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By Kun Wang, Xinhui Li, Huaqing Xie, Qingbo Yu, Qin Qin

"Three typical model compounds of bio-oil (ethanol, acetone and phenol) were studied in the steam reforming process for hydrogen production. In the thermodynamic analysis, the three componds showed the similar trends. The hydrogen yields increased with the increase of steam/carbon (S/C) ratios, and the temperatures of the maximum hydrogen yields moved afterward to low temperature zone. However, the hydrogen contents were just about 70%. For improving hydrogen yield, a new system for steam reforming of bio-oil with site CO2 capture was put forward. This system required the catalst with the larger granularity having greater mechanical strength and higher abrasion resistance. So, six Ni-base catalysts loaded on Al2O3 particles prepared were used and among them, Mg-Ni/Co catalyst showed the best catalytic performance. For the simulated bio-oil (the mixture of the compounds), the hydrogen yield can attain 63% with Mg-Ni/Co catalyst with the good stability and regeneration ability.IntroductionCurrently the interest in the use of hydrogen as a clean energy carrier is increasing, and the main way for producing hydrogen is steam reforming of fossil fuels, containing steam reforming of nature gas, naphtha and coal. But this way caused substantial amounts of CO2 emitted, and these sources of hydrogen which are non-renewable energy will eventually be used up [1, 2]. As a kind of renewable energy, biomass is recognized as an attractive alternative to fossil fuels, because of its neutral CO2 emissions [3]. There are mainly two thermochemical processes using biomass to produce hydrogen, gasification and flash pyrolysis followed by steam reforming (SR) of the biooil produced in the flash pryolysis process [4]. The latter was known as one of the most promising and economically viable methods for hydrogen production [5]. In the last decades, the biomass flash pyrolysis technology was adequately developed and fairly mature [6]. But the steam reforming of bio-oil is still at the research stage and yet has been leading to more and more concerns by the researchers. In their research, the catalysts were widely studied and yet mainly were powdery[7-10], and the reactors manily were fixed bed reactors[11-13], readly causing the carbon deposition and the catalyst deactivation, against the continuous running. In this paper, a new systerm was put forward and could realize continuous production of hydrogen, yet needed catalysts with the larger granularity having greater mechanical strength and higher abrasion resistance, as well as powdery CO2 sorbents which mainly calcium oxide based ones.In this paper, the thermodynamic analysis of the steam reforming processes of three typical bio-oil model compounds (ethanol, acetone, phenol) was performed, and the effect of S/C ratio and temperature on the hydrogen yield and the compositions of gaseous products were investigated. Then, a new systerm for steam reforming of bio-oil with site CO2 capture was put forward, and the catalysts with a certain granularity were prepared and studied."

Jan 1, 2014

By Thomas E. Weyand

Prior to 1975, lead-based paints were commonly used in protecting steel structures. Because of the toxic effects of lead on human health and the environment, their use has been significantly reduced. However, problems with these paints persist when they are removed during normal maintenance by pneumatic blasting with mineral abrasives. Technologies are developed to contain the spent abrasive and paint during blasting operations. This paper reports on A study to identify beneficial reuses for the spent blasting material. Nine samples were gathered from different projects within Pennsylvania. The samples were thoroughly characterized with regard to composition, morphology, and EP and TCLP leach test performance. Potential reuse applications will be reviewed with regard to technical adequacy, economics, and environmental constraints.

Jan 1, 1992

By D. A. Robbins

The Resource Conservation and Recovery Act. of 1976 (RCRA) requires testing of waste materials as part of the determination of whether these materials are classified and managed as hazardous wastes. The adoption of one standard testing procedure and its application to all types of waste materials has stirred much controversy. In the center of this controversy is the appropriateness of this testing procedure in characterizing non-ferrous metal intermediates and slags. The authors have evaluated the relative availability of metals in several types of copper and lead slags as defined by various testing protocols. Also discussed is the relationship between the chemical character of the slag and the availability of metals to leaching and certain metallurgical practices that can influence metals availability.

Jan 1, 1983

By K. Robinson

Following the longest Smelter campaign in BCL?s history it was planned to completely rebuild the flash smelting furnace in 1987. This was the fourth major overhaul and the most extensive so far attempted. Detailed planning took place over several year$ preceding the shutdown and implementation was completed in 54 days. The key to minimising shutdown time was the method designed for installation of the new uptake shaft and reaction shaft. Major repair work was also undertaken in the waste heat boiler and electric furnaces. Both of these activities had an impact on the critical path of the flash smelting furnace overhaul.

Jan 1, 1993

By Yang Jian-guang, Deng Zi-xiang, Zhang Xu-liang, Li Jun-yuan

"Hyperaccumulator biomass harvested after heavy-metal phytoremediation must be considered as hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable bio-energy resource, the hydrothermal upgrading process was applied to remove heavy metals and upgrading crude bio-oil from Pteris vittata stems and leaves harvest. Parameters such as material granularity, temperature, Liquid/Solid (L/S, ml/g), pressure, duration and catalysts were examined for their effect on the removal efficiency of heavy metals and upgrading efficiency of crude bio-oil. Maximum heavy metal removal efficiency of>99% and crude bio-oil upgrading efficiency of 83% were attained with an 200 mesh (75 µm) granularity, LIS 40:1and23 MPa at 380°C in the presence ofO.l mol L-1 K2C03 for 30 min. GC-MS analysis results show that the resulting bio-oil mainly consists of benzene 11 %, ketone 42%, alcohols 14%, alkene 15% and ester 11 %, etc., and the relative molecular weight distribution lies in 94-282, carbon number distribution lies in 6-18, calorific value is 32MJkg-1.IntroductionPhytoremediation of soil or water with hyperaccumulator has been extensively explored in recent years [1-4]. Living plants can clean up soils or waterways. This approach exploits the ability of various plant species to thrive in high metal environments where large amounts of toxic elements are accumulated, such as heavy metals, and is particularly appropriate when slow remediation of relatively low metal concentrations is acceptable. Advantages compared with existing remediation methods include the minimal site destruction and destabilization, low environmental impact, and favourable aesthetics; advantages compared with biosorption include continuous in situ regeneration of the biomass, and the ability of living plant cells to supplement passive sorption of metals with metabolic mechanisms of metal uptake and detoxification [5-8]."

Jan 1, 2014

By R. E. Burleigh

'Gold-telluride mineralization was deposited in quartz veins which cut a Late Cretaceous tonalite pluton emplaced near the southern margin of the Peninsular tectono-stratigraphic terrane in south-central Alaska. The gold-bearing veins formed shortly after the development of a widespread Cu-Mo sheeted quartz vein system. Early mineral assemblages consist of quartz, white mica, pyrite, and arsenopyrite (wall rock only). Subsequently, pyrite. sphalerite, chalcopyrite, zoned tetrahedrite and gold precipitated within multiply fractured veins. Late stage galena, tellurides (altaite, nagyagite, coloradoite), and Pb-Sb or Pb-Cu-Bi sulfosalta with gold constitute bonanza ore assemblages that are variably associated with quartz, white mica, ankerite, and calcite. Fluid inclusion evidence coupled with mineral assemblage paragenesis suggests the depletion of volatiles (C02, H2S) and cooling resulted in the precipitation of high grade gold mineral assemblages.

Jan 1, 1988

By W. H. (Bill) Jay

The destruction of cyanide creates a significant impost on the financial returns of gold mines. These losses increase substantially when ores containing cyanide-soluble copper are treated. Failure to remove or destroy free or WAD cyanide before it is discharged into tailings dams has, on a number of occasions, led to significant fish, bird and animal deaths. Thus, the retention of cyanide within the leach circuit and the recovery or removal of stable metal cyanide complexes needs to become standard practice for all gold mining operations. Furthermore, reducing cyanide purchases will minimise the quantity of cyanide transported to the mine site thereby reducing the opportunity for spillage of this chemical. Many different physical and chemical methods have been investigated for the removal of cyanide from process solutions. All cyanide destruction methods create a financial impost on the economic viability of the gold mine. To reduce these costs, the recycle of cyanide and the economic recovery of the metals solubilised by cyanide is of prime importance. The alternative methods currently in use, or under consideration for the treatment of copper cyanide, entail high reagent costs, produce the recovered metal in a contaminated form and require the safe handling of hydrogen cyanide. These processes will be briefly discussed within this report Environmental and financial benefits are enhanced by recent laboratory and pilot plant studies conducted by Oretek Limited. The Oretek CPC process for the recovery of copper and the recycle of cyanide from copper cyanide-containing solutions does not require pH adjustment to the alkaline cyanide leach conditions. Copper ions are coordinated to a water-soluble and/or an organic soluble polychelating agent under alkaline conditions and the cyanide ions are displaced Membrane separation, or phase separation of the polychelated copper from the cyanide ions enables the cyanide ions to be recycled and the copper to be directly electrowon from the polychelating polymer. The polychelating polymer is then recycled. Ion exchange resins and solvent extraction systems which may be incorporated into the above process will also be discussed in detail.

Jan 1, 1998

By Benjamin P. Hay

Complexation of a metal ion to a ligand often results in structural changes that introduce steric strain within the ligand. A design criterior:1 for ligands that will complex metal ions more strongly is to choose Iigar:1d architecture, that minimizes this strain. This paper describes how molecular mechanics models can be used to define the degree of ligand binding site organization in terms of' ,strain energies associated with conformational reorganization and distortion of the binding conformer. This approach yields a method to predict how modifications to ligand structure will affect metal binding affinity.

Jan 1, 1999

By Bryce Clark

An outline of the current world's known sources and resources of cobalt, looking at both land and possible undersea deposits, is given as a prelude to an examination of current and historical actual world production on geographic/company basis. These production figures will be compared to apparent consumption by segments, both geopraghically and end-use based. Consumption of cobalt has been regarded as price sensitive and a historical look at prices against all other figures will be considered. Included in this scenario will be a brief overview of cobalt's uses and a comment on future trends. Tables will include: Resources, Production, Consumption, Prices, Markets.

Jan 1, 1993

By Joseph Bloch

The hydriding of bulk metals and alloys is a gas-solid reaction in which a hydride product layer is initially nucleated adjacent to the gas-solid interface and continues to grow until a complete transformation of the parent (a) phase into the hydride phase. The combination of measurements of the overall hydriding kinetics of samples having defined shapes and dimensions, together with examinations of partially hydrided samples, enables the presentation of the reaction rate in terms of an appropriate reaction model. A common and important type of topochemical development of the hydride in bulk metals and alloys involves a hydride layer formed on the metallic surface. The continuity of the layer can affect the reaction rate. The rate of hydrogen absorption in a sample, in the presence of a hydride layer, is usually analyzed using a model combining several sequential steps in which the hydrogen is transferred from the gas phase into the reaction site. Coupling the flux equations across the layer under proper steady state conditions, results in a complex rate equation in which the steady state rate of hydrogen absorption (proportional to the hydride layer velocity) is expressed in terms of the pressure, temperature, the rate constants of the sequential steps and the critical concentrations of hydrogen in the hydride. Generally, the rate constants of the individual microscopic processes are comparable in magnitude, so that the overall rate is not controlled by any of the specific sequential steps. However, there are two limit cases related to the first stage, the adsorption, for which the general rate equation is much simpler, namely, the fast and the slow adsorption approximations. Using this limit cases, equations are derived for the steady state hydriding rate of a given system. These equations provide means to anticipate the pressure dependence of the steady state absorption rate under low pressures, close to Peq and under very high pressures. At the low pressure regime both the fast and slow absorption cases yield linear pressure dependence. For the very high pressure range, it is found that the rate become independent of the applied pressure. The rate is given then by a combination of the individual rate constants of the system and the critical hydrogen concentrations. The model is shown to apply in several real cases, such as ZrCo, LaNi5 and titanium.

Jan 1, 2002

By D. Raghavan

In recent years, the environmental issues related to the landfill shortage received considerable importance. Many polymeric solid wastes have high resistivity to chemical and biological degradation, and options are sought by which these wastes can be recycled and reused, or reduced in volume. The present study investigated the biodegradation of polyethylene by Aspergillus niger, and biodesulfurization of rubber by pure and mixed cultures of Thiobacillus thiooxidans and Thiobacillus ferrooxidans. The fungus, A. niger, was found to metabolize portions of polyethylene. Quantitative calorimetric measurements revealed that the amorphocity of the sample decreased during biodegradation. Removal of sulfur from synthetic rubber samples containing 2 to 15% sulfur, was studied in shake flask experiments and the associated oxygen consumption was studied in Warburg respirometers. The mixed bacterial cultures were more effective in the desulfurization of rubber samples than the pure cultures of T. thiooxidans and T. ferrooxidans. The data obtained in these studies may have far reaching consequence for the development of new effective processes regarding the remediation and management of discarded polymeric packaging wastes and car tire rubber materials.

Jan 1, 1993

By Michael J. Nicol

Growing environmental and occupational safety concerns about the use of cyanide in gold processing has increased the interest in more acceptable alternatives. The most likely of these is thiosulfate. However, the thiosulfate process lacks a proven in-pulp method of recovering the dissolved gold, because activated carbon is not effective for the absorption of the gold thiosulfate complex .. Anion exchange resins do offer a possible route for in-pulp recovery. This paper describes work aimed at the evaluation of the effectiveness of commercially available anion exchange resins for the recovery of gold from thiosulfate leach liquors? and pulps. It has been found that strong-base resins are superior to weak-base resins in that they have a larger capacity, which assists in reducing the competition from other anions within a leach solution. Further studies with a selected commercial strong-base resin have shown that competing polythionateanions (particularly tri-and tetrathionate). Lower the maximum possible gold loading but that gold is selectively recovered over other base metal anions in solution. Kinetic experiments found that while? competilig anibns did not affect the initial rate? of gold loading it was important to minimise the contact time of the resin in solution so to prevent displacement of loaded gold by competing anions over longer times. A small-scale resin-in-pulp plant investigation showed gold can be recovered from a leach pulp by a strong-base resin to yield gold loadings of 3000 mg/L, barren pulp containing less than 0.05 mg/L of dissolved gold and. copper loadings of 500 mg/L. Loaded copper was displaced gold and at a loading of 2000 mg/L gold the copper loading was minimal «500 mg/L). The resin was found to recover gold adsorbed on the solids that would, otherwise have. reported to tails if a solid/liquid separation method were used. A patented two-step elution process in which copper and then gold are separately eluted from the resin is also discussed.

Jan 1, 1998

By Kevin L. Gering

A detection method and apparatus have been developed to perform real-time measurement of aqueous free cyanide, C-. A laboratory prototype can measure cyanide ranging from 5 micrograms ,per liter to 100 milligrams per ?liter for analysis times as short as 2 minutes per measurement. Sample size per measurement is typically only a few mI, thus? minimizing the waste volume produced from spent samples. The basis for this detection device is a quantifiable, stable affinity between the electrode material and free cyanide in the sample; The electrode exhibits piezoelectric behavior, allowing it to be used as a microbalance. This technology 'has experienced two generations of laboratory prototypes, and has been thoroughly tested to determine the operational sensitivity toward process variables such as pH, competing reactions, etc. The speed and ,accuracy of this method make it superior to conventional wet chemistry methods used for quantifying cyanide levels in water. A device based on this technology could be useful in areas involving process monitoring and environmental compliance, .particularly in the cyanide-based leach mining industry. Interest for this detector has been shown by the gold mining industry and others. Patent application is in progress.

Jan 1, 1998

By M. L. Apel

A conceptual approach to the bioremediation of uranium mill tailings (UMT) is presented., This approach focuses on, biosorption to remediate the. effluent solution and bioleaching remediate the. solid fraction. Comparative biosorption studies were performed with synthetic single metal solutions using a commercially available biopolymer. The maximum rate of metal sorption by calcium alginate was found to be 5.43, 6,39, 6.48, and 9.74 mg dm-3 min-1 for U022*, Ba2+, Cd2+ and Zn2+, respectively. Activation energy (AEa) for barium uptake by calcium alginate beads was determined to be 11.5 kJ, indicating a diffusion controlled reaction mechanism. Thermodynamic values (AG+ AH+ and ASt) of the metal-alginate activated complex, as reported in the literature, were found to be in agreement with those calculated from this research. Results show that this biopolymer can be effectively applied in the removal of select metals prevalent in uranium mill tailing effluents and associated waste streams.

Jan 1, 1991

By Yasushi Sawada

An experimental investigation was carried out to study the rates of reduction of iron oxides dissolved in liquid Ca0-SO2-A203 slags by Fe-C droplets at temperatures ranging from 1325 OC to 1550 OC. The %FeO in the slag was varied from 5.5 to 18. Flash X-ray images were employed to observe the behavior of Fe-C droplets in the slags during the reactions and for determining the slag-gas-metal interfacial area. Effect of P205 in the slag and sulfur in the droplet was also investigated. The reduction rates were determined by measuring the volume of CO evolved as a function of time and the estimated slag-gas- metal interfacial area. The reduction rates have increased with increasing %FeO in the slag and the slag temperature. The experimentally established relationship between the reduction rates and FeO (wt%) in slag is given by

Jan 1, 1992

By Roy J. M. van Lier

In industrial aqueous solutions, germanium generally occurs in trace amounts amid high concentrations of other metals, such as zinc, copper and iron. Separation of germanium from these metals as well as its isolation from gallium and indium pose a real challenge to the hydrometallurgist. After a brief discussion of the aqueous chemistry of germanium, this paper reviews the flowsheet of the Apex Mine in Utah. The Apex property was the only mine in the world to be operated primarily for production of gallium and germanium, but apparently closed due to great operating difficulties. Several process variants proposed for the treatment of the Apex ore, including bioleaching methods, are addressed. Following a more general description of the behavior of germanium in hydrometallurgical zinc processing streams, available technology for its recovery from aqueous solutions is summarized. Precipitation, solvent extraction, ion exchange, electrowinning, ion flotation and liquid-membrane separation are all outlined in terms of the aqueous chemistry of germanium. Finally, the production of high purity germanium dioxide and metal is briefly discussed

Jan 1, 1995

By Michael B. Mooiman, David J. Kinneberg, Philippe Cettou, Leo W. Simpson, Pierre Ramoni

"The demand for high purity precious metals began with certain industrial applications having uncompromising requirements for quality and performance. As industrial uses proliferated and as the jewelry industry became increasingly sophisticated, the demand for high purity gold has reached the point where 99.99% is now the standard in the marketplace. A similar evolution is expected for other precious metals.In this paper, we examine both the production and use of high purity precious metals, specifically gold, silver, platinum and palladium. After defining what is meant by ""high purity"", we discuss the various analytical techniques used for measuring impurity concentrations. Next, we review process strategies employed by extractive metallurgists to produce high purity precious metals. Lastly, we describe some of the principal applications for high purity materials including thick films, thin films, bonding wire, thermocouples and jewelry manufacture.Precious metals have unique physical properties that, despite their expense (and the ever-continuing search for more economical alternatives), make substitution difficult if not impossible. These physical properties are dramatically affected by small concentrations of certain impurities. As long as manufacturers continue to demand quality and performance, there will be a need for high purity precious metals.IntroductionIn the precious metals industry, the qualifier ""high purity"" describes any specification over and above commodity grade. High purity specifications delineate lower limits on overall metal purity or upper limits on individual impurities or both. Sometimes, if these special requirements become commonplace, either because of improved refining technology or because of market pressures, yesterday's ""high purity"" material becomes tomorrow's commodity. This transition is now occurring with gold bullion and probably will soon occur with platinum and palladium as industrial use of these materials grows."

Jan 1, 1998

By Bowen Li, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"Magnetic iron sulfide ore particles heat rapidly by microwave (MW) irradiation generating plasma during oxidation of surfaces. The high temperatures produced by the exothermic event decompose local portions of samples forming a differentiated flux of partially melted silicate (si-mt) with entrained metal-sulfide (sul-mt) droplets. The si-mt forms crystals of olivine (01) in Ca-rich pyroxene (Cpx) melt that resorbs a portion of iron sulfide (Po). The immiscible sul-mt droplets of (Fe,Ni,Cu)1-xS contain magnetic subsolidus Ni-pyrrhotite (Ni-Po) with Cr-bearing ferrospinel (Mag). Sub-micron sized flecks of Au are found on the surface of a sul-mt droplet with scanning electron microscope (SEM).IntroductionSulfide ore deposits supply the world's mineral resource in the production of non-ferrous metals. Particularly, Cu-Ni deposits are chemically enriched in metals from high sulfur saturation during magmatic formation that creates the proper geochemical environment for metals enrichment [1, 2]. The sulfur and oxygen fugacity control redox conditions of a differentiated silicate/sulfur magmatic melt with the concentration of iron playing a dominate role in the chemical partitioning of metals in sulfide liquid [3, 4]. The initial magnetic crystallization of (Fe,Ni)i-xS monosulfide solution (mss) from metal-sulfide liquid has an exclusive effect on the fractionation of mineral assemblages (zoning) [5].Phase equilibria of sulfide melt (sul-mt) components are related by a miscibility gap with mss forming Ni-rich pyrrhotite (Ni-Po) followed by the crystallization of (Fe,Cu)1-xS intermediate sulfide solution (iss) [6]. Precious metals form stable chacogenides and are retained in solution until the final liquid solidifies. The redistribution of metals now occurs by subsolidus cooling of mss and iss that exsolve low-temperature Fe-Cu-Ni bearing mineral assemblages [7]. The proper interpretation of ore genesis increases processing capabilities by isolating chemically enriched zones during extraction and should be used to aid in sustainable mine site development [8-11]."

Jan 1, 2013

By Kathryn C. Sole

A novel solvent-extraction process for the refining of gold was recently commercialised, with the commissioning in May 1997 of a 24 t a-' refinery at Harmony Gold Mine in Virginia, South Africa. The MinataurTM Process (Mintek Alternative Technology for Au Refining) uses solvent-extraction technology to produce gold of 99.99% purity from the cathode sludge arising from a conventional carbon-in-pulp / electrowinning circuit. Implementation of this process introduces significant cost benefits compared with the conventional dore smelting / toll-refining route previously followed. This paper outlines the process, presents selected operating results obtained during the first few months of operation, and provides some details of the associated techno-economic advantages.

Jan 1, 1998

By Abbas H. Mirza

Arsenic and selenium are found in low quantities together with other metals in several nonferrous metallurgical process streams such as scrubber blowdown solution, acid plant wastewater, gas cleaning plant water, etc. Normally, the other metals in these streams are present as cations and can be precipitated by conventional lime treatment and sulfide polishing. However, arsenic and selenium are invariably present as anions, AsO33-and AsO43 in the case of arsenic and SeO32 and SeO42 for selenium. Conventional lime treatment removes most of the arsenic, but it does not remove selenium. The present paper reviews the processes and technologies developed to date on the removal of arsenic and selenium from metallurgical process streams.

Jan 1, 1996