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By Tatiana Pereira Moreno, Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"Nowadays, End-of-Life (EoL) Liquid Crystal Displays (LCDs) are traditionally disposed in landfills. The increasing access to LCD technology over the last years by Brazilian consumers has intensified LCD' s disposal as an environmental and economic issue. This study aims to characterize used LCDs to identify the main components for recycling. Characterization was performed through scrap disassembly and its components were identified, separated, and weighted. LCDs were disassembled and the following divisions were applied: screen, metal frame, polymeric frame, polymeric sheets and electronic part. Some techniques were used to determine the concentration of Indium in the LCD, the glass/plastic ratio and the different kinds of polymers that compose the screen. The techniques used for characterization included inductively coupled plasma optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). This method, when applied to a wide range of LCDs, can allow the development or improvement of an EoL management of LCD.IntroductionWaste Electrical Electronic Equipments (WEEEs) are waste from discarded equipment, such as computers, monitors and cellphones [1]. Over the past years, treatment of WEEE has been emphasized. It occurs due to the technology's advancement that leads to an even larger increase of WEEES [2].Among WEEEs, there are the liquid crystal displays (LCD). LCD technology is applied in cell phones, tablets, computers and monitors. Nowadays, it's the most well known technology when it refers to monitors, due to its advantages over the Cathode Ray Tube (CRT) technology. Some of them are energy saving, smaller size and no radiation emission [3].This feature in the LCD's global market along with the speed at which electronic equipment becomes obsolete affects society economically and ambiently.This issue becomes even more serious when considering the final destination of the liquid crystal displays. LCDs are lead to landfills as other WEEEs. Besides the different materials long degradation time, the environment is damaged by the disposal of the potentially reusable and hazardous materials [ 4]."

Jan 1, 2014

By Rajesh S. Ransing

An intelligent tool has been developed to analyse the quality of diecast components. The influence of both design and process parameters has been studied in great detail. The tool, based on expert systems related technologies, can identify the causes for the defective castings manufactured. Design related causes such as gate position; gate area, runner design etc. as well as process related causes such as cycle time, cavity filling time and melt temperature are suggested by analysing the data on defective castings for a manufacturing campaign. This intelligent analysis is useful for both design as well as production engineers in the decision making process. All the causes for the occurrence of defects are classified into two categories. The firs category is the 'rootcauses' i.e. the causes which are related to the actual process, material and design parameters and which can be directly monitored. The second category is more abstract in nature and is classified as `metacauses'. These capture the scientific rationale implicit in the cause and defect relationships. This knowledge on causes and defects is represented in the form of a structured graph rather than by a set of rules, which, coupled with forward reasoning and heuristic search techniques results in an elegant and efficient approach. Uncertainties and the degree of relationship among causes and defects are represented by a fuzzy probabilistic model.

Jan 1, 1994

By Zhou Jun

Water-quenched samples were taken from a commercial flash furnace at three levels along its reaction shaft during operation at high feed rate. The samples were subjected to a series of analysis and observation. Such processes of the feed in reaction shaft as oxidation, desulfurization, melting, slag and matte formation and etc., variations of particle size along axial and radical direction of the shaft are investigated. The following smelting mechanism in reaction shaft named as “Multi-particle and multi-phase fusion model” is proposed: (1) Fragmentation and collision of concentrate particles take place simultaneously in reaction shaft with particle size growing up. Collision produces large-size “unit melt” which falls into the reaction layer in the settler bath. (2) In the settler reaction layer below the shaft, weak bath smelting reactions take place among the shaft products, producing final matte and slag which separate into two layers. (3) The processes in the shaft are all progressive along the whole height of the shaft. The predominant reaction in the shaft is oxidation, not reduction.

By Nagy El-Kaddah

One of the emerging technologies for the production of ultra-clean metals is electromagnetic filtration. The theory and the mechanism of electromagnetic separation of inclusions from molten metal are briefly reviewed along with basic electromagnetic separation systems. This paper focuses on inclusion removal in the induced current separators, with specific reference to a new separator developed at the University of Alabama. A simple analytical model is presented for the analysis of particle separation in such a system. The role of the applied magnetic field on inclusion removal will be discussed. It is shown that particle velocity increases exponentially with increasing magnetic field strength. At moderate field strengths, the velocity of 50 to 100µ inclusions are an order of magnitude larger than those achieved by buoyancy. The separator developed at the University of Alabama is described together with experimental results of laboratory and large scale experiments on purification of molten aluminum. These results demonstrate ?the capability of the system for producing super-clean metals.

Jan 1, 1996

By G. D. Sandrock

The science and technology of roan temperature rechargeable metal hydrides began about 1969 with the discoveries that the intermetallic Compounds LaNi5 and TiFe could be, conveniently hydrided and dehydrided at roan temperature and modest H2 pressures. Subsequently, this lead to the development of a broad family of REE-containing AB5 hydrides and numerous applications that make use of the extraordinary H2-absorption and reaction-heat properties of these materials. Some of the applications include H2 storage, compression and separation, as well as heat pumping, heat to mechanical energy conversion and electric energy storage. This paper briefly reviews the fundamental phenomenology of metal hydrides, the history of the use of REE's in rechargeable metal hydrides, the practical engineering properties of these materials and the applications that have evolved around them. The rechargeable nickel metal hydride battery, a new vial alternative to NiCd cells, stands at the forefront of the applications.

Jan 1, 1992

By Kathryn A. Mrotek

The textural growth patterns of nodules from two areas in the North Pacific and the South Pacific are characterized by mottled, columnar and compact-type zones. Amorphous material (mainly iron and manganese hydrox-ides) is a botryoidal-forming phase in the mottled and columnar zones. Crystalline material (platy crystals of birnessite and crystallites of todo-rokite) is found primarily in the mottled zones on botryoidal structures or as long-protruding structures growing onto that portion of the nodule in contact with the underlying sediments. The long-protruding mottled zones contain little or no biogenic debris, suggesting that these zones grew un-interruptedly within the underlying sediments. The coalition of spheroidal knobs comprising some of the nodules also suggests a relatively long residing time within the sediments. It appears that crystalline material (the usual host to associated valuable metals) forms in a quiet environment and as a result of direct nodule association with the underlying sediments.

Jan 1, 1982

By Leonard Harris, Rosa H. Harris

"It is becoming increasingly obvious to mining and exploration companies, when operating overseas, that their activities should not conflict with the interests of the surrounding communities. The world's largest gold heap leach operation, Minera Yanacocha has installed community assistance programs in Peru concerned with health, education, electrification, agricultural assistance and road improvements. The programs are conducted with joint venture partners consisting of the company, the community people, the contractors and suppliers, government and non government organizations and a ladies association composed of the employees' wives and female staff.IntroductionThe l 990's is the decade highlighted by enormous investments in mineral exploration and mining projects in the developing world. Figure 1 illustrates the distribution of exploration spending by mining companies in 1995."

Jan 1, 1997

By R. G. Hilton

This paper deals with application of Super Detox? stabilization technology to the treatment of electric arc furnace dust (US-EPA listed hazardous waste KO61 ). The process has been used on approximately 170,000 tons of electric arc furnace dust. In addition to the nearly four years of commercial experience at Sterling, Illinois, the process is now being permitted for application at two other locations. The process was originally developed by the Bethlehem Steel Corporation and then further improved by Conversion Systems, Inc. (Bethlehem Steel's Licensee). The treatment process offers many unique bases for its selection, including: A) Low cost compared to the treatment alternatives; B) Lowest available TCLP leachate levels for any process treating K061. Many other processes leave some residue that represents a disposal requirement, although often not addressed; C) Produces minimized final waste disposed, including the fact that the total volume of dust generated and less than the volume occupied by the residue slag from HTMR; and, D) Opportunities for the beneficial utilization of part or all of the waste stream through the development of chemical and physical characteristics. Each of these aspects will be specifically discussed in the paper, including that status of the operations now under permit.

Jan 1, 1994

By Junji Shibata

Some fundamental studies were carried out in order to produce composite powders comprising of two or three metal salts by using liquid-liquid extraction and to develop the control technology of the particle size. The combination of samarium and cobalt was selected as the two component composite powders. Both stripping and crystallization occurred at the same time by emulsifying the organic phase loading the two metals extracted with Versa tic Acid 10 and the aqueous solution containing oxalic acid. The effect of aqueous pH, oxalic acid concentration and agitation speed was examined on some properties such as crystallization percent, particle size and shape of each metal oxalate powders obtained in this process. The analysis by using EDX showed that the two metal oxalates were distributed uniformly at the same ratio as the organic phase composition.

Jan 1, 2001

By Nagy El-Kaddah

"One of the emerging technologies for the production of ultra-clean metals is electromagnetic filtration. The theory and the mechanism of electromagnetic separation of inclusions from molten metal are briefly reviewed along with basic electromagnetic separation systems. This paper focuses on inclusion removal in the induced current separators, with specific reference to a new separator developed at the University of Alabama. A simple analytical model is presented for the analysis of particle separation in such a system. The role of the applied magnetic field on inclusion removal will be discussed. It is shown that particle velocity increases exponentially with increasing magnetic field strength. At moderate field strengths, the velocity of 50 to 100 u. inclusions· are an order of magnitude larger than those achieved by buoyancy. The separator developed at the University of Alabama is described together with experimental results of laboratory and large scale experiments on purification of molten aluminum. These results demonstrate the capability of the system for producing super-clean metals.IntroductionThe nature of extraction, refining and processing of metals is such that oxides and other non-metallic particles will always be present. This is due to the highly reactive nature of metals with oxygen and other non-metallic elements. The presence of these type inclusions in metals, even in minute amounts, can seriously flaw the reliability and performance of the final product. They not only reduce the strength and the stiffness of the metal/1/, they are the reason behind many of manufacturing defects such as porosity in castings, surface and internal cracks in continuously cast ingots and rolled products, etc., which act to cause premature failure of manufactured parts. In fact, for critical applications such as turbine blades, there is virtually no tolerance for inclusions above ten microns in size /2/. Therefore, removal of inclusions from the liquid metal is an essential processing step.The demand for cleaner metals has brought major changes in the technology and practice of metal refining and casting. Inclusion removal from the melt is currently achieved by passing the melt through a series of melt treatment systems, including induction stirring furnaces, argon-stirred ladle, and ceramic foam and deep-bed filters /3,4/. These systems are generally capable of removing all inclusion particles above 50 microns in diameter, which meets current cleanliness requirements for most applications. However, they may not be able to meet the projected cleanliness levels for critical applications due to kinetic and operational limitations of these systems in removing smaller particles /5/."

Jan 1, 1996

By Jennifer Mager, G. P. Martins, Dean Mussatti

"The role of lead, at low concentrations in high pH cyanide-electrolytes, on the dissolution behavior of gold, has been a topic of scientific and industrial concern for well over a century. The recent paper by Kondos et al [1] at CANMET (1995) this continuing interest and apparent importance. Nevertheless, the mechanism(s) by which this (and other heavy metal) component influences the electrodics of this electrochemical system has still not been unequivocally demonstrated. Instead, several plausible hypotheses, by pioneering researchers in this field, have been advanced and reiterated OVer the ensuing years. While it is generally accepted, based on equilibrium elctrode-potential calculations, that reduction (or co-reduction when oxygen is present in the electrolyte) of lead on the gold surface may occur due to cementation (contact reduction), the cemented lead has never been characterized. The work presented has reexamined the role of lead in this system, by delineating the species distribution of these system components and by interpreting the results of potentiodynamic studies in conjunction with SEM analyses of a gold electrode.1. INTRODUCTIONThe leaching of gold ores in cyanide electrolytes has been practiced for well over a 100 years. Research conducted on this topic has been primarily focused on the effects of operating parameters such as concentrations of oxygen and cyanide, and the pH of the electrolyte; or the leaching behavior of carbonaceous and sulfitic gold-bearing materials.Mechanisms by which pure gold is leached in alkaline cyanide media, with oxygen serving as the oxidant, have been subjected to continual examination and re-examination in the published technical literature during this century. Recently, it has been speculated that without the presence in the electrolyte of trace heavy metals, such as lead or mercury, that gold would not be leachable. Researchers who have tackled this topic, have either considered heavy metals to be a natural occurrence in these systems and ignored the role they may serve in the leaching process, or they have deliberately focussed on controlling their concentrations in the system to undetectable limits. As a result, conflicting findings have been reported for what would appear - depending on the details provided in these reports - to be identical systems."

Jan 1, 1997

Two pilot-plant investigations were conducted in which strong-base resins were compared with activated carbon for the extraction of gold cyanide from leached pulp from the Golden Jubilee Mine. The results show that gold can be recovered with carbon, but that the extraction efficiency is poor, probably because high concentrations of humic and fulvic acids are. present m the pulp. .However the extraction of gold cyamde from this material with strong-base resins JS very effo:1ent, and the overall efficiency of extraction is better with resin than with carbon, even when the concentration of resin is one-third that of carbon, and the flowrate of resin is one-third that of carbon. The results of the pilot-plant campaign reported in this paper led to the conversion of the Golden Jubilee plant from carbon-in-pulp to resin-in-pulp in February 1988.

Jan 1, 1989

By A. G. Merma

In this work, the electrocoagulation technique was studied in order to treat chemically stabilized concentrated oil-water emulsions. This study was mainly focused on the effects of operating parameters such as initial pH, current density, reaction time, electrode distance and inlet concentration on the separation of oil as measured by the chemical oxygen demand -1(COD) method. The synthetic emulsion was prepared from Shell - Talpa 30 oil (3g.L-1) and sodium dodecyl sulfate (1.0 g.L), having a Zeta potential around -70 mv at pH 8.7. The process was carried out in an electrocoagulation cell with a set of four parallel monopolar electrodes. This set consisted of two aluminum plate anodes and two 316L stainless steel plate cathodes. Kinetic curves showed that the electrocoagulation process exhibits three phases: (1) an initial phase, where the COD did not decrease because the solution had not reached the minimum amount of dissolved aluminum required to cause the break-up of the emulsion, (2) a reactive phase during which COD decreased due to possible agglomeration of the precipitates and (3) a steady-state phase where the COD did not change. The results showed that the period to reach the reactive phase decreased as the current density increased and the pH values decreased.

Jan 1, 2009

By J. E. Dutrizac

Fracture-exposed surfaces of sphalerite samples having five different solid solution iron contents ranging from 0.0 wt% to 14.8 wt% Fe were leached for 15 to 120 s at 100°C in 0.3 M Fe(S04)1.5 -0.3 M H2S04 media. The reacted samples were examined using X-ray photoelectron spectroscopy (XPS) which provides chemical state information on the first few nanometers of the solid surface. Surface compositions show that the leaching rate increases with increasing solid solution iron content of the sphalerite. Detailed evaluation of high resolution S2p spectra show that the leaching progresses via the formation of polysulphide species. Disulphide species were not detected in any of the experiments. Examination of the Zn2p and Fe2p spectra indicate little change in the chemical states of these elements over the duration of the experiments. Longer leaching times resulted in the generation of elemental sulphur. The ratios of elemental sulphur to dissolved ferrous ions and zinc suggest that less than 5% of the sulphide is oxidized to sulphate. Morphological studies showed that the elemental sulphur commonly formed at a few isolated sites, such as the grain boundaries. Furthermore, euhedral sulphur crystals were often identified. These observations suggest that at least part of the elemental sulphur forms via dissolved sulphide species which are oxidized in solution by ferric sulphate.

Jan 1, 2003

By Guy Deschênes

In spite of the wide use of lead compounds to enhance cyanidation of free milling sulphide-bearing gold ores, an industrial control method was only implemented four years ago. This study presents the results of the investigation that led to the development of the on-line control technology. Two free milling sulphide-bearing gold ores and high purity minerals were used to develop and test the concept. The first ore contains 2.8 g/t Au, 6.2% pyrrhotite, 2.1% pyrite 0.6 % arsenopyrite, 0.1% chalcopyrite and 0.1% organic carbon. The second ore contains 10.4 g/t Au, 3.2% pyrite, 0.8% pyrrhotite and 0.38% chalcopyrite. The first ore showed a much higher oxidation rate in the pre-leach than the second one and consumed seven times more cyanide. A relation between the formation of thiosulphate and thiocyanate and the additions of lead nitrate were quantified. The ?reducing power?, a titration with permanganate, predominantly determines the concentration of thiosulphate and thiocyanate in cyanide solution. The relation between the reducing power and the addition of lead nitrate at various concentrations of pyrrhotite and chalcopyrite in the ores was established, providing a monitor/control strategy for lead nitrate addition.

Jan 1, 2006

By S. N. Monteiro, E. B. Zanelato, J. Alexandre, M. T. Marvila, A. R. G. Azevedo, G. C. Xavier

The incorporation of industrial waste into ceramic tiles is a major trend in the search for alternative raw materials, and also in the search for environmentally correct disposal of waste. In order to evaluate the effect of the incorporation of residues from the ornamental stone industries, in the properties of ceramic tiles, incorporations of up to 40% by weight of the residue in ceramic mass were studied. It is noteworthy that this residue is constituted basically by limestone and its characterization was performed by grain size analysis, Atterberg boundaries, grain density and chemical analysis by X-ray fluorescence. The specimens were burned at 800 °C and the following properties were evaluated: linear retraction, water absorption and bending rupture stress. The results indicated that the residue of ornamental rocks is a material with potential to be used as a component in the mass of red ceramic tiles.

Mar 1, 2018

By G. B. Harris

Much has been written over the past decade concerning the disposal of arsenic from metallurgical processes. In Canada, there are proposed regulations which would classify arsenic in the Primary Group of twenty one persistent, toxic pollutants to be banned or phased out. Since many nickel and cobalt ores, not to mention those of copper, gold and uranium, contain significant amounts of arsenic, it is pertinent to assess the current state-of-the-art of its disposal. The literature is reviewed, and it is demonstrated that from a purely chemical point of view, the family of ferric arsenates largely immobilize arsenic. There is clear evidence from laboratory studies that both crystalline ferric arsenate (scorodite) and amorphous ferric arsenates in which the molar Fe/As ratio is at least three (Fe/As = 3) have very low arsenic solubility; plant data are given to support this. The debate over the long term stability of these compounds continues however; the evidence presented for long term stability and for compound breakdown is critically reviewed in the light? of the recent structural studies, and the role of base metals in these compounds evaluated. Finally, conclusions are drawn as to the viability of a purely chemical process for the long term disposal of arsenic from metallurgical processes.

Jan 1, 1993

By Ximeng Zhu

The electrochemical behavior of mineral and coal pyrites in stirred and quiescent alkaline boratelsulfate solutions @H 7.9-10.5) have been investigated using cyclic voltammetry. Significant differences in the electrochemical response of these pyrites were observed. At the mineral pyrite surface, three anodic peaks at about -0.8 V, -0.1 V and +0.5 V (SCE) have been detected along with their corresponding reduction peaks. The first two peaks correspond to FeIFeOI) and FeOI)lFe(III) oxidation. The third peak is present for quiescent conditions but disappears as a distinct peak when the electrolyte is stirred. In the upper voltage region +0.30V (SCE), the current increases markedly during stirring and the reactions correspond to the oxidation of pyrite with the formation FeOII) oxides plus elemental sulfur. Also there is evidence that Fe oxy-ions form. Coal pyrites, under rapid sweep conditions display only the first two anodic peaks, the associated reduction peaks and an additional reduction peak corresponding to one or more of the high voltage oxidation products. After prolonged exposure to high potentials, coal pyrite displays reactions similar to those of mineral pyrite but at much higher current densities demonstrating the much higher reactivity of the coal pyrite. The reactivity sequence was Upper Freeport coal pyrite > Pittsburgh coal pyrite > mineral pyrite.

Jan 1, 1991

By A. Bilodeau

A new hydrometallurgical process for the production of refined gold and the recovery of palladium and platinum from silver anode slimes has recently been developed and installed at the, CCR Division of Noranda Inc. The process, which facilitates the production of gold of >99.99% purity in the face of increasing palladium receipts comprises; leaching silver anode slimes with hydrochloric acid and hydrogen peroxide at 95°C to solubilize gold, palladium, platinum and base metals while simultaneously rejecting silver as insoluble silver chloride; precipitating gold from the leach solu¬tion with sulphur dioxide gas in two stages to produce a first-stage high purity gold product and a second stage impure gold which is recycled to the leach; washing, melting and casting of the pure gold; precipitation of a palladium-platinum concentrate from the gold-free solution by reduction with sodium formate at pH 4 and 95°C; and neutralization of the palladium precipitation effluent to pH 10 with lime. The results of laboratory and pilot plant studies leading to the adop¬tion of this process are discussed, and data are presented for each of the unit operations. Details of the engineering of the commercial plant are given, and plant start-up experience is described.

Jan 1, 1987

By K. Walanabe

Kosaka Smelter & Refinery has a history of more than a century as a metallurgical department belonging to Kosaka mine. It has treated for a long time the "Black Ore" or the complicated concentrates dressed from it. The "Black Ore" is composed of black sulfides. It contains not only valuable metals such as gold, silver, copper, lead and zinc but also some impurities like arsenic, antimony and bismuth. With the development of Kosaka's floatation technology, five kinds of concentrates (copper, zinc, lead, pyrite and barite) have been separated from the "Black Ore" but the separation was not complete and each concentrate contained some unfavorable impurities. In 1980s the highly appreciated yen and the drop of the metals prices forced many domestic mines to close their operations. Since then Kosaka Smelter has changed its way of operation to a custom smelter. Now more than 95% of copper concentrates are imported to take advantage of this technology of "Black Ore" treatment. It mainly treats the raw materials that contain high gold and silver like the "Black Ore". Recently, Kosaka has been working on the recycling of the metals from the printed circuit board scraps and sludge which contain some precious metals. The volume of the recycled metal is continuously increasing.

Jan 1, 2003