased energy in deoxidation3-the process is highly expensive.In the recent trends, this problem has been solved by using reformed natural gas as a source of reduction gases (CO+ H) .This results in 1-Reduced pollution during smelting.2- High efficiency in the removal of oxygen from copper to produce oxygen free copper. The surface of copper produced from this method is smooth which helps in forming and machining.3- Low cost and natural gas is more readily available in Egypt than wood."

Jan 1, 2010

By Wei Lv, Xuewei Lv, Senwei Xuan, Chenguang Bai, Kai Tang

The contact angle between six iron ores and water were determined by the capillary pressure method with cyclohexane as the perfect wetting liquid. The factors influencing the contact angle were discussed, and a relationship between the content of oxy–hydroxides and the contact angle of iron ores was obtained. The results show that the ore F has the lowest contact angle but the ore D get the biggest, which are 32.09° and 78.16°, respectively. The volume fraction of oxy–hydroxides is linearly dependent on the contact angle. The contact angle decreased with increasing the volume fraction of Fe2O3*H2O.

Mar 1, 2017

By Toshihide Takenaka

Improvement of corrosion resistance of Mg metal by addition of rare earth metal (RE) was studied, and the effect of surface oxide layer with RE was investigated. The corrosion resistance of Mg was remarkably improved by adding a small amount of RE, and the suitable RE content was clarified. The corrosion resistance of Mg was particularly bettered by conversion coating using a solution including both RE(NO3)3 and Mg(NO3)2. This result indicates that the surface oxide layer consisting of both Mg and RE gives good corrosion resistance to Mg metal. In this study, direct electrodeposition of Mg metal containing RE was also tried in molten chloride with RE chloride, and it was shown that electrolysis could be performed stably. The RE content in the deposited Mg metal was depended on the concentration of RE chloride in the bath and the cathode potential, and Mg metal containing the suitable RE content for its corrosion protection was obtained easily by direct electrolysis.

Jan 1, 2006

By L. J. Davies

Refractories usage in furnaces for the extraction of nickel from both sulphides and lateritic ores is reviewed. Recent changes in raw materials and basic brick qualities developed to meet the increasing demands of existing and new processes are outlined. Examples of used brick examinations to establish mechanisms of wear are given. The importance of physical and chemical properties are discussed. The use of simulative laboratory testing to aid in refractories development and selection is described.

Jan 1, 1988

By Ki Bui Ma

Momentum wheels with superconducting bearings can integrate both attitude control and energy storage functions, with attendant savings in the total volume and weight of hardware, and power consumption, all of which are in short supply on mini-satellites. We have built and tested a prototype with a wheel of mass 1.9 kg, diameter 3.25 in, and height 3 in, which can store 3.5 J-sec of angular momentum and 5 kJ of energy when it rotates at an angular speed of 15000 RPM. The energy density of 2.5 kJ/kg achieved is comparable with the lower range for lead-acid batteries. To show that the wheel is energy efficient, we have performed spin down tests and measured the input power required to sustain rotational speed. Results indicate that power consumption, even accounting for the needs of cooling system, is significantly smaller than that for state of the art commercial reaction wheels.

Jan 1, 2002