Thesis (PhD (Process Engineeering))--University of Stellenbosch, 1995. / The hydrometallurgical leaching of sulphide concentrates was introduced in the 1950's. Generally the leaching mechanisms of these processes are not understood fundamentally. The reasons for this are the inherently complex nature of sulphide chemistry and that the sulphide concentrates usually consist of highly intergrown sulphide minerals. The leaching kinetics of sulphide concentrates where only one metal-sulphide mineral occurs have been investigated intensively, but not for sulphide concentrates with more than one metal-sulphide mineral. The behaviour of these mixed metal-sulphide minerals has mostly been investigated on plant scale to qualitatively determine the leaching trends of the process. The consequence of the relatively unKnown leaching mechanism and kinetics is that these processes are not controlled efficiently. This study was conducted on the acid-oxygen pressure leaching of Ni-Cu matte (the first stage leach process at the Ni-Cu refinery of Impala Platinum Ltd.). As a first step to improve the control efficiency of the process, the process must be stabilised. Therefore, an off line computer simulation program is proposed to control the repulping section of the plant that has previously been controlled solely by an operator. Controlling the repulping section is very important, because conditions exist in the repulping tanks for leaching to occur. This causes perturbations in the pulp entering the pressure leach autoclave. Due to the fast reaction kinetics of the matte in the pressure leach autoclave the perturbations entering the autoclave will influence the performance of the acid-oxygen pressure leach process. The simulation program was tested on the plant and indicated that considerable improvement in the stability of the operation could be achieved. In obtaining a better understanding of the behaviour of this process, it is essential that key variables and trends are identified. A methodology is proposed to analyse and model this ill-defined and poorly understood process from historical data by v artificial neural networks (ANN), inductive learning by decision trees and statistical techniques. The back propagation neural network, learning vector quantization neural network and the decision trees yielded comparable classification rates between 73% and 84%, and could serve as a basis for the adjustment of operating conditions to improve the efficiency of the process. The relative importance of the process variables is determined by a method of sensitivity analysis and together with the statistical mean, the effect of an increase or decrease in the variable on the process is quantified. These results are substantiated by experimental findings. A leaching mechanism for the acid-oxygen pressure leach of Ni-Cu matte is postulated. The leaching sequence of the nickel and copper sulphides is Ni3Sr Ni7S" NiS-Ni3S4, and CU2S-CU31SWCU1.BS-CUS, respectively. Ni7Sa and CU31 S1a are intermediate nickel and copper sulphide phases that form during the leaching process. Ni alloy has a galvanic effect on the sulphide minerals which inhibits the overall leaching rate and results in the formation of H2S and the intermediate nickel and copper sulphides (Ni7Sa and CU31 S1a). A semi-empirical kinetic model was developed based on the chemical reaction rate expressions of the leaching mechanism. This model can accurately simulate the batch leaching process for variations in the oxygen partial pressure, oxygen flowrate, temperature, particle size, initial acid concentration and pulp density. A sensitivity analysis on the model indicated that for a matte with a lower initial Ni alloy content the leaching rate of nickel is much faster.

Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This thesis investigates the control of calcium and magnesium in a base metal sulphate leach solution containing nickel and cobalt. The presence of calcium and magnesium in the hydrometallurgical processing of base metals, result in a number of difficulties. These problems range from the contamination of the final product, to high energy consumption and large bleed streams during electrowinning. Calcium poses a greater problem in sulphate solutions due to the low solubility of its sulphate salts. No conventional method exists for the control of calcium and magnesium. As part of this study a review of possible control methods was conducted, which is listed within. From this list the precipitation of fluorides was selected for further investigation. The results showed that it is possible to control calcium and magnesium through the precipitation of their respective fluorides, without the co-precipitation of nickel and cobalt. For 10% stoichiometric excess of fluoride 96.5% calcium and 98.5% magnesium were removed during batch experiments. It is known that mixing and hydrodynamics plays an important role on the characteristics of the formed precipitate, making these processes inherently difficult to scale-up. To evaluate these effects on a continuous process, the three-zone model proposed by Gösele and Kind (1991) was used. A precipitate with consistent characteristics was produced while varying the mixing on the macro, meso and micro scale. Additionally, methods were investigated for the removal or possible recycling of the unreacted fluoride, for which activated alumina was identified. It was observed that activated alumina could adsorb fluoride to low levels in the presence of the base metal solution, after which it could be regenerated again. The activated alumina (AA) had a capacity of 8.65 gF/lAA at a 10 mg/l fluoride breakthrough level during column tests. Based on the experimental results a conceptual process was devised whereby only a portion of the leach stream is subjected to the fluoride precipitation process, after which it is returned to lower the overall calcium and magnesium concentrations. This method would reduce the effect of the observed dominance of magnesium precipitation, in processes where the maximum removal of both elements is not required. The fluoride precipitation process consisted of three steps being precipitation, solid-liquid separation and adsorption of the unreacted fluoride. Sufficient information is provided on the process for a cost estimation to be carried out. Should this found to be feasible, a continuation of the project is recommended. Different reactor configurations could be evaluated for precipitation. The scaling observed during the continuous experiments should also be investigated to minimise its effect. The investigation of activated alumina was only a secondary project and more work is required on optimisation, particularly for the desorption cycle to enable the recycling of the unreacted fluoride. / AFRIKAANSE OPSOMMING: Saamgestel in hierdie tesis is 'n studie van die beheer van kalsium en magnesium in 'n basismetaal-sulfaatoplossing, bevattende nikkel en kobalt. Die teenwoordigheid van kalsium en magnesium in dié oplossings veroorsaak 'n verskeidenheid van probleme, wat wissel van produkkwaliteit verlaging tot hoë energieverbruik en groot bloei strome tydens platering. 'n Groter probleem word ondervind met kalsium as gevolg van die lae oplosbaarheid van sy sulfaatsoute. Geen konvensionele metode kon gevind word vir die beheer van kalsium en magnesium gedurende die oorsig van moontlike metodes nie. Hierdie moontlike metodes is geïdentifiseer en kortliks bespreek in die tesis. Van die moontlike metodes is die presipitasie van fluoried-soute gekies vir verdere eksperimentele ondersoek. Die ondersoek het getoon dat dit moontlik is om kalsium en magnesium te beheer deur die presipitasie van fluoriede sonder om die basismetale saam te presipiteer. Vir 'n 10% oormaat fluoried toevoeging is 96.5% van die kalsium en 98.5% van die magnesium gepresipiteer gedurende die enkelladingstoetse. Dit is bekend dat vermenging en hidrodinamika 'n groot rol speel in die kwaliteit van die presipitaat wat gevorm word. Dit bemoeilik die opskalering van presipitasie prosesse. Vir die ondersoek oor die invloed van vermenging op 'n kontinu proses is die drie-sel model van Gösele en Kind (1991) gebruik. Dit is gevind dat die karakter van presipitaat relatief konstant gebly het vir variasies van vermenging op die makro, meso en mikro skaal, wat opskaling behoort te vergemaklik. Addisioneel is die verwydering of moontlike hersirkulasie van die ongereageerde fluoried ondersoek, en geaktiveerde alumina is geïdentifiseer as 'n moontlike adsorbeermiddel. 'n Eksperimentele ondersoek het getoon dat geaktiveerde alumina fluoried tot lae vlakke kan adsorbeer in die teenwoordigheid van die basismetale, waarna dit weer geregenereer kan word. Die kapasiteit van die geaktiveerde alumina (GA) was bereken as 8.65 gF/lGA by 'n 10 mg/l fluoried vlak gedurende die kolom toetse. 'n Konsep-proses is opgestel na aanleiding van die eksperimentele resultate, waarvolgens slegs 'n gedeelte van die logingstroom na die fluoried presipitasie proses gestuur word, waarna dit weer teruggevoeg word om die algehele kalsium en magnesium konsentrasie te verlaag. Dié metode sal voorkom dat magnesium presipitasie domineer vir 'n toepassing waar slegs 'n gedeelte van kalsium en magnesium verwyder word. Die fluoried presipitasie proses behels drie stappe waarvolgens die fluoriede eers gepresipiteer word, waarna dit geskei word, en dan die ongereageerde fluoried geadsorbeer word. Genoeg inligting is versamel sodat 'n kosteberaming van die proses gedoen kan word. As die koste van die proses aanvaarbaar is, word dit voorgestel dat die ondersoek voortgesit word. Verskillende reaktor konfigurasies kan vir die presipitasie stap getoets word en daar moet ook ondersoek ingestel word hoe om die korslaag wat gedurende die kontinu eksperimente geobserveer is, te verminder. Die ondersoek van geaktiveerde alumina was ondergeskik in die projek en nog werk sal gedoen moet word om dit te optimiseer, spesifiek gedurende die desorpsie siklus vir die hersirkulasie van die ongereageerde fluoried.

This thesis explores the use of mass spectrometry to define the strengths, and understand solution phase speciation of phenolic oxime-based solvent extractants of the types used in the hydrometallurgical recovery of copper. Chapter 1 reviews briefly the current extraction technology for copper and focuses on hydrometallurgy and the use of phenolic oximes such as 5-nonylsalicylaldoxime. The modification of the latter to improve extraction efficiency is discussed, focussing on the introduction of X-substituents in the 3 position of the benzene ring. Modern mass spectrometry techniques are also discussed with a focus on their application to inorganic systems and their use in achieving the aims of this thesis, as defined above. The work described in chapter 2 involves the development of collision induced dissociation (CID) techniques to determine the relative gas phase stabilities of copper complex anions of the type [Cu(L)(L-H)]-, where LH is a 5-alkyl-3-X-2- hydroxybenzaldehyde oximes and X a range of substituents. The importance of interligand interactions in the outer-coordination sphere and their influence on gas phase anion stability, as defined by CID, is reported. The work described in Chapter 2 on CID is extended in chapter 3 and looks at the effect of charge, of ligand type, LH, and of the nature of the metal on the stability of ionic forms of [M(L)2] complexes, where LH is extended to include 5-alkyl-2- hydroxyphenylethanone oximes. The effects of substitution at the azomethine carbon atom and at the 3-position of the benzene ring and of variation of the nature of the metal on the ion dissociation mechanisms are shown to have a major influence on ion stability under CID conditions. In chapter 4 density functional theory calculations have been used to investigate the influences of substitution at the azomethine carbon atom and at the 3-position of the benzene ring and of variation of the nature of the metal on the gas phase structures of the neutral complexes, [M(L)2]. Gas phase deprotonation and dimerisation enthalpies of the ligands, LH, and enthalpies of formation of [M(L)2] complexes have been calculated and correlates with experimentally determined ligand extraction strength. The ligand type has been extended to include 3-X-2-hydroxybenzaldehyde hydrazones, which have previously been shown to have lower distribution coefficients for copper than the analogous 3-X-substituted oximes. The calculated gas phase formation enthalpies for [M(L)2] show a strong correlation with the strengths as extractants LH, measured as their pH0.5 values for metal uptake. Chapter 5 considers whether mass spectrometry can be used to define the solution equilibria when two different oxime-based ligands, LXH and LYH, compete for Cu(II) in a single phase solution. It has been established that shifts in the relative peak intensities of deprotonated ions derived from the Cu(II) complexes, [Cu(LX)2], [Cu(LY)2] and [Cu(LX)(LY)] reflect changes in the solution composition. The work described in chapter 6 extends the study of solution phase speciation using mass spectrometry. When the Cu(II) and proton concentrations of solutions were varied distinct changes in the resulting electrospray mass spectra were observed and the resulting species were identified using CID and high resolution mass spectrometry. A novel, [Cu3(L-H)3-μ3-O/OH]- species is determined to be a major component of solutions where Cu(II) concentrations are equal to/greater than the LH concentration. Various 3-X-2-hydroxybenzaldehyde oximes (X = CH2NR2) were synthesised. The incorporation of a protonatable arm in the 3-position enabled trinuclear complexes, [Cu3(L-H)3-μ3-OH], to be isolated and fully characterized, including two X-ray determined crystal structures.

A Dissertation submitted to the Faculty of Engineering, University of the Witwatersrand Johannesburg, in fulfillment of the requirements for the Degree of Master of Science in Engineering / High extractions of the platinum group metals' from a refractory tailings concentrate (PGM Concentration : Pt 81.5ppm, Pd 21.5ppm, Rh 17.5ppm) was achieved after short. low-temperature roasting and subsequent leaching with a zinc chloride based leach reagent containing nitric acid under atmospheric pressure at temperatures from 105-C to 120-C. [Abbreviated Abstract. Open document to view full version] / AC2017

Os resíduos de equipamentos elétricos e eletrônicos é um dos fluxos de resíduos que mais cresce no mundo. O aumento na produção destes equipamentos como resultado dos avanços tecnológicos e a sua rápida obsolescência promovem o aumento de geração deste tipo de resíduos. Portanto, este trabalho tem como objetivo estudar a recuperação de níquel presente no licor de lixiviação de placas de circuito impresso de telefones celulares obsoletos, através da aplicação de processos hidrometalúrgicos e eletrometalúrgico. Inicialmente, foram preparadas soluções sintéticas a partir da composição química do licor de lixiviação das frações magnética (MA) e não magnética (NMA) das placas de circuito impresso cominuídas. Os elementos presentes nas soluções são: ferro, zinco, níquel e alumínio. Posteriormente, foi realizada uma etapa de remoção do ferro, através de precipitação seletiva. A morfologia e a composição química do precipitado foram analisadas através de Microscopia Eletrônica de Varredura (MEV) e EDS, respectivamente. A composição química das soluções resultantes da precipitação foi determinada através da técnica de espectrofotometria de absorção atômica. Através do processo de precipitação conseguiu-se uma porcentagem de remoção de ferro na solução NMA de 99,6% e na solução MA de 99,9%, porém, observou-se também a coprecipitação de zinco, alumínio e níquel. Com as soluções resultantes desta etapa, foi realizada a purificação das soluções através de extração por solvente, utilizando Cyanex 272 como agente extratante. As variáveis estudadas nos ensaios de extração por solvente foram: pH, concentração do extratante, relação fase aquosa/orgânica (A/O) e temperatura. . Além disso, também foi determinado o número de contatos necessários para a extração de ferro, zinco e alumínio, obtendo assim, uma solução aquosa contendo unicamente níquel. Finalmente, foram realizados os ensaios de eletrodeposição para a obtenção de níquel metálico. Foi avaliado o efeito da temperatura sobre o filme depositado. A morfologia dos depósitos e a espessura da camada foram analisadas através do MEV, verificando que o aumento da temperatura influencia nas características do depósito obtido. / Electric and electronic waste (e-waste) is one of the fastest growing waste streams in the world. Continuous increasing production owing to the technological advances and the products consumption rise, all together with the rapid obsolescence of this scrap promotes the necessity of exchange and the increasing of generate waste. Therefore, the aim of this work is to study a recovering of nickel from leach liquor of cell phones printed circuit boards, through of hydrometallurgical and electrometallurgical process application. Firstly, was prepared synthetic solutions of both magnetic (MA) and nonmagnetic (NMA) fractions of printed circuit boards. The metal ions present in the synthetic solutions are: iron, zinc, nickel and aluminium. Afterwards was realized the iron removal stage, through both selective precipitation and solvent extraction process, in order to make a comparison of these techniques. The precipitates were analyzed across of scanning electron microscope (SEM), and the chemical composition of these solutions through atomic absorption spectrometry (AAS). With selective precipitation it was obtained 99,6% and 99,9% of iron removal with selective precipitation in NMA and MA solutions, respectively. Therefore, it was also observed co-precipitation of zinc, aluminium and nickel. With solutions after precipitation stage was carried out the solutions purification through solvent extraction using cyanex 272 as extractant. Solvent extraction test were studied different parameters, such as: equilibrium pH, extractant concentration, aqueous-organic (A/O) ratio and temperature. It was also determinates the stages number required for iron, zinc and aluminium extraction, to obtain nickel in aqueous solution uniquely. Finally, was carried out the electrodeposition test for obtain metallic nickel. Was analyzed the effect of temperature on the deposited layer. Surface Morphology and thickness of the deposits were evaluated by MEV, verifying that temperature increasing influences on deposited layer.

O avanço da tecnologia de aparelhos eletro-eletrônicos favorece a troca constante dos equipamentos. O freqüente descarte de aparelhos obsoletos se torna um problema de sustentabilidade e também um problema ambiental devido ao seu acúmulo em aterros. A solução para minimizar estes impactos é a reciclagem de seus componentes. Por esta razão, o principal objetivo deste trabalho é estudar o processamento das placas de circuito impresso de telefones celulares através de operações unitárias de Tratamento de Minérios e hidrometalurgia a fim de se recuperar o cobre contido nas placas. Para isso, inicialmente, placas de circuito impresso foram processadas em moinho de martelos, a fim de liberar os materiais, em seguida foi feita a separação magnética do material cominuído. Com a fração não magnética foi feita a separação eletrostática e o material foi separado em: fração condutora, mista e não condutora, com cada fração foi feita a classificação granulométrica e, posteriormente, realizaram-se ensaios de caracterização como pirólise, digestão em água régia e análise química de espectroscopia de emissão óptica por indução de plasma. Os processos hidrometalúrgico aplicados para a recuperação de cobre nas placas de circuito impresso de aparelhos celulares obsoletos envolvem etapas lixiviação com ácido sulfúrico na ausência e na presença de peróxido de hidrogênio. Os resultados da caracterização mostraram que as placas de circuito impresso de celulares após a moagem possuem 24% de cerâmicas; 12,7% de polímeros e 63,3% de metais. Além disso, após a classificação granulométrica e a separação eletrostática os materiais não se concentraram em nenhuma fração especifica, portanto o processamento mecânico visando a recuperação de metais deve contemplar a moagem e a separação magnética. / The technology advancement of electro-electronics devices favors the constant equipment exchange. The frequent disposal of obsolete equipment becomes a sustainability problem and also an environmental problem due to their accumulation in landfills. One possible solution to minimize these impacts is the recycling of their components. For this reason the aim goal of this study is processing of printed circuit boards of mobile phones utilizing unit operation of ore treatment and hydrometallurgy to recover the copper contained in the printed. Therefore, initially printed circuit boards were processed on a hammer mill to release the materials, then it was made magnetic separation of comminuted material. With the non-magnetic fraction was made electrostatic separation in which the material was separated into: conductive, mixed and non-conductive fraction, with each fraction was made grain sized classification and then assays were performed analysis of characterize as pyrolysis, digestion in aqua regia and chemical analysis of inductively coupled plasma atomic emission spectroscopy. Hydrometallurgical processes applied to the cooper recovery in printed circuit boards of obsolete mobile phones, involve steps leaching with sulfuric acid in the absence and presence of hydrogen peroxide. The characterization results showed that the printed circuit boards of mobile phones after grinding have ceramics 24%, polymers 12.7% and metals 63.3%. Moreover, after grain sized classification and electrostatic separation the materials didn\'t concentrate in no specific fraction, therefore the mechanical processing in order to recover metals should include grinding and magnetic separation.

Com o avanço da tecnologia aplicada em aparelhos celulares, são lançados no mercado modelos menores, mais leves e com maior rapidez em seu sistema operacional. Tudo isso atrai muito os consumidores, que por sua vez, trocam seus antigos aparelhos celulares por novos e modernos. Essas adesões e trocas freqüentes de aparelhos celulares geram um descarte significativo de todos os seus componentes e dentre eles a bateria. Assim, pelo fato do cobalto estar presente nesse tipo bateria e ser um metal com alto valor agregado, ele faz parte do estudo do presente trabalho. Este trabalho tem por objetivos estudar as etapas de condicionamento físico e de lixiviação como fases iniciais do processo de reciclagem de baterias de íons de lítio. Para a caracterização das baterias, as mesmas foram desmanteladas manualmente para a separação dos componentes. Os eletrodos foram caracterizados por espectrofotometria de absorção atômica, difração de raios-X e microscopia eletrônica de varredura com analise de microrregiões. Os ensaios de lixiviação foram feitos usando-se os seguintes parâmetros: pH entre 3 e 5, temperaturas de 25 e 50ºC, relação sólido/líquido de 1/5, tempos de 1 a 4h. Foram utilizados como meio lixiviante soluções de acido sulfúrico, clorídrico e nítrico. Peróxido de hidrogênio foi adicionado ao acido sulfúrico como agente oxidante. Os resultados alcançados mostraram que entre os moinhos de martelos, de facas e de bolas o que apresentou o melhor desempenho para a moagem de baterias de íons de lítio foi o moinho de facas. O bombardeamento com ultra-som faz com que haja a liberação do material ativo dos eletrodos que fica aderido aos suportes de cobre e alumínio mesmo apos moagem. A diminuição do pH de 5 para 3 e o aumento da temperatura de 25 para 50ºC causam o aumento da velocidade de lixiviação em meio sulfúrico do oxido de cobalto. A presença de agente oxidante na lixiviação acida faz com que diminua o tempo de lixiviação do oxido de cobalto. A lixiviação com acido nítrico e com acido sulfúrico com adições de peróxido de hidrogênio são os melhores meios de lixiviação quando comparados ao acido clorídrico e ao acido sulfúrico sem oxidante para as mesmas condições de pH e de temperatura. Nas etapas de extração liquido-liquido e reextração foram utilizados os seguintes parâmetros: relação orgânico-aquoso de 1/1, temperatura de 50ºC, pH 4 e tempo de 5 minutos na etapa de extração e como solução aquosa na fase da reextração o acido sulfúrico 2M. Nas duas etapas foi utilizado como extratante o Cyanex 272 diluído em querosene. Os resultados alcançados mostraram que nos primeiros dois contatos das fases orgânicas e aquosas já se obtém as melhores porcentagens de extração e reextração. A eficiência global dos quatro contatos na etapa de extração foi de 94% e na etapa de reextracao foi de 98%. / The fast changes in technologies applied to mobile phones causes an incredible appearance of new and even better models each day. As a consequence, each year increase the amounts of waste of electronic and electric equipments including batteries that should be disposed of. The goal of the present work is to study methods of physical conditioning and acid leaching of Li-ion batteries. Hand disassembling Li-ion batteries was performed to identify and characterize the components of scrap Li-ion batteries. Materials extracted form the electrodes were characterized using X-ray diffraction, atomic absorption spectrophotometry and scanning electron microscopy coupled with EDS micro-probe. Leaching tests were carried out using the following parameters: pH (3 - 5), temperature (25 and 50ºC), solid/liquid ratio equal to 1/5, leaching time (1 to 4h). Sulfuric acid, chloridric acid and nitric acid were tested as leaching media. Hydrogen peroxide was tested as an oxidizing agent during leaching tests using sulfuric acid. The results obtained showed that knives mill presented better results to grind the scraps in comparison to hammer and balls mills. Ultrasonic treatment was effective to release the active cell materials from copper and aluminum. Decreasing pH from 5 to 3, and increasing the temperature from 25 to 50ºC cause the increasing of the leaching rate of cobalt oxide. Oxidizing conditions also increase the rate of cobalt oxide leaching. Nitric acid and sulfuric acid plus hydrogen peroxide leaching results in better leaching rates compared to chloridric acid and sulfuric acid.

Batteries have found wide use in many household and industrial applications and since the 1990s, they have continued to rapidly shape the economy and social landscape of humans. Lithium ion batteries, a type of rechargeable batteries, have experienced a leap-frog development at technology and market share due to their prominent performance and environmental advantages and therefore, different forecasts have been made on the future trend for the lithium ion batteries in-terms of their use. The steady growth of energy demand for consumer electronics (CE) and electric vehicles (EV) have resulted in the increase of battery consumption and the electric vehicle (EV) market is the most promising market as it will consume a large amount of the lithium ion batteries and research in this area has reached advanced stages. This will consequently be resulting in an increase of metal-containing hazardous waste. Thus, to help prevent environmental and raw materials consumption, the recycling and recovery of the major valuable components of the spent lithium ion batteries appears to be beneficial. In this thesis, it was attempted to recover lithium from a synthetic slag produced using pyrometallurgy processing and later treated using hydrometallurgy. The entire work was done in the laboratory to mimic a base metal smelting slag. The samples used were smelted in a Tamman furnace under inert atmosphere until 1250oC was reached and then maintained at this temperature for two hours. The furnace was then switched off to cool for four hours and the temperature gradient during cooling was from 1250oC to 50oC. Lime was added as one of the sample materials to change the properties of the slag and eventually ease the possibility of selectively leaching lithium from the slag. It was observed after smelting that the slag samples had a colour ranging from dark grey to whitish grey among the samples.The X - ray diffractions done on the slag samples revealed that the main phases identified included fayalite (Fe2SiO4), magnetite (Fe3O4), ferrobustamine (CaFeO6Si2), Kilchoanite (Ca3Si2O7), iron oxide (Fe0.974O) and quartz (SiO2). The addition of lime created new compound in the slag with the calcium replacing the iron. The new phases formed included hedenbergite (Ca0.5Fe1.5Si2O6), ferrobustamine (CaFeO6Si2), Kilchoanite (Ca3Si2O7) while the addition of lithium carbonate created lithium iron (II) silicate (FeLi2O4Si) and dilithium iron silicate (FeLi2O4Si) phases.The Scanning Electron Microscopy (SEM) micrographs of the slag consisted mainly of Fe, Si and O while the Ca was minor. Elemental compositions obtained after analysis was used to identify the different phases in all the slag samples. The main phases identified were the same as those identified by the XRD analysis above except no phase with lithium was identified. No lithium was detected by SEM due to the design of the equipment as it uses beryllium planchets which prevent the detection of lithium.Leaching experiments were done on three slag samples (4, 5 and 6) that had lithium carbonate additions. Leaching was done for four hours using water, 1 molar HCl and 1 molar H2SO4 as leaching reagents at room temperature. Mixing was done using a magnetic stirrer. The recoveries obtained after leaching with water gave a lithium recovery of 0.4%. Leaching with HCl gave a recovery of 8.3% while a recovery of 9.4% was obtained after leaching with H2SO4.It can be concluded that the percentage of lithium recovered in this study was very low and therefore it would not be economically feasible. It can also be said that the recovery of lithium from the slag system studied in this work is very difficult because of the low recoveries obtained. It is recommended that test works be done on spent lithium ion batteries so as to get a better understanding of the possibilities of lithium recovery as spent lithium ion batteries contain other compounds unlike the ones investigated in this study.

Abstract is not available

M. Tech. Metallurgical Engineering. / A novel process of leaching copper refractory ore from Nchanga mine, Zambia, in two stages consisting of a pre-oxidation step and an acid dissolution stage was investigated by means of a leach test rig.