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By Wilson Acchar

The accelerated growth of urbanization processes and current environmental concerns brought to light the existing enormous quantity of construction and demolition waste (C&DW). Considering the frequent lack of adequate landfill areas available for the disposal of these materials, their use in the manufacture of ceramic products has been attracting a growing interest from researchers and is becoming common practice, with the consequent relief in public administration concerns for the C&DW appropriate management. This work describes the study of clay-based products added with C&DW collected directly from the construction industry. Samples containing up to 50 wt.% C&DW were uniaxially pressed and sintered in air in an electric furnace (950-1150 °C, 1 hour). Sintered test pieces were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that up to 50 wt.% C&DW can be added to the clay material, with no degradation in the final product properties.

Jan 1, 2009

By Qingzhu Li

The brewing industry byproduct, spent grain (SG), was evaluated for its ability to adsorb Ag(I) from aqueous solutions. Ag(I) adsorption was dependent on solution pH, contact time, adsorbent dose, initial Ag(I) concentration and temperature. The kinetic data were well described by pseudo-second-order kinetic model, indicating that chemical adsorption was the rate-controlling step. The equilibrium data followed Freundlich isotherm rather than Langmuir isotherm, suggesting heterogenity of the adsorption sites on spent grain. Ag(I) desorbed from Ag(I)-loaded spent grain was also evaluated in this study. HCl, NaOH, Na2S2O3 and ultrapure water were chosen as eluants and desorbed Ag(I)-loaded spent grain for 30min, Ag(I)-loaded spent grain desorbed in 0.1M Na2S2O3 exhibited higher elution efficiency as compared with other eluants. The results indicated that application of spent grain for adsorption and recovery of silver from aqueous solutions was feasible.

Jan 1, 2009

By Luciano R. G. Santos

Keywords: biosorption, cadmium, copper, biomass, spent zeolite. The majority of the industrial activities produce some kind of solid wastes. In this work two industrial residues (spent zeolite and wood sawdust) were chemically modified to increase their heavy metals sorption capacities. Manilkara longifolia (a Brazilian plant known as parajú) sawdust was first treated with NaOH and modified with different citric acid concentrations (0.6-1.2 mol/L) at 120°C, for 90 min. Infrared spectroscopy confirmed the presence of carboxylate groups in the wood structure as result of their mixing. Similarly, spent zeolites were also submitted to a chemical treatment (NaOH) to remove carbon deposited during oil cracking and to recover its sorption capacity. Batch experiments carried out at ambient temperature showed that both materials present sorption capacity for copper and cadmium comparable to weak acid ion exchange resins. A maximum of 78 mg-Cd/g and 59.7 mg-Cu/g as well as 29.9 mg-Cd/g and 14.6 mg-Cu/g were observed for the sawdust and the zeolite, respectively. The results were modeled according to the Freundlich and Langmuir equilibrium isotherms and compared with results of other studies.

Jan 1, 2005

By Hong-ying Xia, Bao-bao Wang, Jin-hui Peng, Bing-guo Liu, Li-bo Zhang, Zhi-qiang Li

Based on optimization using response surface methodology designed by Box- Behnken, to study the interaction of wet industrial salt with moisture drying temperature (50-90 ); duration (10-50s); and the weight of the materials (20-60g). The results show that: the experimental parameter conforms to the quadratic equation model to influence the moisture content and the dehydration speed., in analyzing the significance and the interaction of various factors, the optimum by the Design Expert software conditions for drying with microwave radiation include temperature of 90 , duration of 10s, and sample mass of 26g. Verified by experiment, the moisture content after drying is less than 0.25% and the dehydration rate reached 1.37g/min, between the predicted value and the actual value confirmed good fitting degree.

Jan 1, 2015

By R. Hurman Eric

Within the Ag-Pb-S ternary system, the boundaries of the immiscibility region together with the tie-line distributions were re-established at 925°C by the equilibrium-quenching technique where samples were kept in evacuated and sealed silica capsules. Activities of Pb were measured by the dew-point method along the Ag-Pb binary at 925°C, 1100° and 1200°C. positive deviations were observed and the results were modeled by the Krupkowski formalism. Activities of Ag, Pb, and S, along the ternary miscibility gap were calculated at 925°C by utilizing the boundaries binary thermodynamics, phase equilibria and tie-lines. Activities of PbS within the pseudobinary Ag2S-PbS mattes were also measured by the dew-point technique and the results were again modeled by the Krupkowski formation Where negative deviations were observed.

Jan 1, 2003

By Jesús Contreras

Within its programme for continuous improvement and cultural change, Atlantic Copper has installed the Six Sigma methodology as a basic tool for the improvement of management techniques in all its production centres. Following an implementation period, the methodology is widely used for analysis and improvement, not only in the fields of production and maintenance, but also in other areas of the business such as supplies or energy management. The present paper describes, phase-by-phase, the project that was developed to improve the quality of converter slag through the application of Six Sigma techniques, from the initial set up to the final results obtained.

Jan 1, 2005

By María Eugenia Castro, Silvia Galasso, Jorge Duca, Claudia Osuna, Ernesto Esparza

"We present a procedure for treatment of non-active solutions equivalent to the solutions obtained from dissolution of ionic exchange resins used in purification of a nuclear reactor primary cooling system containing Co, Ni, Cs and its isotropic varieties as main radioactivity source. Finally it is immobilized into a ferritic matrix by calcination which avoids its future leaching into environment.In order to achieve the objective of this treatment, a bivalent and a trivalent iron salt is added to the solution. Then, either a base or an acid is added, depending on the initial pH of the treated solution, with a Cs precipitating additive in order to reduce Co and Cs by precipitation, flocculation and adsorption. Controlling the amount of precipitating reactives it is possible to modify the activity/volume rate becoming a medium into a low radioactivity waste.The leaching test result applied over the ferritic sample is lower than the minimum limit established by law. Therefore, it can be kept safely in a interim storage."

Jan 1, 2008

By Kiyoshi Shibata

A new assessment model has been proposed for metal production and its recycling system. The model consists of three processes, smelting of ore, cascading and upgrading of metal scrap. The present approach is to assess the total energy consumption of the system, by introducing two equations for describing the relationships between critical impurity content and the mass of production or scrap recycling. The total energy consumption in the system can be described as a function of recycling rate and performance of the upgrading process. The present model suggests that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in the systems. Especially, such points should be explicitly controlled in recycling of aluminum. The potential capability of this model was also discussed by obtaining several quantitative information required for the process design and the operational control of beneficial recycling of metals.

Jan 1, 1998

By Joseph Sofra

It has become increasingly evident that sustainable metals production in the 21" century requires producers to balance the needs of cost effective, high value production with that of responsible plant operation. This is becoming more difficult as lower grade and more complex feed materials, including recycled scrap and residues, arc being processed to reduce production costs and decrease exposure to primary metal market fluctuations. One particular facet of the metals industry facing these challenges in the 21 st century arc copper producers. The recent steady decline in the copper price has seen the industry cut expenditure, tighten control on income streams and focus on high returns on capital investment. For these reasons copper producers arc looking towards flexible technologies that can deliver high value products, with minimal environmental impact at low capital and low sustainable operating costs. Ausmelt's Top Submerged Lancing (TSL) technology for copper production is a low cost, proven technology for the processing of both primary and secondary copper materials. Both the smelting and converting operations introduce significant advantages in environmental performance, improved process efficiencies and high rates of metal recovery. Ausmelt has made significant gains in the past 4 years in establishing a strong market position for its copper technology. New installations in China, South Africa and India as well as existing operations in Zimbabwe and China have demonstrated its effectiveness. This paper reviews the application of Ausmelt Technology for both smelting and converting of primary and secondary sources. It discusses Ausmelt's design and implementation philosophy, and how this philosophy meshes with the needs of the end user.

Jan 1, 2003

By Zhigang Liang

Investigation into the mixing of 150t ladle furnace by two-nozzle jetting was performed by a water model simulation of 1:4. The effects of nozzle arrangements including separation angle, radial position and asymmetry as well as tracer adding position on the mixing time were studied. The most favorable mixing is achieved when the two nozzles are symmetrically arranged at half radii in the ladle, with 45o separation angle. The empirical relationship between the mixing time and stirring power intensity has been established for two-nozzle jetting based on the present experimental results. In addition, the swelling above bath surface is also investigated with two-nozzle jetting.

Jan 1, 2009

A novel, low-pressure adaptation of Praxair?s coherent jet technology utilizing CoJet lances was developed for application at Inco&apos;s Copper Cliff Smelter where oxygen is available in large tonnage quantities but only at relatively low supply pressures (< 193 kPa header pressure). The project objectives were to evaluate the effect of coherent jet technology on controlling oxygen lance accretion (?horn?) formation and to increase oxygen efficiency in the Inco Oxygen Top-Blowing Nitrogen Bottom Stirring (TBBS) MK Reactor used for converting nickel- contaminated chalcocite to semi-blister copper. This paper describes the development and subsequent implementation and testing of two CoJet lances in this application.

Jan 1, 2005

By J. Antrekowitsch

Keywords: residues, fluorides, chlorides, zinc, steel mill dust The recyclability of various nonferrous metal wastes often suffers from a relatively high fluorine and chlorine content. Both are inserted in most cases by the use of plastic contaminated scrap and a wide variety of different coatings. These halogens lead to poor product qualities and off gas contamination. Especially the history of zinc recovery from steel mill dusts shows, that the today common hydrometallurgical options are on their limit and therefore are not sufficient in most cases. This thermochemical study should give more information about different pyrometallurgical options, that offer both a chlorine and fluorine reduction and efficient zinc recovery, preferably in one process step. Selective evaporation in different atmospheres and conversion with the use of hydrogen are the main parts in this study. The results combined with the relatively small information available from literature should provide a basis for further investigations in this field.

Jan 1, 2005

By Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By Zhaohui Xie, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

A high carbon low-grade gold ore, in which gold mainly occurs in carbonaceous matters, is a typical refractory gold ore whose conventional cyanide leaching extraction is only 12.9 %. In this paper, by the process of flotation-roasting-leaching, gold was effectively enriched and extracted. The flotation results showed that the enrichment ratio of gold was relevant to that of carbon, indicating that gold occurred in close association with carbon. A concentrate containing gold 7.26 g/t and carbon 12.37 % was obtained, with gold recovery 83.10 % and carbon recovery 90.24 %. Subsequently, the roasting of flotation concentrate favorably made the removal rates of carbon and sulfur reach 99.81% and 98.79%, respectively. After roasting, the gold in the roasted product was further enriched to 29.70 g/t and the optimal gold cyanide leaching extraction reached 93.66%.

Jan 1, 2015

By F. F. Aplan

Though over 100 minerals are known to contain the rare earth (RE) or lanthanide elements, only a few provide the bulk of the world&apos;s source of these elements. The principal RE-containing mineral, monazite [(Ce,La,Th,Y)PO4], is recovered by gravity, magnetic, electrostatic and flotation concentration methods, while the other important source mineral, bastnasite [CeFC03], is concentrated by flotation. The processing of the lesser important source minerals is discussed, as is the recovery of the lanthanides from apatite [Ca5(P04)3(F,OH)] where the rare earth elements are present from trace amounts to over 10% as the mixed oxides.

Jan 1, 1989

By Peng Lv, Shiqian Liu, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

The treatment process of a low-grade refractory gold ore containing sulfide minerals and carbonaceous matters was studied in this work. The gold extraction of this ore by all-sliming cyanidation was only 11.75%. Hence, a pretreatment was necessary. In this paper, a flotation-preoxidation-cyanide leaching process was developed. The concentrate from the flotation procedure was processed using different preoxidation methods. A concentrate containing 34.08g/t of gold with the gold recovery ratio of 81.20% was obtained by flotation. After roasting, microwave heating or alkaline pressure oxidation, the gold cyanidation ratio reached 82.37%, 81.26% and 71.09% respectively. Roasting was an effective, reliable and mature technique to oxidize sulfide minerals and carbonaceous matters. Roasting and microwave heating both produced dangerous environmental pollutants while alkaline pressure oxidation was eco-friendly.

Jan 1, 2015

By Viviane Tavares

The liquid crystal display (LCD) are currently known by its vast application in electro ? electronic devices, amongst them can be detached the devices of TV, laptops, electronic date, calculators and even though the mobile telephones (mobiles). The mobiles are changed more frequent of the TV for example, this happens due to the technology advance. With the constantly mobile exchange, the batteries, printed circuit board and liquid crystal display accumulation its become an environmental problem. To minimize the environmental impacts caused by mobile telephones residues are considered the segregation process of the LCDs main components, to goal to recover the recycle material. This process involves the use of treatment ore techniques with disc, hammers and balls mills. The process with best efficiency (about 98%) of LCD glass release was the hammers mill. The glass recovered can be used in the glass recycling and the sand substitution in the production of concrete blocks.

Jan 1, 2009

By D. D. Rodier

Most zinc concentrates contain some silver and varying amounts of such valuable trace elements as gold, indium, germanium and gallium. With increasing similarities in plant installations, the predominance of electrolyte process and the increasing environmental constraints on iron disposal, it is essential that zinc smelters optimize the recovery of any valuable elements in their feed stocks. The process options, to date, of smelting, flotation or leaching of silver-rich leach residues cannot be applied economically to all installations. It is therefore necessary that new innovative processes, to recover silver and other valuable metals from relatively low grade feeds, be developed. This paper attempts to place this strategy in the context of today&apos;s constraints and will also provide a simple evaluation tool for any process alternatives.

Jan 1, 1990

By M. Fujikawa, S. Goto, M. Nishikawa

"The semi-pilot scale plant for injection smelting of zinc calcine was operated under the committee of Joint Research Organization of Injection Metallurgy. The capacity of the plant is 10 ton metallic zinc per day. The plant was designed by the resul ts of basic and bench scale tests of the capacity of 1 ton metallic zinc per day which was published at ""Zinc '85"". The equipments of the plants, operational conditions, results of the operation such as recovery of zinc in injection furnace and condenser, combustion rate of powdered coke and consumption of energy in this process are presented in this paper. The results of the study of the feasibility of the commercial plant of 100,000 ton zinc per year by the injection smelting are also discussed in the paper. IntroductionThe research committee of new smelting process of zinc by injection was established in 1981 under the finantial support of Mining Promoting Foundation of Japan. Six zinc producing companies joined in this organization. The price of zinc was very low at that time and the energy cost, especially, cost of electric power in Japan was extremely high. Invention of a new economical process for zinc extraction had been stronglydesired. The author proposed a injection smelting of zinc as a economical process in energy saving after a calculation of thermodynamical equilibrium and heat balance(1 )(2).The research committee has been studying the injection process since 1981. The small basic experiment by using a crucible furnace was carried out from October 1981 to March 1983 and the reaction of reduction of calcine by injection smelting was ascertained (2). Vaporizatipon of zinc and behaviours of impurities were examined. After the basic experiment, the bench scale test with the production capacity of zinc of 1 ton per day was carried on from November 1983 to October 1984.The bench scale tests were carried out to obtain the proper design of feeding devices of calcines and coke into a furnace and also to obtain fundamental data for enlargement of this smelting process(3,4). The recovery of metallic zinc in this small equipments was about 50% and main loss of zinc was formation of dross in the condenser."

Jan 1, 1988

By Valery M. Paretsky

The effect of the degree of nickel oxide reduction and the reaction gas composition on the furnace productivity has been estimated by computations and the established relationship is in good agreement with the practical data obtained in the process of electric smelting at the Severonickel smelter. An increase in the reduction degree within a range of =0.65 - 0.9 results in an increase in the furnace productivity by 19% to 37% and in a decrease in the unit electric power requirement by 16% to 27% depending on the reaction gas composition. The agreement between the computed and practical data has confirmed that the decisive factor for the process of treatment of reduced nickel oxide in an electric-arc furnace under the given conditions is the specific heat absorption, which is dependent on the nickel oxide reduction degree and the reaction gas composition.

Jan 1, 2005