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By A. G. Merma

In this work, the electrocoagulation technique was studied in order to treat chemically stabilized concentrated oil-water emulsions. This study was mainly focused on the effects of operating parameters such as initial pH, current density, reaction time, electrode distance and inlet concentration on the separation of oil as measured by the chemical oxygen demand -1(COD) method. The synthetic emulsion was prepared from Shell - Talpa 30 oil (3g.L-1) and sodium dodecyl sulfate (1.0 g.L), having a Zeta potential around -70 mv at pH 8.7. The process was carried out in an electrocoagulation cell with a set of four parallel monopolar electrodes. This set consisted of two aluminum plate anodes and two 316L stainless steel plate cathodes. Kinetic curves showed that the electrocoagulation process exhibits three phases: (1) an initial phase, where the COD did not decrease because the solution had not reached the minimum amount of dissolved aluminum required to cause the break-up of the emulsion, (2) a reactive phase during which COD decreased due to possible agglomeration of the precipitates and (3) a steady-state phase where the COD did not change. The results showed that the period to reach the reactive phase decreased as the current density increased and the pH values decreased.

Jan 1, 2009

By David Norval

Ni, Co, Cu and Pt, mattes are common materials that require granulating and milling of the resultant granules for further processing. This route is acceptable if the material is brittle (friable) which is a property associated with the higher sulphur mattes. For lower sulphur levels, where the matte is less amenable to milling, the costs of the milling increases. This paper will compare water granulation with certain dry granulation processes and the downstream processes required for Hydrometallurgy. It will further introduce and expand on atomisation which offers a further safety benefit in the control of the metal flow into the 'wet zone' with the use of a tundish flow control also reducing the conversion from the matte to powder in one fairly straightforward operation.

Jan 1, 2006

By S. Uddin

An integrated device has been developed to measure sedimentation potential, conductivity and pH simultaneously of particulate systems. Maxwell?s model was used to calculate volume fraction of solid from the conductivity data. In this approach, all system variables are known and zeta potential can be calculated from Smoluchowski?s equation. The technique is validated by comparing zeta potential vs. pH for alumina and silica suspensions with electrophoresis measurements. The technique was extended to mixed alumina/silica systems. Sufficient column height along with size difference between the two minerals allowed gravity fractionation during settling. Sedimentation potential measured over time identified the transition from one mineral to the next. Using XRD analysis the results supported the correlation between surface charge and sample composition. This is a step towards characterizing surface charge of mixed systems of interest in mineral processing.

Jan 1, 2010

By Art Cooper

Granulation systems are customarily viewed as problem areas in metallurgical operations. The inherent risk of explosion when combining a high temperature melt with water creates a safety hazard. Separation of the granulated material from the quenching medium generally involves equipment that can have significant maintenance and operating costs. Granulation systems' reliability and availability can negatively affect the plant production. Against this background, granulation systems have been treated by design firms and producers as an add-on and a necessary evil. The technology is becoming better understood and solutions to common problems are being found. This paper will discuss typical problems in common systems, and some of the improvements that have been made, with particular reference to non-ferrous applications.

Jan 1, 2006

By J. M. Tannenbaum

A depth-sensing micro-indentation technique is developed for evaluating mechanical properties of materials at elevated temperatures (to 1200°C). System description and design considerations of the test apparatus are described. Based on Hertzian spherical indentation approach, the micro-indentation test apparatus is capable of determining Young?s modulus and creep strength of test materials with flat, tubular, or curved architectures from room to 1200°C under either air or controlled gaseous environments. Calibration tests were conducted on a H13 Tool Steel coupon from 22°C to 500°C and single crystal Haynes 230 alloy at 1000°C with excellent agreement to the literature values. Indentation creep tests of Haynes 230 alloy were carried out at 1200°C with preliminary results showing good correlation to creep exponents. Further system refinements will be investigated, and additional testing will be conducted.

Jan 1, 2010

By Viviane Tavares

The liquid crystal display (LCD) are currently known by its vast application in electro ? electronic devices, amongst them can be detached the devices of TV, laptops, electronic date, calculators and even though the mobile telephones (mobiles). The mobiles are changed more frequent of the TV for example, this happens due to the technology advance. With the constantly mobile exchange, the batteries, printed circuit board and liquid crystal display accumulation its become an environmental problem. To minimize the environmental impacts caused by mobile telephones residues are considered the segregation process of the LCDs main components, to goal to recover the recycle material. This process involves the use of treatment ore techniques with disc, hammers and balls mills. The process with best efficiency (about 98%) of LCD glass release was the hammers mill. The glass recovered can be used in the glass recycling and the sand substitution in the production of concrete blocks.

Jan 1, 2009

By Jinhui Li

Silver is a very important metal used in a wide range of applications. It is necessary to recovery of Ag from electronic wastes for increasing of Ag price and circumstance protection. For separating and recycling Ag from Ag-Cu composite materials, thermodynamic data of reaction is calculated and some experiments have been proceeded with Ag-Cu composite material scraps, time, temperature, nitric-sulfuric mixed acid volume ratio and the volume ration of mixed acid vs. water have been discussed. The results show that the optimization conditions is that nitric-sulfuric mixed acid volume ratio 5:95, volume ratio of mixed acid vs. water 10:1, temperature 55?, time 25min. In the conditions, Ag can be selectively leached from Cu-based composite material, Cu base is not eroded nearly.

Jan 1, 2009

By M. Potesser

One of the main targets in the automotive mass industry and supplying industry is the weight reduction of the vehicle for decrease of the fuel consumption. For that reason combinations of different kinds of materials and connections of, for example, steel and aluminium are developed or are already successfully field-tested. A determining factor concerning the quality assessment of the welded joint during hybrid welding is the characterization of the intermetallic Fe-Al layer regarding strength, hardness, morphology and mainly the different phases in which Fe occurs together with the Aluminum (FeAl, Fe2Al5, FeAl3.). A combination of conventional light microscopy, SEM - EDX - analysis, the usage of an atomic force microscope including a Nanoindenter and theoretical thermodynamic calculations turned out to be highly effective. Based on the attained results, the constitution of the intermetallic FeAl layer, influenced by silicon, manganese and zinc, can be predicted.

Jan 1, 2006

By Ryo Sasai, Takeshi Itakura, Haruki Imaizumi, Hideaki Itoh

"Emission of industrial wastewater containing harmful oxoanions is one of the serious problems on account of its toxicity and the environmental pollution, especially caused by boric, phosphinic, arsenic and antimonic species. In this study, we developed a novel treatment technique of such polluted-water by hydrothermal mineralization. The treatment is “Geomimetic” method for precipitating oxoanions in aqueous media as natural ore resources by using hydrothermal treatment with calcium salts mineralizer. The treatment made it possible not only to detoxify the polluted-water, but also to recover the calcium minerals such as Ca2B2O5·H2O, Ca5(AsO4)3(OH), etc. Concentration of each ion in treated-water was lower than that of effluent standard in Japan. Moreover, the residual concentration of each ion was independent of the initial concentration, but it depends only on the solubility of the formed mineral under hydrothermal condition. Therefore, the hydrothermal treatment could be recommended as one of the treatment techniques of polluted-water.IntroductionVarious oxoanions such as boron and arsenic oxo-anions have high toxicity against human health and the environment. They are important resources, however, for plating or advanced material manufacturing industries[1-3], from which the wastewater containing these oxoanions is generated every day. An appropriate treatment is often required for industrial wastewaters to attain national effluent standards of Japan (NESJ, B: 10 mg/dm3, As: 0.1 mg/dm3). On the other hand, there is no production of arsenic and boric resources in Japan, and they are expected to be recycled. Therefore, the establishment of a system for the removal and recycling of arsenic and boron from wastewaters is of global significance.Several methods to remove them from aqueous media have been already reported by using adsorption[4], electro-coagulation[5], membrane separation[6-8] and biological techniques[9]. However, these methods have the following problems because of their stability in water. (1) Removal yield is low, especially for tri-valent arsenite ion (AsIIIO3 3-) and borate ion. (2) The applicable concentration range is narrow. In addition, the used adsorbents or collected residues after treatments are sill hazardous wastes, so that they must be treated by a proper method. But, it is very difficult to convert them to recyclable resources at most industrial plants. These problems are caused by the difficulty to recover these oxoanions as stable solid precipitates with low solubility in water. The establishment of recycling system of these hazardous compounds will be one of the world-important issues, especially, in Japan, which is poor in natural resources. On the other hand, compounds that contain high arsenic concentrations and are insoluble in water, are often found in natural minerals, for example, as haidinglite (Ca(AsO3OH)·(H2O) or Johnbaumite (Ca5(AsO4)3(OH)). This fact suggests that nature has an ability to produce insoluble As-bearing minerals. Similar phenomena can be found in case of boron, antimony, etc."

Jan 1, 2008

By Helga Larravide

A new on-line database of literature about copper has been created through a joint undertaking by the Copper Development Association Inc. and PROCOBRE-Chile, with funding provided in part through the International Copper Association, Ltd. The new database will permit Spanish-speaking technologists to access publications maintained by PROCOBRE-Chile by means of standard keyword searches. In addition, a new Spanish- English thesaurus has been written to enable Spanish-speaking individuals to search d access the Technology and Environmental databases of the Copper Data Center, which together comprise more than 80,000 publications dealing with the production, properties, uses and environmental effects of copper. Planned expansion of the new Spanish literature database is described.

Jan 1, 1999

By Sutham Niyomwas

Silicon-Silicon Carbide (Si-SiC) composites were synthesized by self-propagating high temperature synthesis (SHS) from a powder mixture of SiO2-C-Mg. The reaction was carried out in a SHS reactor under static argon gas at a pressure of 0.5 MPa. The standard Gibbs energy minimization method was used to calculate the equilibrium composition of the reacting species. The effects of silica sources and carbon mole ratio in precursor mixture on the Si-SiC conversion were investigated using X-ray diffraction and scanning electron microscope technique. The as-synthesized products of Si-SiC-MgO powders were leached with 0.1M HCl acid solution to obtain the Si-SiC composite powders.

Jan 1, 2009

By Jae R. Lee

Keywords: Self-propagating high temperature synthesis, AlN, Powder synthesis The particle size and shape effects of starting raw powders on the synthesis of aluminum nitride by self-propagating high temperature technique under high nitrogen pressure were investigated with various AlN diluents and Al reactants. It was found that the structure of beds of the starting raw particles largely affected the pore channels for nitrogen gas infiltration as well as the passages for combustion propagation before and during the reaction, resulting in the morphology and purity changes of the synthesized products. The AlN product of purity over 98% with about 30 microns was obtained.

Jan 1, 2005

By Pengfu Tan

A program ?SlagVis? has been developed to simulate the liquidus temperature, phase compositions and viscosities of ZnO-CaO-SiO2-Al2O3-?FeO? slag, such as Imperial Smelting Furnace (ISF) slag and lead blast furnace slag, combined with F*A*C*T slag database and the mathematical model of slag viscosities based on a modified Urbain formalism. The modeling results have been validated by a number of measurements. The effects of slag compositions on viscosities of ISF slag and lead blast furnace slag have been simulated and discussed.

Jan 1, 2005

By Heikki Jalkanen

The mineralogical composition and morphology of solidified copper smelting and converting slags are of some interest from slag cleaning (by froth flotation), impurity elimination, and environmental points of view. Properties result from both the state of molten slag before solidification and processes taking place during solidification and cooling. In solidification and cooling, copper and sulfur dissolved in molten slag are .precipitating substantially from the silicate phase. Even in water quenching of slag, dissolved copper is pushed out of the solution in the form of finely divided precipitate. Elements present in the raw materials are distributed in a distinct manner between the solidified slag and non-silicate solidification products. Arsenic, antimony, and tin are strongly accumulated in copper precipitate, but not the other metallic constituents common in copper concentrates. Smelting and converting slags differ remarkably on their mineralogical composition and morphology although resulting principally of same chemical processes. Converter slags are more inhomogenous; they often contain solid particles and copper content is .as a rule higher than in matte smelting slags. The final copper content of converter slags was observed to be in a distinct manner dependent on iron oxide - silica ratio. Slag forming, solidification, and precipitation phenomena are discussed on the basis of mineralogical and morphology analysis of smelter slags and laboratory scale experiments.

Jan 1, 2002

By Valentine A. Chanturiya

The aim of this paper is basically to show progress in the study of nanosecond processes involved in the disintegration and breaking-up of mineral complexes with fine noble metals. We studied the influence of nanosecond High-Power Electromagnetic Pulses (HPEMP) on the physical and technological properties of refractory gold-containing ores and beneficiation products. Experimental data are presented to confirm the formation of breakdown channels and selective disintegration of mineral complexes as a result of pulse irradiation, which makes for efficient access of lixiviant solutions to precious metal grains and enhanced precious metal recovery into lixivia during leaching. Preliminary processing of gravity concentrate with a HPEMP resulted in significant increase of gold and silver extraction into lixivia during the cyanidation stage, with gold recovery increased by ~31% (from 51.2% in a blank test to 82.3% after irradiation). Gold recovery from stale gold-containing dressing tailings products increased after pulses-irradiation from 8-12% to 80-90%.

Jan 1, 2006

By Guomin Jiang

Potassium ferrate is an excellent multifunctional reagent for wastewater treatment, but its preparation is crucial. The improved hypochlorite oxidation method was used to prepare potassium ferrate in this study. Iron nitrate, the preferred iron source, was added into hypochlorite solution and then the stabilization agent was added during the purification process of product. The influence of available chlorine content, iron molecular proportion, reaction temperature and reaction time on potassium ferrate preparation was investigated. The optimal condition for potassium ferrate preparation is 15% of available chlorine content , 0.6 of iron molecular proportion , 30i of reaction temperature , 45min of reaction time. The yield of potassium ferrate is about 67% with high purity (> 99%). The structure and performances of the product was characterized by XRD, EDX, SEM, TG and IR and the results show that the prepared product is consistent with the properties of potassium ferrate(VI).

Jan 1, 2010

By Ji-He Wei

Keywords: stainless steel, AOD refining, side and top combined blowing, mixing characteristics, water modeling The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon-oxygen decarburization) refining process of stainless steel have preliminarily been studied on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model have more reasonably been determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics has been examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a well mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from top lance could make the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27° between each tuyere, and five side tuyeres with an angular separation of 22.5° or 27° between each tuyere. The relationships of the mixing time with the gas blowing rates of main-tuyeres and sub-tuyeres and top lance, the angle between each tuyere, and the tuyere number have been obtained.

Jan 1, 2005

By Tammy G. R. Portela

A comparative characterization of the dimensional and mechanical properties as well as structural aspects of two different types of fibers extracted from the leaves and petioles of the buriti palm tree was performed. A statistical analysis revealed that both types of fibers present a significant dispersion in length and equivalent diameter. However, the corresponding intervals of dimensional variation are sensibly different. The tensile properties showed that both types of fibers display a tendency of higher strength for smaller diameters. Moreover, the fibers extracted from the leaves depict a comparatively lower strength. By contrast, the fibers from the petiole present an average strength sufficiently high for the use as reinforcement of polymeric composites. The structural aspects of tensile-rupture fibers, characterized by scanning electron microscopy, showed marked distinction in the microstructure and fiber behavior of both types of investigated fibers. This could explain the differences in mechanical behavior

Jan 1, 2010

By Youze Xu

The leaching and reduction of Cr(VI) in soils contaminated by chromium-containing slag were investigated with column experiments. The results showed that Cr(VI) concentration in leachate decreased from 988 mg L-1 to 407 mg L-1 after 7 days when water was used as leaching agent. However, Cr(VI) in leachate in culture medium treatment was not detected at above periods. In comparison, Cr(VI) concentration in leachate from autoclaved soil remained 398 mg L-1 at the end of experiment. The results indicated that the indigenous microorganism was capable of reducing Cr(VI). The amount of Cr(VI) reduction was 335 mg at the whole experiment period and the reduction rate was 67.09 mg d-1. Carbon supply showed minor effect on Cr(VI) reduction. However the reduction capability of Cr(VI) could be improved by combination of the carbon and the nitrogen. The optimal quantity was 5 g L-1 of yeast extract and 4 g L-1 of glucose.

Jan 1, 2009

By Alex Del Castillo

The mineral processing industry has followed the development of database control systems, and various systems have been installed in existing and new plants. The goal is to improve product quality, raise productivity and lower production costs. Improvements in different units for mineral .processing .have been applied. This has led to increasing information for the operators. To support the operators and for an easy overview of the process, a complete concept for an integrated process-control system is required. This paper describes the plant-wide [process control system for the Collahuasi copper project located in northern Chile. The total investment for the project was $1,700,000,000 and included a port area and two copper processing plants, an oxide plant with a cathode production of 50 tons per year and a sulfide plant with a concentrate production of 330 kilotons per year. The main characteristics of the plant-wide process control system include a 200- kilometer long redundant control network and a 24-kilometer long redundant serial network providing coverage for the entire plant. The plants are located around 4,700 meters above sea level, serial communication lids allow the integration of over 2,700 SCADA data units, and the system handles over 7,500 physical signals plus the SCADA data integration. The main equipment consists of 39 different sized controllers, 16 operator stations, 5 engineering stations, 2 information management systems and 4 X- terminals. The project management, control configuration, factory acceptance test, system integration test, training, commissioning and start-up were carried out in close cooperation with the customer. The result was completely satisfactory for the customer.

Jan 1, 1999