京都大学 / 新制・論文博士 / 博士(地球環境学) / 乙第13628号 / 論地環博第18号 / 新制||地環||53(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 准教授 高井 敦史, 教授 安原 英明, 教授 越後 信哉 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第25469号 / 地環博第255号 / 新制||地環||51(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 准教授 高井 敦史, 教授 安原 英明 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

Phytomining is a promising method for metal recovery, but rare studies have been devoted to metal recovery from hyperaccumulator biomass. The objective of this study was to propose efficient and sustainable methods for treating REE hyperaccumulators, aimed at enhancing REE recovery and obtaining value-added byproducts. Firstly, grass seeds fed with a solution containing Y, La, Ce, and Dy, were found to have the capacity to accumulate around 510 mg/kg (dry basis) of total rare earth elements (TREEs) in grass leaves. With the use of conventional hydrometallurgy, around 95% of Y, La, Ce, and Dy were extracted from the GL using 0.5 mol/L H2SO4 at a solid concentration of 5 wt.%. Subsequently, microwave-assisted hydrothermal carbonization (MHTC) was used to convert the leaching residue into hydrochar to achieve a comprehensive utilization of GL biomass. Scanning electron microscopy (SEM) analysis revealed that the original structure of GL was destructed at 180 °C during MHTC, producing numerous microspheres and pores. As the reaction temperature increased, there was a concurrent increase in carbon content, HHV, and energy densification, coupled with a decrease in hydrogen and oxygen contents of hydrochar. The results showed that the waste biomass of the GL after REE extraction can be effectively converted into energy-rich solid fuel and low-cost adsorbent via MHTC. In addition to utilizing conventional hydrometallurgy for REE recovery and employing MHTC to convert leaching residue into hydrochar, MHTC was also applied to directly recover REEs and produce hydrochar from the GL as a more efficient approach. The effects of acid type and acid concentration on REE extraction from GL using MHTC were investigated. The utilization of 0.2 mol/L H2SO4 led to the extraction of nearly 100% of REEs from the GL into the resulting biocrudes. Concurrently, the acid-mediated MHTC system also caused the degradation of amorphous hemicellulose and crystalline cellulose present in the GL, thereby enhancing the thermal stability of the resulting hydrochar. The physiochemical properties of the hydrochar were also influenced by acid type and acid concentration. Using 0.2 mol/L H2SO4 as the reaction medium, MHTC resulted in a yield of 28% hydrochar with enhanced high heating value and energy densification. These results suggest that MHTC in the presence of an appropriate concentration of H2SO4 is an effective way to extract REEs and produce hydrochar from the GL. A process that combines solvent extraction and struvite precipitation was developed for the treatment of biocrudes containing REEs and other elements. In the extraction step, 95.6% of REEs were extracted using 0.05 mol/L di(2-ethylhexyl)phosphoric acid (D2EHPA) with an aqueous to organic (A/O) ratio of 1:1 at pH 3.0. However, other impurity metals were co-extracted into the organic phase with the REEs. To solve this issue, a subsequent scrubbing step using deionized water was applied, with the removal of over 98% of these impurities, while incurring negligible loss of REEs. After the scrubbing step, over 97% of REEs were ultimately stripped out from the organic phase as REE oxalates using 0.01 mol/L oxalic acid. Furthermore, phosphorous (P) was found to be retained in the raffinate after the solvent extraction process. 94.4% of the P was recovered by forming struvite precipitate at pH 9.0 and a Mg/P molar ratio of 1.5. In general, high purity and value-added REE products and struvite precipitate were eventually achieved from biocrudes in environmentally friendly and economically viable ways. In summary, this study contributes a sustainable and efficient framework for REE hyperaccumulator treatment that integrates acid leaching, MHTC, solvent extraction, and struvite precipitation. This work supports a circular economy, minimizing waste and promoting resource reuse. / Doctor of Philosophy / Rare Earth Elements (REEs) are essential for technologies like smartphones and electric vehicles, but traditional mining is environmentally harmful and resource-intensive. Innovations are needed to reduce waste and enhance resource reuse. In this study, grass, a natural accumulator, was found to be able to extract REEs from contaminated soils. Nearly all REEs can be recovered efficiently using a mild sulfuric acid solution, and the residual biomass was also transformed into valuable byproducts such as energy-rich solid fuel and low-cost adsorbents. Furthermore, a more sustainable and efficient method, microwave-assisted hydrothermal carbonization, was also investigated to treat grass aiming at recovering REEs and achieving value-added products. High purity REE product and phosphorous-rich fertilizer were finally produced. This method reduces the environmental impact of REE mining, utilizes renewable resources, and cuts costs, thereby supporting economic sustainability. By turning environmental challenges into opportunities, this research highlights how innovative, greener methods can drive a more sustainable future in resource management.

La produzione e l’uso del Metile di Bromuro, un fumigante estesamente usato in agricoltura, sono stati sottoposti a severe restrizioni dovute alla sua azione di depletore dello strato di ozono. Questa tesi è rivolta ad indagare il destino e le caratteristiche ambientali di due tra le più importanti alternative chimiche all’uso del Bromuro di Metile: l’ 1,3-Dicloropropene (1,3-D) e la Cloropicrina (CP). 1,3-D è un fumigante del suolo, con spiccata attività nematocida, consistente di due isomeri (Z), e (E)-1,3-D; nella sua formulazione sono presenti, inoltre, un esteso numero di impurezze clorurate potenzialmente correlate al processo produttivo. In laboratorio, è stato effettuato uno studio per valutare la stabilità idrolitica delle impurezze clorurate e per prevederne, quindi, il destino ambientale. Allo stesso tempo un piano di monitoraggio è stato svolto per valutare il leaching dell’1,3-D, dei suoi metaboliti, e delle impurezze clorurate. La CP è anch’essa un fumigante del suolo, caratterizzato da un importante profilo tossicologico. Questo lavoro ha valutato l’esposizione degli operatori e l’emissione in atmosfera durante e dopo l’applicazione nel suolo, secondo le pratiche agronomiche vigenti. Infine tramite l’applicazione di modelli matematici quali FOCUS PELMO e FOCUS PEARL si è valutato il destino ambientale della CP rispetto alle acque di falda. La simulazione è stata eseguita in 5 scenari europei realistici. / Production and use of methyl bromide, a soil fumigant, are being restricted because of this chemical’s deleterious effects on stratospheric ozone concentrations. This research examines the environmental fate and properties of methyl bromide replacement: 1,3-Dichloropropene (1,3-D), and Chloropicrin (CP). 1,3-D is a broad-spectrum soil fumigant used to control numerous species of soil-borne plant-parasitic nematodes. 1,3-D consists of two isomers, (Z)- and (E)-1,3-D, and has a number of low-level chlorinated compounds that could potentially be part of the manufacturing process. This study has investigated the hydrolytic stability, under biotic and abiotic conditions, of an extensive representative list of 1,3-D potentially related chlorinated compounds. Furthermore, a monitoring programme was carried out to investigate the leaching of all of this compounds. CP is a broad-spectrum fumigant chemical which is extensively used in agriculture and has an important toxicological profile. This study has assessed CP emission in the atmosphere and operator exposure during and after application in soil through injection of the test substances with routine agronomical application. Finally the environmental fate of CP and its metabolite dichloronitromethane in groundwater were investigated through the use of simulation model FOCUS PELMO and FOCUS PEARL using fully justified input parameters in five realistic scenarios.

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No description available.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A 2 stage heap leach process to extract base and precious metals from the Platreef ore is currently being investigated industrially. A first stage bioleach is used to extract the base metals. In the 2nd stage, cyanide is used as the lixiviant at high pH to extract the platinum group metals and gold. By analogy with current gold recovery practices, the present study investigates the preferential and quantitative adsorption of precious metals (Pt, Pd, Rh and Au) over base metals (Cu, Ni and Fe) from an alkaline cyanide medium, by means of granular activated carbon. Experiments were designed statistically to optimise the process parameters using synthetic alkaline cyanide solutions close in composition to those expected from plant leach solutions. The statistical approach allowed the development of a reliable quantitative approach to express adsorption as a response variable on the basis of a number of experiments. A 2IV(7-2) fractional factorial design approach was carried out in a batch adsorption study to identify significant experimental variables along with their combined effects for the simultaneous adsorption of Pt(II), Pd(II), Rh(III) and Au(I). The adsorbent was characterized using SEM-EDX, and XRF. Precious metals adsorption efficiency was studied in terms of process recovery as a function of different adsorption parameters such as solution pH, copper, nickel, free cyanide ion, thiocyanate, initial precious metal (Pt, Pd, Rh and Au) ion and activated carbon concentrations. It was shown that adsorption rates within the first 60 minutes were very high (giving more than 90% extraction of precious metals) and thereafter the adsorption proceeds at a slower rate until pseudo-equilibrium was reached. Among the different adsorption parameters, at 95% confidence interval, nickel concentration had the most influential effect on the adsorption process followed by the adsorbent concentration. Adsorption of Ni was found to proceed at approximately the same rate and with the same recovery as the precious metals, showing a recovery of approximately 90% in two hours. The kinetics of Cu adsorption were slower, with less than 30% being recovered at the 120 minute period. This suggests that the co-adsorption of Cu can be minimised by shortening the residence time. Adsorption of Fe was found to be less than 5%, while the recovery of Rh was negligibly small. The effect of thiocyanate ion concentration was not as important as the effect of free cyanide ion concentration but still had some influence. The correlation among different adsorption parameters was studied using multivariate analysis. The optimum experimental conditions resulted in a solution with pH of 9.5, [Cu(I)] of 10 ppm, [Ni(II)] of 10 ppm, [CN ] of 132.44 ppm, [SCN ] of 98.95 ppm, [PMs] of 2.03 ppm and [AC] of 10 g/L. Under these conditions, predicted adsorption percentages of Pt, Pd and Au were approximately 98, 92 and 100%, at the level of 95% probability within two hours as an effective loading time. The negative values of ΔG° for all ions under optimum conditions indicate the feasibility and spontaneous nature of the adsorption process. Chemisorption was found to be the predominant mechanism in the adsorption process of Pt(II), Pd(II) and Au(I). Based on their distribution coefficients, the affinity of activated carbon for metal ions follows the selectivity sequence expressed below. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Finally, it is important that additional research and development activities in the future should prove the economic viability of the process. Future work is also needed to investigate the adsorption of precious metals (PMs) by comparing the efficiencies and kinetics of adsorption when using sodium hydroxide (in this study) or lime, respectively, in order to control the pH. / AFRIKAANSE OPSOMMING: ʼn Tweefasige hooploogproses vir die ontginning van basis- en edelmetale van die Platrif-erts word tans industrieel ondersoek. ʼn Eerstefase-bioloog word gebruik om die basismetale te ontgin. In die 2de fase word sianied gebruik as die uitloog by hoë pH om die platinum-groepmetale en goud te ontgin. Na analogie van hedendaagse goudherwinningspraktyke het die huidige studie die voorkeur- en kwantitatiewe adsorpsie van edelmetale (Pt, Pd, Rh en Au) bo basismetale (Cu, Ni en Fe) vanuit ʼn alkaliese sianiedmedium met behulp van korrelrige geaktiveerde koolstof ondersoek. Eksperimente is op statistiese wyse ontwerp om die parameters van die proses te optimaliseer deur van sintetiese alkaliese sianiedoplossings wat in hulle samestelling nou ooreenstem met dié wat van oplossings van plant-loog verwag word, gebruik te maak. Die statistiese benadering het die ontwikkeling van ʼn betroubare kwantitatiewe benadering om adsorpsie as ʼn responsveranderlike op grond van ʼn aantal eksperimente uit te druk, moontlik gemaak. ʼn 2IV(7-2) -Fraksionele faktoriale ontwerp-benadering is tydens ʼn lot-adsorpsiestudie gevolg om beduidende eksperimentele veranderlikes tesame met hulle gekombineerde uitwerkings vir die gelyktydige adsorpsie van Pt(II), Pd(II), Rh(III) en Au(I) te identifiseer. Die adsorbeermiddel is met behulp van SEM-EDX en XRF gekenmerk. Adsorpsiedoeltreffendheid van edelmetale is bestudeer ten opsigte van proseskinetika en herwinning as ʼn funksie van verskillende adsorpsieparameters soos oplossing-pH, koper, nikkel, vry sianiedioon, tiosianaat, aanvanklike edelmetaal (Pt, Pd, Rh en Au)-ioon en geaktiveerde koolstofkonsentrasies. Daar is aangetoon dat adsorpsietempo‟s binne die eerste 60 minute baie hoog was (het meer as 90% ekstraksie van edelmetale opgelewer) en daarna het die adsorpsie teen ʼn stadiger tempo voortgegaan totdat pseudo-ekwilibrium bereik is. Onder die verskillende adsorpsieparameters, by 95%-vertroubaarheidsinterval, het nikkel-konsentrasie die grootste invloed op die adsorpsieproses gehad, gevolg deur konsentrasie van die adsorbeermiddel. Daar is bevind dat die adsorpsie van Ni teen nagenoeg dieselfde tempo en met dieselfde herwinning as die edelmetale voortgegaan het, wat ná twee uur ʼn herwinning van nagenoeg 90% getoon het. Die kinetika van Cu-adsorpsie was stadiger, met minder as 30% wat teen die 120-minute-tydperk herwin is. Dit dui daarop dat die ko-adsorpsie van Cu tot die minimum beperk kan word deur verkorting van die verblyftyd. Daar is bevind dat die adsorpsie van Fe minder as 5% is, terwyl die herwinning van Rh onbeduidend klein was. Die uitwerking van die konsentrasie van die tiosianaatione was nie so belangrik as die uitwerking van die konsentrasie van vry sianiedione nie maar het steeds ʼn mate van invloed gehad. Die korrelasie tussen verskillende adsorpsieparameters is met behulp van meerveranderlike analise bestudeer. Die optimale eksperimentele toestande het gelei tot ʼn oplossing met ʼn pH van 9.5, [Cu(I)] van 10 dpm, [Ni(II)] van 10 dpm, [CN] van 132.44 dpm, [SCN] van 98.95 dpm, [EM‟e] van 2.03 dpm en [AC] van 10 g/L. Onder hierdie toestande was die voorspelde adsorpsiepersentasies van Pt, Pd en Au nagenoeg 98, 92 en 100%, op die vlak van 95%-waarskynlikheid binne twee uur as ʼn doeltreffende laaityd. Die negatiewe waardes van ΔG° vir alle ione onder optimale toestande dui op die uitvoerbaarheid en spontane aard van die adsorpsieproses. Daar is bevind dat chemiesorpsie die deurslaggewende meganisme by die adsorpsieproses van Pt(II), Pd(II) en Au(I) is. Gebaseer op hulle distribusiekoeffisiënte volg die affiniteit van geaktiveerde koolstof vir metaalione die selektiwiteitsvolgorde soos hieronder voorgestel. Au(CN) > Pt(CN) > Pd(CN) > Ni(CN) > Cu(CN) Laastens, dit is belangrik dat addisionele navorsing en ontwikkelingsaktiwiteite in die toekoms die ekonomiese haalbaarheid van die proses bewys. Werk in die toekoms is nodig om die adsorpsie van edelmetale (EM‟e) te ondersoek deur vergelyking van die doeltreffendhede en kinetika van adsorpsie wanneer natriumhidroksied (in hierdie studie) of kalk, onderskeidelik, gebruik word ten einde die pH te beheer

For Sweden to achieve the environmental goal of a nontoxic environment, knowledge is required about harmful elements’ movement and mobility in nature. One of those elements is arsenic that for a long time has been known to cause health ailments. The most common and dangerous path into the human body is through drinking water. It is therefore of great importance to study sources that can impact and contribute to elevated concentrations of arsenic in the groundwater. One such path is the anthropogenic soil called rödfyr, which is what is left after the burning of black shale. This activity was common in areas rich in limestone, which after being heated can be used as cement in concrete. Heaps of rödfyr of varying sizes have been found at a number of localities in the area around Kinnekulle in Västergötland. Earlier studies of leach water indicate arsenic content high enough to be considered hazardous to health. At Kinne-Kleva south of Kinnekulle there is an unusually large heap of rödfyr, situated around land used for agricultural purposes as well as some houses. To have a good understanding about how rödfyr impacts the environment is key to predict and negate negative environmental consequences. The aim of this independent project is with fieldwork and leach tests study in which concentrations arsenic can be found in rödfyr at the Kinne-Kleva heap. Results show that high concentrations of arsenic exists, up to 137 mg/kg rödfyr. They also indicate that arsenic leakage occurs to a large extent, both in high and low pH environment. The amount of arsenic is however expected to be drastically reduced due to dilution, which increases with distance. Exposure is therefore confined to the close vicinity of the pile. / För att Sveriges miljömål om en giftfri miljö ska kunna uppnås krävs kunskap om skadliga ämnens rörelse och transport i naturen. Ett av de ämnena är arsenik, som sedan länge förknippats med nedsatt hälsa. Den vanligaste och farligaste vägen in i människokroppen är genom dricksvattnet. Därför är det av stor vikt att undersöka källor som kan påverka och tänkas bidra med förhöjda halter arsenik i grundvattnet..En sådan källa är den antropogena jordarten rödfyr, vilken är en restprodukt vid förbränningen av alunskiffer. Denna aktivitet var vanligt i områden rik på kalksten, som efter upphettning sedan kan nyttjas som cement i murbruk.I området kring Kinnekulle i Västergötland har rödfyr hittats på flera platser i varierande mängd. Tidigare undersökningar av lakvatten pekar på att halterna arsenik är så höga att långsiktigt intag kan anses hälsovådligt. I Kinne-Kleva söder om Kinnekulle finns en ovanligt stor rödfyrshög, belägen i ett område med åkermark och även några bostadshus. Att ha en god uppfattning om hur rödfyr påverkar sin omgivningen är av ytterst vikt för att förutsäga och hindra negativ miljöpåverkan.Syftet med detta kandidatarbete är att med platsbesök och laktester undersöka i vilka halter arsenik kan förekomma i lakvattnet vid rödfyrslokalen i Kinne-Kleva.Resultatet visar att rödfyren innehåller höga halter arsenik, uppemot 137 mg/kg. De visar också att läckage av arsenik förekommer i stor utsträckning, både under höga och låga pH. Halterna arsenik som lakas ut väntas dock minska kraftigt med avståndet från högen till följd av utspädning. Den främsta exponering föreligger således i högens närområde.

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: In this study the chromosomal arsenic resistance (ars) genes shown to be present in all Acidithiobacillus. caldus isolates were cloned and sequenced from At. caldus #6. Ten open reading frames (ORFs) were identified on a clone conferring arsenic resistance, with three homologs to arsenic genes, arsC (arsenate reductase), arsR (regulator) and arsB (arsenite export). This ars operon is divergent, with the arsRC and arsB genes transcribed in opposite directions. Analysis of the putative amino acid sequences of these arsRC and arsB genes revealed that they are the most closely related to the ars genes of Acidithiobacillus ferrooxidans. These ars genes were functional when transformed into an Escherichia coli ars deletion mutant ACSH50Iq, and conferred increased levels of resistance to arsenate and arsenite. ArsC was required for resistance to arsenate, but not for resistance to arsenite. None of the other ORFs enhanced arsenic resistance in E. coli. A transposon located arsenic resistance system (TnAtcArs) has been described for highly arsenic resistant strains of the moderately thermophilic, sulfur-oxidizing, biomining bacterium At .caldus #6. In the latter study it was shown that TnAtcArs confers higher levels of resistance to arsenate and arsenite than the chromosomal operon. TnAtcArs was conjugated into a weakly ars resistant At. caldus strain (C-SH12) and resulted in greatly increased arsenite resistance. RT-PCR analysis revealed that arsR and arsC are co-transcribed. Despite ORF1 (cadmium inducible-like protein) and ORF5 (putative integrase for prophage CP-933R) not being involved in resistance to arsenic, ORF1 was co-transcribed with arsRC and ORF5 with arsB. Using arsR-lacZ and arsB-lacZ fusions it was shown that the chromosomal ArsR-like regulator of At. caldus acts as a repressor of the arsR and arsB promoter expression. Induction of gene expression took place when either arsenate or arsenite was added. The chromosomal located ArsR was also able to repress TnAtcArs, but the transposon-located ArsR was unable to regulate the chromosomal system. / AFRIKAANSE OPSOMMING: In hierdie studie is die chromosomale arseen weerstandbiedendheidsgene (ars gene), teenwoordig in alle Acidithiobacillus caldus isolate, gekloon en die DNA volgorde daarvan vanaf At. caldus #6 bepaal. Tien oopleesrame (ORFs) is geïdentifiseer op ‘n kloon wat arseen weerstandbiedend is, met drie homoloog aan ars gene, nl. arsC (arsenaat reduktase), arsR (reguleerder) en arsB (membraan-geleë pomp wat arseniet uitpomp). Die ars operon is gerangskik met die arsRC en arsB gene wat in teenoorgestelde rigtings getranskribeer word. Analise van die afgeleide aminosuurvolgorde van dié ars gene het getoon hulle is naverwant aan die ars gene van Acidithiobacillus ferrooxidans. Die ars gene was funksioneel na transformasie na ‘n E. coli ars mutant (ACSH50Iq), en het ‘n hoër vlak van weerstand teen arsenaat en arseniet gebied. ArsC was nodig vir weerstand teen arsenaat, maar nie vir weerstand teen arseniet nie. Geen van die ander ORFs het arseen weerstandbiedendheid in E. coli bevorder nie. Voorheen is ‘n ars operon, geleë op ‘n transposon (TnAtcArs), in ‘n hoogs arseen-weerstandbiedende stam van die middelmatige termofiliese, swawel-oksiderende, bio-ontgunning (“biomining”) bakterie Acidithiobacillus caldus #6 beskryf. In laasgenoemde studie is gevind dat TnAtcArs hoër vlakke van weerstand bied teen arsenaat en arseniet as die chromosomale operon. TnAtcArs is na ‘n lae arseen-weerstandbiedende At. caldus stam (C-SH12) gekonjugeer. Die resultaat was ‘n groot verhoging in arseen weerstandbiedendheid. RT-PCR analise het onthul dat arsR en arsC saam getranskribeer word. Benewens die feit dat ORF1 (kadmium induseerbare protein) en ORF5 (afgeleide integrase vir profaag CP-933R) nie betrokke is in weerstand teen arseniet and arsenaat nie, is ORF1 saam met arsRC getranskribeer en ORF5 saam met arsB. Deur gebruik te maak van die fusie-gene arsR-lacZ en arsB-lacZ is bewys dat die chromosomale ArsR reguleerder van At. caldus as ‘n inhibeerder van die arsR en arsB promoter uitdrukking funksioneer. Indusering van geen uitdrukking vind plaas wanneer arseniet of arsenaat bygevoeg word. Die chromosomaal-geleë ArsR is ook in staat om TnAtcArs te inhibeer, terwyl die transposon geleë ArsR nie daartoe in staat is om die chromosomale ars sisteem te reguleer nie.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: In a first stage atmospheric leach at the Lonmin Marikana base metals refinery, nickel-copper-iron-sulphur Peirce Smith converter matte is leached in recycled electrolyte from the electrowinning section. The electrolyte contains sulphuric acid, copper and nickel sulphates, and a small amount of iron sulphate. The converter matte contains mostly nickel, copper and sulphur (typically 48 %, 28 % and 23 %, respectively), but also minor amounts (<5 %) iron and cobalt. The matte also contains platinum group elements (PGEs) and other precious metals totalling 0.2 – 0.7 % (platinum, palladium, iridium, rhodium, ruthenium, osmium and some gold). The predominant mineral phases are heazlewoodite, chalcocite and a nickel-copper alloy phase, as well as some entrained slag and spinel minerals. The purpose of the first stage leach is to extract nickel, while simultaneously precipitating copper and PGEs contained in the recycled electrolyte. Nickel, cobalt and iron are leached by acid and oxygen. Copper is precipitated by a redox reaction in which copper ions oxidise nickel from the matte. The purpose of this study was to determine the effects of key variables on the performance of the first stage leach (specifically on the removal of PGEs and copper from solution and the overall extraction of nickel) and to improve fundamental understanding of these effects. Batch leaching tests were carried out to investigate the effects of the following factors: availability of oxygen, initial acid concentration, initial copper concentration, iron endpoint (iron content of the matte), solids/liquid ratio and stirring rate. Liquid samples were analysed with Atomic Absorption Spectroscopy (AA) to determine leaching kinetics. Characterisation of solid samples from leach tests by quantitative X-Ray diffraction (XRD) and scanning electron microscopy with an energy dispersive system (SEM-EDS) helped to improve understanding of the leaching mechanism. The oxidative leaching mechanism entails an initial period in which the alloy phase is leached by acid and oxygen, while copper reacts with the nickel-copper-alloy and heazlewoodite phases (which react galvanically with each other) to form a chalcocite precipitate. In a second reaction period, heazlewoodite was transformed to millerite by acid leaching and the particle structure became more porous. The rate of copper precipitation and nickel extraction were faster during the second reaction period than the first reaction period. Some copper leaching occurred once the leachable nickel (60 – 70 %) had been dissolved, provided that the solution was strongly acidic (pH < 2). The non-oxidative leaching mechanism entails a galvanic interaction, between the nickel-copper-alloy and heazlewoodite phases, in which nickel is leached from both phases and copper is precipitated as chalcocite. Leaching by acid was negligible in most non-oxidative tests. An initial fast period of copper precipitation was followed by a second slower period. The decrease in reaction rate can probably be linked to the decreasing availability of the nickel-copper-alloy phase. During non-oxidative leaching, the particle structure remained mostly intact. Copper precipitation kinetics under non-oxidative conditions was found to be slower than under oxidative conditions. The faster copper precipitation kinetics under oxidative conditions is most likely caused by an increase in porosity and reaction area as nickel is leached from the matte by acid and oxygen. The initial acid concentration, solids/liquid ratio and Fe-endpoint were the most important factors determining reaction kinetics under oxidative conditions. Low initial acid concentrations (37 g/L) and a high solids/liquid ratio improved the extent of copper precipitation. Nickel extraction was enhanced by low solids/liquid ratios and high initial acid concentrations (74 g/L). Nickel extraction was significantly less (56 % less in one instance) when leaching high iron mattes (5.7 % Fe) rather than low iron mattes (< 1 % Fe). Copper precipitation was initially faster when leaching a high iron matte, but slower nickel leaching from high iron mattes led to an excess of available acid, which resulted in copper being leached. The results suggest that high iron mattes will lead to poor copper and PGE precipitation in the first stage leach and also to lower nickel extractions. Consequently, Peirce Smith converting at the plant must be carefully controlled to avoid high iron mattes. Under non-oxidative conditions, the solids/liquid ratio and Fe-endpoint were the most important factors. The rate of copper precipitation was faster when a high iron matte was leached, so that a higher percentage copper was precipitated and more nickel was extracted from the matte. / AFRIKAANSE OPSOMMING: As ‘n eerste stap in die Lonmin Marikana basis-metale veredelingsaanleg word nikkel-koper-yster-swawel Peirce-Smith-converter-mat geloog in elektroliet wat hersirkuleer word vanaf die aanleg se koper-elektroplaterings-afdeling. Die loging word by atmosferiese druk uitgevoer. Die elektroliet bevat swawelsuur, koper- en nikkel-sulfate en ‘n klein hoeveelheid ystersulfaat. Die mat bevat hoofsaaklik nikkel, koper en swawel (tipies 48 %, 28 % en 23 %), maar ook klein hoeveelhede (< 5 %) yster en kobalt. Verder maak Platinum Groep Elemente (PGE’s) en ander waardevolle metale (platinum, palladium, iridium, rhodium, ruthenium, osmium en goud) 0.2 % tot 0.7 % van die massa van die mat uit. In terme van minerale bestaan die materiaal hoofsaaklik uit heazlewoodite, chalcocite en ‘n nikkel-koper allooi fase, asook slak en spinel minerale, wat tydens Peirce-Smith-converting weens meesleuring in die mat rapporteer. Die doel van die eerste stadium loog is om nikkel op te los, terwyl koper en PGE’s wat in die elektroliet voorkom presipiteer moet word. Nikkel, kobalt en koper word geloog in reaksies met suurstof en swawelsuur. Koper word presipiteer deur middel van ‘n redoks reaksie waarin koper-ione nikkel in die mat oksideer. Die doel van hierdie studie was om die effekte van sleutelveranderlikes op die proses te bepaal (spesifiek hoe nikkel-loging en koper presipitasie affekteer word) en om fundamentele begrip van die veranderlikes en hul effekte te verkry. Lot loogtoetse is uitgevoer op ‘n laboratorium-skaal en die effekte van die volgende faktore is ondersoek: beskibaarheid van suurstof, begin suurkonsentrasie, yster eindpunt (die ysterinhoud van die mat), vastestof/vloeistof verhouding en die roertempo. Vloeistof monsters geneem tydens loogtoetse is geanaliseer met behulp van Atoom Absorpsie Spektroskopie (AA) om kinetika te bepaal. Vastestof monsters is ook geneem tydens loogtoetse en kwantitatiewe X-straal diffraksie (XRD), asook skanderings-elektron-mikroskopie met ‘n energie dispersie sisteem (SEM-EDS) is gebruik om die materiaal te karakteriseer en die logingsmeganisme te verduidelik. Die oksidatiewe logingsmeganisme behels ‘n aanvanklike periode waartydens die allooi fase geloog word deur suur en suurstof, terwyl koper presipiteer om chalcocite te vorm as gevolg van ‘n reaksie waarin galvanise interaksie tussen die nikkel-koperallooi en heazlewoodite fases ‘n belangrike rol speel. In ‘n tweede reaksie periode is heazlewoodite geloog deur suur om millerite te vorm. Tydens hierdie tweede fase het die partikel struktuur meer porieus geword. Die tempo van koper presipitasie en nikkel loging was vinniger tydens die tweede reaksie periode as tydens die eerste. Koper is geloog indien die oplossing baie suur was (pH < 2) en die loogbare nikkel (60 – 70 %) reeds opgelos het. Die nie-oksidatiewe logingsmeganisme behels galvaniese interaksie tussen die nikkel-koper-allooi en heazlewoodite fases, wat lei tot koper presipitasie as chalcocite. Loging deur swawelsuur was onbeduidend. ‘n Aanvanklike vinnige periode van koper presipitasie tydens nie-oksidatiewe toetse is gevolg deur ‘n tweede stadiger periode. Die afname in reaksietempo kan waarskynlik verklaar word deur die afnemende beskikbaarheid van die nikkel-koper-allooi fase. Tydens nieoksidatiewe loging het die partikel struktuur redelik onveranderd gebly. Koper presipitasie kinetika in nie-oksidatiewe toetse was stadiger as in oksidatiewe toetse. Die belangrikste faktore wat kinetika in oksidatiewe toetse beïnvloed het was die suurkonsentrasie, vastestof/vloeistof verhouding en die yster-eindpunt. Lae beginsuurkonsentrasies (37 g/L) en ‘n hoë vastestof/vloeistof verhouding het gelei daartoe dat meer koper uit die elektroliet herwin is. Nikkel ekstraksie was hoër indien die vastestof/vloeistof verhouding laag was en die begin suurkonsentrasie hoog (74 g/L). Nikkel ekstraksie was beduidend laer (56 % laer in een geval) wanneer hoë-yster mat (5.7 % Fe) geloog is, eerder as lae yster mat (< 1 % Fe). Wanneer ‘n hoë yster mat geloog is, was koper presipitasie aanvanklik vinniger, maar weens stadige nikkel-ekstraksie-tempos was ‘n oormaat van suur beskikbaar sodat koper uiteindelik geloog is. PGE presipitasie is ook nadelig beïnvloed wanneer koper geloog is en veral tydens toetse met hoë yster mat. Die mees belangrike faktore wat nie-oksidatiewe loging beïnvloed het was die vastestof/vloeistof verhouding en die yster-eindpunt. Die tempo van koper presipitasie was vinniger in toetse met ‘n hoë yster mat, sodat ‘n hoër persentasie koper presipiteer het en meer nikkel opgelos het wanneer ‘n hoë yster mat geloog is.