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By Courtney A. Young

All cyanide species are considered toxic and can be found predominantly in industrial effluents generated by metallurgical operations. For example, cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent water contamination. Various methods of cyanide remediation by separation and destruction are available, but certain methods are more effective than others depending on the cyanide species being remediated. Photolytic destruction is regarded as the one technique that is independent of the cyanide species involved. The destruction of various cyanide species by several photolytic techniques has been investigated for the past few years. A literature survey suggests heterogeneous photocatalysis with anatase (TiO,) should behave similarly to homogeneous photolysis with hydrogen peroxide (H,O,) since proposed reaction mechanisms for both processes involve hydroxyl radicals. However, experimental evidence on a suite of cyanide species suggests otherwise. A new mechanism for the photocatalytic destruction of cyanides, especially SAD species, is therefore proposed.

Jan 1, 1998

By M. A. Usman, E. I. Akpan, S. O. Adeosun

Preliminary studies on the extraction and characterisation of biodegradable lignin from palm oil fruitbunch (POFB) for carbon fibre production has been conducted. Centra lComposite Design was used to determine the optimum operating conditions for maximum yield and properties of the extracted lignin. Soda concentration (1–3 wt/vol%), temperature (50–90 °C) and reaction time (20–30 min) were analysed using Rcore software. Experimental results show that using reaction temperature of 90 °C, time of 30 min and 3 wt/vol% soda concentration yields 3.3 g of lignin from 30 g of the POFB. The path of steepest ascent from ridge analysis shows that with temperature of 130 °C, time of 40 min. and soda concentration of 3. wt/vol%, 8.7 g of lignin can be extracted from 30 g of POFB. Analysis of FTIR and SEM show that the lignin has the same structure in all cases with minimal impurities.

Mar 1, 2017

By G. T. Lapidus, O. J. Solis-Marcial

"The oxidative dissolution of copper from refractory minerals, such as chalcopynte, represents a technological challenge that has occupied hydrometallurgists for more than half a century. Innumerable processes have been suggested, but the majority operates at high temperatures or employs corrosive media. The origin of this refractory nature is the formation of passivating phases of iron(III) or copper. One option is to add non-corrosive ligands that complex these metal ions, thereby facilitating their dissolution. In the present work, the effect of acetone in sulfuric acid solutions was studied. The initial experiments were on chalcopynte carbon paste electrodes using cyclic voltammetry, where greater reactivity was observed. Later, leaching tests with hydrogen peroxide, cupric sulfate and ozone and, as oxidants, were performed. High extractions were achieved in three hours at 50°C. The solid residues contained the iron in the form of Fe203 and FeOOH.IntroductionChalcopyrite is the most important mineral of polysulfide copper ores [1] and accounts for approximately 70% of the world's copper reserves [2]. Currently, the copper present in chalcopyrite is extracted mainly by pyrometallurgical processes, which generate environmental concerns because of the formation of SO2 gas and submicron particulates [3]. The development of a less aggressive hydrometallurgical process for the extraction of copper would constitute a possible solution to these problems. For that reason, studies of the dissolution behavior of chalcopyrite are of great technological importance [4], However, the proposed oxidative leaching routes for chalcopyrite, generally at high pressures and temperatures, have not been implemented on an industrial scale, because of the elevated costs required to equal the high copper extractions obtained in thermal processes. These extreme leaching conditions are required because of the refractory nature of chalcopyrite. Passivation has been used to explain this phenomenon, although researchers have disagreed on the composition of the layer, which is various have assumed to be sulfur, copper sulfides, and iron-bearing jarosites or hydroxides [5]. If the latter compounds are the cause, an alternative solution would be the use of polar organic solvents in the oxidative leach to decrease the formation of the passivating iron layer. In this work, the influence of acetone on the oxidative leaching of a chalcopyrite concentrate at room conditions is explored."

Jan 1, 2012

By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

By J. Borlée, J. P. Birat

"ULCOS is a large European program launched by a consortium of 48 partners led by arcelor and a core group of steel producers, which was started in 2004 with the support of the European Commission (RFCS and 6FP programs) to search for breakthrough process routes that could, in the future, when fully developed, demonstrate the potential of large cuts in CO2 emissions for the production of steel from iron ore.The timescale for commercial implementation is the post-Kyoto period, i.e. 15 to 20 years from today.The present paper presents the progress made in the first 2 years of this 5 year program.Several concepts are being investigated in parallel: re-engineering of the blast furnace to incorporate CCS in the core of the process, smelting reduction with CCS capabilities, massive use of natural with more CO2-lean technologies than today, hydrogen steelmaking and electrolysis of iron ore. Biomass also offers very attractive perspectives, while raising major challenges.None of these new steelmaking routes are ""no regret"", which means that the European Steel Industry has already incorporated extensive energy saving steps in its present process technology and is working as close to thermodynamics limits as is cinematically and economically feasible, and that decreasing GHG emissions further means introducing breakthrough technologies that add significant costs to the operation of the Steel Mills.They will also require much research and development before they can be proven and implemented commercially.IntroductionThe ULCOS program (Ultra Low CO2 Steelmaking) is a large research program of the European Steel Industry and its industrial and research partners launched in September 2004 to investigate steelmaking technologies that have the potential of reducing the CO2 emission of the Industry by a large amount, typically in the order of 50%. It is supported in the European Community by the 6th Framework and the RFCS programs through 3 complementary European projects [1,2].The present paper summarizes the work carried out in the phase 1 of ULCOS and in framing the program of phase 2."

Jan 1, 2008

By Zhong Zheng, Xiaoqiang Gao, Zhaojun Xu, Shipeng Huang, Shenglong Jiang

Steel enterprises in China are trending to improve material and energy conversion effect, because they are facing great challenges including energy saving and emission reduction, quality and efficiency improvement. According to the theory of metallurgical process engineering, with the process data in steel manufacturing, some novel indices are designed for quantifying the conversions in different metallurgical unit processes. By analyzing common technologic characteristics in different units, the main manufacturing units are divided into two categories: metallurgical reaction unit and other manufacturing unit. The novel concepts named as “material dissipation rate of unit process”, “material accumulation rate of unit process”, “enthalpy change of unit process” and “energy dissipation rate of unit process” are proposed for describing the effect and dynamic characteristics of the conversions in manufacturing units. Finally, material dissipation rate and energy dissipation rate in unit processes are calculated and analyzed respectively with the real-world process data from a steel plant in China.

Mar 1, 2018

By Zhihe Dou, Yan Li, Qiuyue Zhao, Guozhi Lv, Yan Liu, Hongliang Zhao

"Abstract: How to reduce carbon dioxide emissions has become a vexing problem, meanwhile, there exist high energy consumption and low efficiency problems in the existing CO2 capture and storage technologies. For CO2 comprehensive Utilization, this paper researches a new technology of absorbing the CO2 emission with high alkaline calcium or high alkaline wastewater sludge mineralization of calcium and invent a core device for multi-level jet carbonation. The industrial test has been carried out in China Xinyu slag Engineering Co., Ltd. The wastewater flow is 150m3/h in the pilot scale. The prepared calcium carbonate has a whiteness greater than 90%, particle size less than 150nm. The mineralization of aluminum exhaust with waste carbide indicates that the CO2 absorption rate is greater than 99.0%, CO2 concentration in the exhaust gas is lower than 0.08%, the purity of mineralized calcium carbonate is greater than 99.0% and particle size is less than 100 nm.InstructionAccording to the statistic data from IEA (2009), the carbon dioxide discharge from fossil fuel consumption in China has exceeded it in the US by the year of 2007, China, has become the largest emitter of carbon dioxide all over the world. Meanwhile, the economic scale is still on an increasing trend in the next 50-100 years, leading to a continuous increment in carbon dioxide discharge. According to the international energy agency forecasts, the energy-relative CO2 discharge in China will rise to 11,615 million tons, 91.3% higher than it in 2007. In the year of 2012, the CO2 gross discharge has reached 10,000 million tons, obviously higher than the predicted value. It is a tremendous task to reduce the emission. Non-ferrous metals industry is one of the largest emitters of carbon dioxide among the industrial circle, the whole industry might discharge a huge amount of carbon dioxide (over 600 million tons), in which the electrolytic aluminum industry is the largest energy consuming industry and CO2 emitter. At present, the CO2 discharge has focused by the whole world due to the environmental problems it causes; meanwhile, supplement of new carbon source is needed due to the exhausting oil and coal resources, so that various countries in the world are attaching importance of the recycle and purification of CO2. Many countries are studying on the cyclic utilization of carbon dioxide. Gas CO2 is mainly applied in chemical, pharmaceutical raw materials, beverage filling agent, refrigerant, inert medium, solvents, pressure source, the welding protective gas, antioxidant and fire extinguishing agent, etc. Solid CO2 is mainly applied in penicillin production, fish, cream, ice cream and other food storage and transportation at low temperature, etc. nowadays, such methods as absorption method, membrane separation, adsorption, etc. are widely used to recycle CO2, with such problems as high investment cost and technical constraints etc."

Jan 1, 2014

By J. Daniel Bryant

Deformation processing of rapidly solidified powder alloys presents a technical challenge different in several ways from the processing of ingot based alloys. The metastable phases formed during planar flow casting of aluminum alloy 8009 (FVS0812) must be safe-guarded from high temperature excursions during processing to avoid decomposition; this restriction prohibits liquid phase sintering of particles during consolidation. The development of strong particle-particle adhesion, therefore, relies on the imposition of very large strains during forming operations to insure sufficient mechanical meshing of the aluminum particles and break-up of prior particle oxide boundaries. These strains are generally much greater than those required for metallurgical transformations in ingot based alloys. In an attempt to quantify the deformation required to improve interparticle bonding, the finite element method (FEM) was employed. Preliminary results which predict the metal flow and strain distribution in several workpiece configurations are discussed. These predictions are then correlated to measurements made on experimental subscale forgings. Lastly, experimentally measured quantities which reflect the degree of interparticle bondingg are related back to FEM model predictions.

Jan 1, 1992

By B. J. Elliot

The Outokumpu Oy flash smelting furnace was designed for a capacity of 69,5 mtph of concentrate. The history of developments on the flash furnace, from the original operating capacity of 55 mtph to a proven capacity of 115 mtph of concentrate, is summarised. The new feature of operation at BCL Limited is ?the use of screened lump coal reduction in the settler region of the furnace. This paper considers the effects of settler bath reduction on the furnace smelting capacity, the condition of the furnace ?lining and bath, and ,the slag losses generated from the flash furnace and ultimately to discard. By using the settler bath reduction technique the capacity of the furnace for smelting new concentrate has been increased by 15% and hearth accretion has been eliminated by direct reduction with coal, which has also allowed the generation of a substantial protective lining on the furnace walls and roofs. As a result of improved slag losses from lump coal charging the metal recoveries on the flash furnace have increased from 70% to 87% for nickel, 68% to 82% for copper, and 28% to 45% for cobalt.

Jan 1, 1983

By Alan James Parker

Chalcopyrite can be converted to pure copper by the following five steps. An exothermic sulfation roast of chalcopyrite; leaching of cupric sulfate from the calcine with dilute acid; precipitation of Chevreul's salt and or other copper sulfites with ammonium sulfite or precipitation of crude copper by autoclaving ammonium sulfite and cupric sulfate at 150°C; dissolution of Chevreul's salt, or the crude copper, as cuprous sulfate, using acidic cupric sulfate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulfate solution. Acetonitrile and acidic cupric sulfate solution recycle. Advantages over conventional processes include lower cost, lower energy consumption as waste heat, sulfur removal as ammonium sulfate or gypsum, rather than as sulfur dioxide and rapid throughput. The net reaction is: 2 CuFeS2 + 4H20 + 15/2 02 + 8 NH3?2Cu + 4 (NR4)2 SO4 + Fe2O3

Jan 1, 1976

By Ann E. Visser

Aqueous Biphasic Systems (ABS) form upon the admixture of certain water-soluble polymers or polymers and salts above critical concentrations, and thus represent liquid/liquid extraction systems whose nature is entirely aqueous. We are currently investigating the utility of ABS (and its solid phase analogs) as "green" alternatives to the use of volatile organic diluents in separations of metal ions. Chaotropic (water-destructuring) metal ions with small negative AGhyd (e.g., Tc04) tend to partition quantitatively to the PEG-rich phase of an ABS, but even hydrated metal cations can be partitioned to the PEG-rich phase if a suitable extractant (e.g., halide, dye, crown ether, etc.) is used to produce a more chaotropic ion-complex.

Jan 1, 1999

By Huyang Xie, Rishi Raj, Vera A. Versteeg

"A new method for MOCVD has been developed in which a precursor solution is directly injected into a reaction chamber. The vaporization of short pulses of liquid is facilitated by atomization with a piezoelectrically-operated nozzle. The system has been used successfully to grow oriented, thin Ti02 (rutile) films on sapphire substrates with the crystalline relationship (101)[010]R I (1120)[0001]s. A growth rate of approximately 2 monolayers per pulse was achieved at 650°C for a reactant impingement rate of about 800 monolayers per pulse. Also, epitaxial LiTaO3 thin films were grown on (0001) sapphire from a single source, bimetallic precursor, lithium tantalum hexa-t-butoxide as the precursor. X-ray diffraction shows that the LiTaOa c-axis is normal to the sapphire surface. The x-ray pole figure and crosssection TEM diffraction show that the films were also in-plane oriented, with sapphire [1010] parallel to lithium tantalate [1010]. These films are shown to have extremely low optical attenuation, and refractive index that compares well with bulk values.IntroductionMetalorganic chemical vapor deposition (MOCVD) techniques have come into increasing use in recent years, due to the growing versatility and availability of precursors and improved environmental advantages over the halogenated compounds used for conventional CVD. Most commonly, the films are deposited by dissolving the metalorganic reactant (typically a metal alkoxide) in a carrier gas, which is carried through heated lines to a heated substratel . The metal alkoxides decompose by pyrolysis, leaving the films on substrates. While this method has been used to produce excellent epitaxial and heterepitaxial films, it has the disadvantages of complexity: the precursor must be heated to fix its vapor pressure, the gas flow rate carefully controlled, and the carrier lines heated to prevent condensation before reaching the reactor. Additionally, this conventional method cannot be used with certain low-volatility precursors that decompose upon heating."

Jan 1, 1994

By A. Rosenfeld

The feasibility of applying laser induced optical emission spectroscopy to the high speed sorting of mixed alloy aluminum scrap is investigated. The basic spectroscopy for analysing aluminum alloys for the major alloying elements over their full concentration ranges is established. Materials handling issues are also described and the components of an overall sorting system are presented.

Jan 1, 1995

By Xiaohui Li, Lianyun Liu, Hongmin Zhu, Chunfang Zi, Kai Huang, Hongjie Li

"The dissolution kinetics of steelmaking slag in pure water was studied, and the relative influential factors were investigated. The dissolution behavior of slag particles in water was well described by Noyes–Whitney equation, and for this kind of sparingly soluble rigid mineral this simple model was extensively applicable to describe their dissolution process. Experimental data were also obtained to confirm the significant promotion effect on the growth of some algae.1 . IntroductionIt has been found that the population of phytoplankton distributed in the ocean was significantly related to the concentration of some elements [1]. For example, silicon and iron were very low in the high-nitrate low-chlorophyll (HNLC) areas, which was the main factor limiting phytoplankton and other biomass growth in these open ocean surface water [7]. The silicon and iron-rich test also confirmed that the supply of these elements had the direct effect on the growth of phytoplankton processes at HNLC areas [2-8]. So in order to promote the growth of phytoplankton in these ocean areas, providing some of these elements into these ocean areas is a natural idea for choice. Steelmaking slag is a good resource for consideration because it usually contains silicon, iron, phosphorus and other elements that are necessary for the growth of phytoplankton [8-10].Haraguchi has proposed the following idea that [5-6], if steelmaking slag can be spread to the open ocean, the trace components like silicate, iron and phosphate as the indispensable nutrients for the growth of phytoplankton, will be leached into the sea water, not only promoting the growth of phytoplankton, but also making good use of these huge amount of steelmaking slag produced every year. Based on this idea, they have carried out studies in recent years and they found that silicon and iron in the slag could be extracted into seawater effectively and play a positive role in the growth process of many algae. About the dissolution of the steelmaking slag, the Japanese scholars' research work mainly focused on the thermodynamic analysis of its dissolution possibility, and in the process of dissolution they tried to adjust the pH value of the seawater by continuously adding hydrochloric acid, which was deviated from the natural conditions of dissolution, and so the laws drawn under these special conditions can not give the identical guide to the practical application. Therefore, it is quite necessary to investigate the dissolution behavior of the steelmaking slag in the seawater at the normal pH range without adjustment to simulate the dissolution possibility under the natural conditions. In the present study, the silicon extraction behavior from the steelmaking slag was investigated and the dissolution kinetics in this process was also discussed in detail. Further studies were also performed here to evaluate the promotion of steelmaking slag on the growth of algae."

Jan 1, 2011

By S. K. Utimurd, D. C. R. Espinosa, J. A. S. Tenório

"Waste Electrical and Electronic Equipment (WEEE) has become an environmental issue due to technological advance and waste plastic is one of the main polluters. The excessive discard of these plastics result in a difficult to dispose it to landfill and need further separation with technique in order to produce high added value plastics. There are many kinds of plastics in extensive use at the present time and the co=on are the acrylonitrile-butadiene-styrene (ABS) and high impact polystyrene (HIPS) used in the production of electric appliances. These plastics are difficult to separate because they have similar densities. Flotation of plastics is one possible separation technique and using selective wetting agents. The separation may be possible given close control at particle size and the concentration of the reagent. The process was able to produce a concentrate of HIPS with at least of 93% purity and a concentrate of ABS with 99% purity.IntroductionThe current situation of municipal solid waste (MSW) management especially in emerging economies like Brazil, the growing population and economic activity will result in a significant increase in the generation of waste in the coming decades. It is worthwhile to review and update the sources, amounts and recovery technologies of specific materials from waste, particularly from municipal solid waste (MSW).The growing impact of the current waste management practices stresses the need for a change in how waste is handled. The 2012 survey and the Brazilian Association of Public Cleaning and Special Waste Disposal Companies (ABRELPE) reports the generation of 62 Mt urban MSW in that year, which is an increase of 13% compared to 2011. It has been reported that in Brazil about 90.17% of the generated MSW is currently collected, which indicates an increase in the coverage of collection services compared to 2011 [ l]."

Jan 1, 2014

By Rafael Padilla

In the production of copper from chalcopyrite (CuFeS2) concentrates by the smelting and converting technology, the ambient pollution with gaseous S02 and toxic metals such as arsenic compounds is still a serious problem, especial1y in the converting step due to the batch nature of the conventional Peirce Smith process. Non-SO2 emitting alternatives are leaching processes. However, few of them have had a limited industrial application and they are not very effective in discarding safely the toxic impurities. A combination of pyro-hydrometal1urgical methods: the sulfidation of chalcopyrite and subsequent leaching of the sulfidized material is a non-polluting alternative to treat not only clean chalcopyrite concentrates but also complex chalcopyrite-enargite concentrates. In this article, this alternative is discussed concerning the thermodynamics and kinetics of the sulfidation of chalcopyrite with gaseous sulfur. The kinetics of the leaching of the sulfidized concentrate in an H2SO4-NaCI-O2 system is also discussed.

Jan 1, 2003

By Miguel N. Herrera

The electrochemistry of coal pyrite is relevant to coal desulfurization by chemical or bacterial leaching, flotation and oil agglomeration. The electrochemical behavior of polished and etched Upper Freeport and Pittsburgh coal pyrite samples was investigated from pH 1.0 to 10.5. The open-circuit potentials decreased with increasing pH, as expected, but were well above the thermodynamic stability region of pyrite, and decreased with time. Cyclic voltammetry revealed behavior highly sensitive to pH and scan rate (2.0 and 20.0 mV/s). The behavior on the first cycle was always substantially different from that on subsequent cycles. The anodic and cathodic reactions were correlated with the Eh-pH diagram for the Fe-S-H20 system to identify the reactions occurring at different pH values. There was also evidence that the buffers used to maintain basic pH values are themselves electrochemically active, which should be considered in interpreting many earlier electrochemical studies of sulfide minerals.

Jan 1, 1994

By Peter Ehren

Global Geoscience is developing a Rhyolite Ridge project, a shallow boron-lithium resource deposit, located in Nevada about 25 km from Albermarle’s Silver Peak operation. The main minerals of interest are the boron mineral searlesite (40%wt) and lithium containing clay minerals. These minerals are found among principally calcite, feldspar, muscovite, dolomite, and quartz. The equivalent commercial value is about 7–9% boric acid (H3BO3) and 0.8–1.0% lithium carbonate (Li2CO3) equivalents. Selective agitated leach tests at SGS Lakefield laboratory showed that searlesite can be acid leached between 20 and 75 °C and at a pH lower than 4. On the other hand, lithium can be leached between 20 and 75 °C and at a pH lower than 1. In other words, lithium can be recovered at low temperatures if sufficient free acid is available, which gave the motivation to investigate heap leaching of the mineral. The PLS contains boric acid, magnesium, sodium, lithium, potassium aluminium, and iron sulfates.

By J. L. Jambor, H. W. Nesbitt

Oxidative dissolution of pyrrhotite and pyrite is largely responsible for the sulfate-rich waters of the vadose zone in the Waite Amulet tailings. Although the shallowest of the sulfate-rich waters are of the Fe-SO4 type, they change to Mg-SO4-type, near-neutral waters within 1-2 m of the tailings surface. Phyllosilicates and amphiboles are the only minerals present in sufficient quantity to ameliorate the amount of acidity produced. X-ray diffraction and microscopic studies of bulk sample indicate that quartz, chlorite, talc, amphiboles, magnetite, albite, and micas are the major and minor non-sulfide minerals, but their variations with depth do not give clear indications of depletion in the vadose zone. Mineralogical and bulk chemical compositions of the tailings confirm that Fe2O 3 has accumulated in large quantity in the vadose zone, with the Fe having been derived from Fe sulfides. When the effect of Fe2O3 is accounted for, the bulk compositions suggest that SiO2 is slightly more abundant in the vadose zone than in the saturated zone. This may be the result of residual enrichment of siliceous minerals such as quartz and albite in the vadose zone. Weathering of the tailings since the cessation of deposition in 1962 has resulted in a well-defined zone of sulfide depletion and secondary sulfate-mineral development. Although some silicate dissolution is indicated by pore-water compositions, the role of silicates in providing neutralization seems to have been minimal. The contribution by silicate minerals in laboratory tests of neutralization potential may be excessive relative to that in natural settings.

Jan 1, 1999

By M. E. Huckman

In this paper, we review the equations needed to construct an ion exchange column model. These models contain three major components: 1) a differential material balance around the colunm, 2) a differential material balance around an ion exchange particle, and 3) a constitutive equation for diffusive flux We then examine the ability of a fairly simple mathematical model to predict ion exchange column experimental data. This model contains the traditional absorption theory equations and is used to predict the behavior of a column filled with a hydrous crystalline silico-titanate and which is removing trace amounts of Cs+ from a high pH, complex electrolyte solution. Finally, we propose replacing Fick's law with the Nernst-Planck equation as the constitutive equation for diffusive flux We use a Nernst-Planck type model to predict batch experimental data, then evaluate it by comparing it's ability to predict experimental data to that of a more traditional Fick's law type model? The data from this comparison suggests that the Nemst-Planck type model yields better results.

Jan 1, 1996