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By Karl-Michael Zett, Marcus Kirschen, Ashraf Hanna

"Bottom purging systems are well established practice in refining metallurgy and an increasingly important technology for the EAF process in steel industry. Direct bottom purging provides efficient mixing of the entire melt volume, increases turbulence intensity in the melt, and improves mass exchange of alloy additions or oxygen. Continuously rising columns of dispersed gas bubbles helps to increase removal of volatile components carbon monoxide and hydrogen avoiding boiling retardation. Direct purging (DPP) systems provide cost benefits especially for EAF processes where metallurgical constraints have to be considered, e.g. for alloyed and stainless steel production, foundries. Case studies are presented.IntroductionCurrent EAF Technology and Production Constraints in Steel IndustryApproxinlately 30 % of steel, 446 Mio. tonnes in 2011, was melted in the electric arc furnace (EAF) with increasing tendency due to its large flexibility in production volume and raw materials. With recent increase of prices for ferrous raw materials the requirements for production of high quality steels from low quality scrap, direct reduced iron (DRI) and blends of ferrous raw material in various qualities increased. Maximum yield of ferrous raw material, oxygen, carbon, and alloys and minimum energy costs are of high importance. At modem high productivity levels even small process improvements provide considerable cost savings. Such improvements are caused, e.g., by efficiency increase of mass and energy transfer in the EAF. Optimization of flow pattern in the steel bath is therefore important for efficient melting of scrap and DRI and high homogeneity of the melt [1-4]."

Jan 1, 2013

By Junji Shibata

The waste acid mixture whose main component is phosphoric acid, is discharged from the etching process in the liquid crystal production industry. In order to separate impurity acids from the phosphoric acid, trioctyl phosphate (TOP) is used as an extractant. TOP can extract acetic and nitric acids selectivity. The extraction and stripping operations are carried out for the acid mixture by beaker-scale experiments and countercurrent multistage operations with mixer-settler equipment. TOP selectively extracts the acetic and nitric acids in the acid mixture. From the results of the McCabe-Thiele analysis obtained by beaker-scale tests, the extraction for acetic and nitric acids are approximately 100%, respectively, by 6-stage extraction with a phase ratio (A/O) of 0.4. On the other hand, almost all of acetic and nitric acids are stripped with water from the organic phase by 4-stage stripping with a phase ratio (A/O) of 1.0. About 95% of acetic and 98% of nitric acids can be removed from the acid mixture without extracting phosphoric acid in case of the mixer-settler equipment operation. There are several steps such as slicing, lapping, chemical etching and mechanical polishing in the silicon wafer production process. The chemical etching step is necessary to remove any damaged layer caused in the slicing and lapping steps. The typical etching liquor is the acid mixture comprising nitric acid, acetic acid and hydrofluoric acid. The waste acid is treated by a neutralization method with a high alkali cost and balky solid residue. A solvent extraction method is applicable to separate and recover each acid. Acetic acid is first separated from the waste liquor using 2-ethlyhexyl alcohols as an extractant. Then, nitric acid is recovered using TBP (Tri-butyl phosphate). Finally hydrofluoric acid is separated with TBP solvent extraction. The expected recovered acids in this process are 2mol/L acetic acid, 6mol/L nitric acid and 6mol/L hydrofluoric acid. The yields of this process are almost 100% for acetic acid and nitric acid. On the other hand, it is important to recover and reuse the metal values contained in various industrial wastes from a viewpoint of environmental preservation. Most industrial products are made through processes to separate impurities in raw materials, solid and liquid wastes being necessarily discharged as industrial wastes. Chemical methods such as solvent extraction, ion exchange and membrane separation, and physical methods such as heavy media separation, magnetic separation and electrostatic separation are considered as the methods for separation and recovery of the metal values from the wastes. Some examples of the application of solvent extraction to the treatment of wastes such as Ni-Co alloy scrap, Sm-Co alloy scrap, fly ash and flue dust, and liquid wastes such as plating solution, the rinse solution, etching solution and pickling solution are introduced.

Jan 1, 2003

By Jeffrey Shepherd, Scott R. Smith, Eduard Guerra

"Electrochemical and spectroscopic evidence for the dissolution of a Au electrode by meso-2,3- dimercaptosuccinic acid (DMSA) from an acidic LiCl04 electrolyte is presented. Near the potential of zero charge, DMSA was determined to form a stable layer on the metal surface but at more anodic polarizations, DMSA was displaced from the metal through an oxidative process. The anodic displacement of the layer from the electrode resulted in a small amount of Au that was detected in the electrolyte using atomic absorption analysis. The extent of Au dissolution, was monitored while holding the potential of the electrode for 24 hours at the thermodynamic Eo/H,O in LiCl04 electrolytes containing 10 mM DMSA. This routine resulted in detectable quantities of a soluble Au-DMSA complex in the electrolyte and the greatest leaching was observed at a pH = 2.0. At room temperature, the leaching rate was stable at 10.9 µg cm·2 hr·' however, upon increasing the temperature to 50.0°C, the rate of Au dissolution increased yielding an average rate of extraction of 40.1 µg cm·2 hr- 1. Interestingly, after the first 12 hours of leaching at 50.0°C, the leaching current decreased dramatically suggesting surface passivation which prevented further Au extraction. The implications of this process in the industrial leaching of Au will be discussed.IntroductionThe use of cyanide in the industrial process of leaching Au from ores has raised concerns regarding both operational safety and environmental issues surrounding the disposal of spent leaching eftluents in tailings ponds. Depending on the chemical nature of the processed ore, the spent solutions that are released into the tailings ponds can contain toxic cyanide, either dissolved or complexed with different metals and may pose serious risk to wildlife as well as freshwater contamination to nearby water systems. Because of these issues, some recent studies have focused on the exploration of more environmentally-friendly molecules to selectively leach Au with appropriate kinetics. However, to effectively leach Au into an aqueous solution, a suitable ligand that reacts to form a stable chemical bond with Au is needed to form soluble Au complexes that can be later recovered [I]. Recently several sulfur bearing alternatives have been shown to leach significant quantities of Au in aqueous solutions. These include thiourea [2], thiocyanate [3], and thiosulphate [4]. However, alkylthiols are also known to quickly form a stable covalent Au-S bond [5], but have been relatively understudied in term of their ability to leach Au in solution, even though some short chain thiols are water soluble and relatively nontoxic."

Jan 1, 2012

By Chao Zhang, Kexin Jiao, Yi Qian, Jianliang Zhang

Now low-grade iron ore were widely used. However, one prominent problem is that the content of trace elements is higher than that in high quality iron ore. For the requirement of the content of Mn, Cr, Ni, Cu, and Ti in hot-rolled steel sheet and strip, the upper limits of these elements in sinter will be studied in this paper. Using the activity model of aggregation of electronic phased slag composition, the distribution ratio of each element in converter is analyzed and the content of each element in hot metal is calculated. Furthermore, through the thermodynamics method, the distribution ratio of each element in BF is analyzed and the content of each element in raw material is calculated. The upper limits of Mn, Cr, Ni, Cu, and Ti in sinter can be determined by calculating, the values are as follows: Mn 0.767%; Cr 0.552%; Ni 0.055%; Cu 0.159%; Ti 0.108%.

Jan 1, 2015

By S. W. White

Plasma arc technology is increasingly being used to process a number of waste materials. In present research, plasma technology is being investigated to treat waste magnesium baghouse dust, which is a waste material from the Magnetherm process. This dust contains mostly MgO, but also contains NazO, CaO, and KzO. Plasma energy is to be used along with a reducing agent to produce pure gaseous magnesium while keeping the other materials in a slag. The magnesium will then be collected by rapid quenching. A non-transferred arc plasma torch is ideal for this reaction because of its high enthalpy and improved energy efficiency over conventional methods. Another advantage of plasma is that it allows for the pre-heating or pre-reacting of fine particles before contact with the melt. Thermodynamic calculations using the Gibb energy minimization method were used to determine the most stable compositions of the materials at various temperatures. Energy balances have also been calculated. These results conclude that we can recover approximately 98% of the magnesium with a proper quenching technique. The calculated results are compared with the experimental data, and good agreement between them was observed.

Jan 1, 1999

By Kimio Itagaki

As a fundamental study for smelting the copper matte with high contents of arsenic and antimony in a strongly reducing condition, phase relations between the liquid matte and copper-rich alloy phases in the Cu-Fe-S-As or -Sb quaternary system and between the liquid matte and iron-rich alloy phases in the Cu-Fe-S-As or -Sb system saturated with carbon were determined at 1473 K by a quenching method. Activities of arsenic and antimony in these systems were also measured at 1473K by Knudsen cell-mass spectrometry. Furthermore, distribution ratios of silver, gold and platinum between the liquid matte and copper-rich or iron-rich alloy phases were determined in relation to the arsenic or antimony content in the systems. On the basis of these data, the elimination of arsenic and antimony from the matte to the iron-rich alloy (speiss) and the recovery of precious metals in reduction smelting of the copper matte were evaluated. It was suggested that the addition of pig iron to make a strongly reducing condition and form the iron-rich alloy, which is fluid at smelting temperatures, will be useful for fixing arsenic in the speiss.

Jan 1, 2006

By Emily Chen, Randolph Kirchain, Gabrielle Gaustad

"As prices and demand for aluminum metal have increased over the past few years, secondary production has begun to outpace primary aluminum production. However, while recycling of packaging and automotive scrap has continued to increase, aerospace secondary materials remain a largely untapped resource. Shredded or co-mingled aerospace scrap has a high degree of compositional uncertainty due to the prevalence of high copper and high zinc alloy series. Although it is clear that upgrading strategies enable increased usage of aerospace scrap, it is not clear that they would be economic or efficient. Previous studies by the authors have shown that modeling techniques, specifically chance-constrained optimization, provide the ability to evaluate upgrading options in terms of potential aerospace scrap utilization and production cost. Three specific cases are analyzed: a dismantled case, a sorted case, and a shredded or co-mingled case; sensitivity analysis of resulting compositional uncertainty is also presented.IntroductionAluminum recycling has a number of key environmental and economic benefits. Secondary recovery forestalls depletion of non-renewable resources and avoids the deleterious effects of extraction and winning (albeit by substituting some effects of its own). For most metals, the latter provides strong motivation for recycling; for light metals, like aluminum, the motivation is compelling[1]. Fortunately, as prices and demand for aluminum have increased greatly over recent years, secondary production has begun to outpace primary production (Figure 1). However, while the recycling rates of many aluminum products such as used beverage cans and cars have increased over this period, aerospace secondary materials remain a comparatively untapped resource.This untapped resource for scrap aluminum is a very large one; aluminum is the primary aircraft material comprising about 80% of a planes unladen weight[2]. It is used extensively for airframes, landing gear, engine components, propellers, and interior trim. A standard Boeing 747 jumbo jet, for example, contains approximately 75,000 kilograms of aluminum[2]. At an approximate rate of 300 per year, more than 6,000 civil aircraft are forecast to arrive at end-of-life in the next 20 years, potentially creating a large aerospace scrap market[3]. Many military aircraft are already available for possible scrap use, however, most are currently in storage at air force bases around the world[4]. The underutilization of these aerospace scrap materials indicates a lack of economic end-of-life options."

Jan 1, 2008

By Padmavathy Mahadevan, Samir Chefai, Eduard Guerra

"Electrocoagulation is a technique for treating wastewater streams from metallurgical plants whereby electrodes are corroded to generate gases (most notably oxygen at the anode and hydrogen at the cathode) and solid particulates which acts as substrates for coprecipitation of impurities. The performance of electrocoagulation reactors, in terms of their efficiency for removing a particular impurity, is highly dependent on several factors, most notably: the nature of the electrodes, the spacing between electrodes, the current density, the height of the electrodes, the solution flow rate, and application of periodic current reversal. Because these variables have complex interactions, in order to ensure reliable scale-up of laboratory results, experiments should be conducted under conditions that closely match those that would be employed at an industrial scale. To that end, this article describes the design and commissioning of a versatile laboratory scale electrocoagulation reactor that allows for the control of all the aforementioned variables along with the ability to measure the instantaneous spatial distribution of current within the reactor.IntroductionArsenic is often removed from metallurgical waste streams in stirred tank reactors by coprecipitating it with ferric ions as an arsenical ferrihydrite [ 1]. Electrocoagulation is an electrolytic technology that can accomplish the same task, but has not yet been widely adopted to treat metallurgical waste streams [2]. The electrocoagulation process involves the use of an external DC power supply to drive the dissolution of a relatively non-toxic metal into the wastewater stream, usually either iron or aluminum, which then largely precipitates as oxyhydroxide phases that adsorb undesired impurities [l]. At the anode, the metal is dissolved and oxygen is often evolved, lowering the local pH and enhancing metal ion solubility."

Jan 1, 2012

By M. Jennings

In 1987, Echo Bay discovered a major silver/gold ore body at their McCoy property in Nevada, and quickly made a decision to build a 5000 tpd mill which was expanded during the design to 7500 tpd. Since the ore reserves consisted of cyanide leachable oxide as well as sulfide, the plant flow sheet involved an oxide leach, a gravity circuit, and lead sulfide and a pyrite sulfide recovery by flotation. The paper describes the process development, equipment selection, plant design and the startup of the oxide treatment.

Jan 1, 1990

By Hiroshi Maeta, Takao Kino, Hirota Osono, Kikuo Matsusaka, Azusa Shida

"Prior to refine an ultra-high purity material, it is necessary to estimate the surface cleanness of a base material. In this report, the cleaning method of a surface for refining of an ultra-high purity aluminum has been studied. Aluminum sample of 99.999% purity was p9lished mechanically and electrically and washed with various solvents. Surface composition and a depth profile near the surface were examined. Based on the experimental results, surface structure of an ultra-high purity aluminum was discussed.IntroductionRecently, studies on high purity metals have become of interest, and we have reported .various properties of an ultra- high purity aluminum1- 2)In order to purify a metal, it is necessary to clean a work area and to make vacuous as possible. So, we are studying the purification of aluminum by an ultra-high vacuum refining system and a zone refining system set up in a clean room with cleanliness class of 1000.Now, in order to avoid a mixing of impurities into the refining metal, a surface cleanness of a base metal is very important factor. The purity of the base aluminum used our work is 99.999%, but the surface state of the base aluminum is not clear. Aims in this work .are to investigate the surface state and to obtain the cleaning method of the base aluminum.Experimental procedureSamples used in this work were 99.9% (3N), 99.99%(4N) and 99.999% (SN) aluminum produced industrially and 99.9999% (6N) aluminum purified by us."

Jan 1, 2000

By Donghai Li, Cheng Pan, Xuyang Liu, Xuewei Lv, Chenguang Bai

"Fine chromite ore is the common raw material to produce ferrochrome alloy through the submerged electric furnace process. The electric resistivity of fine chromite ore plays an important role in the operation efficiency because it determines the current distribution. The effect of particle size and the contact area of the particles on electric resistivity for several of chromite were investigated at room temperature, and the relationship between the electric resistivity of mixed particles and the volume fraction of lump ore to fine ore was also studied. The results shown that the electric resistivity increases with the increase of particle size, and the electric resistivity of mixture decreases with the increase of volume ratio of fine ore.IntroductionChromium is one of the most important alloying elements in manufacturing of stainless steel that used at high temperature and corrosive environment applications [I, 2]. As the raw materials to be charged into the steel, ferrochromium alloys and charge chromium are produced directly by smelting of chromite ore with the reducing agent in submerged electric arc furnace (SAF). During the process, the oxides of chromium and iron were reduced by carbon and meanwhile the electrical energy were consumed [3,4]. The ideal industrial process is to achieve high recovery level of Cr and Fe with minimal power consumption. In SAF process, the electric resistivity of charge stock has significant effect on the current distribution, which determines the heat distribution, molten bath structure and chemical reactions in the furnace. High resistance of the charge is desired to reduce the current distribution through the charge stock, thus the electrodes may insert into the charge stock with proper depth to form a high temperature arc heat source, and proper smelting can be realized[5]."

Jan 1, 2012

By K. Abe

Onahama Smelter has two green-charge reverberatory furnaces and the annual smelting capacity is 600 thousand tons copper concentrate. In addition to the concentrate, various kind of industrial wastes has been processed and utilized. First, the brick waste from converter is ground and used as raw material of castable for repairing the copper melt launders. Second, the slag containing calcium-sulfide from other foundry is fed to the reverberatory furnaces. Calcium sulfide is oxidized to CaO. The melting rate of concentrate is accelenlled and the slag loss is decreased. Third, the tip tire made of waste car tire is charged into the reverberatory furnaces as fuel. The steam of waste heat boiler for turbine generators has been increased so as to decrease the electricity cost. Fourth, the sulfur accretion from other chemical plant is blended into the copper concentrate and the sulfur is recovered as the gypsum for sale. Fifth, the processed waste oil has been utilized in the copper concentrate dryer by which the smelting capacity was increased effectively. Consequently, Onahama smelter contributes to the society by processing the wastes to the harmless slag and utilizing them as fuel through the copper smelting.

Jan 1, 1996

By Jing Zhang, Chenguang Bai, Fusheng Pan

"The microstructure and hot deformation behaviour of an Er-modified Mg-Zn-Ai alloy were evaluated. The results showed that the addition of rare-earth Er changed the morphology of the quasi-continuous grain boundary networked eutectic compound to globular particles. Moreover, a self-strengthening effect was identified for the alloy, which determined its deformation behavior. After hot extrusion, the yield strength and elongation to failure of the Mg-Zn-AI-Re alloy at 200°C were increased by 105% and 120%, respectively, due to an emerged dynamic precipitation strengthening mechanism.IntroductionMagnesium alloys are attracting increasing attention for applications in automobile, electronic devices and hand tools for weight reduction and higher fuel efficiency, because of their lightweight and a high specific strength. However, application of Mg is still very limited. The largest applications are still those non load-bearing castings used at room temperature, such as box case, housing, and covering. One of the main reasons is the inadequate absolute strength both at room temperature and elevated temperatures (> 100°C) of the commercially used AZ, AM series alloys, due to the incoherent interface between the secondary phase y-Mg17AI12 and Mg matrix, as well as the low thermal-stability of the y phase [1]. Besides, the heat-resistant magnesium alloys which contain rare earth (Re) as the main alloying element are very expensive. The other reason is their poor deformability. The key solution is therefore to develop low-cost heat -resistant wrought alloys."

Jan 1, 2012

By Alan DonaldsoN

Plasma Quench production of titanium is the thermal dissociation of titanium tetrachloride into gaseous titanium and chlorine followed by rapid quenching to prevent back reactions. Titanium tetrachloride dissociates into titanium and chlorine atoms at 5000 K. Expansion through a Delaval nozzle accelerates the gas to supersonic speed cooling it very rapidly. Cooling rates are as high as 7exp 1 0 Kelvins per second. Injected hydrogen reacts with condensed titanium particles to form titanium hydride and with the chlorine to form hydrogen chloride. We have produced titanium powder at 20 kglh in a continuous reactor. Costs are projected to be lower than the Kroll Process at large enough scale. Most of the cost reduction would result from elimination of magnesium as a reducing agent and much lower capital costs.

Jan 1, 2001

By V. B. Telles, D. C. R. Espinosa, J. A. S. Tenório

"The purpose of this work was to study the reutilization of the steelmaking dust, derived from steel production in the electric arc furnace (EAF), in iron ore sintering process aiming zinc elimination. In each sintering process were collected sintered samples, these materials were analyzed by chemical analysis using atomic absorption spectrophotometry in order to determine the zinc content. Samples of not sintered mixtures were also characterized by chemical analysis aiming to determine the initial amounts of zinc, i.e. in order to check the zinc amounts present in the mixture before the sintering process. The comparation among the zinc contents of samples sintered and not sintered allowed to determine the elimination of zinc during the experiments. Results showed that the zinc elimination in the process is proportional to the ratio reducer/waste. The zinc removal was lower when the reducer/waste ratio was decreased.IntroductionThe electric arc furnace dust (EAFD) is a residue generated in the steelmaking process using electric arc furnace. Aproximately 30% of all steel produced (in the year 2009) was obtained through electric arc furance (EAF). In the United States of America the percentage of this process in the total crude steel production was about 62% in 2009, while in 2000 this percentage was only 47% [1].The iron ore sintering is a process that reuses wastes generated in metallurgical industries. However, the materials used must be physical and chemical characteristics compatible with the blast furnaces.The quantity of zinc, cadmium, chrome and other metals present in the EAFD depends on the quality of the scrap used to feed the EAF and the type of steel that it is been made [2,3]. The reuse of EAFD waste is interesting to steelmaking processes because of its iron content. However the presence of zinc inside a blast furnace is undesirable since the zinc oxide can be deposited on the blast furnace walls and in the drivers of gas output, interrupting the flow. Another part of the zinc oxide can form deposits on the refractory lining of the blast furnace [4,5]."

Jan 1, 2012

By Kohei Yajima

The dusts and fly ash generated from the steelmaking processes and municipal solid waste incineration processes contain metallic elements such as Fe, Zn, Pb and Cd with considerable amount of halogens. In Japan, zinc in dusts is recovered by Waelz kiln or MF process, etc. However, the presence of halogen in the dust affects the evaporation and condensation behavior of zinc and other metals, and disturbs the direct recycling of dust to steelmaking processes, because alkali or heavy metals reacted with halogen vaporize easily as halides and/or oxyhalide compounds in pyrometallurgical process. Recently, the formation mechanism of zinc oxychloride vapor was investigated and the formation of zinc oxychloride such as ZnOCl was proposed. However, considering the practical operation, the effect of water vapor on the evaporation behavior of oxychloride is not fully clarified yet. This study is focused on the investigation of evaporation behavior of ZnO with Ar- O2-HCl-H2O atmosphere.

Jan 1, 2008

By Ning Wang, Bing Xie, Hong-Yi Li

"Compared to traditional sodium roasting, calcified roast inhibits chlorine pollution. A vanadium extraction technique based on a calcified roast is especially suitable for vanadium slag with high calcium content. In this report, V205was extracted from vanadium slag by calcified roast followed by acid leaching and hydrolysis precipitation. In optimized conditions, the high silicon low vanadium slag was roasted at 850'C for 2 hours without CaO addition. The roasted materials were leached with 35 % H2SO4 in liquid/solid ratio of 5:1 (mL/g) at 95OC for 4 hours. The extraction of vanadium was as high as 97.66 %. These results are instructive to V2O5 production in industry.IntroductionVanadium slag is produced in converter, sodium salt roasting is the commonly used technique to extract vanadium. In sodium salt roasting, vanadium slag is roasted with sodium salts including sodium chloride and soda as additives, followed by leaching with acidic or basic solution [1]. However, in this process chloride reacts to produce corrosive gases including HC1 andCl2- SO2 and SO3 can also corrode equipment severely and are also an environmental contaminant. The low melting point of sodium salts leads to fusion agglomeration, which blocks vanadium oxidation and thus decreases the extraction rate of vanadium. A large amount of sodium salts consumed as roasting additives increases the production cost. Moreover, sodium salt roasting requires low CaO content in vanadium slag. When the CaO content increases to 1%, V2O5 extraction can amount to 4.7%-9% [2]. For vanadium slag with high CaO content, the sodium salt roasting technique leads to low vanadium extraction rate."

Jan 1, 2012

By Cz. Mazanek

Specific biostimulating and anticancerous properties have been observed in peat, Ash Vacanta, and in an amorpous silica that is obtained as a by-product of alumina production from Turow clay in Poland. The anmphous silica was characterized and found to have a large specific surface area. This property may account for the beneficial characteristics of the material.

Jan 1, 1989

By Heinz Böni, Christian Ludwig, Bernhard Steubing, Uca Silva

"Chile will soon have to find solutions for dealing with rapidly growing quantities of Waste Electrical and Electronic Equipment (WEEE) due to its strong economy and fast increase of internet and communications technology usage. To support this process, the state of the Chilean recycling infrastructure as well as government, industry and consumer efforts to deal with ewaste were analyzed. Current e-waste quantities were assessed and future flows were predicted using a material flow analysis model. In this model computer hardware was used as tracer equipment for WEEE. Best available numbers indicate that today’s formal recycling infrastructure receives less than 3% of the annual quantities of computer waste. This study represents the most comprehensive analysis regarding e-waste in Chile, identifying relevant streams of e-waste and providing a basis for authorities and producers of electronic goods in order to take the necessary actions to establish an adequate recycling system.IntroductionSince 1991, Chile has experienced a period of strong economic growth. It is amongst the countries with the fastest development in the sector of Information and Communication Technologies (ICT) in Latin America and the number of people with access to ICT has been growing rapidly. The high growth rates of the computer market over the last years are representative for the ICT sector with the consequence that the generated quantities of electronic waste are increasing rapidly [1, 2].Waste Electrical and Electronic Equipment (WEEE) or e-waste is “any appliance using an electric power supply that has reached its end-of-life” as defined by the OECD [3]. Even though the overall waste management in Chile has improved much over the last decade, the issue of ewaste was hardly addressed. Due to the value of the materials contained in computer waste - such as precious metals, basic metals as copper or plastics - it may be assumed that an important quantity is already being recovered. This usually takes place on the informal market under questionable conditions for human health and the environment [1, 2, 4]."

Jan 1, 2008

By Núbia Suely Silva Santos, Alexandre da Silva Crespo, Frederico Muylaert Margem, Sergio Neves Monteiro, Anderson de Paula Barbosa, Michel Picanço Oliveira

"Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. The fibers extracted from the petiole of the buriti palm tree is a relatively unknown but promising natural fiber for composite reinforcement. In this work, a statistical analysis of the density of buriti petiole fibers using the Weibull methodology was performed. An attempt to correlate the fiber density with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the buriti petiole fiber diameter and corresponding density. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.INTRODUTIONIn the past decade polymer composites reinforced with natural fibers obtained from cellulose-based plants, known as lignocellulosic fibers, have been applied in several engineering sectors, specially the automobile industry as both interior and outside component [1-4].Environmental benefits as well as economical, social, and technical advantages are actually promoting the substitution of these lignocellulosic for the traditional glass fiber in polymer matrix composites [5]. Today several lignocellulosic fiber are being extensively investigated [6-11] and considered for reinforcement of polymer composites. Some relatively unknown lignocellulosic fiber with reinforcement potential, however, still need to be characterized aiming at future application in composites. This is the case of the fibers stripped of from the petiole of the buriti palm tree, which is endemic in the central and northern regions of South America [12,13]. Preliminary works on the possibility of using the buriti petiole fibers as composite reinforcement, has shown favorable results [14,15]."

Jan 1, 2012