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By Zhang Yongzhu

In hydrometallurgical processes of PGMs separation and refining, differences between 1-PGMs (Ru;Rh;Pd) and h-PGMs(Os;Ir;Pt) in thermodynamics and kinetics have been observed. The successful practice in the separation and refining of PGMs in China, is mainly based on the following two kinetically extraction sequences of: (1) for the extraction of PGMs complexes in different configurations with coordination mechanism (AuCI,) -> (MCl6)2-> (MCl4 )2-> (MCI6) 3- , and the substitution rate for h-PGMs complexes with higher effective nuclear charge Z' is much more slow than that of I-PGMs. and (2) for the extraction of PGMs in different configurations with oxonium (or ion -exchange) mechanism (AuCl4)-> (MCl4)2--> (MCl6)2-> (MCl6)3- and the extraction of h-PGMs complexes with low surface charge density is more fast than that of I-PGMs complexes. In view of atomic structure theory, the similarity of atomic radii and chemical properties and difficult separation of PGMs resulted from the Lanthanide Contruction between 5th period (1-PGMs) and 6th period (h-PGMs). The differences between h-PGMs and 1-PGMs are due to the loss shielding of 4f subshells on 5d electrons for h-PGMs with higher nuclear number, which makes h-PGMs have a higher Z' (effective nuclear charge) and strong attraction for outer space electrons. As a result, h-PGMs metals and complexes are thermodynamically more stable and kinetically more inert than the corresponding 1-PGMs. The differences between h-PGMs and 1 -PGMs in aspects of elements properties, complexes, hydration, substitution and redox reactions , are discussed.

Jan 1, 1993

By Jiang Feng, Li Chuanhua, Zhang Libo, Peng Jinhui, Ju Shaohua

Solvent extraction of Cu2+ from the leaching liquor contain Cu and Fe use a microfluidic technology. Currently, the conventional copper extraction process has many problems such as long distance and small driving force of mass transfer. In order to solve the problems, studies are carried out on the extraction process of low grade copper leaching liquid using Lix984N as an extractant with a new microfluidic solvent extraction technology. The effects of flow rate on the separation and extraction efficiency between Cu and Fe are studied, and the results show that a steady liquid-liquid interface of laminar flow is form in the micro-extractor, and extraction efficiency is 78 % and 2.5 % for Cu and Fe at the contact times of 0.84s respectively. Besides, the separation coefficient between Cu and Fe is as high as 140.04. The studied microfluidic technology has the advantages like improving extraction efficiency and reducing reaction time and providing the potential application in the hydrometallurgy extraction of Cu.

Jan 1, 2015

By Shihan Zhang, Qingguo Xue, Jingsong Wang, Yaxing Du, Guang Wang

The rotary hearth furnace iron nugget process is in line with China’s energy and resource condition. It has the advantages of short reaction time and high quality iron nugget. The fundamental study on the novel ironmaking process is meaningful. Based on CaO-SiO2-Al2O3-FeO quaternary slag system, the effects of slag basicity and Al2O3 content on the melting of slag were studied. Using the iron concentrate as raw material, the effects of different slag basicity and Al2O3 content on the reduction and melting separation behaviors of carbon composite pellets, such as the starting temperature of melting separation and the morphology of melting separation were studied. Then, the relationship between the properties of slag and melting separation quality was established, which could provide standard for the selection of iron ore for the rotary hearth furnace iron nugget process.

Mar 1, 2018

By F. Raupp-Pereira, G. G. Cunto, J. A. Junkes, D. Hotza, V. P. Della

"The present work investigated the valorization of wastes as alternative raw materials for ceramic industries. Different industrial wastes based on the SiO2-Al2O3-CaO system and classified as non-hazardous were selected: sludge from varvite cutting process, sludge from gneiss breaks processes, sludge from filtration/clarification of potable water and a clay classified also as waste. All as-received residues were characterized by X-ray fluorescence, differential thermal analysis, thermogravimetry and particle size distribution. The applicability of these materials in ceramic formulations was then evaluated. The formulated mixtures were subjected to forming by pressing and extrusion followed by thermal treatment. After optimization of the processing conditions, the properties of the samples sintered at different temperatures were also evaluated. The waste materials studied proved to be alternative raw materials to natural mineral resources for the ceramic industry.IntroductionOne of the most important problems that have accompanied the humanity in recent decades is the environment’s degradation. In the same context, the natural resources exploration and technological development are phenomena which, if aren’t controlled, can cause ecological disequilibrium with unpredictable consequences [1]. It is in this perspective that recycling of various wastes assumes relevant importance.The recycling, understood here as the waste process reuse, is a common practice in the First World countries, where the raw materials have strategic aspects and the disposal techniques of solid wastes have considerable economic costs. In Brazil, the ecological conscience begins to be aroused due to, in the last ten years, the implementation of stricter laws for environmental control, in general, and licensing of waste generating from industrial activities, in special. The terms “residue” or “waste” are normally used to describe what remains of a production process; when an application for this material is not found. When wastes or residues are susceptible to be incorporated as raw materials or energy sources in a new material production, they can be understood as by-products [2].The valorization of industrial wastes is important, due to the need to pollute less and give an ecologically correct destination for wastes. The waste recycling, independent of its kind, presents several advantages in relation to using primary natural resources, such as reduction in the volume of raw materials extraction, lower energy consumption, lower levels of pollutant emissions and improvement of the health and safety of the population. The most visible advantage of recycling is the preservation of natural resources, extending its life and reducing the destruction of landscape and ecosystems [3]."

Jan 1, 2008

By K. S. Han, M. Yoshimuura, H. Fujita, Y. Sato, S. W. Song

"Film of LlCoO2 as cathode material for rechargeable lithium microbatteries has been fabricated on the platinum metal substrate by electrochemical-hydrothermal method in concentrated LiOH solution at 200 °C as Soft Solution-Processing. The film fabrication has been understood in terms of dissolution of cobalt metal powders and subsequent oxidative deposition on the substrate. The film structure was characterized using scanning electron microscope, X-ray diffraction analysis; X-ray photoelectron spectroscopy and micro-Raman spectroscopy.IntroductionRapid growth of wireless communications and emerging integrated optoelectronic circuits caused the miniaturization· cif electronic devices, thus the demand for high energy density microbatteries as a power source for the microelectronics increases. In this regard, all solid-state lithium microbatteries including LiCoO2 and LlMn2O 4 [l-4], the most promising intercalation cathode material, have been developed. However, major difficulty of .fabrication of a lithium microbattery arose from the preparation of cathode film, according to a· recent report on Rare Metal News [5]. Although many attempts have been made to deposit the cathode films, all those methods are mostly chemical vapor deposiiton (CVD), various evaporation, sputtering techniques and spray pyrolysis. These methods require preparation of bulk cathode materials cir its precursor, then deposition with complicated instruments including high· vacuum system, and even postsynthesis annealing to obtain desire electrochemical 'properties. It is clear that all of these techniques are neither economic nor environmentally friendly. Compared to those methods, film form.ation from an aqueous solution is thought to be simpler and more economical, and requires much· less energy consumption. Our .group has demonstrated the utility of Soft SolutionProcessing [6,7], which is defined as environmentally friendly processing using (aqueous) solutions, to produce films of a variety of functional solid materials. According to the Pourvaix's diagram [8], some metal can be dissolved in an alkaline solution and consequently combined with hydroxyl group or oxygen anion forming metalate or metalite. Cobalt also seemed to form cobaltite, HCoOi in strong alkaline solution in the Pourvaix's pH-potential diagram. Based on this information, it was expected that LiCoO2 could be prepared using the cobalt metal in Li OH solution by Soft Solution-Processing. Recently, we reported the successful single step fabrication of electrochemically active LlCoO2 films on the cobalt metal substrate by hydrothermal methods without any post-synthesis annealing as Soft SolutionProcessing [9,10]. Film formation mechanism could be elucidated by the following evidences. . As expected from Pourvaix's diagram, cobalt metal was dissolved in concentrated LiOH solution forming dissolved cobalt species which was detected by an observation of absorption band in UV-VIS absorption spectrum [10]. Thus the reaction was assumed to be started from dissolution. Time dependent potential of Co electrode exhibited only one-step evolution with 0.6 eV from Co metal to LiCoO2 [10]. Another strong evidence was the finding of LiCoO2 powder precipitates at the bottom of tetlon beaker after the reaction [11]. Based on those experimental findings, it was understood that film is formed by dissolution-precipitation mechanism [9-11]."

Jan 1, 2000

By Jun Zhu, Jilai Xuel, Tao Li

"Coal gangue is industrial waste containing Al2O3 and SiO2 with great recycling and reuse values. This work is aimed at extracting Al2O3 content in the coal gangue by a process of carbonthermal reduction - alkaline leaching. The Al2O3 and SiO2 contents first became a mixture of SiC and Al2O3 in the process of carbonthermal reduction, and then Al2O3 was separated by leaching in NaOH solution, thus producing the sodium aluminate solution for Al(OH)3 precipitation. The products generated at various stages in the process were inspected using XRD and chemical analysis. The effects of parameters such as reduction temperature, carbon ratio, NaOH concentration, leaching time, leaching temperature, stirring speed, etc were investigated in details.IntroductionCoal gangue is an industrial residue resulted from the process of coal mining and washing, accounting for 100 - 150 kg with 1 ton raw coal mined. The existence of coal gangue in large quantities has become a serious problem for environment pollution. On the other hand, the chemical compositions of coal gangue are Si02 and Ah03 primarily. In China, the accumulation storage capacity of Ah03 in coal gangue is not less than 600 million ton at a rough estimate, which should be considered as an abundant second resource [1]. If the alumina can be recycling and reused effectively from coal gangue, it will not only reduce the imperilments caused by coal gangue, but also yield good economic returns.Generally, the processes of extracting Al2O3 from coal gangue can be divided into acid leaching (vitriol or hydrochloric acid) and alkaline leaching (mostly NaOH) [2]. The acid leaching processes have many problems, such as lower leaching ratio, corroding the equipments, recycling the spent acid hardly, etc. The primary matter of alkaline leaching process is silica dissolving with alumina, which brings perplexing desilication process, alumina loss seriously and higher energy consumption."

Jan 1, 2011

By Qingcai Liu

The effect of the TiC addition on corrosion resistance of the Al2O3-C refractories in smelting reduction melts has been studied by quasi-station immersion and rotary immersion. The corrosion rate of Al2O3-C refractories is decreased with the TiC addition. The corrosion mechanism of Al2O3-C refractories is oxidization of graphite carbon by the oxides of the melts and the formation of deteriorate layer.

Jan 1, 2006

By Denis Shishin

The pyrometallurgical production and recycling of non-ferrous metals involves the use of complex feed stocks, having awide range of chemical compositions from sources that include mineral sulphide concentrates, high value obsolete materials and process wastes. The commercial viabilities of these operations hinge on the ability to extract value from these materials. Increasingly, modern computer-based tools are used to describe and predict process outcomes, including mass and heat balances, the partitioning of elements and phase equilibria. At the heart of these predictive tools are thermodynamic databases that describe the fundamental chemical properties of a system and all the components present. A comprehensive research program has been established to develop an accurate, self-consistent thermodynamic database describing all gas-slag-matte-metal-speiss-solid phases in the system Cu2O-PbO-ZnO-Al2O3- CaO-MgO-FeO-Fe2O3-SiO2-S-(As-Bi-Sb-Sn-Ag-Au). The database can be used in conjunction with the FactSage computer platform. The accuracy of the database and its application to industrial practice is demonstrated.

By Ming-Feng Ye, Guang-liang Wu

The microstructure and mechanical strength variations of chromite pellets preheated and roasted in air were studied systematically. The results show that the chromite (Fe,Mg)(Cr,Fe,Al)2O4 is oxidized to magnesium-rich (Mg,Fe)(Cr,Fe, Al)2O4 and ferrochromium complex oxide (Cr,Fe,Al)2O3 in the preheating process over 500 °C. When the temperature is higher than 1000 °C, the new phase (Cr,Fe, Al)2O3 is formed, which is mainly distributed in the outer layer of a single chromite particle. Inner the particles there are acicular (Cr,Fe,Al)2O3 and unoxidized (Fe,Mg) (Cr,Fe,Al)2O4, which forming an interwoven structure together. The oxidation rates of pellets can reach to superior limits in 20 min. With the temperature increasing from 950 to 1300 °C, the mechanical strength and oxidized rates increase to varying degrees correspondingly.

Mar 1, 2018

By M. I. Novgorodova

An overview of the systems Au-Ag and Au-Cu is given. The nature and levels of concentration of various elements occurring with native gold is reviewed. The examples cited are mainly from the USSR. The lack of homogeneity within naturally occurring Au-Ag solid solutions is examined.

Jan 1, 1991

By P. Hajiani

Rare earth elements (REEs) are critical materials in many leading-edge technology products. However, REE separation outside China has remained a challenge in addressing environmental concerns of current production. The author has worked on a technique employing the emphasised variability in the electrophoretic mobility (μi) of REE for the purpose of REE separation. In continuation of the results presented in IMPC 2016 [1], this contribution summarizes the progress achieved in 2016 and 2017. The major goal was to increase the REEs concentration by a factor of 1000 and to attenuate the consequent drawbacks, specifically joule heating effect. Amphiprotic hydroxylic solvent was selected to replace water, which has a major impact on the complexation mechanism and buffer requirement. Non-aqueous media result in a significant drop in the specific molar conductivity of the electrolyte, whilst μi reduces several times only. Moreover, a quasi-steady state electrophoretic separation in conjunction with temperature gradient focusing is adapted to improve scalability.

By W. D. Cho

Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking -ladle and tundish - to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-A12O3 and CaO-A12O3-SiO2 slags at the temperatures between 1450 and 1550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopies. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al2O3, Siq, CaF2 and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase has been observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.

Jan 1, 2002

By D. A. R. Kay

Phase stability diagrams are used to predict the abilities of lanthanum and cerium oxides to desulfurize coal gasification products in the temperature range 800-1000 C. Results of desulfurization studies in laboratory fixed bed reactors illustrate the effects of i) sorbent preparation, ii) input gas quality and iii) temperature, on the desulfurization reaction. 2CeO(2-x)(s) + H2S(g) + (1-2x)H2 = Ce2O2S(s) + 2(1x)H2O(g) The results of desulfurization/oxidation regeneration cycles are also reported.

Jan 1, 1989

By François Larouche

Since their commercialization in the early 1990s, lithium-ion batteries (LIBs) have become ubiquitous for powering a myriad of portable electronics. Their usage now extends to the automotive industry and stationary energy storage market. With an average life of 6.2 years and the strong demand, the volume of spent LIBs has increased exponentially, making recycling mandatory. Currently, recycling/ recovery of spent LIBs is limited in comparison to all other types of batteries. The current processes focus mainly on the recovery of the most valuable metals such as cobalt and nickel, leaving lithium and phosphate in a low value end-product. It is necessary that new advanced recycling technologies are developed for the recovery of spent LIBs both from an economic and environmental perspective. In this paper, the current R&D status of LIBs recycling is reviewed with the emphasis placed on hydrometallurgical processing opportunities for Li-ion and Li-solid state batteries.

By Xin Li, Hai-Xing Fang, Bing Xie, Hong-Yi Li

Chromium-containing vanadium slag (V-Cr slag) was obtained by an industrial smelting process of Hongge Ore, which is valuable vanadium-titanium magnetite to extract V and Cr in China. Sodium roasting thermodynamics of V-Cr slag in presence of oxygen were calculated to evaluate the reactivity of chemical compounds. Results showed that the oxidation of FeV2O4 was intensified in presence of Na2CO3 while the oxidation tendency of FeCr2O4 was far lower than that of FeV2O4. It was probably that reactions of impurities including Al2O3, SiO2 and Fe2O3 with Na2CO3 happened and the products can promote the oxidation of vanadium or chromium compounds in lower valence. Based on thermodynamic analysis, a two-step selective extraction process of vanadium and chromium was proposed. Extraction rate of vanadium was 88.6% while 7.0% for chromium in the first extraction step; extraction rate of 90.7% and 95.4% for vanadium and chromium, respectively, were obtained in the second step.

Jan 1, 2014

By Sepideh Abolghasem, Juan Pablo Casas Rodriguez, Juan Camilo Osorio

Predicting flow stress at high strain-rates is a desirable practice for material behavior characterization. Sub-grain size has shown a huge influence in cutting forces and the workpiece surface finish determination during orthogonal cutting process. Hence, a prediction of flow stress as a function of thermomechanical conditions and sub-grain size is of great important which is studied in this work for OFHC copper. The principal thermomechanical conditions being strain, strain-rate and the accompanying temperature rise are characterized in Plane Strain Machining (PSM) and the resulting microstructure, sub-grain size, is quantified. Material maximum flow stress (a constitutive model) as a function of thermomechanical conditions and sub-grain size is predicted considering a saturated state in microstructure using optimization algorithms for reaching the validated temperature rise based on modified Hahn’s model. Evaluated models suggest a major influence of strain-rate and dislocation in temperature rise estimation and flow stress prediction leading to consideration of mechanical failure phenomenon involved in machining-based manufacturing processes.

Mar 1, 2018

By Akram Alfantzai, Farzad Mohammadi, Maysam Mohammadi

"Degradation of lead anodes has always been a major concern among the electrowinning industries. In this study, the effect of agitation of the zinc electrowinning solution on the integrity of lead anodes was investigated. Galvanostatic experiments were performed at 37±0.5°C using 0,600 and l000rpm magnetic stirring rates for 24 hours. The Pb02 layer formed on the anode surface was reduced to PbS04 (discharged). The discharge information was used to calculate the amount of Pb02 present on the surface. Weight loss measurements along with the discharge calculations revealed that the degradation rate of the lead anode increased as the solution was stirred more vigorously. Furthermore, the amount of remaining Pb02 on the surfaces was decreased as a function of solution velocity. Therefore, it may be concluded that, degradation rate oflead anodes is controlled by detachment of the corrosion products from the surface rather than by electrochemical reactions. IntroductionElectrowinning is one of the extraction stages of zinc, in which pure zinc is deposited from acidic solution after froth flotation, roasting and leaching processes. The anode electrode materials play important roles in the electrowinning process. Their electrocatalytical capacities determine the oxygen evolution overpotential, and consequently the cell potential and energy efficiency of the zinc electrodeposition [l]. Purity of the zinc deposited on the cathode is affected by the solubility and corrosion resistance of the anode materials. Using insoluble materials as anode in the electrowinning leads to the higher purity of the deposited metal on the cathode[2]. Lead (Pb) and its alloys have been used as the anode in the zinc electrowinning because of its special properties such as relatively low cost, low melting point, insolubility in solutions containing sulphuric acid and high conductivity in both states of metallic and oxidized [3, 4]. In zinc electrowinnig, zinc reduction occurs on the cathode (reaction 1) and the oxygen evolution reaction (OER) (reaction 2) is the main anodic reaction [5, 6]."

Jan 1, 2013

By Ruirui Wei, Mingrui Yang, Xuewei Lv

Copper slag is a by-product obtained during smelting of copper from copper ores. In China, for one ton of metal production about 2.2 tons of copper slag was generated, and approximately 15 million tons slag is produced in 2013. Dumping and disposal of such huge quantities of slag will cause environmental and space problems. Most importantly, copper slag cannot be made full use of to maximize its value. In this study, copper slag was used to take the place of scrap iron and part of silica in traditional process and to produce FeSi alloy as the main material. Utilizing silica and copper slag as the raw materials and coke as the reducing agent, FeSi45 was produced in the induction furnace. In addition, the effect of different n(C)/n(O) on FeSi45 has been investigated.Increasing n(C)/n(O) is beneficial to form the stable phase of FeSi. Meanwhile, n(C)/n(O) greatly affects the reduction and recovery of silicon than iron. When n(C)/n(O) equals 1.10, the recovery of silicon and iron is about 77 and 95%, respectively.

Mar 1, 2017

By Yong Hwan, Wang Jian-Jun, Cai Jiu-Ju, Chen Chun-Xia

"The quantity of residual-heat and its recovery in some Chinese sinter plants are investigated. The main factors affecting energy consumption are analyzed using exergy analysis combining energy level analysis. It is indicated that the “gradation recovery and cascade utilize” of discharged gas and sinter residual heat in different temperature is the direction and the available approach to reduce energy consumption of the sinter process. Taking an iron& steel enterprise as an example, the three-ranked scheme of residual-heat recovery is put forward: ?Part of the sinter gas is used for warm-up and dryness; ?The high-temperature part of the cooler and exhaust-heat boiler are actualized as a closed-circuit, which can produce high-quality steam to generate electricity. ?The waste air in low-temperature part is introduced to sintering machine to support combustion. According to the CDQ which can recover the coal heat, the assumption of pot-recovery is put forward to replace the belt cooler. The two equipments of residual-heat recovery are analyzed in the aspect of energy consumption and CO2 reduction.1. IntroductionEnergy consumption in sintering is only inferior to iron-making in iron& steel enterprises, accounting for 10%~20% of the total energy consumption. A lot of residual heat is produced during sintering, and mostly from the sinter ore and waste gas. Sensible heat of hot sinter ore and discharged gas have accounted for 60%[1] (equals to 40 kgce/t-ore), which are the key point of sintering waste heat recovery. Discharge gas of sintering is mostly composed of flue gas deriving from sinter bed’s combustion, and the content distribution of H2O and O2 and the temperature of the gas along the length of belt-type sintering are shown in Figure1[2,3]. Currently, the sensible heat of hot sinter ore is mainly recovered by circular cooler and cooled by blasting air: the temperature of cooled discharge gas brings down from 350? to about 100? along with the decrease of sinter ore temperature. It is significant to recovery and reuse the waste heat as 4000~6000m3 discharge gas per ton of ore can be produced"

Jan 1, 2008

By Zhang Chuanfu

The fibrous nickel oxide powder was prepared by the method of chemical precipitation and pyrolysis, that is, the NiO precursor was firstly precipitated from nickel ions solution with addition of oxalate salt and then the final NiO powder was obtained by pyrolysis of the prucursor. The effects of the pH, reaction temperature, reactant concentration, addition of surfactant on the morphology of the precursor particles were investigated. The influences of the various conditions, including the temperature and time, the air flow and the speed of the temperature increase on the morphology, average size and specific surface area of the NiO particles were also addressed. The fibrous NiO particles with IOO~ 120 in axis/diameter ratio and 5.5 m2/g of the specific surface area may be produced under certain operation conditions by this process.

Jan 1, 2003