Search Documents

By Liu Wei-feng

In this paper, the practice of separating precious metals from base metals in gold-antimony alloy by selective chlorination leaching under controlling potential in China has been introduced in detail. The precious metals and the base metals can be separated completely when the complex gold-antimony alloy is treated by this process. The impurity metals were removed effectively since the leaching efficiencies of copper, nickel and antimony are over 99%, with direct recovery of gold being 99.83% that is about 20% higher than that of the original process and silver, antimony, copper and nickel are also recovered effectively. The gold grade of the resulting crude gold powder can reach to 94%.The new process has been applied in the treatment of gold-antimony alloy for two years, and many former procedures have been cancelled, such as electrolysis, Anode slime leaching by nitric acid, smelting in crucible and blowing in muffle. The new process is more shorten, lower cost and friendly to the circumstance comparing to the original process.

Jan 1, 2008

By D. M. Fermino, C. G. Bastos Andrade, V. F. Justo, F. R. Valenzuela-Diaz, M. G. S. Valenzuela, C. Volzone

The present paper presents the study of light green smectite clay, from Paraiba, Brazil, submitted to mild acid attack under moderated conditions. Usually, clays are subjected to treatment with strong inorganic acids at temperatures near the boiling point and at high acid concentrations and then, widely used as bleaching agents. The treatment occurred under bellow boiling temperature and at short times of reaction (90°C, reaction times of 1, 6, 12, 18 and 24 hours in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5 M, clay/acid solution ratio of 1g/10mL). The purpose of these attacks is to reduce the concentration of impurities providing color, with minimal change in the clay minerals structure, aiming at use in products of high value such as cosmetics and polymer/clay nanocomposites. The raw clay and the attacked samples were characterized by X-ray diffraction (XRD), cation exchange capacity (CEC), stereomicroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray detector (EDS).

Jan 1, 2015

By Rainer Köster, Tobias Wagner, Markus Delay, Fritz Hartmann Frimmel, Wolfgang Ferstl, Wolfgang Höll

"The mobilization of contaminants from industrial residues like ashes from municipal solid waste incinerators in case of leaching is investigated world wide. In classical leach tests only soluble species are considered. In addition the geochemical behaviour of residues has to be completed by assessing the mobilization via colloidal particles. This transport is well known from natural aquatic systems. Quantification of aquatic colloids is associated with considerable difficulties, because they are often found in low concentrations and in a size distribution where small particles with diameters below 0.1 µm predominate. In the past years, the Laser-induced Breakdown Detection (LIBD) has been developed as a novel sensitive method for quantifying colloids. Column leaching experiments with directly coupled LIBD were used to quantify the release of heavy metals and colloids out of bottom ashes. Some typical colloid bound heavy metal concentrations in the leachate are in some cases exceeding the limits defined by German authorities. The LIBD with a flow-through cell allowed to assign absolute values to colloid size and concentration."

Jan 1, 2008

By Dhanesh Chandra

Metal carbonyls are of great importance in chemical vapor deposition (CVD), composite materials fabrication, and other near-net shape technologies. Carbonyl CVD application applies to deposition of high-purity metallic/alloy coatings. Vapor pressures of solid Os3(CO)12,Rh6(CO)16, Ru3(CO)12, Ir4(CO)12, Re2(CO)10, Co2(CO)8, Cr(CO)12,, and W(CO)6carbonyls have been measured using gravimetric-torsion effusion system. The vapor pressure data is used for many low and high temperature CVD applications. Interesting decomposition/disproportionation vaporization behavior has been notedfor Rh6(CO)16, Ru3(CO)12 and Co2(CO)8. The vaporization studies of Rh6(CO)16 showed virtually complete decomposition to Rh metal and the measured molecular weight of the effusing gas from the solid Rh6(CO)16 was 27.75 g/mol, close to that of carbon monoxide as compared to 1065.56 g/mol for the value of solid Rh6(CO)16. Electron microscopic characterization, X-ray line broadening results for Rh carbonyl has been performed on the vaporization product. However, Ru3(CO)12, Co2(CO)8 showed very complex behavior. The molecular weights of the vaporizing species have been estimated and the numbers of vaporizing species are proposed. For example, there was partial decomposition of Ru3(CO)12to(approx. 52%) metallic Ru and CO gas during vaporization, as suggested by the difference in the molecular weight of the vaporizing species of 107.58 g/mol compared to the actual value of 639.33 g/mol. The dimer Co2(CO)8 partially disproportionates to tetramer Co4(CO)12, monomer Co(CO)4, and CO gas. Whereas, the Os3(CO)12, Cr(CO)12,, and W(CO)6have shown virtually no disproportionation. The total vapor pressures of all the above-motioned carbonyls, partial pressures of various species, average molecular weights of the effusing gases, equilibrium constants for the vaporization reactions, their enthalpies, entropies, and Gibbs energies will be presented.

Jan 1, 2006

By J. Rajesh Kumar

The extraction equilibrium study of tetravalent platinum was carried out using tri-octyl/decyl amine (Alamine 336) and bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302) in kerosene from hydrochloric acid media to investigate their extraction capacity, since they have different donor atoms, ?N? and ?S?. Their distribution equlibria were studied as a function of acid, extractant, diluents and temperature. The title metal shows the inverse behavior at higher acid concentrations. Extraction of tetravalent platinum increases with increase of extractant concentration. The plot of log D vs. log [Extractant], mol.L-1 is linear with slopes 1±0.3, indicating the association of one mole of extractant with the extracted metal species. Stripping of metal from the loaded organic (LO) with mineral acids and bases such as hydrochloric, sulphuric, nitric acids and ammonia, hydrogen peroxide, sodium hydroxide, thio- urea were studied. Regeneration and recycling capacity of Alamine 336/Cyanex 302 and extraction behavior of associated elements was also studied.

Jan 1, 2009

By Gjergj Dodbiba, Toyohisa Fujita, Takahiro Kikuchi, I-Chen Wu

"In order to separate molybdenum (Mo) from the high-level radioactive liquid waste (HLLW), Pb-Fe based adsorbents were synthesized. The adsorbents were precipitated by adding sodium hydroxide in mixture of 1 mol/L lead nitrate and 1 mol/L ferric nitrate aqueous solutions. Each precipitate was then filtered, dried and ground to obtain a fine powder, which has been used as an adsorbent. Two main parameters were considered when synthesizing the adsorbents, i.e. the pH value at precipitation of adsorbent precursor and the calcination temperature of Pb-Fe based adsorbent. Moreover, the structures of the synthesized adsorbents were investigated by means of an X-ray diffractometer.The experimental results indicated that the calcination temperature of the Pb-Fe based adsorbent has a great influence on adsorption capacity of the adsorbent for Mo. It was found that when the Pb-Fe based adsorbent was calcinated at 500 oC, the sorbed concentration of Mo was the highest.1. IntroductionThe high-level radioactive liquid waste (HLLW), arising from the reprocessing of nuclear fuel are generally immobilized in an alkali borosilicate glass matrix. Broadly speaking, alkali borosilicate glasses are the matrix of choice for the immobilization of the HLLW, since they permit vitrification of waste stream of variable composition, [1]. Within this frame, the incorporation of molybdenum (Mo) is of particular interest in the vitrification of HLLW. Molybdenum is know to have a low solubility in borosilicate glass compositions and its presence in excess results in the phase separation of a complex yellow molten salt during vitrification, [1]. The formation of so-called “yellow phase” material during the vitrification process is undesirable since it leads to the accelerated corrosion of the inconel crucible liners. Furthermore, the “yellow phase”, which is reported to contain also other fission products, is soluble in aqueous solution providing a potential route for the leaching of radionuclides from the vitrified waste, should it come into contact with water, [1]."

Jan 1, 2008

By A. G. Guézennec

Electric Arc Furnace (EAF) steelmaking co-produces amounts of dust (15 to 25 kg per ton of steel), which require to be collected and stored in specific landfills. The collection, handling, and possible beneficiation of EAF dust depend on its composition and morphology. We first studied theoretically the chemical evolution of dust particles along the fume extraction system, from the furnace down to the filters, using thermodynamic calculations of the Fe-Zn-O system. We show how it would be possible to favor zincite formation in dust and therefore increase further zinc recovery. Then, we developed a new morphological model, based on population balances, for predicting the granulometric evolution of dust particles as a result of agglomeration and sintering in the fume extraction ducts. The contribution of the various mechanisms (Brownian, turbulent, and sedimentary agglomeration; thermophoretic deposition; coalescence and sintering) is assessed. The influence of the exhausting conditions on dust granulometry is detailed. For the extraction system studied, intense agglomeration of the sub-micronic particles and complete coalescence take place inside the furnace; micronic particles then undergo little evolution from the elbow to the water-jacket, whereas big agglomerates are formed downstream. These results are in good agreement with dust particle observations.

Jan 1, 2006

By Krishna Kumar

"Growth of electronics waste (e-waste) and lack of appropriate disposal mechanism are the great concern for developing countries like India. The domestic generation of e-waste in India is rapidly growing with the development. The imported substance is also substantially contributing to the e-waste inventory. Recycling of e-waste is mainly carried out in unorganized units in India. The primitive recycling technique used by the unorganized sector is a great threat to the environment and the health of the operators involved in these profession. Therefore, improvement of technology used by these units towards a cost effective, environmental friendly alternative could be the solution to the present crisis. Few initiatives of recycling have, however, come up in recent years in organized units. The precious metals are still recycled in the developed countries. This report discusses the inventory, technology status, legal legislative and existing practices of e-waste management in India.1. INTRODUCTIONInnovation, research and development in the field of electronics and information and communication technology (ICT) lead to convenient, independent human life. Consumption of electronics and hardware products has enhanced by manifold. Electronics and hardware sectors have, thus, become the fastest growing sector in the world. Faster obsolescence of these products is forcing users to replace products with an advanced technology. Life cycles of these products are few years. Discarded electronics products are, therefore, accumulating alarmingly in our society. Electronics waste (e-waste) is a crisis not only due to its volume but also for presence of its toxic ingredients, like heavy metals (e.g. lead, mercury, cadmium, hexavalent chromium) and flame retardants such as poly brominated biphenyles and poly brominated diphenyles ether. These substances create potential occupational and environmental health hazardous."

Jan 1, 2011

By Denise Corrêa de Oliveira

Household zinc based batteries, dry and alkaline, has become the most popular sources of electrical energy, and are widely used. Because of their heavy metals content such as mercury, zinc and manganese, spent batteries cannot be directly placed in common landfills without a pretreatment. As a municipal solid waste, these batteries may cause serious health problems and environmental impacts. These damages can be reduced by recovery (which means saving natural sources and energy), recycling and adoption of cleaner technologies. Although this worry has been increasing recently, and producers are doing efforts to reduce the mercury content, batteries still need proper safe disposal conditions or recycling processes. This work presents the efforts in progress to characterize and recycle mixed - dry and alkaline - spent batteries, by using low cost unit operations. Some possible recycling stages and recovery parameters of metals as zinc and manganese are also discussed.

Jan 1, 2001

By Chai Liyuan

This paper focused on the preparation of porous ceramic pellets for microorganism carriers. A new method for the process was developed using simple gel-casting and bubble-in-water-in-oil type of multiphase double emulsion. The globules, consisting of a foamed sepiolite slurry suspension, were dispersed and consolidated in spherical shape in liquid paraffin as gelation progressed. The green pellets were sintered at 1100°C. The influence of surfactants, extension ratio and impeller revolution rate on the process and characteristics of the pellets was investigated. The pellet size was in the range of 1~4mm and determined directly by impeller revolution rate. The fine cell diameter of porous ceramic was in the range of 100~500m and the micropore diameter was less than 5m. The inner macropores were interconnected and extend to the external surface. It is impossible to analyze a result by SEM micrographs and digital camera.

Jan 1, 2006

By Roberto Parra

The selective reduction smelting of Cu2O in Cu2O-FeOx-SiO2 melts has been studied at laboratory level, using as a feed a dead roasted calcine from a copper concentrate. The purpose of the study was to evaluate the kinetic and mechanisms of the indirect reduction with CO and the direct reduction with graphite from 1260°C to 1350°C. The reduction rate by CO was found to be 10-2 to 10-1 mole Cu2O m-2s-1. The graphite reduction macrokinetics for FeO and. Fe2O3 containing melts, was found to be a first order reaction with respect to the Cu2O concentration, with a kinetic constant of 104 to 10-3 s-1. The reduction rate was not sensitive to temperature nor to stirring, in the range studied. The measured reduction rate is almost one order of magnitude larger than the observed rate for the direct reduction of FeO.

Jan 1, 1999

By Sundarrajm Suresh, Hrushikesh G. Pimpalgaonkar, Thiyagarajan Paramadayalan

In this paper, a model of a fuel cell system has been proposed to account for the membrane physics at the micro level which is coupled with the macroscopic flow and mass transport phenomena occurring in a single channel of a Polymer Electrode Membrane Fuel Cell (PEMFC) system. We have developed a novel approach to model the catalyst layer electrochemical processes in a Membrane Electrode Assembly (MEA) and coupled it with mass transport and fluid flow calculations at the channel level using STAR-CD commercial software. The predicted values of the cell voltage from this micro-macro model are validated with experimental data available in the literature. A sensitivity analysis has been carried out to study the effect of the design and operating parameters such as catalyst loading and initial temperature on the overall performance of the PEMFC. The results indicate that the cell voltage increases at higher platinum catalyst loading and is also independent of the choice of initial cell temperature.

Jan 1, 2012

By J. W. Whitney

Itronics Inc., through its wholly owned subsidiary Itronics Metallurgical, Inc. (IMI), has successfully developed technology that allows it to be fully integrated as a photochemical recycler. IMI is now using this technology to expand its regional operation, which collects used photographic chemicals, chemically removes 99.997% of the silver and uses the residual to make a line of high quality liquid multinutrient liquid fertilizer products. Elevated silver discharges from the Reno-Sparks sewage treatment facility, that were traced back to incoming waste photographic chemicals and which were seriously impacting the sensitive fishery, provided the impetus for this project. This paper is updated from a paper presented at the Twenty-Second International Precious Metals Conference Toronto, Ontario, Canada in June 1998. It presents an overview of the scope of the problem solved by the technology, some of the permitting and development issues, and some of the specific fertilization formulations that are now being marketed.

Jan 1, 2000

By H. Virtanen

Outokumpu copper refining operations have a long history of expansions and application of new technologies. Outokumpu is a name known around the world for technological excellence in the field of base metals, and part of the policy of operations is continuous investment and investigation in new technologies. The results of this hard work sometimes are immediate and sometimes take years. The work done during the last years at the Outokumpu Harjavalta Metals copper refinery, together with a sister technology group Outokumpu Wenmec, has started to bear fruit in terms of the following radical developments and advances that are and will be applied to assure Outokumpu's position as the technology leader and a low cost and safe producer. Some of the developments discussed include the new anode and cathode design, mechanised electrode handling, cell design incorporating features facilitating full automation, automated short circuit detection and removal, automated on line anode slime removal, and high efficiency and intensity refining.

Jan 1, 1999

By John M. Rapkoch

In the continuing search for copper matte converting methods, commercially available and feasible choices remain Peirce-Smith Converters, Hoboken Converters, Mitsubishi Converting, Ausmelt converting, and Outokumpu/Kennecott Solid Matte Oxygen Converting (?Flash Converting?). While each alternative improves on Peirce-Smith Converters? limited fugitive gas capturing capability, the Peirce-Smith Converter is relatively easy and economic to operate and has an unmatched ability to accept valuable but difficult-to-handle material such as scrap anodes and purchased scrap copper. Recent experience with designing, building, and starting up an ISASMELT facility, applied in primary smelting of copper concentrates, has led the authors to speculate on how suitable the ISASMELT process would be for copper converting, given its low fugitive gas release and its ability to accept a variety of feed types. This paper reviews the potential metallurgical challenges posed by converting copper matte in an ISASMELT vessel and considers possible engineering and design challenges posed by the inclusion of this technology into a new or refurbished copper smelter.

Jan 1, 2006

By Ping-Ping Fan, Yong-Quan Wu

The polarized Brillouin scattering spectra were systematically measured to study the elastic properties of bulk hexagonal close-packed (hcp) ZnO single crystal in this paper. The peak polarizations of all modes in spectra were analyzed firstly. The elastic properties, such as the whole set of Elastic constants were accordingly calculated and compared with the previous literatures. Also investigated were the effects of the rotation of the sample in the (0001) plane perpendicular to the z axis on different acoustic modes. The results show that the quasi-longitudinal and quasi-transverse modes perpendicular to the (0001) plane act as the expected trigonometric function of the rotation angle,while the longitudinal and transverse modes on the (0001) plane remain constant.

Mar 1, 2017

By Staia. Mariana H.

Thermochemical equilibria of the heterogeneous system Ti-N-H-CI-Fe-Cr-Mo-Ni-Mn-C were calculated by using a commercial software based on the minimization of the free energy. Equilibrium calculations were done for temperatures varying between 800" and l 100°C and an initial molar relationship between reactants, a=NJTiCI,, of 0.1 to 2. The deposition process was considered to occur at atmospheric pressure. The activities of the alloying elements of the stainless steel were considered equal to their molar fractions. It was shown that for the conditions studied the substrate is no inert with respect to the gaseous phase. The existence of liquid chlorides was predicted for temperatures between 800" and 850°C and a ratio between 0.3 and 0.9. The most important metallic chlorides which appears to be present from the calculations in appreciable quantities in the gaseous phase are iron dichloride and manganese dichloride. In the low-temperatures zone and for low initial nitrogen contents, it result that the appearance of the liquid chlorides seems that partially inhibits the production of gaseous HCI. The highest deposition process efficiency calculated is obtained at a temperature 2 900°C and a N2/TiCI, ratios 2 0.7.

Jan 1, 1995

By Yunqing Tian, Wenbin Huang, Weidong Zhang, Xiaopeng Wang, Gele Qing, Xiangjuan Duan

Pellet production requires iron ore concentrates have fine particle size, high specific surface area and good balling performance, so iron ore concentrates appropriate for pelletizing is limited compared to sintering. In order to extend the iron ore resources for pelletizing, the iron ore fines for sinter are studied in this paper.The effect of grinded iron ores o npelletizing, roasting and pellet quality were studied in this paper. The bond grinding index of iron ore fine is between 12.5 and 16.98 kwh/t. The grinded iron ore fine has good balling performance, the drop number and compressive strength of green pellet were improved with increase of grinded iron ore fine ratio. The compressive strength of roasted pellets were decreased with increase of grinded iron ore fine ratio, however it can be reached 2500 N.P −1 while proportioned with more than 80% of magnetite iron ore concentrate.

Mar 1, 2018

By Thomas Havlik

It is proposed to realise the direct leaching, during which will be generated elemental sulfur and not sulfate or sulfuric acid as end product, under conditions that sulfur will not cover the leaching surface and Hot hinder the leaching course. The following improvements have been considered: -use of organic sulfur solvents -ultra high-frequency leaching -ultrasonic leaching -use of surface detergents or surfactants in leaching processes -simultaneously crushing and leaching These proposals are under investigation and preliminary results are promising

Jan 1, 1996

By Thomas Brynjulfsen, Merete Tangstad

"Manganese ore fines, generated during mining and transportation, can not be added to the submerged arc furnace directly as they will prevent even gas flow through the burden. Low gas permeability in the burden will lower the degree of pre-reduction of ore and subsequently increase the carbon and energy consumption of the process. In order to utilize manganese ore fines in the furnace they are agglomerated into sinter, pellet or briquettes. The agglomeration process will however change the reduction properties of the ore. In this work the melting and reduction properties of sinter has been investigated.The melting temperature and melting mechanisms has been studied. The mineralogy of the raw ores and agglomerated has been found using XRD, and the composition established using EPMA(WDS). The effect of adding fluxes such as dolomite and quartz has also been investigated.IntroductionManganese metal is produced in a submerged electric arc furnace or in blast furnaces. The reduction of manganese oxide in blast furnace has in the recent years become more unusual due to the high consumption of reducing carbon material[5]. Manganese metal for alloying in steel usually contains silicon and iron, and are therefore called ferro manganese and silicomanganese.During mining, transportation and handling the manganese ore is broken up into different size fractions. The larger lump are used directly in the electric arc furnace, but the finer materials can not be added without treatment. The fine ore can disrupt the flow of CO and CO2 gas through the burden, subsequently reducing the degree of pre-reduction. The fine fractions must therefore be agglomerated into larger lumps, in order to promote gas flow. This can be achieved through a number of different processes. The agglomerate used in this work has been sintered, which means that is has been partly molten and reduced, in order to create bigger lumps."

Jan 1, 2012