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By Tomoya Nihei, Hiroshi Hayashi

"A novel selenium removal process called Recycled Green rust/Ferrite Process is developed by MMC. In this process, a mixed Fe2+-Fe3+ hydroxide compound, green rust (GR), reduces selenate to elemental selenium, while GR is consequently oxidized to magnetite Fe3O4. Sequencing batch-mode experiment showed that the residual selenium concentration gradually decreased with the number of batch test increased. Stable selenium removal was achieved when the number of batch test exceed 15 times. Optimum selenium removal ratio reached 99.95% where initial Se concentration 2.1mg/L decreased to 0.001mg/L. Furthermore, the continuous feeding test carried out through a pilot-scale plant with a feeding capacity 600 L/hr. Approximately 860-hour-feeding test was carried out for the selenium-contaminated groundwater which had an averaged selenium concentration of 0.88 mg/L. Selenium concentration in the effluent from thickener maintained less than 0.01 mg/L (selenium removal rate of 99%) until a net operating time reached 800 hours.IntroductionJapan is one of the largest producers of selenium, and thus there are potential environmental impacts of selenium on soil and aquatic environments. The Mitsubishi Material Corporation (MMC) owns some real estate properties whose soil and groundwater was polluted by selenium and other heavy metals. These sites include former industrial plants: a smelter for nonferrous metal and a fabricating semiconductors and pigments. Selenium in aquatic environment commonly exists in four oxidation states, namely, VI, IV, 0 and -II. Selenate ion (SeO4 2-), the most oxidized form of selenium, and selenite ion (SeO3 2-) are highly soluble and mobile. Elemental selenium (Se0) is insoluble in water and therefore has much lower toxicity. Because selenium is carcinogenic and teratogenic at high concentration, the national effluent standard in Japan is fixed at 0.1 mg/L and the environmental standard at 0.01 mg/L. Although there are several selenium removal techniques, the most conventional process is coprecipitation with a ferric hydroxide because of its simplicity and low cost. It is known that selenite is adsorbed strongly on the surface of ferric hydroxide, but selenate is not. The low affinity of selenate on oxide mineral surfaces was demonstrated by the fact that selenate could be easily displaced by adding competing anions, particularly sulfate ion. Selenate removal from polluted water is one of the most difficult techniques, and more effective methods are desired. MMC developed a novel selenium removal process [1]. In this process, the concentrated slurry that contains Fe(II)-Fe(III) hydroxyl-salts known as Green Rusts (GRs) contributes to selenate removal. The main components of the iron precipitate in the reactor are GRs and their oxidation product, magnetite (Fe3O4)."

Jan 1, 2008

By Yuan-bo Zhang, Gui-hong Han, Yan-fang Huang, Tao Jiang, Guang-hui Li

"Under isothermal conditions, the reduction behavior of oxidized pellets balled with bentonite was investigated with CO-CO2gas mixers in the temperature range from 900°C to 1100°C. The whole reduction of oxidized pellets was followed up by means of weight-loss technique. And the swelling index of pellets was examined by visualizing physical changes of pellet in a horizontal tube furnace. The results present that the reduction rate of oxidized pellets is increased with the increase of reduction temperature. While the swelling index is firstly increased and then decreased with the increase of reduction time and reduction extent, which can be ascribed to the disruptive stresses induced during the transformation of hematite to magnetite. The maximum swelling index is gradually increased with the increase of reduction temperature and CO content.IntroductionWith the rapidly development of iron and steel industry, direct reduction iron has been considered as one kind of high quality burdens in electric furnace steelmaking [1]. At present, ""Two-step"" coal-based direct reduction process, which employs oxidized pellets as raw materials, has been used in industrial production [2]. The reduction behavior of iron ore oxidized pellets has been becoming one of the most frequently studied topics in extractive metallurgy[3]. The heat and mass transfer in direct reduction processes results in a series of stepwise reduction reaction (hematite--magnetite--wustite--iron), accompany with the volumetric swelling of pellets[4]. A lot of literatures have been reported on the reduction model of ferrous oxides and swelling behavior of pellets. A. A. El-Geassy K, et.al [5-7] revealed that the reduction process was controlled by chemical reaction at early stage by employing pure Fe203 as raw materials and CO as reduction gas. Chen Y [8] made research on the reduction kinetics of porous oxidized pellets and obtained the rate constant and activation energy of at different reduction stage. In addition, the swelling and disintegration of iron ore pellets was affected by chemical composition of pellet and reducing parameters, which have been studied by numerous investigators [3,9, 1O]."

Jan 1, 2013

By Katsunori Yamaguchi

A new technique for the removal of tramp-elements from steel scrap has been required from the viewpoint of saving energy and protection of environment. In order to obtain fundamental information on the removal of copper, tin and zinc from molten iron, the extraction method by using of phase separation in the liquid Fe-Pb-C system was investigated at 1453K A mixture of iron, lead and carbon melted in a carbon crucible separates into two phases of lead and iron containing carbon. The compositions on the miscibility gap in' the Fe-Pb-C system are 95A%Fe-4.5%C-0.l %Pb and 99.9%Pb-0.1 %Fe. The distribution ratios of copper, tin and zinc between the lead and the iron phases, Lx=[masso/uX in molten Pb]/(masso/uX in molten Fe), are 2.2, 2.2 and lA, respectively. Seventy percent of copper and tin from iron scrap can be eliminated with comparable lead addition. Gold, silver and palladium are enriched in the lead rich phase, on the contrary platinum and rhodium are more distributed to the iron rich phase than to the lead phase.

Jan 1, 2003

By Katsunori Yamaguchi

A new technique for the removal of tramp-elements from steel scrap has been required from the viewpoint of saving energy and protection of environment. In order to obtain fundamental information on the removal of copper, tin and zinc from molten iron, the extraction method by using of phase separation in the liquid Fe-Pb-C system was investigated at 1453K. A mixture of iron, lead and carbon melted in a carbon crucible separates into two phases of lead and iron containing carbon. The compositions on the miscibility gap in the Fe-Pb-C system are 95.4%Fe-4.5%C-0.1 %Pb and 99.9%Pb-0.I%Fe. The distribution ratios of copper, tin and zinc between the lead and the iron phases, Lx [mass%X in molten Pb]/(mass%X in molten Fe), are 2.2, 2.2 and 1.4, respectively. Seventy percent of copper and tin from iron scrap can be eliminated with comparable lead addition. Gold, silver and palladium are enriched in the lead rich phase, on the contrary platinum and rhodium are more distributed to the iron rich phase than to the lead phase.

Jan 1, 2003

By Jeremy Gregory

The disposal of end-of-life electronics is an issue receiving increasing scrutiny. This paper evaluates several alternatives for recycling cathode ray tubes (CRTs) within monitors and televisions. The primary recycling options for the glass, reuse in new CRTs or as a smelter flux, are examined from economic and environmental standpoints. The economics are modeled using a cost model that includes dependencies on processing costs, transportation logistics, and incoming material composition. The environmental consequences are modeled using life cycle assessment methodologies to determine the energy embodied in each processing alternative. Results map out preferred processing alternatives across a range of technological and operational conditions. The results indicate that economic costs and environmental consequences are heavily impacted by transportation. The preferred destination of CRT glass for a recycler is highly dependent on the proximity of the consumer to the recycler, although it is generally economically advantageous for the recycler to extensively dismantle the CRTs.

Jan 1, 2006

By J. R. Sarazin

Density driven convection during solidification has been recognized for some time to result in macrosegregation particularly when lower density alloying elements are rejected into the interdendritic liquid. The resulting segregates are commonly referred to as channels, freckles or A-segregates. Buoyancy driven convection leading to channel formation has been examined in three model systems possessing somewhat different materials parameters. They are the Pb-Sn eutectic system, the transparent aqueous-salt NH C1-H 0 4 2 eutectic system and the transparent organic succinonitrile-ethanol monotectic system. Convection in these systems is controlled by a balance of buoyant and viscous forces, which are strong functions of composition and temperature. Composition, temperature and flow velocity were measured and elimination of channels through heavier ternary additions is discussed.

Jan 1, 1991

By Pertti Pekkala

Outokumpu has 25 years of experience in the SX area. The development of the solvent extraction plants responds to an ever increasing demand for lower operational costs wd for adaptability to process disturbances with minimized risks. In this paper the features of the VSF ("Vertical Smooth Flow") SX technology are described, such as the separated pumping and mixing, the homogenous gentle mixing, the droplet coalescence and the ultra pure settling. A major advantage of the mixing technology is the high stage efficiency of above 99 per cent. The connection between this and some features of the settler front section is clarified. The present design of VSF plants is based on experience of existing operations at, for example, Zaldivar, Radomiro, Morenci, Kokkola and Harjavalta. These production plants cover a unit capacity range of 60 to 3,600 m3/h expressed as a total flow. It is evident that there are no restrictive factors to increase the total flow up to 5,000-6,000 m3/h by introducing the VSF technology. The copper SX technology has a long history reflecting many individual features of the separate copper SX plants. Still it is necessary to verify all actual running parameters by pilot tests taking into account impurities, chemicals used etc. The design of SX plants is not only about the delivery of equipment but also a process concept, and it is best tailor-made and adapted to specific local requirements.

Jan 1, 1999

By James M. Lockwood

"Eureka Technology has developed and patented a technology for the recycling of EAFD. Through this process all constituents of the material become salable commodities or are returned to the steel making process. In transforming the EAFD ""waste"" stream into a ""process"" stream the Steelmaker eliminates potential liabilities and the uncertain future of current processes while further reinforcing its role as a recycler. This is a cost-effective and energy efficient technology that combines hydrometallurgic and electrolytic processes resulting in the recovery of salable metals. For instance, unlike pyrometallurgic processes, zinc is recovered in metallic form and no elements are volatilized. This on-site operation also eliminates expensive transportation costs. In summary this technology reduces the cost of dealing with EAFD by recycling material currently being landfilled.IntroductionWorld crude steel production reached a new record level in 2007 - 1.34 billion tons of which 31% was produced by EAF steel makers [1]. This resulted in the generation of over 6 million tons of EAFD. This steel byproduct contains significant amounts of lead, cadmium and other hazardous metals. In the United States the Environmental Protection Agency (EPA) has designated EAFD a hazardous waste (EPA waste code K061). With over 50% of steel production in the US coming from EAF steel making this byproduct represents the single largest source of solid hazardous waste generated."

Jan 1, 2008

By Chen-Ming Kuo, Esher Hsu

"The importers and manufacturers who import or produce products with packaging containers are charged a recycling fee in Taiwan. The amount of waste packaging containers used for calculating the recycling charge is based upon the amount declared by importers and manufacturers which might be underestimated. This study aims to estimate the amount of waste packaging containers generated by households in Taiwan and also explores its distribution. The sampling survey and ratio estimation are conducted for estimating the recycled amount; while the refuse sampling method for municipal solid waste composition is employed to estimate the un-recycled waste packaging containers. The estimated total amount of waste packaging containers in 2011 generated by households in Taiwan is 696,511 m.t., of which, 79.49% of the waste packaging containers were recycled and 20.51 % were landfilled or incinerated. This study shows that the amount of waste packaging containers declared by importers and producers is underestimated around 20%.IntroductionWaste packaging containers including iron cans, aluminum cans, glass bottles, plastic containers, paper containers, aluminum foiled paper packs are officially announced to be recycled in Taiwan. In order to create the economic incentive for raising recycling performance, associated manufacturers and importers are charged a recycling fee to subsidize recyclers. The amount of packaging containers declared by importers and manufacturers is used for calculating the recycling charge and recycling rate. The importers and manufacturers might underreport their producing (importing) amount to pay less recycling fees. Therefore, the estimated waste packaging containers based upon the amount declared by importers and manufacturers is usually underestimated. Related previous studies about waste packaging containers recycling in Taiwan are done by Hsu and co-workers [1-4]. Hsu and Kuo [1] estimated total production values of recycling and evaluated the performance of recycling performance based upon the estimated production values. Hsu and Liu [5] provided a cost analysis of recycling for waste packaging containers in Taiwan. Bor, Chien, and Hsu [2] presented a market-incentive recycling system for waste packaging containers in Taiwan. Hsu and Kuo [4] provided an amending mechanism for product charge and recycling subsidy in response to the social economic changes for waste packaging containers recycling. Lee and Hsu [ 6, 7] explored the distribution, fee rates, and collection rate of waste containers. This study aims to estimate the amount of waste packaging containers generated by households in Taiwan and also explore its distribution."

Jan 1, 2014

By Renxing Li, Yongyong Gong, Yufeng Cheng, Zhenxing Yin, Xin Cao, Qijie Zhai

"This paper investigated the refinement effect of pulse magneto-oscillation (PMO) on the solidification structures of medium carbon steel S45C in metal mould. The induction coil was positioned at the middle of ingot. The results showed that solidification structure of the treated ingots was remarkably modified with a transformation from well-developed dendritic structures to small dendritic structures or globular structures compared to the untreated ingot. The area fraction of modified microstructure regions reached more than 80 percent. A further experimental investigation had been done to understand the influence of refinement effect on the solidification structure under different mould size. Theoretical analysis demonstrated that the mechanism for the refinement of solidification structure was that PMO promoted nucleation near the mould walls and changed the interface temperature gradient and concentration gradient in liquid, eventually leading to a transition from the columnar crystals to the equiaxed crystals.IntroductionIn recent two decades, the electromagnetic processing of materials (EPM) has been widely used in many fields such as ironmaking, steelmaking, and solidification processing [1-6], where EPM can control melt flow, modify melt shape, reduce macro-segregation and refine microstructure. Pulse magneto-oscillation [7-9] (PMO), as a novel technique of EPM, has a remarkable effect on grain refinement and high potentiality to be used in industrial production. Compared with ultrasound refinement technique, PMO can be easily employed to metal solidification processing for long time in no contact with hot metal liquid by using a water-cooled coil. Another important advantage is that PMO needs smaller energy compared to pulsed magnetic field which needs a very high current to obtain a strong magnetic field to get a satisfactory effect. These advantages mentioned above are beneficial for industrial application, which make it potential to be widely used in future. Gong et al. [7] have studied the refinement effect of PMO on pure aluminum and find that PMO can significantly modify the solidification structure of pure aluminum. Li et al. [9] have reported the effect of temperature field on solidification structure under the influence of PMO. On the basis of these works, this paper has studied the effect of PMO on solidification process of medium carbon steel S45C in a metal mould, which can also provide some information for industrial application of this new technique."

Jan 1, 2012

By Katsumi Ogi, Hiroto Uchida, Masamitsu Sato, Atsushi Itsuki

"(BTMSE)Ag(hfac) (BTMSE = trans-bis(trimethylsilyl)ethene) was chosen as a suitable precursor for the XeCl laser (308nm) MOCVD of Ag. Iso-propanol solution of (BTMSE)Ag(hfac) was used as a liquid source for the liquid delivery method, high deposition rate 9nm/min at substrate temperatures of 100°C and 120°C were obtained at the vaporizer temperature of 90°C. This deposition rate is three times faster than by conventional bubbling method and life of the source and reproducibility of the deposition were also improved. Electric resistivities of the laser deposited film shows significantly low resistivity of 10-6Q-cm compared to 1 o-3Q-cm of thermal MOCVD film. These results indicates that the laser MOCVD is one of the effective method for the preparation of the high quality silver film.IntroductionSilver films are a potentially important metallization material in electronic and photonic devises due to their lowest resistivity (1.6µ0-cm) among the metals, high optical reflectance and chemical stability. The MOCVD technique has advantages to sputtering or evaporation in the point of conformal growth and better coverage on sharp steps and narrow gaps[l-2]. For MOCVD application, silver precursors must have sufficient vapor pressure without decomposition at their evaporation temperature. To achieve stable precursor gas supply, liquid delivery of precursor material is promising[3-4] especially for materials that have not enough heat stability and high vapor pressure like silver complexes[S-10]. Several new silver complexes for MOCVD and UV irradiation effect to their MOCVD silver film quality were reported by same authors[5]. In this paper new solvent system for liquid delivery system of silver MOCVD were investigated to suite XeCl(308nm) laser MOCVD application."

Jan 1, 1998

By Min Chen, Lei Xu, Liang-yu Jin, Xue-liang Yin

For the purpose to reduce the high cost and heat storage loss of Al2O3-MgO bricks used as ladle linings, Al2O3-MgO-CaO bricks with lower theoretical density were fabricated and the densification behavior as well as mechanical property of this refractory was investigated. With addition of CaO, the initial sintering temperature of Al2O3-MgO refractory was decreased from 1300 to 1100°C associated with the expansive formation of CA2, and the compressive strength was also enhanced owing to the formation of bond linkage between CA6 and spinel. At high temperature, brick with 4% CaO content showed poor sinterability with high porosity because of the formation of platelet structure of CA6 grains, whereas brick with 8% CaO content was well sintered with higher relative density but lower bulk density than Al2O3-MgO brick, indicating that the densification as well as lightweight of Al2O3-MgO refractory was effectively promoted.

Jan 1, 2015

By Yuanbo Zhang

Zinc leach residues produced by hydrometallurgical zinc plants contain many valuable elements (zinc, iron, lead, gallium, indium silver, etc), while they have not been utilized effectively hitherto. In this paper, a new process of flotation-reduction roasting-magnetic separation to recover these valuable elements from zinc leach residues is developed on a basis of mineralogy investigations of them. The results show that silver concentrate with grade of 4321.6 g/t and recovery of 80.69% have been obtained, using 1750 g/t Na2S as conditioner, 750 g/t ammonium dibutyl dithiophosphate and SN-9 (assistant collector) as combined collector and 100 g/t terpenic oil as frother, if zinc leach residues with 523 g/t silver are floated at pH = 5.0. When the flotation tailings are subjected to reduction roasting at 1100? for 2 h, the volatilizations of zinc, lead and indium are over 96%. After roasted products are treated by wet-grinding and magnetic separation, the grade of gallium and gallium in the concentrates achieved respectively reaches 1805 g/t and 1536g/t, and the recovery of them is high to 94.67% and 93.20%, respectively.

Jan 1, 2006

The present work is mainly focused on developing intermetallic inert anodes for aluminum electrolysis. The anode alloy based on Al-Ti-Cu system was prepared by casting, followed by the application of a protective coating. Behaviour of corrosion and the passivation under anodic condition was characterized using the electrochemical and microscopic techniques. The results obtained clearly demonstrate that the oxide coating can provide good corrosion resistance via surface passivation of alloy anodes, rendering them inert in cryolite melt.

Jan 1, 2006

By Fanke Meng

Electrolyzing oxides of titanium, aluminum and niobium could prepare high-Nb bearing TiAl alloy (Ti-45Al-9Nb) at 1500°C. The chosen electrolysis voltage is 3.5V, which is lower than reducing voltage (~4.7V) of electrolyte CaF2, but higher than that of titanium, aluminum and niobium oxides. The investigation shows that compared with traditional methods, this method for preparing high-Nb bearing TiAl alloy is of many advantages such as few steps, friendly environment, low energy consumption, low cost and high current efficiency.

Jan 1, 2009

By Tomás Vargas

The catalytic role of Thiobacillus ferrooxidans in the dissolution of chalcopyrite was studied by leaching pure massive samples of this sulfide with a pure strain of Thiobacillus ferrooxidans (ATCC 19859). Monitoring of the bacterial activity showed that an important fraction of the total bacteria generated during leaching remained attached to the chalcopyrite surface. Bacteria grown in the system, which were the offspring of bacteria adhered to chalcopyrite, was well explained as the result of the utilization of ferrous ion and sulfur as energy sources. The potential for indirect and direct action was fully utilized by the existing bacteria and the leaching process was controlled by the kinetics of chalcopyrite dissolution.

Jan 1, 1990

By Pekka Taskinen, Hannu Johto

"Copper sulfide concentrates often contain impurities such as lead and iron. The phase stabilities of the sulfide impurity systems in metallurgical process conditions are in many cases unsatisfactorily known. Thermodynamic information of a system gives better understanding of its behavior of metal making processes, but also has effects on the economic and environmental factors of the production process. In this study, isothermal equilibrium and quenching experiments of the stable phases of the system Cu2S-FeS-PbS at 700 and 900 °C were carried out and based on the experimental results, Gibbs triangle of equilibrium phases of the system was outlined.IntroductionThe knowledge of stabilities of phases and the thermodynamic properties of many sulfide systems in the temperature range of 500-1200 °C are quite limited. Especially, the knowledge of liquidus surfaces of multicomponent sulfide systems is essential for making many metallurgical processes more environmental friendly and allowing the utilization of complex concentrates. In this work, the aim was to investigate the phase stabilities of the quasiternary system CU2SFeS- PbS using evacuated silica ampoules. Of greatest interest were the properties of the liquidus surface in the system, in order to be able to predict better the formation of a liquid phase in metallurgical processes."

Jan 1, 2012

By A. René Silva

The separation of Fe(III) from simulated Ni(II) solutions using different ion exchange resins was studied. The resins tested included cation exchangers with sulfonic and carboxylic groups and chelating resins with iminodiacetic, aminophosphonic, and mixed sulfonic and phosphonic groups. The dosage of resins was varied from 0.1 to 0.5 g/mL to study the impact of resin type and dosage on iron separation from simulated nickel leach solution containing 25 g/L Ni(II) and 25 g/L Fe(III) at pH 1.5. Also, the effects of different metal ion concentrations, Fe (III):Ni(II) ratios in solution, pH, and adsorption times were investigated. Experimental results demonstrate that all the chelating resins selected favored the adsorption of Fe(III) over Ni(II) with high Fe(III) loading. Soft cation exchange resins also favored the adsorption of Fe(III) over Ni(II), but no significant Fe(III) loading was observed. In contrast, strong cation exchange resins did not show adsorption preferences. The most efficient separation was observed using resin with aminophosphonic groups at resin dosage of 0.2 g/mL, having a Fe(III) adsorption over 94% and Ni(II) adsorption below 5%.

By E. Ilgar

"Deposition studies were conducted in acid copper electrolyte to determine the influence of chloride ions on cathode morphology. A statistically designed screening test was carried out in the absence and presence of 20 ppm CI- using a three factor, two level factorial design, in an electrolyte containing 36 gl'! Cu2+ and 150 gl-! H2S04, The independent variables evaluated were agitation; current density and temperature and their influence on surface roughness was determined. The copper deposited at current densities where activation was the primary control mechanism appeared similar in morphology whether stirring was used or not. The addition of 20 ppm CI- to the electrolyte gave rougher deposits under the same conditions. In the mixed control regions, considerably rougher, dendritic deposits were obtained when CI- was present. Agitation was effective in reducing the copper surface roughness both in the apparent activation and mixed control regions in the presence ofCI-. The results of this study showed that 20 ppm Cl- polarized the copper deposition at low overpotentials but caused depolarization at higher overpotentials.IntroductionChloride ion is inherently present in copper electrolyte, either as an additive or from other sources such as make up water. The behavior of the chloride ion is well documented in electrorefining operations, but its role in copper winning is less obvious. However in both cases there is evidence that cathode growth and solution chemistry are strongly influenced by its presence. The mechanism and electrochemical action of the Cl"" have been shown to be very complex, therefore a better understanding of its influence on electrocrystallization is essential for improved cathode deposit growth control. It was proposed that Cl"" polarizes the copper deposition reaction at low concentrations due to CuCI formation but depolarization occurs at higher concentrations due to the formation of a soluble CuCI2"" complex [1,2]. Franklin [3] reviewed the mechanism of additives in the electrodeposition process and proposed that the Cl"" complexed with copper, adsorbed on the cathode as an induced anion leading to an increase in the reduction rate. At cathodic overpotentials less than 100 mY, lppm NaCl had a polarizing effect, i.e. an increase in impedance of the charge transfer step. At higher Cl"" concentrations up to 100 ppm, depolarization occurred as evidenced by a decrease in impedance, which was attributed to soluble cuprous complexes [4]."

Jan 1, 1997

By Oliver Zach

To know as much as possible about the condition of the refractory material (lining thickness, slag layer, build ups, ...) in an high temperature furnace is very important due to the safety and economic impacts. The new CONSCAN system offers the possibility to measure the inner surface of an furnace, and based on this results to calculate the thickness of the refractory lining, slag layer, build ups,.... The CONSCAN System provides this results as figures and graphics. This system is also working under hot conditions so it is not necessary to cool down the furnace. Based on these results the process control and the refractory lining concept could be optimized for maximum campaign life of the furnace.

Jan 1, 2006