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By Ying Qin, Shujing Zhu

The characterization of adsorption of natural and composite bentonite in lead aqueous solution has been studied. The results showed that adsorption of both natural and composite bentonites strongly depended on the pH values of the solution. At lower pH values, the mechanisms that govern the adsorption of bentonites were dissolution of crystal structure and competition between the metal ions and the H+. To composite bentonite, the lead ion removal capacity was close to 250 mg/g. At higher pH values, formation of lead hydroxyl species might lead to either participation to the adsorption or precipitation onto the bentonites. Hence, a rapid increase in the equilibrium removal capacity of lead was obtained when pH > 7.0. An increase in the initial lead ion concentration led to the increase in the equilibrium adsorption capacity increased to a certain degree; and then, a plateau was obtained at higher concentrations. As a result, the adsorption performance of composite bentonite was better than the natural bentonite in both physical and chemical changes. The data fitted well with both Langmuir and Freundlich isotherms.

Mar 1, 2017

By Wenjun Duan, Qingbo Yu, Qin Qin, Junxiang Liu

In the study, the coke-oven gas (COG)-steam reforming process using hot blast furnace slag (BFS) as the heat carrier is explored for producing hydrogen and recovering high-grade waste heat of hot BFS. The method of the Gibbs energy minimization approach through Lagrange multiplier is adopted in the thermodynamic analysis of reforming process. The simulation is carried out to study the operation pressure, temperature and steam to carbon ratio (S/C) based on the chemical equilibrium calculations. The optimal operation conditions are determined to improve the yield and fraction of hydrogen in the COG-steam reforming process. The results suggest that the preferential operation conditions for COG-steam reforming process to produce hydrogen are achieved at 600ºC, 1.5MPa and S/C (5.0). Due to the CaO and other melts in BFS, CH4, CO and CO2 in COG are converted and removed efficiently, especially CO2. The hydrogen fraction reaches to 86.7% and its production is about 1.22mol with 1mol of the COG.

Jan 1, 2016

By William Petruk

The behaviour of sphalerite during mineral beneficiation of base metal ores has been studied at CANMET and other institutes for at least 15 years by determining the liberations of sphalerite in mill products and calculating the recoveries of liberated and unliberated sphalerite in zinc concentrates. Sphalerite in base metal ores commonly occurs as layers and as interstitial material between pyrite. Layered sphalerite is generally liberated during primary grinding, but interstitial sphalerite requires re-grinding to achieve liberation. Around 95% of liberated sphalerite is generally recovered in zinc concentrates frau zinc circuit feeds. A series of tests was conducted on sphalerite in the ore of Brunswick Mining and smelting during a continuous fine tuning operation of the concentrator. It was found that a grind of 80% minus 37 micrometres was required to liberate the interstitial sphalerite. The fine grind increased Zn recoveries from 75% to 78-80%, but produced liberated slimed sphalerite which was lost. Since regrinding to a fine grain size is needed to obtain the desired sphalerite liberation, a method of recovering the slimed sphalerite is required.

Jan 1, 1990

By Sh. Najisi, O. Lashkari, M. R. Ghomashchi, A. Charette

"One of-the important parameters in casting and foundry technology is the fluidity of molten metal. This parameter becomes particularly important when casting thin wall parts. Therefore, understanding and controlling fluidity plays a major role in fabricating sound and defect-free cast components.Semi-Solid Metai SSM, slurry is a mixture of solid and liquid, mushy zone, with solid volume fractions of 0.1-0.5 and apparent viscosity close to oil viscosity at room temperature. It flows easily under pressure and capable of making complicated shapes with high degree of die filling and integrity.In this study, the ability of the semi-solid slurry to continue to flow is investigated through the effect of different fraction solids and holding temperatures. The results show that in mechanically stirred, MS, semi-solid 356 Al-Si alloy, increasing fraction solid reduces fluidity. Furthermore, the results of MS-alloy are compared with a newly patented Rheocasting route, i.e. SEED, Swirl Enthalpy Equilibrium Device to highlight the differences of the two processes. In addition, the interrelationships between microstructural evolution and fluidity are discussed."

Jan 1, 2004

By M. J. Adam

As part of its research program, the U.S. Bureau of Mines is investigating the partitioning of complex minerals to simpler phases using sulfidation reactions for selective extraction of mineral constituents of value from extraneous elements early in processing schemes. This report describes research in which thermal processing of the complex Ti -bearing mineral ilmenite (FeTiO, ) resulted in partitioning of the valuable Ti metal to the simpler compound rutile (Ti0 ). Samples of ilmenite were blended with elemental S for thermal treatment a2 various temperatures under controlled atmospheres in an effort to dissociate the Fe from the ilmenite complex. Product characterization revealed that the Fe was partitioned from the ilmenite, forming a rim of pyrrhotite/pyri te (FeS/FeS,) on a rutile core. The products were agate milled and then subjected to cursory magnetic and flotation techniques in an attempt to physically separate the partitioned phases. Partitioning results and phase concentration data are reported relative to thermal treatment variables and physical separation techniques.

Jan 1, 1993

By Clara María Lamus Molina

The following minerals found in the residual black sands from gold mining in El Bagre Antioquia (Colombia) were identified as having major economic interest: Ilmenite (FeTiO3), with an average of 49% of TiO2, frequently altered presenting crowns; lamellaes of rutile and alteration textures; titanomagnetite with up to 25% of TiO2; magnetite (Fe3O4) in individual grains or associated with others minerals as hematite and ferromagnesian silicates rutile (TiO2) with considerable quantities of Nb2O5(0.1-3.7%Wt); zircon (ZrSiO4) with 66%Wt of ZrO2 and monazite with an average of 63.43%Wt of REE, this frequently associated to xenotime and thorite forming textures as little drops. Analysis in EPMA and SEM/EDS showed percentages of minor elements and traces, thereby clearly establishing the applications of these minerals in diverse industries. Furthermore, a detailed granumetric study of the different minerals and textural relationships among them also allowed for establishing the basis for possible processing and exploitation.

Jan 1, 2006

By Daniel Gauthier, Patrick Sharrock, Cedric Verwilghen, Gilles Flamant, Ange Nzihou, Jocelyn Ramaroson

Clean processes are needed to dispose of many wastes. The incineration of 1 ton of municipal solid waste generates 6000 Nm3 of combustion gases contaminated with heavy metals and other pollutants. Gas scrubbing processes are required to clean incineration fumes in order not to transfer pollution to the atmosphere. We are investigating the use of Hydroxylapatite (Ca-HA) particles for use as sorbent for the removal of volatile heavy metals. We have carried out the synthesis of Ca-HA by two precipitation methods from solution and obtained solids with specific surface areas reaching more than 100 m2/g. Preliminary adsorption experiments were conducted in a horizontal furnace by mixing Ca-HA with 5% by weight of cadmium chloride in solid state. The mixture was heated to 600°C under air atmosphere during 6 hours. Chemical analysis of the solids confirmed that 85 % of the cadmium was retained in the solid phase. Such laboratory results showed that Ca-HA is capable of adsorbing cadmium chloride vapors, and pilot scale studies confirmed cadmium abatement in an industrial context.

Jan 1, 2008

By Hiroshi Nakazawa

An acid mine drainage in abandoned Horobetsu mine in Hokkaido, Japan, contains arsenic and iron ions; total arsenic ca.10ppm, As(III) ca. 8.5ppm, total iron 379ppm, ferrous iron 266ppm, pH1.8. Arsenic occurs mostly as arsenite (As (III)) or arsenate (As (V)) in natural water. As(III) is more difficult to be remove than As(V), and it is necessary to oxidize As(III) to As(V) for effective removal. 5mL of the mine drainage or its filtrate through the membrane filter (pore size 0.45m) were added to arsenite solutions (pH1.8) with the concentration of 5ppm. After the incubation of 30 days, As(III) was oxidized completely with the addition of the mine drainage while the oxidation did not occur with the addition of filtrate, indicating the microbial oxidation of As(III). In this paper, we have investigated the microbial oxidation of As(III) in acid water below pH2.0.

Jan 1, 2006

The physico-chemical principles of chloride hydrometallurgy are reviewed to rationalise the complex chemistry in chloride-based processes for metal sulphides in terms of the predicted Eh-log[Cl-] relationships, measured changes in activity of H+, Mz+, Cl- and solubility of Ag(I), Cu(I), Cu(II), Pb(II), Ni(II), Au(III), Sb(III) and Bi(III). These changes reflect the nature of chemical speciation, competing effect of hydration/hydrolysis and chloro-complexation,composite effect of increasing acid and/or salt concentration and decreasing water activity. Rate data for the dissolution of PbS and ZnS in HCl containing Fe(III) or Cu(II) are compared and contrasted to highlight the effect of acid and chloride concentration, water activity, and the nature of oxidant. It is shown that LiCl, NaCl and HCl influence the kinetics of oxidative PbS leaching based on their effect on solubility of PbCl2 co-precipitated with elemental sulphur on the mineral surface. Evidence for the beneficial effect of Cu(II) in sulphide leaching is discussed.

Jan 1, 2003

By D. Nozadze

A new method of isothermal electro-contact diffusion welding of layered composites under pressure is offered. The scheme is developed and laboratory installation is created on which preproduction models of the layered composite of steel and aluminum is produced. A new method of electro-contact hot deformation is proposed for realization of diffusion welding by pressure of stratified blanks providing high-temperature isothermal process. In this case a rolling process or composite pressing is meshed with simultaneous electric current transmission in deformation center. Considering that a resistance of transient layer far exceeds the resistances of composite components, the heat release takes place intensively just in this layer. As the surfaces are approached over a distance of inter-atomic forces, the energy of boundary atoms easily reaches the energy threshold of capture with a formation of qualitatively new metallic bond. Proposed method, providing isothermal process in deformation center, excludes a necessity of previous preparation and prevention of surfaces. In this case strength of layer connection may approximate or exceed strength limit of cladding layer.

Jan 1, 2006

By Ian M. Ritchie

Cementation or metal displacement reactions such as Cu2+ + Fe Cu + Fe2+ are among the oldest known hydrometallurgical reactions. They are still used in the recovery of some metals and in the purification of process liquors and waste water streams. However, they are often more complex than the stoichiometric reaction would suggest because they involve the simultaneous deposition of one metal onto a second which is dissolving. For example, sometimes a cementation will not take place, even though it is thermodynamically favoured. On other occasions, a cementation reaction will start but come to a halt as the depositing metal blankets the reacting surface. On yet other occasions, side reactions, catalyzed by the deposit, can be important. In this paper, the electrochemical basis of cementation reactions is described. The conditions for each of the complications encountered in these reactions are described and illustrated by examples drawn from a number of hydrometallurgical processes. The cementation reaction between activated carbon and gold thiosulfate is also briefly described, this reaction being unusual in that no dissolution of the carbon occurs.

Jan 1, 2003

By Ian M. Ritchie

Cementation or metal displacement reactions such as Cu2+ + Fe Cu + Fe2+ are among the oldest known hydrometallurgical reactions. They are still used in the recovery of some metals and in the purification of process liquors and waste water streams. However, they are often more complex than the stoichiometric reaction would suggest because they involve the simultaneous deposition of one metal onto a second which is dissolving. For example, sometimes a cementation will not take place, even though it is thermodynamically favoured. On other occasions, a cementation reaction will start but come to a halt as the depositing metal blankets the reacting surface. On yet other occasions, side reactions, catalyzed by the deposit, can be important. In this paper, the electrochemical basis of cementation reactions is described. The conditions for each of the complications encountered in these reactions are described and illustrated by examples drawn from a number of hydrometallurgical processes. The cementation reaction between activated carbon and gold thiosulfate is also briefly described, this reaction being unusual in that no dissolution of the carbon occurs.

Jan 1, 2003

By Y. W. Miao

Along the south-west coast of Taiwan is about 550,000 metric tons of heavy sand deposit containing about 10 % black monazite. The Institute has developed a separation process to recover the individual rare earths and the developed process has been commercialized by a local private company. The decomposition of the local black monazite by sodium hydroxide through hydrothermal and fusion methods has been investigated. In the hydrothermal process 4.5 wt. % of aqueous alkali solution was used in an autoclave. In the fusion process, caustic soda (9.8% NaOH) was employed in am open cylindrical reactor. The same product of hydrous rare earth oxides were obtained and then dissolved by hydrochloric acid and the p-H adjusted in order to separate the thorium from the rare earths. After filtration, the filtrate contained rare earth chloride and the cake contained mainly the silica and thorium hydroxide. Both methods give a yield of 90 % with respect to the rare earths recovery. A detailed description of operation and comparison of the two methods are given.

Jan 1, 1989

By Burkhard Seeger et al.

The oxidation of copper sulfides can be highly accelerated in the presence of nitrous gases (NOx) as reaction catalysts. Sulfur and sulfate are simultaneously produced in this highly exothermic reaction. This process, carried out in sulfuric acid medium, is performed at an approximately normal pressure and at a temperature of around 110 °C, in a closed container, adding either oxygen or air. The oxidation is automatically controlled through a computer. The process covers the following steps: Catalytic oxidation, filtration and crystallisation of the hot concentrated liquid, electrowinning, mother liquor treatment through jarosite formation, recovery of dissolved copper and zinc and regeneration of industrial water, and non-soluble residue treatment with extraction of sulfur and recovery of silver and gold. No combustibles are needed. No air is contaminated, and no waste water is produced. Solid residues are in a stable, non-toxic and non-corrosive state of equilibrium. Risk of accident is low. Investment costs are small compared to those of the comparable pyrometallurgical process, and production costs are competitive.

Jan 1, 1999

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 David G. Dixon

From its first implementation for the recovery of gold from low-grade ores by cyanidation in the early 1970s, heap leaching has developed into a key hydrometallurgical technology, in conjunction with solvent extraction and electrowinning, for the recovery of base metals, including most notably copper from both oxides and secondary sulphides, and more recently, nickel and zinc. And, given recent advances in bioleaching with thermophilic microbes, the successful application of heap leaching technology to low-grade primary copper ores seems only a matter of time. However, with each new development, it becomes increasingly apparent that the successful application of heap leaching technology will ultimately depend on our having an ever more complete understanding of the fundamental processes underlying it. Much work has been done toward the development of this understanding, on many different fronts. In this paper, a critical overview of heap leach modeling work to date is presented in terms of the most important phenomena which occur during heap leaching, and potential directions for future work are discussed.

Jan 1, 2003

By Hong Yong Sohn

A thermodynamic and experimental investigation has been performed to develop a new process for converting sulfur dioxide to elemental sulfur by a cyclic process. The most promising new process is a cyclic reaction scheme involving calcium sulfide and calcium sulfate. In this process, the reaction between sulfur dioxide and calcium sulfide produces elemental sulfur vapor and solid calcium sulfate. The latter is reduced by a suitable reductant such as hydrogen to regenerate calcium sulfide. 'Experimental results showed that up to 60 % of calcium sulfide powder was converted to calcium sulfate in 10 min at 1153 K under a sulfur dioxide partial pressure of 25.8 kPa. More than 95 % of nickel-catalyzed calcium sulfate powder was converted to calcium sulfide in 20 min at 1123 K under a hydrogen partial pressure of 86.1 kPa, water vapor being the only gaseous product. Sulfur dioxide-containing streams from certain new sulfide smelting plants contain much higher partial pressures of SO2. The rate of the first reaction is expected to be accordingly higher than in the test conditions reported in this paper.

Jan 1, 2002

By V. L. Stolyarova

As part of an effort to develop the fluoride electrolysis route for the production of rare earth metals and alloys, a study of the thermodynamic properties of DyF3 has been carried out by Knudsen cell mass spectrometry. A quadrupole mass spectrometer QMS 420 was used in conjunction with the Knudsen cell arrangement. The experiments were carried out in the temperature range 1280-1440 K. Vaporization was carried out from platinum, molybdenum and tantalum cells. The Dy*, DyF+, DyF2+ fragment ions and the DyF3 parent ion were identified in the mass spectrum of the DyF3 vapour. The DyF, vapour pressure was obtained by the complete isothermal vaporizadon method as well as the ion current comparison method, and the enthalpy of sublimation of DyF3 was evaluated. From the DyF3 vapour pressure data obtained at different temperatures, the enthalpies of formation of DyF3 in the gaseous as well as condensed phases have been evaluated. The experimental data are compared with the thermodynamic information available in literature.

Jan 1, 1995

By V. Jiricny

The novel spouted-bed electrode (SBE) is a cathode system where copper is deposited at a high current density in a moving bed of copper particles. Preliminary results on the deposition of copper from acidic sulfate electrolytes using this novel cathode system were described during Copper '95 conference. Despite a high current density, the electrical energy consumption was equal to or lower than that in the conventional electrowinning. The present paper describes more investigations on SBE. The SBE consists of copper particles with approximately 1 mm diameter onto which copper is deposited from acidic sulfate electrolyte whose composition is similar to conventional electrowinning. Three types of anodes were used in conjunction with the spouted-bed cathode, namely, DSA anode for oxygen evolution, and two novel anodes. One anode is less expensive than DSA; however it showed much promise in energy consumption. At a superficial current density of 2200 A/m2, the energy consumption was around 1.0 kWh/kg copper. The research activities described in this paper were supported by BHP Copper.

Jan 1, 1999

By Dhanesh Chandra

Long term stability studies were conducted on four variants of LaNi5; 10,000 hydriding/dehydriding cycles were used to evaluate their suitability for a metal hydride cooling system. Thermodynamic and structural studies were conducted to determine changes in these materials during cycling test period. The hydrogen sorption properties of LaNi5.2, and Lao 9Gd0.1Ni5 and LaNi4.75In0.27 were seriously degraded during the tests but the LaNi4.8Sn0.22 hydride was virtually unaffected. Hydride isotherms were measured at the beginning and at intervals through out the test period to observe the nature and extent of damage degradation in the sorption properties. X-ray diffraction studies of the alloys (LaNi5.2, LaO.9Gd0.1Ni5 LaNi4 8Sn0.22) and their respective hydride, before and after test, provided insight with regards to the observed changes in the hydride properties. Electron microscopic studies were also conducted to evaluate the changes in particle sizes.

Jan 1, 1989