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By P. J. Harrington

The recovery and recycling of low concentration metal and other ions has traditionally been carried out using adsorption or ion exchange processes which, however, become uneconomical at higher concentrations, such as those that occur with many intermediate or waste streams where recycling is now being required. This paper describes the development of a process based on non-dispersive solvent extraction for the recovery of chromium (VI) from electroplating rinse water. During the chromium plating of steel, the concentration of chromium (VI) in the rinse bath rises to concentrations in the order of 100 mg/L when it becomes unusable and is then disposed of. The aim of this work was to investigate processes for recovery and recycling of the chromium in the rinse bath. The recovered chromium is required to be concentrated and purified before reuse. Tertiary amines have been shown capable of concentrating and purifying the chromium (VI) in solution. However, solvent extraction processes that have been applied to the recovery and reuse of metals from waste streams have had only limited success in the past, primarily because of the relatively high solvent losses when existing contacting equipment is used on low feed concentrations. Attempts to eliminate losses by immobilizing these complexing agents on substrates have not been successful. In order to control the losses and maintain specificity, a hollow fibre-contained liquid membrane has recently been trailed in a pilot plant to recover chromium from chromium plating waste streams. Details of the trial and modeling of the results are presented, and show that the level of losses is significantly reduced. However, issues relating to fouling still need to be addressed. This type of equipment has many applications in the recovery and recycling of a range of materials in the manufacturing processes.

Jan 1, 2003

By T. Inami

The chlorine leach of the anode slime was studied in order to improve the treatment process at the Niihama Nickel Refinery. The anode slime originates from the nickel matte electrorefining and, contains 3-5% of nickel as sulfides. A comparative study has been conducted on the filter cake resulting from the sulfur filtration of the molten anode slime. The kinetic factors of the chlorine leach such as temperature, grain size were defined. Under the optimized condition, 70-80% of the nickel is recovered from the slime or filter cake. On the basis of these results, the chlorine leach process for the treatment of anode slime has been established. The leaching plant has been installed and successfully operated since 1986.

Jan 1, 1988

By Qingyun Huang, Wei Lv, Junyi Xiang, Xuewei Lv, Chenguang Bai

The roasting is the key step for the extraction of vanadium from vanadium slag by calcification roasting–acid leaching process. In this study, thermogravimetric analysis and kinetic study of vanadium slag in the presence of calcium oxide was investigated. The maximum oxidation degree was slightly increased by increasing temperature from 700 to 900 °C then almost unchanged further increasing temperature to 1000 °C. The reaction mechanism was analyzed through both Sharp method and ln-ln method. Results showed that the mechanism the reaction in the a range of 0.1–0.8 corresponded to the random nucleation and subsequent growth, as represented as (G( a)=[ −ln(1−a)] 1/3 = kt. The apparent activation energy was calculated to be 3.5 kJ/mol according to Arrhenius equation.

Mar 1, 2018

By Ping Long, Peipei Liu, Xinlin Ren, Yunke Wang, Bin Yang, Jian Wu, Wenli Zhang

In this research, ICP-AES was used for determining ten impurity elements (Fe, Pb, Ca, Mg, Cu, Zn, Al, As, Sb, and Bi)in tin concentrate and smelting products, such as crude tin and slag. Samples were dissolved by hydrochloric acid and nitric acid. Determination conditions were investigated in detail. Influences of matrix and coexisting elements were eliminated by selecting proper analysis spectral lines. Under the optimum conditions, the correlation coefficient of cali- bration curves were higher than 0.999. The detection limits of these ten impurities were in the range between 0.0009 to 0.0621 lg/ml. Relative standard deviation (RSD) values were lower than 6.0%, and the recoveries of standard addition were between 85 and 109%. The proposed method was demonstrated to be reliable by comparingwithstandardanalysismethodsandcertifiedvaluesofstandardsample. It could be applied for determining impurity elements in tin concentrate and smelting products successfully.

Mar 1, 2017

By R. C. Hubli

A panial equilibrium model? to simulate the dissolution of millerite (NiS) in aqueous solutions containing copper(II) chloride as the oxidizing species has been developed. The predominant copper(I) and copper(II) species are CuQ3 and CUO2 respectively. The model computes the initial concentrations of the species present in the aqueous phase under the specified input conditions, prior to the simulation of dissolution. During the dissolution of millerite, nickel enters the leach liquor as NiH and it has been found that the H+ decreases as a function of NiS dissolution. The simulation has been accomplished under conditions prevailing during actual dissolution, with only one mineral undergoing dissolution. The model can be applied for the simulation of co-dissolution of two or more sulfides. Under the given conditions, the precipitation of Cu1(OH»)O is negligible but loss of Cu(1l) could be significant if the initial H+ is lower than 0.03 M. The results of the simulation compare favorably with experimental observations.

Jan 1, 1996

By Eugene Jak

Copper sulphide processing technologies face increasing pressures associated with decreasing concentrate grade leading to increasing thermal inefficiency and lower productivity. Impurity concentrations are on average increasing, creating potential environmental risk and additional treatment costs. In copper flash smelters dust, partially oxidised materials and fume formed from the condensation of volatile impurities, are routinely recycled to the feed. In the converting stage the heat balance is maintained by charging anode reverts and other inert materials. In both cases, the thermal energy available from sulphide oxidation is not fully utilised or optimised. The productivities of both smelter and converter stages can be potentially increased through the addition of a high copper, low iron, low impurity precipitated copper product. Calculations are carried out for fayalite smelter and calcium ferrite converter slags using an optimised FactSage thermodynamic database. The potential for significant increases in smelter and converter productivities using existing technologies are predicted.

By Jinxing Ji

The thiosulfate lixiviant system for leaching of gold has been under extensive investigation for nearly two decades and consists of ammonium thiosulfate, copper and ammonia. There are several challenges with this system. The occurrence of ammonia must be taken into account from a health and hygiene aspect in the workplace, and also from an environmental perspective with significant levels of ammonia and copper in the tailings. Copper accelerates the leaching rate but causes excessive thiosulfate degradation. A new lixiviant system that has been investigated consists only of sodium thiosulfate without copper and ammonia. Gold leaching is carried out in an enclosed reactor with slightly elevated oxygen overpressure and temperature. Extensive leaching experiments were carried out to minimize thiosulfate degradation and polythionate formation while maximizing the gold extraction. For the preg-robbing carbonaceous ore sample tested, gold leaching was essentially complete within six hours and the thiosulfate consumption was lower than in the typical ammoniacal thiosulfate system. The gold thiosulfate complex in the pregnant leach solution was found to be quite stable under ambient conditions. This new leaching system has the advantages of being more environmentally friendly, has a shorter residence time, lower thiosulfate consumption, lower oxygen consumption, and is easier to control.

Jan 1, 2003

By J. W. A. Morris

To investigate the use of centrifugal fields in fused salt electrowinning cells, a high temperature rig has been designed, constructed and commissioned. Initially, the cell has been applied to the fused salt electrowinning of zinc. Current efficiencies of 93% have been obtained for inter electrode gaps as small as 8mm for 70mm diameter electrodes rotating at 100rpm. The construction of a semi-rigorous physical model has shown the potential exists to extend the use of centrifugal fields to the electrowinning of light metals.

Jan 1, 1994

By Liyuan Chai

In this study, spent grain was used as an adsorbent for the removal of Hg(II) from aqueous solutions, the process parameters such as contact time, solution pH, adsorbent dose, and initial Hg(II) concentration were studied in batch experiments. The initial adsorption process was fast, 91.08% of adsorption occurred within 5 min and equilibrium was reached at around 30min. Adsorption process was found to follow pseudo-second-order kinetics. The equilibrium data were better fitted to Langmuir isotherm than Freundlich isotherm with the maximum adsorption capacity 41.36 mg/g. The structure and component of spent grain before and after adsorption of Hg(II) were investigated using scanning electron microscope(SEM) and energy dispersive X-ray analysis(EDAX), these analysis also confirmed the adsorption of Hg(II) onto spent grain. The results indicated that spent grain had potential as a new inexpensive adsorbent for Hg(II) removal from aqueous solutions.

Jan 1, 2009

By I. U. Onyenanu, C. E. Ilochonwu, E. I. Nwonye, C. O. Nwajagu

This work shows how pure silica was derived directly from rice husks ash (RHA) in different temperatures for reduction to Silicon (Si). The processes to form Si materials are usually complex, costly and energy-intensive. The silica in the ash undergoes structural transformations depending on the conditions of combustion. A high purity silica was produced at 650oC after burning the rice husk (RH) for up to 7 hours. The purity of the silica was determined by dissolving the RHA with alkali solution to form sodium silicate solution of pH 11.0. This was added to hydrochloric acid of pH 1.5 which lowered the pH of the solution to 4.0 to form silica gels. The silica gels produced were washed and dried to powder and then characterized using XRD and EDX techniques. This study was done to reduce energy waste and environmental pollution in Nigeria as silica is used to develop many materials.

Jan 1, 2015

By Ragnhild Aune

In fire refining of copper, the affinities of various impurity elements on dissolved oxygen is of great significance. Further, in the design of oxygen probes in liquid copper, the influence of solute interactions on the activity of oxygen need to be considered in order to evaluate the oxygen concentration in molten copper. The present paper presents a series of measurements of the activities of oxygen in liquid Cu-M-o alloys (where M stands for Mn, Zn, As, Se or Te) carned out by the present group employing the solid electrolyte galvanic cell technique. Extreme care was taken to control the oxygen potentials in the inert gas atmosphere, and to keep the oxygen levels very low in the molten metal. The oxygen content was determined by analysis of the samples taken out from the melt. The results obtained showed that Mn has a strong negative influence on the activity coefficient of oxygen in liquid copper. A similar, but less prominent effect was observed in the case of Zn. Arsenic had no influence on the activity of oxygen in Cu (liq.). Se and Te had slight negative effect on oxygen activities in copper at XQ >10-5, while at lower oxygen levels the interaction coefficients were found to be positive. The results obtained were compared with empirical models for the calculation of interaction coefficients available in literature.

Jan 1, 2003

By Ju Shao-hua

Although nowadays gold extraction methods are very abundant, none of them is satisfying, especially, in the field of heap leaching of low grade gold ore. The traditional heap leaching method of cyanide method plays an inglorious role of badly environmental pollution. In this paper, a bran-new and innoxious method of gold extraction system, metal-ammonium-chloride-ammonia (MACA), was proposed, and also analyzed both thermodynamically and practically. Thermodynamically, according to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the thermodynamics of Au-NH4Cl-NH3-H2O system was studied by using the exponential computation method and through MATLAB programming, and the solid figure of its potential - c(NH4Cl) - c(NH4OH) was drawn. The results showed when the concentrate of ammonia is higher than 0.6 mol?L-1, fAu+/Au is only about -0.2 v. Practically, the leaching results of a cuprous gold ore showed that the extraction of gold can reach to 80% in this system. The preliminary results of reduction of the rich solution with copper and zinc powders showed that with deoxygenizing, the reduction effects were relatively good. These new findings and results have established a theoretical and practical base for developing a new process for heap leaching of low grade gold ores in this system. And the new process owns a series of merits such as, non-cyanogens, nontoxic, broader applicability.

Jan 1, 2006

By F. Chabchoub

A mathematical model has been developed to study the influence of process variables on the horizontal Ohno continuous casting process. The model simulates the heat transfer and fluid flow in a wide plate ingot of pure tin. A two dimensional numerical analysis based on a control-volume finite difference approach, the Semi-Implicit Method for Pressure-Linked Equations algorithm (SIMPLER), and an Enthalpy Transforming Model was used. The shape and position of the solid-liquid interface were calculated at different casting speeds, ingot thicknesses, and cooling device characteristics, as well as various mould temperatures. Results of the mathematical model were compared with

Jan 1, 1992

By Tatiana Pereira Moreno, Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"Nowadays, End-of-Life (EoL) Liquid Crystal Displays (LCDs) are traditionally disposed in landfills. The increasing access to LCD technology over the last years by Brazilian consumers has intensified LCD' s disposal as an environmental and economic issue. This study aims to characterize used LCDs to identify the main components for recycling. Characterization was performed through scrap disassembly and its components were identified, separated, and weighted. LCDs were disassembled and the following divisions were applied: screen, metal frame, polymeric frame, polymeric sheets and electronic part. Some techniques were used to determine the concentration of Indium in the LCD, the glass/plastic ratio and the different kinds of polymers that compose the screen. The techniques used for characterization included inductively coupled plasma optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). This method, when applied to a wide range of LCDs, can allow the development or improvement of an EoL management of LCD.IntroductionWaste Electrical Electronic Equipments (WEEEs) are waste from discarded equipment, such as computers, monitors and cellphones [1]. Over the past years, treatment of WEEE has been emphasized. It occurs due to the technology's advancement that leads to an even larger increase of WEEES [2].Among WEEEs, there are the liquid crystal displays (LCD). LCD technology is applied in cell phones, tablets, computers and monitors. Nowadays, it's the most well known technology when it refers to monitors, due to its advantages over the Cathode Ray Tube (CRT) technology. Some of them are energy saving, smaller size and no radiation emission [3].This feature in the LCD's global market along with the speed at which electronic equipment becomes obsolete affects society economically and ambiently.This issue becomes even more serious when considering the final destination of the liquid crystal displays. LCDs are lead to landfills as other WEEEs. Besides the different materials long degradation time, the environment is damaged by the disposal of the potentially reusable and hazardous materials [ 4]."

Jan 1, 2014

By Matthias Merzkirch, Volker Schulze, Kay Andre Weidenmann

"Unidirectionally reinforced light weight compounds based on light metals such as the aluminium alloy EN A W-6082 are adequate materials for the future use in transportation means like automobiles and airplanes. Due to the occurring cyclic loads knowledge about the crack growth behaviour of such composites is needed. The investigations at a load ratio of R = 0.18 show that the crack growth rate of the aluminium matrix is reduced if reinforced by spring steel wire with a reinforcing ratio of only about 1 Vol.-%. Additionally, the acoustic emission analysis allows detecting crack growth within the matrix material, crack propagation along the interface wire/matrix and crack closure which could also be determined with the help of a self designed capacitive displacement measuring gauge. The damage behaviour could be verified by metallographic and SEM investigations.IntroductionIn the field of lightweight structures for transportation means the need for light, strong and stiff materials, in particular composite materials, is increasing in order to save resources and costs. Lightweight materials such as aluminium and magnesium alloys are highly efficient candidates to be used in the composite extrusion process [1] which allows for a simple production of unidirectionally reinforced profiles with a large diversity of geometries at low costs. Figure 1 depicts the principle of the composite extrusion process; within the first part of the tool the billet material is split into several strands whereas the middle part of the tool allows the supply of the reinforcing elements. The third part of the tool rejoins the matrix material and the reinforcing elements and defines the final shape of the profile."

Jan 1, 2011

By M. A. Barron, D. Y. Medina, R. T. Hernandez, I. Hilerio

"Chromium Nitride (CrN) thin fihns were deposited on steel AISI 316 substrates with reactive magnetron sputtering method. CrN films were produced under two different conditions. In the first one, the substrate was heated by a d.c. source. At the second coating was applied a negative substrate bias voltage. X ray diffraction, quantitative energy dispersive and scanning electron microscope, were employed to characterize their phases, chemical composition and microstructure. Additionally microhardness was evaluated using a microhardness tester. The results show that the phase formation of CrN thin films in the first case (with temperature) is better. Both coatings presented homogeneous surface. Their compositions shows differences though that gases flow are same. In attention to their hardness, presents an increment if it's compared with hardness substrate.Nomenclature.P Ar =Argon gas pressure during coating.PN2 = Nitrogen gas pressure during coating.Ts = Substrate temperature during coating.T f = Coating melting temperature. (CrN = 1050°C).E=Potential difference.t =Coating time.P=Target power (Cr) in magnetron sputtering de.HV = Vickers hardness.F = Applied charge.d= Average length of longitude of the two diagonals (mm)Introduction.Wear causes losses in materials surface, generating that components of mechanical systems suffer irreversible changes in their properties, causing a faulty operation of the system. It is important to control their effects, measuring and interpreting their causes clearly."

Jan 1, 2013

By S. J. Macnaughton

The Olympic Dam deposit in South Australia contains 2% copper and 0.06% uranium, which are present as bomite, chalcocite, chalcopyrite, uraninite, coffinite and brannerite. The copper is principally recovered using flotation. The flotation tailings, which contain the bulk of the uranium, and typically 0.3% copper, are leached using sulfuric acid and an oxidant at atmospheric pressure. This paper describes the results from a detailed investigation of the leaching behaviour of this ore. The influence of acid strength, Fe3+ concentration, redox potential and temperature on the dissolution of uranium and copper minerals was studied. Experimental data were obtained from extensive batch leach tests. Mineralogical studies, including SEM analysis of individual mineral grains, were also carried out. The maximum extraction of uranium determined experimentally was in good agreement with that predicted from SEM determination of the proportion of refractory brannerite in the ore. The leaching rate of copper was found to be independent of acidity over the range 20 g L-' to pH 2.0, but was strongly dependent on temperature and Fe3+ concentration. Uranium extraction showed a weak de endence on acidity, Arrhenius temperature dependence and a complex co-dependence on F>+ concentration and redox potential. A kinetic model has been developed, which predicts copper and uranium dissolution. This model will be incorporated into a more comprehensive model that can be used to predict leach performance and reagent consumption for specific ore samples.

Jan 1, 1999

By Ahmad-Bitar¸ Riyad N., Shadia J. Ikhmayies

"CdSi-xTex thin films with O<x<0.3 were prepared on glass substrates by the annealing of CdS:In thin films produced by the spray pyrolysis technique. The annealing was performed in nitrogen atmosphere at 400 --,C in the presence of Te vapor. The compositions of the films were determined by energy dispersive X-ray detection (EDAX) measurements. Scanning electron microscopy (SEM) was used to investigate the morphology of the films. The transmittance of the films was measured at room temperature in the wavelength range 400-1100 nm and used to produce the absorbance of the films. The first derivative of the absorbance was used to estimate the optical bandgap energy Eg by using the minima in the first derivative. The relation between the bandgap energy and the fraction x was found to fit with a parabola and bandgaps in the range 2.196: =Eg: =2.480 e V were obtained. Urbach tailing in the bandgap was also investigated.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The fabrication process of these cells involves the deposition of a p-type CdTe absorber layer on top of an n-type CdS one which acts as a window. The efficiency of the solar cell is affected by the method of preparation of both layers [1, 2].Interdiffusion processes taking place at the CdS/CdTe interface have largely been realized to significantly affect the device performance [3] by changing the bandgap of both CdTe and CdS which modifies the spectral response of the solar cell [ 4]. The formation of a mixed crystal or a graded layer causes a reduction in the lattice mismatch at the CdS/CdTe junction [5] which is about 9% [ 6] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [7, 8]. A complete understanding of the properties of the intermixed layers CdSxTe1-x that usually constitutes the interfacial region in the CdS/CdTe solar cell is essential. According to our knowledge, a lot of research was devoted to the investigation of the diffusion of S into CdTe [3-5, 9]; but little on the direct investigation of the diffusion of Te into CdS [6]."

Jan 1, 2011

By L. Béjar-Gómez

The aim of this research work is to study and characterize precipitates in structural microalloyed steel by transmission electron microscopy and analysis by high resolution (HRTEM). Microalloyed steel with titanium was produced by casting in an electrical induction oven of 25 Kg. capacity. Carbon content in steel was less than 0.1 % and titanium content of 0.04%. Steel was processed thermomechanically; reheated to 1250ºC and hot rolled on a laboratory mill to a 13.0 mm thick plate with a finish rolling temperature of 900ºC and thickness reduction of 80%. Analysis by High Resolution Transmission Electron Microscopy (HRTEM) identified precipitates in the steel; type and morphology. Energy Dispersive Spectroscopy (EDS) analysis was applied to obtain the chemical composition of precipitates and the matrix. STEM-EDS analysis was also applied to obtain the element profile of precipitates. The results showed the presence of carbonitride precipitates of titanium, Ti (CN), with a circular morphology and size of 10 nm and less.

Jan 1, 2006

By Anne C. Chinellato, Alejandra T. Soria, Nelida L. del Mastro, Amanda C. S. Pereiral, Esperidiana A. B. Moura, Anibal V. Abreu

"This work presents a comparative study of the thermo-mechanical and morphological properties of sugarcane bagasse fiber/HDPE composite treated with electron-beam and gamma radiation. The composite samples obtained by extrusion and injection molding processes were irradiated at 50 and 90 kGy using either a 1.5 MeV electron beam accelerator or gamma irradiator EMI-9, at room temperature in presence of air. The irradiated and non-irradiated samples were submitted to mechanical and MPI tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), sol-gel analysis and X-Rays Diffraction (XRD) and the correlation between their properties was discussed. Improvement of the bagasse fiber/HDPE composite properties, using electron-beam or gamma radiation, was found.IntroductionResidues of sugarcane bagasse fiber are widely produced in Latin America and other countries: in Southern Africa, Egypt, South-Eastern Asia, India, China, Australia, Cuba, among other producers, as by-products of the sugar and bioethanol industry. The sugarcane industry in Brazil and Uruguay is well established and expanding with large potential to increase the production of sugarcane bagasse in the next years [1-3]. Although the major portion of the bagasse is currently burnt for energy supply in the sugarcane industry, the disposal of this byproduct is still inefficient and, consequently, it is critical for agricu1ture profitability and environmental protection. Sugarcane bagasse is a lignocellu1ose fiber mainly constituted by around 46 % cellu1ose, containing hemicellu1ose, lignin, fat and waxes, silica and other elements [3, 4]. Studies have reported that sugarcane bagasse can be used to produce thermoplastic polymeric composites with excellent properties for many applications. [5-8]. Based on this survey, the transformation of bagasse into high quality industrial products, such as bagasse-polymer composites, can provide its more effective utilization."

Jan 1, 2012