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By Yavuz Ali Topkaya, Aydin Rusen

"In this study, zinc and lead recovery from zinc plant leach residue obtained from Çinkur using hydrometallurgical methods have been investigated by laboratory scale experiments. Considering more than one million tons leach residue (LR) rich in Zn (12.43%) and Pb (15.51%) in the stockyard and environmentally hazardous, it is essentially necessary to process Çinkur LR. Zinc and lead have been recovered in two main stages. As a first step, Çinkur LR was releached by using hot sulphuric acid for zinc recovery. About 72 % Zn was recovered by using 150 g/l H2SO4 at 95 oC in 2 hours with a pulp density of 200 g/l. Secondly, for lead recovery brine (NaCl) leaching tests were performed on the secondary Çinkur LR obtained after acid leaching process. In brine leaching while lead recoveries up to 95 % could be attained at a low pulp density, the maximum recovery obtained was 84.9 % at a high pulp density (200 g/l) with 300 g/l NaCl concentration in 10 minutes at 95 oC. Introduction Zinc and lead have been known and used by humans since ancient times and also they are important nonferrous metals [1]. Zinc and lead have different properties thus they are used in various application areas, ranging from automobiles to construction, from batteries to textile. Zinc and lead deposits are widely distributed in the Earth’s crust. The principal ore mineral for zinc is zinc sulfide, Sphalerite (ZnS), and lead sulphide, Galena (PbS), is the main source of lead in the world [2].Although zinc is generally produced from sulphidic ores (ZnS) or concentrates by Roast – Leach – Electrowinning (RLE) in the world, in Turkey, zinc production is based on zinc carbonate ores (ZnCO3), and at the Çinkur plant zinc was produced from zinc carbonate from its establishment to 1997 due to high reserves of zinc carbonate in that region. Çinkur is the only plant in Turkey that produces Zn from primary ore containing ZnCO3 by Waelz – Leach - Electrowinning route [3]. However, due to depletion of local high grade ores, oxidized ore concentrates were imported from Iran after 1997, until this plant was shut down. Therefore, there are two different leach residues (LR) which are Turkish LR (TLR) and Iranian LR (ILR) in Çinkur stockpiles. It has been estimated that the total amount of leach residue is more than one million tons of which the major part is Turkish leach residue (TLR)."

Jan 1, 2008

By Cecil Harriss

Philip Environmental Services Corporation's (Philip's) innovative fluidized bed thermal desorption system recovers mercury from contaminated soil. Referred to as the Thermal Recycling System, Philip has constructed a mobile thermal desorption system that has a processing rate up to five tons per hour. The system includes a continuous-feed system, all radiant heat, inert gas atmosphere, hot gas filter, two-stage cooling, and a water treatment system. Based on treatability studies, the processed soil can meet cleanup objectives as low as two milligrams per kilogram and passes the mercury toxicity characteristic leaching procedure test.

Jan 1, 1996

By A. D. Neuman, C. C. Davis, M. R. Lopez, A. C. Martinez, T. A. Nothwang, F. G. Hampel, S. L. Voit

"One of the thrust areas for the Global Nuclear Energy Partnership (GNEP) program is the development of actinide bearing fuels for transmutation in a fast reactor. Mixed Oxide (MOX) fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition from which minor actinides can be incorporated for use as a transmutation fuel. The current study involves characterization of precursor powders and pellets destined for the Advanced Test Reactor in Idaho. These pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of minor actinide mixed oxide (MAMOX) with oxygen to metal ratios (O/M) of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders were characterized using a field emission gun scanning electron microscope (FEG-SEM) to determine particle morphology, size, and size distribution. An electron probe microanalyzer (EPMA) was used to characterize element distributions in the pellets.IntroductionThe fundamental purpose of GNEP is to enable a fuel recycling partnership between member nations. The customer nations utilize the fuel for electricity generation provided by and subsequently recycled by the supplier nation. The supplier nation recycles the actinide constituents, mainly uranium and plutonium, in advanced nuclear power reactors, and thus reducing waste volumes [1, 2]. Nuclear materials are strictly controlled through the International Atomic Energy Agency. One of the thrust areas supported by the GNEP program is the development of actinide bearing fuels for transmutation in a fast reactor under the U.S. Advanced Fuel Cycle Initiative (AFCI) in order to transmute long-lived transuranic actinide isotopes into shorter-lived fission products [3].MOX fuel has an extensive fast reactor irradiation history and thus is being considered for use as a baseline composition into which minor actinides can be incorporated for use as a transmutation fuel [4]. Irradiation performance data on oxide fuels with high concentrations of minor actinides is limited, which has prompted this study. This paper discusses the characterization results of precursor powders and pellets prepared for the Advanced Test Reactor in Idaho to determine the effects of including minor actinides in the fuel, and addresses two fuel test matrices proposed by Hilton et al. [3]. The pellets will have three compositions: one standard MOX composition, (U0.80Pu0.20)O1.98, and two compositions of MA-MOX with O/M of (U0.75Pu0.20Am0.03Np0.02)O1.98 and (U0.75Pu0.20Am0.03Np0.02)O1.95. The precursor powders, uranium oxide (depleted, DUO2 and highly enriched, HEUO2), neptunium oxide, NpO2, americium oxide, AmO2, and plutonium oxide, PuO2, were characterized using a FEG-SEM for particle morphology, size, and size distribution. The morphology of the actinide powders was studied in the areas of flowability and porosity in order to predict manufacturability. The MOX pellets were characterized using an EPMA in order to determine impurity levels and locations."

Jan 1, 2008

By Li Zhang

A novel green technology to recovery Titanium compounds from Ti-bearing blast furnace slag under the dynamic oxidation condition was developed and tested. Air was blown into the molten slag as oxygen resource through a lance during the dynamic oxidation process, in which six important results were found: (1) The TiC, (Ti2O3), Fe and (FeO) in the slag were oxidized; (2) The temperature of slag temperature rapidly increased; (3) The viscosity of slag decreased; (4) The coalescence, growth and drop of the metallic Fe droplets in the molten slag were carried out under an air agitation condition; (5) The dispersed Ti components were selectively enriched into the perovslite phase, and the perovskite phase could be selectively precipitate and grow. And also, the perovskite phase can be separated by the dressing method. The oxidation of molten slag gives off a large amount of heat, which helps chemical reactions proceed, improve the rate of chemical reactions, and promote the precipitation and growth of the perovskite phase. The features of the technique are clean, low cost and a great capacity to deal with a large quantity of slag. It was confirmed by experiments that the precipitation of the perovskite (CaTiO3) in molten slag is obviously affected by operation factors such as temperature, chemical composition, heat-treatment, additives and so on. The precipitating kinetics and mechanism of the perovskite phase from molten slag during the dynamic oxidation processes were also investigated.

Jan 1, 2006

By Maria Kuttig, Christian Ruback, Gerhard Tober, Petra Maier

"It has been demonstrated that there is a strong relationship between work hardening with various post heat treatment and cyclic deformation behavior of structural steel S275. This study contributes to a project developing a process for the complex forming of steel, which combines rolling and bending. Due to the complex geometry of the final work piece, the deformation degree varies greatly. The forming temperature, as well as post heat treatruent, influences recrystallization processes in dependence of the local deformation degree, resulting in inhomogeneous microstructure of the work piece, which affects the quasi-static and dynamic properties. Cyclic creep and hardening or softening has been monitored during constant amplitude loading at stresses near fatigue strength in normalized condition. Work hardening, stress relief or recrystallization influence the cyclic deformation behavior and produces cyclic creep effects. Cyclic softening or hardening and creep were observed to occur in parallel. To what extent these properties are noted depends on the deformation degree.IntroductionThis work is part of a research project developing a new process for the three dimensional forming of steel. For the final product the fatigue strength influenced by the forming parameters is very important. Due to its complex geometry, the formed final plate has different deformation degrees. This leads to different recrystallization behavior and heat treatruent will have different effects on the microstructure. The peak deformation degree cp of the plate will be around -0.5 what leads to the analysis using rolling from 22 mm to 13 mm of thickness. The quasi-static material properties are very important for calculating the preliminary design. However, work pieces which are cyclic loaded need fatigue tests to describe the in-service material behavior. [l] For the prediction and to guarantee the wanted life-time of the part cyclic deformation tests are important. [2, p.23-32] When it is assumed that the work piece will only loaded in cyclic tension, fatigue testing will be done from zero to a maximum force value. In preliminary tests this value is the tensile fatigue strength from a Smith diagram. During processing, here forming, work hardening takes place resulting in strengthening. Therefore, in further tests maximum load can be increased to monitor cyclic deformation mechanism in more detail. However, to study cyclic creep and hardening and softening data should be evaluate over sufficient life time and should not fracture too soon."

Jan 1, 2013

By Tetsuro Sakai

Home appliance recycling law was put into force in April 2001 in Japan. Specified kinds of home appliances, such as air conditioners, television sets, refrigerators and washing machines, should be recycled according to the law. Mitsubishi Materials Corporation (MMC) in cooperation with home appliance manufacturers is operating five home appliance recycling plants in Japan. MMC established complete treatment system of recyclable materials generating from home appliance recycling plants, which is formed by unique collaboration among home appliance recycling plants, copper smelter and refinery, and cement plants. Recyclable materials containing copper and precious metals are only handled and treated within the MMC group. By using this lock-in system, safe treatment and traceability of materials are guaranteed as 100% materials recycle.

Jan 1, 2008

By M. A. Rabah, F. E. Farghaly, M. A. Motaleb

"Wastewater from industrial galvanization industry was reclaimed under current flow stream conditions. Results showed that the raw water contains 0.7 % by weight total suspended solids (TSS) causing turbidity amounting to 30. Measurements of Zeta potential as a function of pH revealed that solid separation takes place at pH 9. Addition of H2O2 to the polmer solution helps to oxdize ions of iron and zinc metals toinsoluble ferric oxide and zinc hydroxide to a higher state of oxidation. Addition of 5 mg/L of cationic magna flocculants polymeric solution helps the rapid separation of the turbidity. Separation of floccules so formed takes place by filtration. Addition of peroxide ions to the turbid wastewater confirms the physical stability of the flocs so formed. Impurity flocculation takes place in few seconds. Maximum temperature for safe solid removal was <30°C. The treated water was pure and safe for recycling or use in domestic purposes.IntroductionStocks and et. al. [1] show that the galvanizing process introduces spent pickling acid waste production, but its major constituent, could be used. Survey of the operational procedures adopted and the acid wastes produced by UK Galvanizers are reported. Various methods to recovery spent acid of suitable composition and to eliminate zinc contamination was considered. Application of the Kleingarn acid management system reduces waste volume, saves hydrochloric acid (HCl) and increases component throughput whilst, in conjunction with zinc elimination, could allow recycling of the majority of galvanizer’s acid wastes.Dahab [2]; Kerney [3] reported recycling of galvanizing products, including pickleliquor. Kerney suggested a mobile treatment plant for recycling pickling acids. Dahab found that pollution reduction could be achieved by relatively simple operational changes to the process that gave fairly short payback times.Rozenblat and et. al.[4] studied the extraction of zinc (II), iron(III) and iron(II) with Tributyl phosphate (TBP) from hydrochloric acid solutions containing high zinc(II) concentration. Two technological approaches for the separation are considered. Firstly, the selective extraction of iron(III) (iron(II) is oxidized to iron(III)) over zinc(II) with TBP deficiency. Secondly, iron(III) reduction to iron(II) followed by zinc(II) selective extraction with an excess of TBP. Prior stripping, the organic phase was washed with small amounts of water. Scrubbing of TBP solutions containing iron(III) contaminated with zinc(II) gives always a mixture of zinc(II) and iron(III) which must be recycled to the extraction step in continuous process. The following technological concept is proposed: reduction of iron(III) to iron(II), extraction of zinc(II) with 5-10 volume excess of TBP, washing of TBP phase contaminated with iron(II) with small volumes of water and recycling of the scrubbings and stripping of zinc with water."

Jan 1, 2008

By C. M. Acuna

Scarcity of high grade copper low impurity content ores is a reality and processing of low grade dirty concentrates is a need. In spite of this fact, innovative strategies have to be looked at to comply with day to day more stringent environmental regulations. From this perspective the production of matte grades over 70% in copper presents several merits, but it must be contrasted with the fractional distribution of impurities reporting to the condensed phases. Converting of white metal high in arsenic content results in moderate fraction of arsenic to gas, but high deportment to blister. Therefore, production of anode copper, as required by the electrolytic refinery, may result in several operational difficulties. Furthermore, by recycling the flue dust and slag produced in the smelting-fire refining cycle, the arsenic content in the feed to smelting increases and so does in the resulting anode copper. The Teniente Converter, as a smelting unity, has probed suitable for production of high matte grade near white metal composition but regarding distribution behaviour of impurities there is lack of reliable data, specially when processing concentrates over 1% in arsenic content. In the new scenario, i.e. low grade copper high arsenic content concentrates, to fully asses the merits of this technology the effect of matte grade, secondary materials recycling and arsenic in feed upon the distribution coefficient of arsenic between slag and matte, mainly, must be evaluated both from a theoretical approach and by use of industrial data. Based on available data correlations of distribution coefficient, matte grade and matte/slag ratios with arsenic in feed and copper content in slag are worked out. Based on these results suggestions as to matte grades facilitating to deal more efficiently with the handling of smelting byproducts are proposed.

Jan 1, 2006

By Bradford C. Wesstrom, Omar Araujo

"Impurities from an electrolytic refinery are typically extracted from the electrolyte utilizing conventional electrowinning cells. These cells are arranged in series with cascading solution flow and are commonly referred to as liberator cells. The Freeport McMoRan Copper & Gold El Paso Refinery has optimized the removal of arsenic in cascading liberator cells by utilizing two separate feed solutions. The primary feed solution is recycled liberator electrolyte and the secondary feed solution is ""neat"" tank house electrolyte. The secondary feed solution is added based on the voltage response across the individual cells utilizing independent variable frequency drive (VFD) pumps. When the voltage across a cell changes, a signal is sent to the VFD pump to maintain a cell voltage of 1.98 volts. By maintaining this voltage the copper content in each cell exits at 2-4 grams per liter. This safely optimizes the arsenic removal as copper arsenides on the liberator cathodes.IntroductionDuring the electrolytic refining of copper, impurities from the copper anode report both to the bottom of the electrolytic refining cell as slimes and to the electrolyte. The impurities which enter the electrolyte are arsenic, antimony, bismuth and nickel. The impurities that report to the electrolyte during the electrolysis process gradually increase. As these impurities increase, they are incorporated into the refined copper cathode. There are many processes that have been used to remove these impurities from refinery electrolytes. Some of them are listed as follows: solvent extraction, ion exchange, hydrogen sulfide reduction, bioreactor, adsorption onto a low - solubility metal-oxide hydrate, adsorption onto activated carbon and EMEW cells. The conventional process used by the copper refining industry for controlling the level of impurities in electrolyte involves multistage electrolytic cascading liberator cells. In these cascading liberator cells copper, arsenic, antimony and bismuth are removed as various mixed deposits from the electrolyte. Removal of these impurities is achieved through an increase in voltage resulting from the depletion of copper in the electrolyte through electrowinning. With this higher voltage, the Group Vb elements, arsenic, antimony and bismuth are deposited on the copper cathode and report as slimes to the bottom of the cells. Nickel is removed in a subsequent process."

Jan 1, 2012

By Shuo Wang, Yu Wang, Bing Xie, Rui Tang, Hong-Yi Li, Kun Wen

"During present converter vanadium extraction process, phosphorus could not be removed from hot metal due to absence of CaO in slag though it is an efficient way for vanadium extraction. In order to improve the phosphorus remove and produce CaO-containing vanadium slag, which could be directly used in subsequent roasting process, during the converter vanadium extraction process, lime dissolution in FeOx-Si02-V203-Ti02 slag was investigated by using a rotating cylinder technique and the slag-lime interface was characterized by SEM/EDS. Results showed that changes in the slag chemistry and phase compositions during the lime dissolution process were similar to that in CaO-Si02-FeOx based slag during the BOF process. The V and Ti in the slag were expected to diffuse into the lattice of2CaO·Si02 solid solution, which formed a rather thinner layer in thickness at the slag-lime interface than that in BOF process, leading to improvement of lime dissolution in the slag.IntroductionVanadium is important material that widely applied in industries. The traditional technique to extract vanadium was to leach vanadium after sodium salt roasting. However, the sodium salt roasting process has several problems including lower yielding rate[!] and environmental pollution[2]. Therefore, the more environment-friendly technique of calcium roasting[3-4] was proposed. In order to increase roasting efficiency of vanadium slag, it is essential to study the dissolution/reaction mechanism between lime and vanadium slag. Many investigations about the dissolution reaction of lime in molten slag have been carried out from the standpoints of rapid slagging to De-Pin steelmaking process[5-6]. However, their studies were focused on BOF slag and the reaction mechanism between solid lime and slag containing vanadium has not been reported yet. In present work, the dissolution process was studied with rotating cylinder technique and the reaction interfaces were observed and analyzed by SEM/EDS to elucidate the dissolution mechanism of lime in vanadium slag. This work was supported by National Natural Science Foundation of China No. 51090382."

Jan 1, 2013

By W. Dutton, D. Simms

"The clearing of tuyeres on copper and nickel converters or similar metallurgical, vessels has, for many years, been done using mainly a manually- operated ""puncher"". One such device is the ""Gaspe Puncher"" developed in 1962 at Noranda's Gaspe Smelter. In an attempt to remove the operator from the cab of the Puncher, and to relieve him of a tedious, uncomfortable job, Noranda's Horne Division, in cooperation with Heath & Sherwood (1964) Limited and the Noranda Research Centre, undertook to automate the Gaspe Puncher used on the Noranda Continuous Smelting Process Reactor.The automated puncher is controlled by a Texas Instruments Model 530C Programmable Controller (PLC). Position measurement and control is done using non-contact position measuring equipment from the Tele-Controls Division of Geodimeter Inc. The entire automation system was installed on an existing Gaspe Puncher with minimum disruption to the operation of the smelting process. The operator's panel allows the user to ""block out"" any individual tuyere, and to select any of a variety of operating modes.The development of the automated puncher is described, and the results of several months operation are given.IntroductionThe tuyeres of copper and nickel converters and similar metallurgical vessels become blocked with solidified material formed by the cooling action of the blowing air. This restricts the converting operation. Clearing these blocked tuyeres has for many years been done mainly using a manually-operated ""puncher"" which uses a hydraulic or pneumatically-operated piston to drive a steel bar into the tuyere. The Gaspe Puncher, developed at Noranda's Gaspe Smelter in 1962 is one such device. It is currently being built and sold by Heath & Sherwood (1964) Limited, under license to Noranda. There are over 200 units in operation world-wide.In an attempt to remove the Puncher operator from the cab of the Puncher, and to relieve him of a tedious, uncomfortable job, and to increase productivity, Noranda's Horne Division, in cooperation with Heath & Sherwood (1964) Limited and the Noranda Research Centre, undertook to automate the Gaspe Puncher used on the Noranda Continuous Smelting Process Reactor. This paper describes the development of the automated Gaspe Puncher, its installation at the Horne Smelter, and the results of its operation after several months."

Jan 1, 1989

By S. S. Babu, T. Hong, T. DebRoy, S. A. David

"Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different temperature regions that may lead to repeated dissolution and growth of inclusions. These phenomena are being studied with the help of computational coupled heat transfer, fluid-flow, thermodynamic, and kinetic models. The results show that the inclusion formation in steel welds can be described as a function of the welding processes, process parameters, and steel composition.IntroductionThe relationship between inclusions and formation of a high-toughness phase, namely acicular ferrite in low-alloy steel welds, is well known (1-4). Past research has focused on maximizing acicular ferrite amount in welds by controlling welding processes, process variables, and welding consumable parameters. Research has shown that there is a complex interaction between inclusion characteristics, prior austenite grain size, and weld metal hardenability. In a low-alloy steel weld, the small addition of titanium lead to a change in the inclusion composition and resulted in a transition in the microstructure from bainitic to acicular ferrite [see Fig. I]. This in turn lead to the best combination of strength and toughness. This paper describes the inclusion formation in low-alloy steel welds."

Jan 1, 1999

By Kurt Westerlund

Three. years operating experience of the FLUXFLOW waste heat boiler (WHB) 20.000 nm /h at Boliden Ronnskar Sweden on a TBRC smelting palena (PbS). Operating experience from the Kivset flash WHB 11.900 nm /h at Samim, Porto Vesme, Sardinia, Italy. Conceptual features of the 93.600 nm3 /h FLUXFLOW (WHB) on the Isasmelt smelting in melt furnace for 180.000 t Cu/a at Mount Isa, Australia.

Jan 1, 1992

By C. Niedersberg, M. K. Almeida, R. M. C. Santana, V. G. Dalenogore

"The major source of environmental pollution in urban areas is the transport sector and its impact on human health and the greenhouse is preoccupying. In many works of literature is monitored the pollutants in urban cities, however in specific areas such as universities, they are scarce. Therefore, the aim of this work is to monitorate the gaseous pollutans in a bus terminal at Santa Cruz do Sul University-UNISC and to develop a control framework of the air quality. Six points were selected for monitoring, being one of them inside a bus. The monitoring of CO, HC and CO2 were carried out on arrival and departure of the bus. Preliminary results conducted in a day of spring showed that the most critical condition was during the night shift, where the concentration of CO (200 ppm) was the highest, caused by the vehicles increase, due to the larger number of students.IntroductionAccording to Mascarenhas et al, 2005, air pollutants are responsible for various effects on vegetation, ecosystems and is recognized as one of major public health problems of today, with harmful effect on humans even at levels considered safe by Brazilian legislation.There are numerous scientific papers linking air pollution with respiratory problems, cardiovascular which hinder the daily life because many of these diseases are chronic and may even lead to death, as was noted by Brook et al, 2004.There is a significant increase in the last decades of emissions to air resulting mainly from human activities. Already being observed the relationship of these emissions with the change in global climate, IPCC, 1995.They are a multitude of pollutants from the atmosphere, and its sources and its effects. The effect of Greenhouse gases (GHG), representing less than 1% of the gases in the atmosphere, controlling the flow of energy in the atmosphere. The increase in emissions of greenhouse gases is affecting the Earth's average temperature, which depends on the balance between these flows, in particular the flow of solar radiation reaching the surface and the flow of infrared radiation sent into space.One of the main greenhouse gases to this imbalance is the gas methane (CH4). Methane is produced by anaerobic decomposition of organic substances, through the action of bacteria metanogenic conditions that require highly reduced to its growth. This gas is released into the atmosphere mainly by transport diffusive by aerenchyma (vascular tissue) plant and also by diffusion through the water slide. (Bont et al., 1978)."

Jan 1, 2008

By Jeffrey Shepherd, Scott R. Smith, Eduard Guerra

"Electrochemical and spectroscopic evidence for the dissolution of a Au electrode by meso-2,3- dimercaptosuccinic acid (DMSA) from an acidic LiCl04 electrolyte is presented. Near the potential of zero charge, DMSA was determined to form a stable layer on the metal surface but at more anodic polarizations, DMSA was displaced from the metal through an oxidative process. The anodic displacement of the layer from the electrode resulted in a small amount of Au that was detected in the electrolyte using atomic absorption analysis. The extent of Au dissolution, was monitored while holding the potential of the electrode for 24 hours at the thermodynamic Eo/H,O in LiCl04 electrolytes containing 10 mM DMSA. This routine resulted in detectable quantities of a soluble Au-DMSA complex in the electrolyte and the greatest leaching was observed at a pH = 2.0. At room temperature, the leaching rate was stable at 10.9 µg cm·2 hr·' however, upon increasing the temperature to 50.0°C, the rate of Au dissolution increased yielding an average rate of extraction of 40.1 µg cm·2 hr- 1. Interestingly, after the first 12 hours of leaching at 50.0°C, the leaching current decreased dramatically suggesting surface passivation which prevented further Au extraction. The implications of this process in the industrial leaching of Au will be discussed.IntroductionThe use of cyanide in the industrial process of leaching Au from ores has raised concerns regarding both operational safety and environmental issues surrounding the disposal of spent leaching eftluents in tailings ponds. Depending on the chemical nature of the processed ore, the spent solutions that are released into the tailings ponds can contain toxic cyanide, either dissolved or complexed with different metals and may pose serious risk to wildlife as well as freshwater contamination to nearby water systems. Because of these issues, some recent studies have focused on the exploration of more environmentally-friendly molecules to selectively leach Au with appropriate kinetics. However, to effectively leach Au into an aqueous solution, a suitable ligand that reacts to form a stable chemical bond with Au is needed to form soluble Au complexes that can be later recovered [I]. Recently several sulfur bearing alternatives have been shown to leach significant quantities of Au in aqueous solutions. These include thiourea [2], thiocyanate [3], and thiosulphate [4]. However, alkylthiols are also known to quickly form a stable covalent Au-S bond [5], but have been relatively understudied in term of their ability to leach Au in solution, even though some short chain thiols are water soluble and relatively nontoxic."

Jan 1, 2012

By Guo-hua Bai, Hong-jing Yuan, Qian Li, Yong-bin Yang, Tao Jiang, Yan Zhang

"The effect of different additives on the bio-oxidation of arsenic-bearing gold ores has been carried out to solve the problems such as long period of leaching, low oxidation rate. The oxidants strengthen the cathodic reaction and thus improve the leaching rate by the increase of electron transfer. Meanwhile, silver catalysis is also effective for the decomposition of arsenicbearing gold ores due to the strengthening of anode reaction. Co-intensification by oxidants and Ag (I) is more efficient to the bio-leaching and the conversion of As (III) because the anode and cathodic reaction of biological oxidation of sulphide ores were both strengthened. The leaching rate reached to 63.94% after bio-leaching 13days by co-intensification of Ag (I) and Fe(III).IntroductionWith the worsening global ecological problems and the gradual exhaustion of available gold resources, metallurgical technology of refractory gold ore has received more and more attention and become possible due to its good advantage of the economic effects and negative effects to the environment. Refractory gold ore, the direct cyanide leaching rate of that is defined as less than 70%, has become an important raw material in gold extraction industry, in which sulfide bearing gold ore represents a large proportion, pyrite and arsenopyrite (FeAsS) is a common gold-bearing mineral. Since the gold is often encapsulated in the crystal lattice of these minerals, destruction or alteration of the ore to liberate the submicron and/or structurally bond gold is necessary[l]. Even if the ultrafine grinding approach also is generally not sufficient for these refractory ores and additional techniques like roasting, pressure oxidation and bacterial oxidation are used to liberate the gold [2]. In the three pretreatment processes, bacterial oxidation is characterized by its new ideas, low cost, no pollution, simple equipment and operation, high leaching index and become the most promising process which has received much attention over time [3-5]. But its further application is limited by some of its own shortcomings, such as long pretreatment time and the toxic effects of arsenic to bacteria on bio-leaching limit."

Jan 1, 2013

By B. Boryczko, J. Norwisz, Jose Escobedo Bocardo, Z. Kolenda, A. Holda

"Classical thermodynamic analysis of any thermal and chemical process is usually based on the first law of thermodynamics. Such an approach is not sufficient when deeper understanding of the nature of each elementary process is required. The use of the first and second law of thermodynamics together is necessary to solve practical process more effectively. Enthalpy and exergy balances allow to enhance our understanding of thermal processes especially when cumulative consumption of energy and exergy is calculated. To ensure reliability of such an analysis the least squares method for adjustment of mass balances of principal chemical elements has been applied and described in detail. Numerical analysis has been carried out to compare two different processes of copper production – shaft furnace and flash smelting.IntroductionClassical thermodynamic analysis of any technological process is usually based on the First Law of Thermodynamics in the form of energy (enthalpy) balances. Such an approach is useful in engineering practice as it makes analysis easier in the global scale neglecting modeling of the elementary processes, allows calculation of the thermal efficiency and makes possible to control quality of the measurement results. Additionally, graphical presentation of the energy balance is simple in the form of Sankey diagram.In the case of aluminum electrolysis process, design of the new electrolyzer or its modernization is always based on the enthalpy balance.However, deeper thermodynamic analysis leads to the conclusion that such an approach is not sufficient. The First Law of Thermodynamics guarantees the exact equivalence of the various forms of energy (allowing all forms to be measured in the common unit such as joules) but it does not guarantee interconversibility. Thermal energy (heat) is in a peculiar and unique position, for whereas all other forms can be completely converted into thermal energy, the reverse process id impossible, only a portion of the heat can be converted into mechanical energy. Explanation comes from application of exergy balances. As we know exergy expresses the amount of mechanical work necessary to produce a material in its specified state from components common in the natural environment, in a reversible way, heat being exchanged only with environment [1]. Consumption of exergy connected with the fabrication of some considered product appears not only in the plant manufacturing the product, but also in all plants delivering raw materials for the final production process"

Jan 1, 2008

By Shan He, Qiang Wang, Xuling Chen, Min Gan, Lishun Yuan, Xiaohui Fan

"The sintering properties of vanadium-titanium magnetite concentrate(VTC) was studied in this paper. Through the optimizing the sintering process of VTC, the suitable granulation moisture and coke proportion were determined. The sintering velocity decreased from 23.05 mm/min to 18.22 mm/min. With the increase of VTC proportion from 0 to 46%, the specific productivity and tumbler index were respectively decreased from 1.55 t/(m2·h) to 1.21 t/(m2·h), and 62.93% to 57.73%. The temperature of liquid phase formations of mixtures increased, the amount of liquid lowered, and the content and sharp of sintering mineral gradually changed with the increase of VTC ,these lead that sinter quality became worse.IntroductionIn recent years, the steel industry of China is developing rapidly. And the steel production was 627 million tons in 2010. At present, the resources of vanadium-titanium magnetite concentrate(VTC) was about 14.4% of the total national iron reserves of China[1]. VTC has been used as sintering material by Magang, Chenggang and Pangang. The amount of VTC in Pangang is maximum. However, there exist many problems in VTC sintering, which involve in high specific productivity, bad sintering tumbler strength and high energy consumption[2~5]. That’s why the proportion of VTC is limited in sintering.The high quality of iron ore resources is worse in China. Therefore, it’s necessary to study the properties of VTC sintering, and to find out the reason how the VTC ratio affect the sinter performance. Purpose and significance of the research is to get high-quality sinter with the proportion of VTC greatly raised."

Jan 1, 2012

By Xi-Shan Li, Qian Li, Yong-bin Yang, Li-na Cui, Tao Jiang, Jie Ge

"With regard to control environment pollution in the roasting pretreatment of sulfur & arsenic-bearing gold concentrate, roasting of double-layered pellet was proposed. In the paper, the characteristics of double-layered pellet roasting were studied. Removal and solidification rates of sulfur and arsenic were investigated as primary factors. The result indicated that the removal and solidification rates of arsenic reached up to 95.91 % and 98.95% while the sulfur was 97.19% and 97.90% respectively on the premise of adopting slaked lime as solidified agent at temperature of 6000, the package proportion of 2.14 and roasting time of 3h. However, pyrite and arsenopyrite were transformed to hematite and magnetite and product of solidification mainly consisted of calcium sulfate, calcium arsenate and calcium sulfite within optimum roasting parameters.IntroductionUtilization of refractory gold resources has been gradually concentrated on with the depletion of the gold resources which are easy to deal with in the world [1]. Sulfur and arsenic-bearing gold ore is a typical refractory gold one, in which ultrafme gold is encapsulated in the structure of metal sulfide minerals [2,3], so it gives poor recovery through direct cyanide leaching. These refractory ores need pretreatment before the process of cyanide leaching to undermine lattice structure of pyrite and arsenopyrite containing gold [4] so that the gold could touch with cyanide solution [5]. Among various methods of pretreatment, conventional roasting method is most effective, but this process generates gases such as S02 and As203 harmful to environment. Therefore solidification roasting was proposed to solve this problem occurring in the conventional roasting at the end of last century."

Jan 1, 2013

By Dennis J. Kemp

Laterite projects are found in the tropical and sub-tropical regions of the world. As a result severe meteorological situations accompany such projects, often in regions of high seismic activity and political uncertainty. Frequently, socio-economic development supported by political interest is a major driver for development, while environmental protection imposes numerous stresses on the project. This paper will review and examine the many social, environmental, technical and financial issues that a mining and extraction process is subject to during development. The options that must be evaluated will be discussed in the context of sustainable development. Issues of project standards and cultural impact through to long-term issues such as greenhouse gasses and climate change will be assessed in redirecting project environmental norms. Although a rationale for sustainable project can be developed many long- term uncertainties around issues remain. Keywords: sustainable development, communities, social issues, standards, energy, waste management, consultation, agreements

Jan 1, 2004