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By Roger N. Kust

Removal of heavy metals from industrial process streams is becoming increasingly important for _the recovery and reuse of values in process tails. Technology has been available for several years which removes heavy metals, from dilute (0.1-3.0 g/L) streams, as hydroxide or hydrated oxide sludges, allowing discharge of washed cakes with up to 60% solids. This paper reports on improvements to this technology which now allows treatment of streams with metal concentrations in excess of 60 g/L while eliminating the need for thickeners. Streams containing copper, iron, aluminum, chromium, nickel, zinc, cobalt and lead have been successfully treated.

Jan 1, 1992

By Hyun Soo Kim, Joon Soo Kim, Myong Jun Kim, Jyothi Rajesh Kumar, Jin-Young Lee

Rare earth materials have an ever growing variety of applications in the modern and hitech technology. They apply to many an industry with crucial materials and they provide numerous a customers with benefits. Rare earth materials utilization increasing day-by-day in the worldwide, at the same time the resources is very limited in many countries like Korea. The present general article divided four sorts such as 1) mineral processing of Korean ore deals the gravity, magnetic separation and froth flotation, 2) decomposition and leaching of concentrates included sodium hydroxide fritting, sodium hydroxide hot digestion, hydrochloric acid leaching, 3) separation and purification of rare earth elements in mixed rare earth chloride solution consists reduction and oxidation method, solvent extraction, 4) preparation of rare earth oxide compound from purified elemental rare earth chloride solution having oxalate salt precipitation by reaction crystallization. The last part consists of a summary of the present study.

Jan 1, 2015

By Dong Liu, Zejian Yang, Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"The structure, composition, morphology, and adsorption property of UV-vis light of as-prepared samples were characterized using XRD, SEM, FTIR-EDS, and UV-vis DRS. UV-visible light induced photocatalytic degradation of methylene blue ~) over Ti02-doped diopside was investigated. Experimental results show that doping Fe + induced the formation of Ti-0 or Ti-0-Si in diopside, and promoted the light adsorption property of diopside. Photocatalytic reactivity of Ti02-doped diopside obviously depended on content of doping Ti02. The diopside with 3% Ti02 exhibited the superior photocatalytic activity with 76% degradation of methylene blue under light irradiation for 3 h.IntroductionPhotocatalytic technology has been extensively studied in the process of dealing with inorganic and organic pollutants. Ti02, with its own non-toxic, stable, low-cost and other advantages, has become the most widely studied photocatalytic materials[l-SJ_ The low utilization quantum made it restricted in the practical application. SrTi03 as the representative of the perovskite[9·121, Bi2W06 for the composite oxide[13,141, also attracted wide interest in the photocatalytic studies. However, these photocatalytic material has been mostly prepared in relatively strict experimental conditions with chemical reagents, they had small production, high cost, which made them difficult for practical applications.In our country, there has 400 million tonnes of ti-bearing blast furnace slag (TBBFS) each year in the process of smelting pig iron, which has lead to waste of titanium resources and pollution of the surrounding environment. In recent years, studies have shown that TBBFS instead of pure Ti02 to be photocatalytic materials is feasible[ 151. TBBFS has not only been higher photocatalytic degradation activity for the o-nitrophenol, methyl orange, nitrobenzene and other organic matter[16-191,but also exhibited excellent in the process of dealing with inorganic heavy metals in waste water (containing Cr6+i201. If TBBFS can be successfully applied to photocatalytic technology, the will make large accumulation of titanium-bearing slag reasonable used, so as promote the re-use of energy. At present, our understanding of the photocatalytic activity of TBBFS is steadily deepening. Photocatalytic activity ofCaTi03 has been reported as one of the main minerals ofTBBFS [21'21J, However, there were few studies for Another major mineral of TBBFS - diopside which had the content of9-15%. diopside would doped with Ti02 In the process of smelting pig iron, therefore, Ti02-doped diopside's photocatalytic activity in the UV-Vis was mainly studied in this paper."

Jan 1, 2013

By Alysson Tadeu Pereira Almeida

Steels with low concentrations of nitrogen, hydrogen and carbon have been in large demand lately. The RH process is a secondary refining process that can simultaneously attain significant levels of removal of these interstitial elements from liquid steel. In the RH process, the melt circulation rate plays a very important role in determining the productivity of the equipment, since it affects the decarburization rate. In the present work, a physical model of a RH degasser in a 1:5 scale of an industrial reactor has been built and used in the study of the circulation rate and of the kinetics of decarburization. The effects of the gas flow rate and of the configurations of the nozzles used in the injection of the gas have been analyzed. The decarburization reaction of liquid steel was simulated using a reaction involving CO2 and caustic solutions. The concentration of CO2 in the solution was evaluated using pH measurements. The experimental results indicated that the kinetics of decarburization can be described by a first order equation. Based on the results, it was possible to determine the contributions of the decarburization in the upleg snorkel and in the vacuum vessel.

Jan 1, 2006

By S. P. Rivers

The stainless steel industry re1ies on nitric-hydrofluoric acid (HNO,/HF) pickling solutions to remove surface contaminants and maintain the corrosion resistance of the steel. More stringent environmental guide1ines are expected to be placed on the disposal of these solutions which could significantly increase processing costs. The U.S. Bureau of Mines has been conducting research to develop a process for recycling depleted pickling solutions, thus reducing the quantity of by product acids generated. Research has shown that F- can be liberated from the predominant iron fluoride species (FeF,') by using oxalic acid in an electrodialysis cell. Ion selective membranes allow dissolved metals in the depleted solution to be replaced with hydronium ions by metathesis, thereby regenerating the HF. The regenerated HN03/HF is then retained in the pick1ing solution. This paper reports on the research effort at the U.S. Bureau of Mines Rolla Research Center to apply electrodialytic recycling to HN03/HF pickling solutions.

Jan 1, 1993

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 F. E. Katrak

Rare earths markets by definition usually include not only the rare earth elements, but also yttrium. They can be subdivided into a very large light rare earth fraction (about 95 percent by weight of all rare earths consumed) consisting mainly of cerium and lanthanum and a smaller fraction (with much higher unit value) consisting of selected high-purity oxides or elements such as yttrium, europium, samarium, or neodymium. CRA estimates that the noncomnunist world market for all rare earths and yttrim was on the order of US$750 million in 1986. The main focus of this paper is on the principal uses for rare earths, some CRA-developed proprietary data on their consumption by region, and the selective nature of business opportunities in the rare earth markets. We also provide forecasts on the future trends in these markets.

Jan 1, 1989

By Han Ilhan

This paper discusses and describes aspects of a cost effective and safe tailings impoundment selection. In light of the current low metal prices and recent tailings embankment failures around the world, it is becoming extremely more important to develop tailings impoundment design that balance cost efficiency with safety. The paper will present critical design components associated with a tailings impoundment which need to be addressed during the planning phase. Procedures for identifying various tailings impoundment alternatives, and evaluation and selection of alternatives are presented.

Jan 1, 1999

By Hirokazu Narita

The extractability for Pd(II) using MOTDA and DHS and their durability against a mixed solution of HNO3 and HCl was investigated by solvent extraction and FT-IR measurements. Both MOTDA and DHS selectively extracted Pd(II) over Pt(IV) from 0.75 M HNO32.25 M HCl solutions. The extraction rate of Pd(II) with MOTDA was much greater than that with DHS. In the durability test, the extraction percentage of Pd(II) and the FT-IR spectra were measured using MOTDA and DHS after stirring with 0.75 M HNO32.25 M HCl solutions. The extraction percentage of Pd(II) with MOTDA hardly changed during the two-month stirring; however, that with DHS decreased with an increase in the stirring time. The FT-IR spectra showed the sulfoxide formation by the oxidation of the sulfide in DHS, but not in MOTDA. Consequently, it was found that MOTDA is more durable than DHS.

Jan 1, 2006

By Beatriz Ribeiro Nogueira, Vijaya Kumar Rangari, Esperidiana A. B. Moura, Anne Chinellat, Arifa Parveen, Angel Visentim Ortiz

"Composite consisting of ethylene vinyl alcohol (EVOH) with short piassava fibers were prepared by extrusion process and their thermal and morphological behavior were investigated. The EVOH reinforced with 5 and 10 % of pi as sa va (Attaleafunifera Mart) fiber particle, based on the percentage weight ratio (wt %), untreated and treated with a commercial silane coupling agent, were prepared and the influence of fiber loading and the effect of chemical treatment on their thermal and morphological behavior were evaluated by SEM, DSC and TG analyses. Melt flow index (MFI) of the composites have been determined to evaluate the effects of fiber reinforcement on dynamic viscoelastic melt of the EVOH. In addition, piassava fibers characterization by SEM, FTIR, and organic and inorganic composition have also been carried out. The SEM results of the composites showed surface micrographs without microvoids and a good distribution, dispersion and compatibility between the fillers and the EVOH matrix. Concerning the piassava fibers characterization, the results showed that piassava has higher lignin content than cellulose and hemicelluloses, and around 0.7 % of ash with 52 % of silica (Si02). This high concentration of silica is consistent with the SEM analysis of the fiber that showed a large amount of ""silica rings"" encrusted on their surface.IntroductionLately, great worldwide interest has arisen in developing new technologies that enable the use of products with less environmental impact. Effort has been put into seeking natural modifier applications, particularly regarding the use of natural fibers. Special attention has been given to the use of natural vegetable fibers, because of the huge variety of species available. Such vegetable fibers are usually referred to as lignocellulosic materials [1]. This work evaluated the effects of piassava (Attalea funifera Mart.) fiber incorporation in an ethylene and vinyl alcohol copolymer (EVOH). The EVOH belongs to a family of copolymers with excellent gas barrier properties and resistance to organic compounds, which allow its application in different segments, from food packaging to gas tanks. However, EVOH is very sensitive to moisture, and in conditions of high humidity its gas barrier properties, thermal and mechanical properties are affected."

Jan 1, 2012

By Hiroyuki Matsuura

Treatment of electric arc furnace (EAF) dusts has become an important issue from the viewpoint of the environmental protection and recycling of variable resources because these dusts contain considerable amount of zinc and lead. A new recovery process of these metals has been proposed, in which the metals in the dusts react with waste polyvinyl chloride to form metal chlorides. Therefore, it is important to clarify the physicochemical properties and behaviors of zinc, lead and those chlorides and oxychlorides. In the present study, the kinetics of chlorination of ZnO, PbO and ZnFe2O4 mainly contained in the EAF dusts were investigated at 1023 K to 1273 K with Ar-O2-Cl2 gas. Based on these results, the selective chlorination and evaporation process of zinc and lead from the mixture of Fe2O3-ZnFe2O4-ZnO-PbO was examined and the high efficiency of selectivity has been demonstrated.

Jan 1, 2006

By Jeong-Hwan Kim

The liquid-liquid reactive process (solution process) is often adopted as a synthetic method for precipitated calcium carbonate (PCC) in laboratory studies for its simplicity in operation or ease in controlling process variables. Still, PCC are produced commercially by passing carbon dioxide through a milk of lime, i.e., by a gas-liquid reacting method (carbonation process). Few studies on the carbonation process have been conducted, since the process variables are interrelated and difficult to control compared to the solution process. In this study, both carbonation and solution processes were employed to study the polymorphs of calcium carbonate and growth rate of PCC crystals. The effects of the characteristics of limestone ores as a raw material in the synthetic system of PCC on the synthetic characteristics of PCC were also investigated. To control the nucleation rate in the synthetic systems, the shape factor was considered most important. Single-phase aragonite PCC could be synthesized under a variety of controlled experimental conditions such as ionic strength, solution composition, concentrations of additive ions, and temperature.

Jan 1, 2006

By V. Gel

An analysis of the operation of rotary tilting furnaces has indicated that they ensure better recoveries of metal when smelting lump scrap from aluminum slags, brass and bronze. On the other hand, processing of slags (concentrates obtained by mechanical upgrading) in pear-shaped furnaces results in much lower performance values as might be expected. At the Novgorod metallurgical plant a process for blister copper production in a rotary TROF converter (Outokumpu, Finland) has been introduced on a commercial basis. Smelting of brass and bronze scrap to produce blister copper is carried out using the technology developed in Russia and differing from the Outokumpu technology by the types of flux used and the blowing conditions in fuel burners and for melt oxidation, as well as by the design of gas removal system, the design of nozzles for melt blowing and the use of carbonaceous reductant (coal) for magnetite reduction in slags. Industrial-scale testing has demonstrated that by means of special techniques the 30-tonne converter productivity can be increased by 30% to 40% as compared with its rated productivity.

Jan 1, 2006

By J. Brent Hiskey

The global copper industry faces a technological challenge to develop processing schemes for more complex and impure ores and concentrates. Group 15 elements (As, Sb, and Bi) represent impurities that are troublesome both in terms of environmental impact and metallurgical processing. The so-call "dirty" copper concentrates are either unacceptable for smelting and refining or incur high penalties. The behavior of the Group 15 elements is of critical importance in maintaining product quality and process performance. During copper electrorefining, these impurities are released to the electrolyte by electrochemical dissolution of the anode. Depending mainly on temperature, concentration, and oxidation state these elements can spontaneously coprecipitate from the electrolyte. Some of these precipitates are referred to as floating slimes and their formation can have extremely detrimental effects on cathode purity. In this paper, the mechanism of floating slimes formation will be discussed and the fundamental thermochemistry will be reviewed and analyzed in relation to solubility properties.

Jan 1, 2012

By C. M. Wai

Metal species in solid and liquid materials can be extracted by supercritical carbon dioxide containing a suitable ligand. This in situ chelation-supercritical fluid extraction technique offers, several advantages over conventional solvent extraction including minimization of organic liquid waste generation and exposure of personnel to organic vapors. One unique feature of this technique is that metal species can be removed from solid materials directly using supercritical carbon dioxide as a solvent. Several ligand systems including dithiocarbamates, ß-diketones, organophosphorus reagents, and macrocyclic compounds have been tested for metal extraction in supercritical carbon dioxide. This novel extraction technique may have important applications for metal recovery and mineral processing.

Jan 1, 1996

By Debbie Marshall

Process water is an important consideration in the development of a nickel laterite project. Depending on the location of the ore body, sufficient fresh water may not be available and it may be necessary to use seawater (or saline groundwater) for ore preparation. This introduces various species, which have major effects on materials of construction and leaching chemistry. This paper summarizes batch testwork completed at the Falconbridge Technology Center. The leaching behaviour of eleven different laterite ore samples were compared using seawater and fresh water. For brevity, six of the eleven samples are reported here-the other five samples showed similar results. Each ore type was leached under identical conditions in both freshwater and seawater and the leaching chemistry compared. The batch test results were confirmed in a continuous pilot plant, and leach kinetics for the two systems were compared. Keywords: high pressure acid leaching, laterites

Jan 1, 2004

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Yuanbo Zhang, Mingjun Rao, Guanghui Li, Chongzhong Ouyang, Shuhui Zhang

Oolitic hematite ore with high-phosphorus content is currently recognized as one of the most refractory iron ore resources in the world. The high-phosphorus content and unique structure of the oolitic hematite ore make it difficult to be beneficiated. The process of direct reduction followed by magnetic separation has significance to the utilization of oolitic hematite ore, and sodium salts can improve the dephosphorization. However, the behavior of phosphorus during reduction roasting, and the intensified dephosphorization mechanism of sodium salts are not clear. In this study, by using chemical analysis, chemical phase analysis, XRD analysis, optical microscopy, and scanning electron microscopy analyses, the behavior of phosphorus during reduction roasting of high-phosphorus content oolitic hematite ore and the effect of sodium salts on behavior of phosphorus were studied.

Jan 1, 2015

By V. A. Bryukvin

A hydroelectrochemical technology has been proposed and experimentally proven for processing metallic gold- and silver-containing concentrates on the basis of copper and copper alloys obtained as a result of preliminary physico-mechanical upgrading of electronic scrap. The proposed technology is based on hydroelectrochemical leaching of scrap using reversible electric current and diluted nitric acid solutions, containing complexing agents, permitting complete separation of gold from the nonferrous matrix without involving gold in the process, and dissolving copper, zinc, lead and tin virtually without any emission of nitrose gases.

Jan 1, 2006

By Ehsan Vahidi, Fereshteh Rashchi, Ataollah Babakhani, Alireza Zakeri

"The synergistic effect of Cyanex 302 on solvent extraction of nickel and cadmium from sulfate solution with D2EHPA diluted in kerosene was investigated with the aim of increasing separation efficiency. Experiments were carried out within a pH range of 0.1-5.0 using sole D2EHPA and D2EHPA-Cyanex 302 mixtures in different ratios. Increasing Cyanex 302 to D2EHPA ratios in the organic phase caused a left shifting of the extraction isotherm of cadmium and a right shifting of the extraction isotherm of nickel. As a result, optimum separation was found with a Cyanex 302 to D2EHPA ratio of 0.1M:0.5M. In the present system, effect of a modifying reagent such as TBP was studied. The influence of various diluents including kerosene and carbon tetrachloride was also investigated.IntroductionBatteries are popular sources of portable energy. Ni-Cd batteries are manufactured in two main groups of small domestic cells and large industrial batteries with 80% being in domestic use. Ni-Cd cells have various uses, for example in cordless electric utensils, cordless telephones, airplane engine starters, and communicational distribution systems [1].Depleted Ni-Cd batteries are classified as hazardous waste since nickel and cadmium are heavy metals and suspected carcinogens. Given the risk associated with uncontrolled disposal, directions for issuing legislation on disposal and recycling of used batteries have been made in industrialized countries [2]. Recycling of Ni-Cd batteries is important from both economic and environmental points of view. Different methods have been used for recycling these wastes through pyrometallurgy [3], biotechnology [4,5], and hydrometallurgy [1,2].Due to the advantages of hydrometallurgical processes, several studies have been implemented on leaching and solvent extraction (SX) of the used Ni-Cd batteries. Leaching of batteries is usually done in sulfate or chloride media; while solvent extraction has been used in different extractants: two-stage solvent extraction by D2EHPA and Cyanex 272 [6]. Solvent extraction of Cd from leach solutions has been studied using various extractants; Cyanex 301 [1], D2EHPA [7], Cyanex 302 [8], Cyanex 923 [9], Cyanex 272, Tops 99, PC88A [10]. Application of phosphorus based extractants for the solvent extraction studies of Ni such as TOPS 99 [11], D2EHPA [12], Cyanex 272 [2], has been investigated. Separation of Cd(ll), Ni(II), and Co(ll) from chloride leach liquor of spent batteries [13], were explored in the earlier studies. Cd extraction with D2EHPA involves co-extraction of both Ni and Co [14], which causes issues in the separation process efficiency."

Jan 1, 2012