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By Zengjie Wang

Investigation on hydrochloric acid leaching of the ilmenite from Panzhihua, China was carried out to prepare synthetic rutile. The leaching parameters were optimized to obtain high content of TiO2 in the products. The experimental data suggest that an optimum leaching can be realized with 30% acid, a solid/liquid ratio of 1/4 at 95°C for 4h, and ore ground for -400 mesh size. After the acid leaching, an additional alkaline leaching process using hot NaOH solution was performed, and then the products was in grain form followed by heat treated at 900°C for 2h in order to extract Si and increase the particle size of synthetic rutile. The final product has a high content of TiO2 (about 95%), a low content of chlorine consuming elements (total CaO+MgO =0.07%) and a suitable particle size distribution for chlorination process.

Jan 1, 2008

By Nobuaki Sato

The electrical conductivity, k, of pure and sodium doped sulfur melts was measured with and without ultrasonic waves at temperatures ranging from 140 to 340° C by the two probe method using an ultra high resistance meter. The II: value of the pure sulfur melt with irradiation jumped at around 170°C by an order of 102 after which it monotonically increased from 10-5 to 10-4 (omega) 1cm-4 with an increase of the temperature. The addition of the sodium metal to the sulfur melt was found to cause a larger jumping in the II: value. The II: value increased with the increase of Na proportion in the melt. For a 10 mol% Na doped sulfur melt it was as high as max. ~30 (omega) 1cm-1 above 180°C under the irradiation of ultrasonics.

Jan 1, 2003

By W. K. Connor, O&apos

The Bureau of Mines has conducted beneficiation, carbothermic reduction, and leaching tests of Mn oxide ores as part of its evaluation of the Mn and Co resources of the West- Central Arkansas District. The major Mn oxides in the ore include cryptomelane, psilomelane, pyrolusite, and lithiophorite. Cobalt is contained within the Mn oxides. Nonbeneficiated ore was reduced at 800' C with coal and leached in ammonium sulfate and ammonium carbonate leach liquors. Ore concentrates were calcined at 600" C prior to reduction under the same conditions as the raw ore. Head analyses reported up to 21 ptt Mn and 0.11 pct Co. Extractions of 70 to 90 pct Mn and 40 to 60 pct Co were achieved.

Jan 1, 1992

By Andre Krzysik

"Fluidized bed technology has been used in the industry for almost 100 years. To fully understand the process hundreds if not thousands of researchers were and are involved in finding the way to predict the behavior of the solids when subjected to the flow of media through them and the conditions of the solids in the fluidized state. The difficulties in predicting the behavior of solids in the fluidized state stem from the complexity and abnormality of the parameters related to the solid particles. Theoretical calculations can in some degree account for some of them. Particle size distribution, their shape, density, moisture content and physical and chemical reaction that may exist in the fluidized bed reactor play an extremely important role and influence the behavior of the fluidized bed. This paper focuses on the practical examples of the fluid bed equipment and the use of different conditions to process various products.IntroductionEach process application has its own unique requirements and the designers of the equipment must take into consideration specific process requirements, specific properties of the material to be processed (both physical and chemical), and physical and chemical reactions/changes that are taking place in the reactor (heat and mass exchange, chemical reactions, isomorphic change etc.). Each individual piece of equipment must also satisfy specific requirements/ preferences of the client that will operate and maintain the equipment. Those often represent greater challenges than the process on its own, and are equally important to the satisfactory operation of the plant. That includes aspects like location of the equipment, environmental effects, and expected life of the equipment, process control, access, maintenance, and many others.Over the period of time a great deal of research, both theoretical and practical have been carried out and the results of that work are available for equipment designers. For the simple applications that information is usually sufficient and the selection of a suitable solution is relatively simple. In many instances, the available information is not sufficient, and often specialized test work needs to be conducted to obtain additional data. In many cases a pilot installation is built in which the required process is tested. Only then the commercial equipment is designed. The following deal with specific installations that were designed to satisfy specific requirements. In some instances, additional problems were discovered during the commissioning of the equipment that required on site modification. The continuous monitoring of the equipment that was supplied to the various clients allowed us to further develop and improve our designs."

Jan 1, 2014

By P. Lussiez

Precipitates consisting of amorphous ferrihydrite and crystalline goethite have been prepared by aging hydrolyzed Fe (III) solutions at room temperature. The precipitates have been characterized by x-ray diffraction and differential thermal analysis. The amorphous ferrihydrite transforms to goethite with time. The ferrihydrite to goethite transformation is affected by the presence of small amounts of copper or nickel coprecipitated with the iron. .The addition of copper decreases the amount of goethite at a given aging time and increases the amount of coprecipitate which is initially dissolved in sulfuric acid, but it does not seem to affect the dissolution of the crystalline part'. It is proposed that adsorption of copper hydroxo species on goethite nuclei delays the ferrihydrite to goethite transformation. The effect of nickel is less dramatic than that of copper. Apparently a portion of the added nickel is adsorbed on the goethite crystallite surface rather than incorporated into the goethite lattice.

Jan 1, 1981

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 Qingchun Yu, Bin Yang, Yong Deng, Heng Xiong, Fei Wang, Minxiu Chen

"Metal aluminum produced by non-electrolysis process received much attention due to its lower energy consumption. In this paper, carbothermic reduction and carbothermic-chlorination of alumina in normal pressure and vacuum were studied. The products were examined by means of XRD, EDS and SEM. During the carbothermic reduction process using carbon reductant in normal pressure, no metal aluminum was found. However, when coal was used as reductant, a mixture containing metallic aluminum, A14C3, and silicon was obtained, but metallic aluminum couldn't be separated from the mixture. During the carbothermic-chlorination process in vacuum, Al404C and Al4C3 were produced by the reaction between alumina and carbon, and Al Ch gas reacted with Al404C and Al4C3 to produce Al Cl gas. Metallic aluminum was produced due to the disproportionation of A!Cl gas and condensed on the collecting plate. Meanwhile, the initial temperature of carbothermic reduction of alumina reduced in vacuum compared with that in normal pressure.IntroductionIndustrial production of primary aluminum is carried out in alumina cell by the so-called Hall- Heroult process, necessitating the use of very high currents of low voltage. The alumina from which metallic aluminum is gained must be chemically pure, otherwise impure metal results. The main drawbacks of the electrolytic production are its very high energy consumption, the release ofperfluorocarbons, and the high specific C02 emissions [1]. During the past years, there were a lot of attempts to produce metallic aluminum by carbothermic reduction of A1203 [2, 3]. Cox [4] determined the vapor pressure over the A1203-C system and performed X-ray diffraction analysis of condensed products. It was demonstrated that an increase in the carbon content in the system leaded to the sequence of transitions: A1203~Al404C~A1zoc~A14C3 ~AI [5]. In any carbothermic reduction process for aluminum, extremely high temperatures (2000 °C ) were required [6]. In spite of considerable effort, the carbothermic reduction of alumina to aluminum remains a formidable technical challenge, due to the high temperatures required, and to the formation of aluminum carbide and oxycarbide byproducts [7]."

Jan 1, 2013

By C. M. Antony

The galvanizing process involves the use of accessory equipment in a series of aggressive environments including zinc ammonium chloride flux, molten zinc at 45S°C (850°F), and acid for stripping of adherent zinc. An Fe-Ni-Cr-Co alloy has been identified which combines excellent strength and resistance to molten zinc and acid attack making it suitable for accessory equipment. The alloy was field tested by a commercial galvanizer as basket material and was found to provide improved life compared to original low-alloy steel baskets while cross-section thickness was reduced 44%. Additionally, other associated processing cost savings were realized.

Jan 1, 1992

By Bing Li, Miao Shen, Qiang Wang, Yuqi Chen

Electrochemical methods including cyclic voltammograms, square wave voltammograms, chronopotentiometry are applied to characterize the reduction potentials of Na+ and Li+ ions in LiCl-KCl melts. According to theoretical calculation, the reduction potential for Na+ is slightly more negative than Li+ in NaCl-LiCl-KCl melts at 450℃. However, by electrochemical measurements, the reduction potential of Na+ is slightly more positive than Li+ in the above melt and the potential difference between Na+ and Li+ reaches 0.16-0.2V on an inert W electrode in 1.0-2.0 wt% NaCl-LiCl-KCl melts. An active Pb electrode is used to improve the removal rate of Na+ from LiCl-KCl melts. The reduction potentials for both Na+ ions and Li+ ions on a Pb electrode shift to more positive values and the reduction currents become larger. After 6h electrolysis on a Pb electrode at -3.0V, the practical removal efficiency of Na+ ions reaches 90.12% and the reduced products contain metallic Na and Li with a Na/Li mass ratio of 4.25/1.

Jan 1, 2015

By Patricio Barrios

The Rio Tinto Metal (RTMetal) copper smelter, located 5 Km from Huelva, Spain, began operations in 1970. Since then a series of expansions and modifications have allowed a progressive increase in copper production. Environmental considerations having become increasingly important, environmental protection has come to represent an important aspect of the investments in production. As a result, modifications have been carried out in the two existing acid plants: -Modification of the RTM I gas cleaning section to closed circuit. -Substitution of cascade filters and acid lines. -Modification of the RTM I plant to double absorption. The Expansion and Environmental Improvement Project, completed end 1995, will allow 270,000 t Cu and 800,000 t H2SO4 to be produced yearly, at the same time achieving a decrease in specific and overall emissions. RTMetal's goal is to be an efficient smelter, with the avowed intention of respecting the environment and adopting the best available technologies.

Jan 1, 1996

By Ivan Imris

The iron production has generated many tonnes of very fine residues with high concentration of iron. In addition, during the recycling of galvanised steel scrap in the steel making processes the zinc and lead are largely concentrated in the dust. These kinds of dusts are usually dumped beside the metallurgical plants and cause environmental problems. Therefore the metal recovery from the metallurgical residues has become a major interest not only from the viewpoint of metals recycling but mainly from the viewpoint of environmental land protection. The thermodynamic analyses and laboratory experiments suggested that the metals could be recovered from metallurgical wastes by reduction roasting and by plasma smelting processes. The iron rich pellets with very high metallization may be obtained from metallurgical wastes by the reduction roasting and the inert slag and pig iron could be produced by plasma smelting processes. In both cases the iron rich products are suitable for the steel production. During the reduction roasting or plasma smelting the high volatile zinc and lead metals were removed and enriched as a secondary dust, Zn-Pb concentrate, which is suitable for processing in zinc and lead smelters. Suggested processes are commercially feasible and environmentally friendly without any solid or liquid waste.

Jan 1, 2003

By Tim B. Vander Wood

Standard methods of determining clay mineral powder aspect ratios involve manual scanning electron microscopy analyses of shadowed particles in order to measure both platelet thickness and diameter. We present a method whereby the diameters of platelets are quickly determined by automated scanning electron microscopy and their images are recorded and digitally transferred to a transmission electron microscope equipped for parallel electron energy loss spectroscopy. Thickness' of platelets whose diameters are known from the previous analyses are determined by measurement of the ratio of scattered and unscattered electrons in the beam after it has been transmitted through the platelet.

Jan 1, 1995

By J. W. Matousek

Cobalt behavior in pyrometallurgical processes is traditionally analyzed using slaglmatte distribution coefficients as functions of matte grades or matte iron contents. L(s/m) = (%Co) I [%Co] = f [%CuNi] or f [%Fe] The method is inconvenient to use in predictive mass balance work because of the interdependence of assays and mass quantities. An alternative procedure is proposed based on cobaltliron ratios for slags and mattes: Js = (%Co) / (%Fe), Jm = [%Co] / [%Fe], and J, = b + m [Jm]

Jan 1, 1993

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 Giacobbe Braccio, Alessandro Blasi, Assunta Romanelli, Massimo Morgana, Corradino Sposato

Yttrium is a strategical material for its several usages in a wide range of industrial production. For this reason, improving the recovery of Yttrium has become a crucial focus for international research. In this scientific activity, the utilization of two extractants, 2-ethylhexyl-mono 2-ethylhexyl ester phosphonic acid (P-507) and sec-octylphenoxy acetic acid (CA-12), working in a synergistic extracting system, has been tested. A series of trials have been carried out to optimize the experimental conditions in order to separate yttrium from a mix of heavy rare earths in chloride media. Tests with different relative concentrations of extractants and a phase modifier (TPB, trybutyl phosphate), with different presaponification rate, have been performed to evaluate the behavior of the synergistic system. Results are very promising to recover and separate yttrium with a high purity.

Mar 1, 2017

By KNona C. Liddell

Goethite is an important naturally occurring sorbent for divalent heavy metals and has often been used as a model compound in studies of adsorption on oxide mineral surfaces. Surface complexation modeling, surface spectroscopy, and electrochemical techniques have all been applied to goethite adsorption. Modeling studies have shown that usually several different sets of fitted parameters are equally successful in representing surface charging and adsorption data. Surface spectroscopic data are proving valuable in determining the nature of the surface sites, and refined models now incorporate structural information on interatomic distances and coordination numbers. Multisite surface complexation models can give very good fits to surface charging and adsorption data, but further improvements are needed to better represent surface reactions involving exchange of protons and divalent cations. Recent experimental and modeling studies on adsorption of divalent transition metals on goethite are described and the present status of the field is assessed.

Jan 1, 1999

By S. Suda

Hydrogen storage materials have been investigated for more than 30 years, particularly on metal hydrides. These materials are, however, considered today impractical because of their poor hydrogen capacity measured by mass density and their poor surface properties and characteristics against impurities. Recent R&D activities have been located in new categories of materials such as complex hydrides and chemical hydrides. Among these materials, NaAlH4 (one of alanates), Li-based complex hydride, and NaBH4 (SBH: sodium borohydride) are 3 major candidates as hydrogen storage materials. In the presentation, SBH as a non-reversible on-site but recyclable off-site is described in view of its practical availability as the source of H- (protide) applied for a new type of fuel cell named Direct Borohydride Fuel Cell (DBFC) and H2 (hydrogen) for Proton Exchange Membrane Fuel Cell (PEMFC).

Jan 1, 2006

By Chang Wei, Zhigan Deng, Yizhao WANG, Cunxiong Li, Gang Fan, Xingbin Li

During the process of hematite precipitation, the transformation of Na jarosite convert into hematite has been studied in a batch reactor at different temperatures, ranging from 170°C to 200°C with 3h of the retention time in the presence of 30g/L Fe ( ) and 4g/L Na+. The composition of precipitation was seriously depended on the temperature, at 170°C hematite and sodium jarosite are the reaction products of iron precipitate, with an increasing in reaction temperature the sodium, sulfur content in precipitated decreased and sulfur mainly exist in forms of SO4 2-, and when temperature over 200°C hematite was the only phase in product. An increasing temperature was not only beneficial to iron precipitation, also conducive to jarosite conversion to form high quality hematite precipitate.

Jan 1, 2016

By Yuanbo Zhang, Zhixiong You, Li Qin, Guanghui Li, Tao Jiang

Low-grade manganese oxide ore is generally characterized by high iron content. In this work, sulfidation roasting of an iron-rich manganese oxide ore with elemental sulfur was characterized. The experimental results indicated that manganese dioxide can be selectively reduced over iron oxide by using elemental sulfur. The manganese phases in roasted product included low-valence manganese oxide, manganese sulfide and manganese sulfate, while those of iron mainly depended on the sulfur addition. Iron oxide would only be reduced or sulfidized at larger sulfur additions. The effect of roasting temperature and S/Mn mole ratio on the phase transformations was also investigated; extractions of Mn/Fe by sulfuric acid were evaluated. An extraction of Mn greater than 95% was obtained while that of Fe was controlled less than 10% under the optimal conditions.

Jan 1, 2016

By G. C. Yao

Iron and silicon impurities can form needle and branch shape intermetallie compounds in molten aluminum when there is no manganese. It is difficult to separate them from molten aluminum by electromagnetic separation. The Fe-Si-AI and Fe-Al intermetallic compounds were transformed into Mn-Fe-Si-Al and Mn-Fe-Al compounds by the addition of manganese into molten aluminum. In molten aluminum the morphology of these intermetallic compound particles is lumpish and spherical. Migration resistance of these impurity particles is small, which is beneficial to separation. FeSiMnA4 and FeMnAI6 are paramagnetic. These impurity particles can be moved by magnetic force and can be separated from the molten aluminum.

Jan 1, 2003