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By Kandipati Sreenivasarao

Ion flotation is a promising separation process for continuously removing toxic metal ions from dilute process effluents. After treating the effluent with appropriate surfactant(s), the metal- bearing species adsorb onto the surface of rising gas bubbles and can be collected as foams. Suitable collectors have been identified for most of the elements of the periodic table. However, a better understanding of the thermodynamic, kinetic and engineering principles that determine the performance of ion flotation systems would facilitate commercial utilization of this technology. A model system of sodium dodecylsulfate-ethanol has been studied for the removal of Cu (11) from dilute solutions, using laboratory-scale flotation columns. This paper reports the effects of the air flow rate, solution height, foam drainage zone height and col1ector:metal ion ratio on the flotation kinetics, ultimate recovery of metal, flotation product grade, foam losses and effluent quality. Preliminary results for Pb (11) removal are also reported.

Jan 1, 1993

By P. D. Nolan

Smelters operating under pollution control orders have become increasingly dependent upon the reliable operation of sulphuric acid plants and no factor affects the long term reliability of those plants more than efficient gas cleaning. The sources and characteristics of contaminants in smelter of fgases and the conventional approaches to removing these contaminants to accepted levels are discussed. New technology is described which offers advantages of lower capital cost, lower operating cost and reduced space requirements over the conventional approaches. This new technology has been developed by LAB s.a. and is licensed for metallurgical gas applications by Chemetics International Company.

Jan 1, 1983

By Robert D. Pehlke

"The evolution of oxygen steelmaking is reviewed and new operating processes are described. The developments which could impact this technology are summarized. Staged and continuous steelmaking are considered in the light of new technologies. The future opportunities for oxygen steelmaking processes are overviewed. IntroductionThe use of oxygen in steelmaking was originally brought on the scene by the development of pneumatic steelmaking. Sir Henry Bessemer in England originally conceptualized the use of gaseous oxygen in steelmaking, and then he and William Kelly in Eddyville, Kentucky independently developed the original pneumatic process which involved blowing air through a bath of molten pig iron to oxidize the carbon and silicon and produce steel. This process and many following processes, including those which would use pure oxygen gas, have been proposed.Beginning with the first commercial oxygen steelmaking vessels at Linz, Austria in 1952, the world steelmaking industry has adopted this style of processing. In general, the process has involved the use of steel scrap in amounts from 20 to 35% of the metallic charge with molten pig iron produced in blast furnaces making up the remainder. The impurities in the charge are oxidized through the use of oxygen gas injected into the steelmaking vessel.However, currently being adopted into commerical practice and on the horizon are a number of advances in this process which include the use of iron ores as a source of iron and oxygen, the use of an all scrap charge, incorporation of pre-reduced iron, the use of auxillary fuels to change the balance of cold and liquid iron-base charge materials and numerous refining techniques."

Jan 1, 1988

By Yunhua Gan, Xiaowen Chen, Yang Tong

Experimental studies of electro-spraying were carried out using ethanol as fuel in a microcombustor under combined electric field. And the effects of different electro-spraying modes on the combustion efficiency were analyzed. Results showed that when ring electrode potential was invariant, there were four different electro-spraying modes with the variations of nozzle potentials, which were varying with the flow of ethanol. The cone-jet mode was the stablest one during the whole experimental process. The atomized ethanol was ignited and combusted stably near the steel mesh, the combustion efficiency increased firstly and then decreased along with the increasing of the equivalent ratios, reached the maximum values when the equivalent ratio equal to 1.0. And the maximum values were the highest at the cone-jet mode, and the lowest at the pulsed-jet mode.

Jan 1, 2016

By Liu Wei-feng

Base on the thermodynamic calculation of vapor pressure of lead, antimony and arsenic at high temperature, the possibility of separating lead, antimony and arsenic in different temperature was analyzed ,and the practice of producing qualified antimony white from lead-antimony alloy by direct blowing was introduced in detail in this paper. The blast furnace reduction smelting was brief introduced firstly, and then alkaline refining was applied to removing arsenic from lead-antimony alloy that contains As1%,Sb39%,Pb58%,the arsenic in the treated lead-antimony alloy could decrease to 0.009% by that method. The antimony white containing Sb2O3 99.5% could be produced by air blowing in the special furnace at 650? from the treated lead-antimony alloy. And the electrolytic lead could be achieved by electrolysis from the lead-rich alloy which contained 83% lead.With high-grade product being obtained the process was shortened. The technology has been applied successfully many years in Guangxi, China.

Jan 1, 2009

By Charles W. Kenney

Mercury contamination of soil at an old chemical plant surrounded by a residential community and adjacent to a river has provided unique challenges for the current owner. Inorganic and organic mercury compounds had accumulated over the past 50 years to levels that require remediation. Hazen Research, Inc. conducted a multi-phased program to characterize contaminants and their occurrences, evaluate various treatment technologies, and demonstrate the selected technology at bench and pilot scales. A combined physical cleaning and chemical treatment was demonstrated to meet treatment goals for the site. This paper discusses the methods of process selection and results of the bench-and pilot-scale testing.

Jan 1, 2003

By C. Lupi

Electric arc furnace dust generated during the production of steels is regarded as hazardous waste because of the presence of leachable elements such as Cr, Pb, Cd .... Different processes are available according to the management policy chosen by the steelmaker: disposal. recycle and/or recovery. The feasibility of an hydrometallurgical Zn recovery process on fumes generated during the pyrometallurgical treatment of EAF dust has been investigated. The recovery of metallic iron, chromium and nickel as molten metal provides fumes very rich in zinc oxide ( 63.1% ) and poor in zinc ferrite. This secondary dust is still an hazardous waste and represents the raw material for the recovery of Zn and Pb. The waste material is first leached in 1.5 M sulphuric acid at 30°C to provide a Zn, Fe and Mn rich aqueous solution and a Pb and Ca sulphate rich sludge. The iron is eliminated by precipitation because is harmful to the following electrowinning process. The ftltered and purified leached solution is acidified in order to obtain good electrowinning conditions. A pure cathodic deposit of zinc is then produced in an electrolytic cell at laboratory scale.

Jan 1, 1996

By Reinhard F. Dobner

After a short introduction about the HK's secondary smelter process and explanations concerning the anodes produced the regulation and buffering of bleed will be described and the principles of technology for processing of bleed will be presented. Modernization aspects, especially installation equipment, and the different types of evaporators used will be described in detail. Besides, experience made with acid-resistant materials - stainless steel, enamel, plastics - will be reported. Environmental aspects such as water and air pollution will be outlined briefly and in conclusion the quality of products obtained as well as quality control will be presented.

Jan 1, 1997

By Tom Marttila

During the last few years, when a new tankhouse or a major modernization has been planned, automatic or semiautomatic crane and grab systems have at least been considered. It seems that in the future tankhouse managers for new, modernized and even old tankhouses will be looking for a proven and reliable system for automatically moving and positioning electrode loads in the tankhouse and in storage areas. In this paper, we will describe the Wenmec solution for automatic electrode handling. The advantages of automatic handling and very accurate electrode positioning will be discussed, and the way Wenmec has solved the problems in mechanical construction and in automatic, accurate and reliable positioning will be presented.

Jan 1, 1990

By William Gregg

Recent environmental and workplace safety legislation has Imposed more stringent limits on the amount and type of particulate emitted Into the air. In the past, the mass of particles contained In a volume of air was the governing criteria. Now the size and precise chemical nature of the particulate must be known and controlled In addition to it's ?mass. Processors of metallic materials have to implement stricter control practices and more efficient control equipment to meet the new regulations. Pulse-Jet dust collector systems are being used to control particulate emissions from various process gas streams. Pulse-jets :are also being used for maintaining a healthy environment In the workplace. this paper will discuss the impact of these regulations, the control techniques used to comply with such regulations, and the equipment needed for compliance.

Jan 1, 1992

By Gus Van Weert

This paper describes the results of autoclave testwork where ferric nitrate was hydrolysed in the presence of certain cations and anions and the resulting hematite analyzed for foreign constituents. For the cations Zn++, Ni++, Cu++, and AI+++, selectivity factors of over 107 were found. Magnesium gave 3.106. These factors are calculated as Me/Fe in solution over Me/Fe in the hematite; Me representing the metal in ion added. As-a result of the testwork at Delft University of Technology, BUDELCO (the Netherlands electrolytic zinc producer) ran a series of ferric nitrate hydrolysis tests in the presence of 10 additional trace elements. Impurity levels were prejudiced on Me2 EPHA extraction of iron from their zinc circuit, followed by HNO3 stripping. Good selectivity against base metals was confirmed, but trace elements forming anions (As. Sb) and sulphate were incorporated in the hematite. These BUDELCO results are also presented.

Jan 1, 1995

By P. G. McCormick

The refining of rare earth metals by the direct solid state reduction of their respective chlorides during mechanical alloying has been studied. Erbium and gadolinium were synthesised by milling their respective chlorides with calcium. The mechanical alloying of SmC13 with calcium resulted in partial reduction of SmC12. Examination of the milled powders using X- ray diffraction and analytical electron microscopy has enabled characterisation of product structure and morphology. The synthesis of Fe17Nd2 by the mechanical alloying of NdC13 and Fe with calcium has also been studied. The Fe17Nd2 phase forms during heat treatment of the mechanically alloyed powder.

Jan 1, 1992

Plastics recycling has become an established national industry in Korea. However, it is still in its infant stage and experiences growing pains. In Korea, mixed plastic wastes generated from households after hand picking and/or mechanical sorting processes amount to 1,700,000 ton per year in 2005, and most of these waste are finally end up with landfill and/or incineration due to lacks of separation technologies and economical reasons. These plastic wastes can not be used as raw materials for chemical and/or thermal recycling because of their high content of PVC (upto 4.0 wt.%). In the present work, gravity separation system has been developed to remove PVC from the mixed plastic waste and recover the individual plastics. The separation system mainly consists of air classification, crushing, feeding system at fixed rate and wet-type gravity separation system. The gravity system based on centrifugal separation also consists of mixing, precleaning, separation, dewatering, recovery system, wastewater treatment system, etc. The main objective of this process to be developed is to achieve high separation efficiency of polyolefins (PE, PP, PS) with less than 0.3 wt.% PVC content and less than 10% moisture content in the final products. The system with a capacity of 0.5 ton per hour is developed and operational results are presented.

Jan 1, 2006

By Jitka Jandová

In this study, hydrometallurgical processing of waste ZnO flue dust arising during zinc removal from galvanized low-alloy steel sheets was investigated on a laboratory-scale to obtain electrolytic zinc. The flue dust was separated from flue gases, generated during heating waste galvanized steel sheets in an electric furnace under air atmosphere at temperatures of about 1000oC. The dust, comprising tetragonal ZnO and insignificant amounts of SiO2, was contaminated by Fe, Mn, Pb, Al, Mg, Pb, Cu and Ca. The dust was leached in 0.5 and 1.0M H2SO4 and/or in 20 and 30% NaOH at different temperatures and different liquid-to-solid ratios to determine the optimum conditions leading to the highest possible selectivity of leaching and efficiency of Zn extraction in minimum time. The subsequent electrowinning process was performed with refined zinc sulphate leach liquors and/or with untreated zinc caustic solutions. Zinc sulphate leach liquors were purified using a combination of a hydrolytic pH-controlled precipitation, cementation and carbon refining. Effects of operational variables on Zn electrowinning have been studied for both sulphate and caustic electrolytes. The conventional plate-plate electrowinning cell has been explored in this study. Comparison of results obtained for both zinc electrowinning from acid sulphate and alkaline solutions is presented contribution.

Jan 1, 2003

By Ian G. H. du Preez

It is illustrated how differences in the basic chemistry of individual metal ions can be exploited to develop new or improved separating agents. Factors like coordination number preferred by the specific metal ion, the degree of coordinate saturation reached by the metal ion and its relation to the phase transferability of the complex species, kinetic factors as opposed to thermodynamic factors controlling the success of the separation, the nature and type of the donor atom employed in a separating agent in relation to the preferences of the metal ion, the significance of stereochemical factors and the hydrophobicity of the media are some of the important factors which are discussed and applied for the development of pa1ladiwn(TI) and nickel(TI) specific separating agents, respectively.

Jan 1, 1999

By Terry C. Cheng

The Akita Hematite Process is currently the only hydrometallurgical iron removal process producing saleable iron by-products in the zinc industry. In this study, McGill University and Akita Zinc Co. have worked together into elucidating the basic precipitation chemistry of the process from the standpoints of hematite product quality and prevailing precipitation kinetics. This work determined that hematite is produced under the applied conditions (T = 195?200oC,PO2 = 103?414 kPa) directly without prior formation of basic ferric sulphate and transformation of the latter to hematite as thought originally. The rate-limiting step responsible for the long retention time (~180 min) was found to be either the re-dissolution of ferrous sulphate according to the batch reactor studies, or the slow hydrolysis of the remaining ferric sulphate according to the continuous reactor studies. Another interesting contrast between the batch and continuous reactor data was the degree of sulphur contamination (1.5 vs. 3.8%, respectively) and the specific surface area of the product (10 vs. 30 m2/g, respectively). These differences in addition to the co-precipitation of SO4-containing phases such as jarosites, alunite, and anhydrite were attributed to the significantly higher supersaturation level prevailing in the industrial continuous autoclaves that yields highly aggregated sub-micron hematite crystallites contaminated with chemisorbed sulphate ions.

Jan 1, 2003

By Masanori Harata

A fundamental study was conducted on a new process for producing scandium (Sc) metal or aluminum-scandium (Al-Sc) alloy by the calciothermic reduction of scandium oxide (Sc2O3). In this study, aluminum (Al) and calcium chloride (CaCl2) were used as the collector metal and flux for the reduction, respectively. A mixture of Sc2O3, Al, and CaCl2 in a tantalum crucible was placed inside a stainless steel reaction container, and the feed mixture was reacted with calcium (Ca) vapor at 1273 K for 6 h. After the reduction experiment, the reaction product (CaO), CaCl2 flux, and excess Ca reductant were removed from the obtained alloy sample by leaching with an aqueous solution. The formation of Al3Sc in the Al matrix phase of the alloy was confirmed by X-ray diffraction (XRD) and electron microprobe analysis (EPMA). This result indicates that Sc2O3 was successfully reduced to metallic Sc and alloyed in situ to form liquid Al-Sc alloy during the reduction. When Al was not used in the reduction experiment, a complex oxide (CaSc2O4) was formed, and the reduction was incomplete. This study demonstrates that the Al-Sc alloy can be directly produced by calciothermic reduction using CaCl2 flux and Al collector metal.

Jan 1, 2006

By Rikiya Kamezawa, Rudiono, Manabu Takeuchi

"Schottky type solar cells based on phthalocyanine (Pc) thin films were fabricated, and their photovoltaic performance was investigated in various ambient atmospheres. Most of cells prepared in this study showed a good rectification and photovoltaic effects in the visible wavelength region. The introduction ofN02 gas into the measuring chamber was confirmed to increase the current both in dark and under light illumination. However, chemical reaction between the Al electrode and N02 formed some oxide and deteriorated the Schottky barrier, resulting in an increase in cell resistivity. SF 6 gas also showed similar effects on the cell performance.IntroductionPhthalocyanine is one of the typical organic semiconductors, which shows high photoconductive sensitivity in the visible to infrared region. Today, several kinds of metal phthalocyanines are used in electrophotographic photoreceptors. In addition, application of phthalocyanines to solar cells have also been trying by many workers [1, 2]. Many efforts have been made for improving performance of phthalocyanine solar cells by modification of device structure [3, 4], doping by dye or pigment [5, 6] and incorporation of metal clusters [7]. It is known that electrical conductivity in phthalocyanine is increased by adsorption ofNO2 [8, 9]. We tried to improve photovoltaic performance ofphthalocyanine solar cell by adsorption ofNO2. This paper describes the influence of N02 adsorption on the photovoltaic behavior of phthalocyanine solar cells."

Jan 1, 2000

By Ann M. Hagni

Electric arc furnace (EAF) dust from the secondary steel industry contains lead, cadmium, and chromium that causes it to be classified as a hazardous waste. Pyrometallurgical treatment of EAF dust is directed at recovering zinc and simultaneously rendering the dust non-hazardous. The mineralogy of the EAF dust is important in determining the occurrence and phase relationships of the zinc, lead, cadmium, and chromium contents. The principle phases in EAF dust as determined by reflected light microscopy, SEM-EDS, and XRD are solid solutions of the iron spinels (franklinite, magnetite, and jacobsite), zincite, hematite, and Ca-Fe-Si glass. Chromium is present in small amounts in solid solution in the spinels. Cyclone sizing of the minus 53 pm particles shows that more than 50% of this size fraction are less than 10 pm in diameter. The <I0 pm particles contain zinc as both franklinite in solid solution with magnetite and jacobsite, and zincite as determined by transmission electron microscopy and XRD. Auger electron spectroscopy did not detect coatings of volatile phases on the surfaces of EAF dust particles.

Jan 1, 1994

By J. Ipinza

The slime formation with several metallic impurities from acidic electrolytes of copper has been studied. On fresh Pb-Ca-Sn anode surface firstly the formation of PbSO4 takes place, then, it is transformed in the conducting PbO2, which covers the anode surface. It has been experimentally established the formation of a manganese dioxide double layer at the anode; this double layer was always composed of a thick external layer of non-adhering and easily removable scales, and of a thin internal layer, which adheres relatively well to the surface of the electrode. It was found that manganese dioxides present in the slime were of different nature: a non-adhering layer produced by electrolysis (-MnO2) on the PbO2 surface and a pure chemical precipitation in the solution (-MnO2). When iron is present in the electrolyte on this last layer of manganese, lead sulfate was found. In the case of arsenic and antimony in the electrolyte the slime generated was found to be lead sulfate and amorphous compounds of those ions. The lower slime generation in Chilean EW plants could be due to the lower contents of iron and manganese in the electrolytes. It was found that this slime formation rate not only is due to the electrolyte composition but also to the poor control of operational parameters at EW plants.

Jan 1, 2003