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By Tom Lewis

The metal finishing and electronic industries are searching for ways to recycle materials · and reduce costs. The areas of heavy metal waste and water recycling has gained new interests with the potential of impacting the operation's bottom line. Lewis Environmental Services, Inc. has completed numerous heavy metal recovery and effluent recycling projects with its ENVIRO-CLEAN PROCESS for government and private sector clients. This patented process utilizes a proprietary chemically treated granular activated carbon with enhanced heavy metal adsorption capabilities combined with electrolytic metal recovery to produce a saleable metallic product. The process generates no sludge or hazardous waste and the effluent meets EPA .limits. This paper covers several heavy metal removal projects, two fullcscale commercial installations, and one treatability case study.

Jan 1, 2000

By A. Dadgar

Extraction of gold and silver from two refractory concentrates using cyanide and bromine reagents was reported at the 12th International Precious Metal Conference (1). The objective of this paper is to present the gold extraction, recovery, and economics for two refractory concentrates using cyanide and bromine reagents. Gold extractions for cyanide leaching (24- 48 hours) and bromine leaching (6 hours) were the same and ranged from 94% to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods, were better than 99.9%. A preliminary economic analysis indicates that chemical costs? for cyanidation and bromine process are $9.50 and $10.50, respectively per ton of calcine processed.

Jan 1, 1989

By N. Menad

The formation of the dioxins can be dependent on the quantities of carbon, hydrogen, chlorine and oxygen present in a given system, as well as on parameters such as temperature and pressure. Inadequate supply of combustion air ( incomplete oxidation ), low combustion temperatures ( incomplete combustion ), and insufficient turbulence in the combustion are factors which can favour their formation. Dioxins were produced also calatytically from chlorinated phenol precursors, non-chlorinated compounds that were chemically, and reaction of phenol with inorganic chloride. In this paper different precursors such as combination of C, H, 0, Cl, rapid formation/combustion intermediates and routes to PCDFs are reviewed, and the influence of PVC amount on the formation of these isomers is discussed.

Jan 1, 2000

By Y. A. Chang, L. M. Pike, C. R. Kao

"Knowledge of the site preference of ternary solute additions is essential to developing an understanding of how these solutes affect the properties of B2 intermetallic compounds. A quasichemical model will be presented which is able to predict the site preferences of dilute solute additions to tliple defect B2 compounds. The only parameters required are enthalpies of formation at the stoichiometric composition. General equations are developed which can be used to determine site occupations and defect concentrations for dilute as well as non-dilute solute additions. These equations use atom pair bond enthalpies as the parameters. It is found that the site preferences of dilute additions are not always in agreement with predictions based on the solubility lobes in ternary Gibbs isothelms. Predictions for dilute additions to NiAl and FeAl are compared to expel1mental results found in the literature. Satisfactory correlation is found between the model and the experimental results. In addition, the predictions from the model on vacancy concentrations in Fe doped NiAl are compared to recent experimental results by the authors.1.0 IntroductionIntennetallic compounds with the B2 crystal structure such as NiAl and FeAl have been investigated recently for possible use as structural materials in high temperature, oxidizing, and/or corrosive environments. The major limiting property of these materials has been a lack of sufficient room temperature ductility. Attempts to improve the ductility have often been made through ternary or higher order alloying. For B2 compounds, substitutional alloying additions can occupy either of the two sublattices and this site occupancy can be crucial in determining how the alloying addition affects the properties of the alloy. In this manuscript we will discuss the use of thelmodynamic modeling to predict the site occupancies of ternary alloying additions in B2 compounds with the triple defect structure."

Jan 1, 1996

By M. J. Collins

A hydrometallurgical process has been tested at the Sherritt Research Centre for separation of zinc, lead, copper and precious metal values from the zinc oxide fume leach residue stockpiled at the HBM&S operations in Flin Flon, Manitoba. Zinc is found primarily as zinc femte and sphalerite in the residue, lead as lead sulphate and jarosite, and copper as sulphide and jarositic compounds. Gypsum and siliceous gangue are significant diluents. The separation process includes hot acid, atmospheric and reducing (sulphur dioxide) leaching; zinc, copper and lead flotation; and atmospheric iron removal steps. Zinc is recovered to a high strength zinc sulphate solution and to a zinc sulphide concentrate suitable for feed to a roaster or to a zinc pressure leach plant; lead to a high grade lead sulphate concentrate suitable for feed to a lead smelter, and copper to a high grade copper sulphide concentrate suitable for feed to a copper smelter. Precious metals are divided between the zinc, lead and copper concentrates.

Jan 1, 1993

By Yuanbo Zhang, Zhixiong You, Daoxian Duan, Guanghui Li, Tao Jiang, Xiaohui Fan

"Presently, high-grade manganese oxide ores are usually utilized by a coal-based reduction roasting process. However, there were some obvious drawbacks, including serious environmental pollution, high energy consumption, etc. The reduction temperature is relatively high (850-900 °C). In this study, a kind of biomass, pine black charcoal, was used as a reductant to reduce low-grade manganese oxide ores. Under the optimal conditions of reduction temperature of 600~650 °C, roasting time of 30~45 min and ratio of ore to reductant 5:1, the leaching efficiency of manganese reached more than 98%. Compared with the traditional coal-based reduction process, the reduction temperature is reduced by 250-300 °C.IntroductionManganese plays a very important strategic role in the national economy, and it is widely used not only in the metallurgical industry, but also in the light industry, chemical industry, medicine, agriculture, etc [1]. The average grade of manganese ores in China is evenly about 21%, which belongs to typical low-grade manganese ores [2]. Therefore, large quantity of high-grade manganese ores is required to import in order to meet the rapid development of Chinese manganese industry. As reported, the conventional treatment of reduction roasting has been widely applied for processing manganese oxide ores, in which coals or reducing gases (CO, H2 or CHi) were usually used as reducers [3]. However, there were some insuperable problems, such as high energy consumption, poor operating conditions, serious environmental pollution, etc [ 4-9]."

Jan 1, 2013

By Jianxin Zhang

A process, in which arsenic in the residue is transformed directly into scorodite and copper dissolves into the solution simultaneously, was studied. The process was carried out in acidic ferrous sulfate solution under oxygen pressure. The optimum conditions of the process were determined as follows: the initial H2SO4 concentration of 10 g/L; liquid/solid ratio of 10; Fe/As molar ratio in the feedstock of 1; the addition of calcium lignosulphonate was 1% of sludge; oxygen pressure, temperature and reaction time were 1.5 MPa, 150 °C and 6 h, respectively. Under these conditions, arsenic transformed to crystalline scorodite in size of 5–10 μm, and the transformation efficiency reached 97.60%; meanwhile, the copper was leached with a high efficiency of 93.34%. The stability of the leaching residue was evaluated by TCLP testing, and the results indicated the concentration of arsenic in the leaching solution was extremely low as 0.04 mg/L and met the standard of safe stockpile.

By Shaik Jeelani, Mahesh Hosur, Esperidiana A. B. Moura, Rejane D. Campos, Emilia S. M. Seo, Kerry Kirwan, Francisco R. V. Díaz, Maria Sotenko

The use of natural fibers with polymeric resins has spread rapidly. In order to improve the mechanical properties of material, in this work, two variables were used: mercerization and electron beam irradiation. This paper describes the preparation and characterization of biocomposites that were prepared in two different routes using green high density polyethylene (HDPE) and Brazil nut pod fiber (BNPF): the first was to irradiate the composite with 150 kGy and the second was to irradiate the matrix with 15 kGy followed by composite preparation. In both cases mercerized and non-mercerized fibers were used. The irradiation process was carried out using a 1.5 MeV electron beam accelerator, at room temperature and in the presence of air. The material was characterized to evaluate the effect of treatment on mechanical properties of material.

Jan 1, 2015

By S. R. Hutchins

Several refractory sulfide and carbonaceous gold ores were examined to determine whether microbial pretreatment could be used to enhance gold recovery. Test samples were biologically leached using unique. thermophilic microorganisms to solubilize iron sulfide minerals. Gold recovery from sulfide ores and concentrates was enhanced following pretreatment with the thermophiles; responses varied widely for the individual materials. Although bioleaching had little effect on the preg-robbing characteristics of the carbonaceous gold ores, cyanidation of the bioleached residues yielded higher gold recoveries than cyanidation of the native ore. By combining bioleaching with abiotic processes designed to inhibit preg robbing, gold recoveries of 83-98% were obtained from carbonaceous ores yielding 10-50% gold recovery by direct cyanidation.

Jan 1, 1987

By Donald R. Fosnacht

An investigation was initiated to obtain the scope of the problems associated with recycling various waste oxide materials generated at Inland Steel and to identify and? test techniques that could possibly aid in increasing the amount of waste oxide materials recycled to primary. operations. Based on the results of this work, several new techniques were developed ?and tested on ?a plant or laboratory scale. These include the use of cold-bond agglomeration methods for producing waste oxide agglomerates for use as a cooling agent or scrap substitute in steelmaking operations, and the use of various techniques for beneficiating blast furnace flue dust and soaking pit rubble so that the upgraded materials can be utilized in sinter plant or ironmaking operations. The physical and chemical characteristics of the waste oxide materials and the results of the laboratory and plant testing are discussed in this paper.

Jan 1, 1985

By Tao Xuea

Gold frequently occurs in nature in the form of a gold-silver alloy. Thus, investigation of the electrochemical behavior of gold-silver alloys in cyanide solution has practical significance. In this paper, the potentiodynamic method is used to determine the anodic polarization curves of gold-silver alloys (Au-10% Ag and Au-50% Ag) in cyanide solutions. To facilitate the interpretation of the results, complementary experiments conducted in NaOH solution in the absence of cyanide are also reported. The results for the Au-Ag alloys are compared with the polarization behavior of pure gold and pure silver. With the aid of potential-pH diagrams for the Au- and Ag-CN-H20 systems and electrochemical kinetics concepts, the dissolution mechanism of gold-silver alloys, the effect of the presence of silver on the cyanidation of gold, as well as the factors which control the anodic reaction rate are clarified.

Jan 1, 1998

By Ludy C. Motta, Denise C. O. Nascimento, Sergio N. Monteiro

"Natural cellulose-based fibers are nowadays of growing interest for modern industrial composites. Relatively unknown fibers like piassava, curaua and gourde have shown promising behavior as reinforcement of polymeric composites. However, the hydrophilic characteristics of the natural fibers impair its adhesion to the normally hydrophobic polymeric matrix. Surface treatments can, in principle, improve this adhesion and the fiber/matrix interfacial strength. In this paper, the effect of alkali treatment of the surface of piassava (Atallea funifera) waste fibers was investigated in terms of the change in strength of epoxy composites reinforced with these waste fibers.IntroductionThe consequences of global warming and the increase in the price of petroleum are motivating the use of natural materials as substitute for energy intensive synthetic materials [1]. In particular, natural fibers obtained both, from cultivated plants such as jute, sisal, hemp and flax as well as from industrial waste such as sugar come bagasse and coir, are being considered to replace synthetic glass fibers [2,3]. These natural fibers, also known as lignocellulosic fibers, present the comparative advantages of being renewable, recyclable and biodegradable. Moreover, lignocellulosic fibers require less amount of processing energy and are neutral with respect to CO2 emission, which causes the atmospheric greenhouse effect responsible for the global warming [4]. Low cost is another important economical advantage of the natural fibers over the synthetic ones and the application of lignocellulosic is also associated with a lower wear of processing equipment and better finishing of molded components [5]. Moreover, for some fibers, properties such as the mechanical strength and impact resistance can be superiors to the corresponding properties of synthetic glass fiber [6]. The characteristics and properties of several lignocellulosic fibers are, nowadays being extensively discussed in the literature. It is beyond the scope of this work to comment on the hundreds of papers dealing with this subject. However, there are still less known fibers with great potential as engineering material that deserves investigation."

Jan 1, 2008

By Guoqiang Lv, Xi Yang, Wenhui Ma

Cast multicrystalline silicon ingots are widely used in photovoltaic manufacturing. A key issue to achieve high solar cell efficiencies is to attain an optimized temperature field during directional solidification (DS) process. This paper reports numerical investigation of multicrystalline silicon (mc-Si) ingot production using two major types of DS furnace. Specific examination is made on thermal distribution, interface shape and stress field. Evaluation is performed for the applicability of thermal system design to reduce thermal stress, improve crystal quality and enhance energy efficiency. The effects of procedure parameters and geometric configuration on temperature distribution are discussed as well to provide the viable solutions for systems optimization.

Jan 1, 2015

By Rak-lun Choi

Plasma-induced damage of InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) has been studied in terms of forward turn-on and reverse breakdown voltages, together with etch rate and surface morphology. The physical degradation of sidewall along with rough surface morphology of n-GaN caused by increased ion scattering induced the deterioration of the forward and reverse voltages. It was found that the turn-on voltage is sensitive to the surface roughness of the etched n-GaN and the breakdown voltage is strongly affected by the sidewall contamination. Annealing under nitrogen after the mesa etching improved the electrical properties of the InGaN/GaN MQW LEDs. Efficient blue light-emitting diodes (LEDs) were fabricated using InGaN/GaN triangular MQWs. The LEDs with triangular QWs showed a lower operation voltage and 2.4 times higher light output power than those with the rectangular MQW LEDs at 20 mA and 20 °C. The intensity of electroluminescence (EL) at 20 mA was almost independent of ambient temperature in the triangular QW LED, but decreased substantially in the rectangular one.

Jan 1, 2003

The concepts of capacity and basicity have proved extremely useful in dealing with a wide range of solute species in metallurgical slags, and as a result have been widely applied. These two concepts are reviewed, and it is suggested that the Lewis approach to basicity has much to commend it. In some cases, it appears that the term capacity has been used without due consideration being given to the nature of the solution being formed, or even to whether a true solution was being formed at all. This paper proposes a rigorous definition of capacity, based on the true nature of the solution process in slags and glasses, and briefly reviews the repercussions of this approach on data available in the literature and the limitations which it may impose on future investigations in this area.

Jan 1, 1994

By W. G. Davenport

The Cu content of industrial flash furnace concentrates varies considerably. It is usually around 30% Cu (Tables 2.1, 3.1) but it may be as high as 55% Cu and as low as 20% Cu. The mineralogy of flash furnace concentrates also varies. The most common Cu mineral is chalcopyrite (CuFeSz), but many concentrates contain bornite (CuSFeS4), chalcocite (CU2S), covellite (CuS) and even native copper (CUO). Pyrite (FeSz) :is also present in many concentrates. This chapter examines how concentrate composition affects flash smelting -with specific reference to 'low-Cu-grade' FeS2-CuFeSz concentrates. Chapter 14 does the same with 'high-Cu-grade' CuzS-CuFeSz?concentrates.

Jan 1, 2001

By M. Benavides

An experimental study is carried out With sulphide ore obtained from Bailadores-Venezuela as well as artificial concentrates. Concentrates of the minerals from froth flotation are fused to study equilibrium between the matte and slag phases. The first part of the work deals with obtaining a concentrate by flotation experiments with collective and selective reagents, with acceptable metallurgical recovery, studying the influence of different parameters in the process. The second part gives the results of the experimental investigation. on thermodynamic equilibrium in smelting which facilitates knowledge of the elemental processes, giving bases for the possibilities of reducing the loss of metal in slag.

Jan 1, 1983

By A. A. Shook

For relatively little capital outlay, the metal delivery control system in the BHP Copper Rod Plant at San Manuel' was significantly upgraded using the UNAC process simulation and control system (CICS Automation, Newcastle, Australia). An accurate simulation of the metal delivery process was developed with UNAC, which was then used to design a robust controller capable of dealing with plant complexities such as noise, time delays, and nonlinearities. This controller was implemented online using UNAC. Thanks to the extensive preparatory simulation, the controller worked immediately and required no additional online "tuning". Operator response has been favorable, and the UNAC control system has become part of the standard operation of the plant.

Jan 1, 1999

By Funsho K. Ojebuoboh

With several "green" applications in the horizon, bismuth has become an even more important minor metal in the smelting and refining of lead. Smelters with a complex sulfide feed invariably deal with bismuth. Its behavior during the smelting of lead in conventional sinter - blast furnace operation is discussed. Because it readily deports to the lead phase during the refining of lead, its separation from refined lead remained unsatisfactory in early lead production. When commercial requirements of bismuth in lead became more stringent early this century, the procedure whereby calcium and magnesium is used to debismuthise lead was developed. The present conduct of this 1936 process, the Kroll Betterton process, is discussed with emphasis on operational improvements.

Jan 1, 1995

By J. P. Rodier

Despite the good years that the non-ferrous business is now enjoying, one should not forget that in this business growth rates are low, fixed assets are high and prices are more cyclical than in other businesses. Increasing environmental concern puts the industry under pressure. Lead and zinc companies are now profitable and profitability in the next ten years will depend on size of units, location, and choice between new technology and upgrading current ones. Implementation of Metaleurope was a strategic move. It produced a company of sufficient size to achieve new steps in cost cutting and yet remain flexible enough to deal with rising variety of primary and secondary raw materials.

Jan 1, 1990