In recent years, technological innovations have resulted in manifold applications using rare earth elements (REEs), leading to a dramatic increase in demand for them. Because of their unique physicochemical properties, REEs are considered indispensable in modern industry. They are extensively used in new materials, energy conservation, environmental protection and IT devices as well as in military weapon systems. They have also significantly contributed to the miniaturisation of electronic components, such as, for example, cell phones and laptop computers. REEs are essential for green technologies such as wind turbines. They are widely applied in the automotive industry for catalysts, hybrid vehicle batteries, motors and generators, etc. (Hurst, 2010). Due to the similarity of the chemical characteristics of each individual REE, the production processes for REEs with high purity are very complex: the processing and separation can be technically challenging. Furthermore, the chemical extraction processes involved have generated severe environmental problems. Currently, the supply of REEs is concentrated in China. To reduce the dependence on China, many countries have started to search for alternative REE sources, which can be classified into “primary sources” and “secondary sources”. Many REE exploration projects outside China and REE recycling projects have been launched. However, the success of the development of these projects is impacted by various risks, such as political risks, technical risks, environmental risks and social risks. The main research aim of this thesis is to establish a model for the evaluation of REE projects and to provide a basis for investment decision making. In order to complete this task, an analysis of REE deposits and the supply chain for REEs is provided. As results, a data base of potential REEs project is compiled, while an overview of the supply chain for REEs and an analysis of risks across the supply chain are presented. In order to assess potential REE production projects, a new real options valuation (ROV) model using a multi-dimensional binomial lattice approach is developed. For the application of the new real options model, a range of risk parameters and the expected production output of REE products are estimated using the Monte Carlo simulation method. The application of the new real options model is presented for the evaluation of the Bayan Obo mine in China, the Kvanefjeld REE project in Greenland, and a REE recycling project from magnetic scrap.

Seit dem 1. Januar 2015 ist die Bemessungsgrundlage für die Erfüllung der Biokraftstoffquote nach BImSchG (§ 37) vom Energiegehalt der Kraftstoffe auf eine Verpflichtung zur Treibhausgas (THG)-Minderung umgestellt worden. Diese Maßnahme soll einen wirksamen und quantifizierbaren Beitrag zur Verringerung der Treibhausgasemissionen des Verkehrssektors leisten. Konsequenterweise haben die Biokraftstoffe die besten Marktchancen, die als Ergebnis der Nachhaltigkeitszertifizierung gemäß der Biokraftstoff-Nachhaltigkeitsverordnung (Biokraft-NachV) die beste THG-Bilanz ausweisen. Die Treibhausgasminderungseffizienz wird damit – in einem globalisierten Biomasserohstoff- und Biokraftstoffmarkt – neben dem Preis für die gesamte Warenkette zum wesentlichen Wettbewerbsfaktor. Ab 2015 ist daher zu erwarten, dass die Verwendung der so genannten Standardwerte aus dem Anhang der Biokraft-NachV stark abnimmt und vorwiegend individuell berechnete THG-Bilanzen im Rahmen der Zertifizierung erstellt werden.

Different aspects of interaction of metals other than iron with metallophore mixtures were elucidated. Metal chelation besides iron and greater than with pure desferrioxamine B is documented by enhanced performance of soil mineral dissolution following application of diverse metallophore mixtures. New insights from genome to product of metallophores from Gordonia rubripertincta CWB2 under different cultivation conditions and under metal stress, particularly induced by rare earth elements are given. This evaluation led to increase by a factor of 13. Structure analyses showed that the strain produces citrate and different desferrioxamines. A robust RP-HPLC-based method quantified metal complexation. Further metal immobilization methods for metallophores for metal extraction from solutions with low concentrations were established. Moreover, catechol and hydroxamate metallophores from Arthrobacter oxydans ATW2 and Kocuria rosea ATW4 demonstrate the enhancement of Ge and rare earth element bioavailability, plant growth promotion and phytoextraction potential.:CONTENTS Abstract ..........................................................................................................1 CHAPTER 1 Introduction ......................................................................................5 CHAPTER 2 Mobilization of trace elements in soil extracts by bacterial siderophores in dependence of the pH-value..................................31 CHAPTER 3 Cultivation dependent formation of siderophores by Gordonia rubripertincta CWB2........................................................................41 CHAPTER 4 Data on metal-chelating, -immobilization and biosorption properties by Gordonia rubripertincta CWB2 in dependency on rare earth adaptation.......................................................................................67 CHAPTER 5 Analysis of desferrioxamine-like siderophores and their capability to selectively bind metals and metalloids: development of a robust analytical RP-HPLC method. ..........................................................97 CHAPTER 6 Secondary metabolites released by the rhizosphere bacteria Arthrobacter oxydans and Kocuria rosea enhance plant availability and soil–plant transfer of germanium (Ge) and rare earth elements (REEs) .........................................................................................120 CHAPTER 7 Conclusion remarks and further perspectives ...............................154 References .......................................................................................................162 Acknowledgement .........................................................................................185 Curriculum Vitae ..........................................................................................187 List of publications ..........................................................................................189 List of oral and poster presentations ..........................................................190 List of proceedings ..........................................................................................191 / En este trabajo se han dilucidado diferentes aspectos de la interacción de los metales con las mezclas de metalóforos desde distintos ángulos. La quelación de metales por debajo del hierro se pone de manifiesto en la mejora del rendimiento de la disolución de los minerales del suelo debido a la aplicación de diversas mezclas de metanóforos en comparación con la deferoxamina B pura. Se ofrecen nuevos conocimientos desde el genoma hasta el producto de los metanóforos de Gordonia rubripertincta CWB2 en diferentes condiciones de cultivo y bajo estrés por metales, especialmente inducido por elementos de tierras raras. Esta evaluación condujo a una sobreproducción de un factor de 13. El análisis estructural muestra que la cepa produce citrato y diferentes desferrioxaminas. Un método robusto basado en RP-HPLC cuantificó la complejación de metales. Se establecieron otros métodos de inmovilización de metales para la extracción de metales a partir de soluciones poco concentradas. Además, los metalóforos de catecol e hidroxamato de Arthrobacter oxydans ATW2 y Kocuria rosea ATW4 demuestran la mejora de la biodisponibilidad de GE y REE, la promoción del crecimiento vegetal y el potencial de fitoextracción.:CONTENTS Abstract ..........................................................................................................1 CHAPTER 1 Introduction ......................................................................................5 CHAPTER 2 Mobilization of trace elements in soil extracts by bacterial siderophores in dependence of the pH-value..................................31 CHAPTER 3 Cultivation dependent formation of siderophores by Gordonia rubripertincta CWB2........................................................................41 CHAPTER 4 Data on metal-chelating, -immobilization and biosorption properties by Gordonia rubripertincta CWB2 in dependency on rare earth adaptation.......................................................................................67 CHAPTER 5 Analysis of desferrioxamine-like siderophores and their capability to selectively bind metals and metalloids: development of a robust analytical RP-HPLC method. ..........................................................97 CHAPTER 6 Secondary metabolites released by the rhizosphere bacteria Arthrobacter oxydans and Kocuria rosea enhance plant availability and soil–plant transfer of germanium (Ge) and rare earth elements (REEs) .........................................................................................120 CHAPTER 7 Conclusion remarks and further perspectives ...............................154 References .......................................................................................................162 Acknowledgement .........................................................................................185 Curriculum Vitae ..........................................................................................187 List of publications ..........................................................................................189 List of oral and poster presentations ..........................................................190 List of proceedings ..........................................................................................191 / Es wurden verschiedene Aspekte der Wechselwirkung von anderen Metallen als Eisen mit Metallophormischungen untersucht. Die Chelatbildung mit anderen Metallen als Eisen, die größer ist als bei reinem Desferrioxamin B, wird durch eine verbesserte Leistung bei der Auflösung von Bodenmineralien nach Anwendung verschiedener Metallophormischungen dokumentiert. Es werden neue Erkenntnisse vom Genom bis zum Produkt von Metallophoren aus Gordonia rubripertincta CWB2 unter verschiedenen Anbaubedingungen und unter Metallstress, insbesondere induziert durch Seltene Erden, gegeben. Diese Auswertung führte zu einer Steigerung um den Faktor 13. Strukturanalysen zeigten, dass der Stamm Citrat und verschiedene Desferrioxamine produziert. Eine robuste RP-HPLC-basierte Methode quantifizierte die Metallkomplexierung. Weitere Methoden zur Metallimmobilisierung von Metallophoren für die Metallextraktion aus Lösungen mit niedrigen Konzentrationen wurden etabliert. Darüber hinaus zeigen Catechol- und Hydroxamat-Metallophore aus Arthrobacter oxydans ATW2 und Kocuria rosea ATW4 die Verbesserung der Bioverfügbarkeit von Ge und Seltenen Erden, die Förderung des Pflanzenwachstums und das Phytoextraktionspotenzial.:CONTENTS Abstract ..........................................................................................................1 CHAPTER 1 Introduction ......................................................................................5 CHAPTER 2 Mobilization of trace elements in soil extracts by bacterial siderophores in dependence of the pH-value..................................31 CHAPTER 3 Cultivation dependent formation of siderophores by Gordonia rubripertincta CWB2........................................................................41 CHAPTER 4 Data on metal-chelating, -immobilization and biosorption properties by Gordonia rubripertincta CWB2 in dependency on rare earth adaptation.......................................................................................67 CHAPTER 5 Analysis of desferrioxamine-like siderophores and their capability to selectively bind metals and metalloids: development of a robust analytical RP-HPLC method. ..........................................................97 CHAPTER 6 Secondary metabolites released by the rhizosphere bacteria Arthrobacter oxydans and Kocuria rosea enhance plant availability and soil–plant transfer of germanium (Ge) and rare earth elements (REEs) .........................................................................................120 CHAPTER 7 Conclusion remarks and further perspectives ...............................154 References .......................................................................................................162 Acknowledgement .........................................................................................185 Curriculum Vitae ..........................................................................................187 List of publications ..........................................................................................189 List of oral and poster presentations ..........................................................190 List of proceedings ..........................................................................................191

These are the abstracts of the presentations of the 7th PhD conference held on 9 June 2023 in Freiberg.

In der Zusammenfassung der Tagung werden die behandelten Themen sowie wichtige Sprecher kurz vorgestellt. Themen sind Innovation im Bergbau, Nachhaltigkeit im Bergbau (New Climate Economy), Aufarbeitung von Halden und Tailings und Industrie 4.0 im chilenischen Bergbau sowie technologische Neuerungen. Wesentliche Kooperationsprojekte werden genannt. Das Deutsch-Chilenische Rohstoffforum wurde durch das „Kompetenzzentrum Bergbau und Rohstoffe“ der Deutsch-Chilenischen Industrie- und Handelskammer inhaltlich vorbereitet. / In the summary the topics of the meeting and important speakers are listed and shortly presented. Topics are the efficency of resources, environmental aspects, secondary mining and human resources in the mining industry of Chile. Technological innovations of the mining industry are also in the focus of the meeting. Some projects for cooperation are introduced. The German-Chilean Raw Materials Forum was organized by the „Kompetenzzentrum Bergbau und Rohstoffe“ of the Deutsch-Chilenische Industrie- und Handelskammer.

In der Zusammenfassung der Tagung werden die behandelten Themen sowie wichtige Sprecher kurz vorgestellt. Themen sind Innovation im Bergbau, Nachhaltigkeit im Bergbau (New Climate Economy), Aufarbeitung von Halden und Tailings und Industrie 4.0 im chilenischen Bergbau sowie technologische Neuerungen. Wesentliche Kooperationsprojekte werden genannt. Das Deutsch-Chilenische Rohstoffforum wurde durch das „Kompetenzzentrum Bergbau und Rohstoffe“ der Deutsch-Chilenischen Industrie- und Handelskammer inhaltlich vorbereitet. / In the summary the topics of the meeting and important speakers are listed and shortly presented. Topics are the efficency of resources, environmental aspects, secondary mining and human resources in the mining industry of Chile. Technological innovations of the mining industry are also in the focus of the meeting. Some projects for cooperation are introduced. The German-Chilean Raw Materials Forum was organized by the „Kompetenzzentrum Bergbau und Rohstoffe“ of the Deutsch-Chilenische Industrie- und Handelskammer.

Mining will remain indispensable for the foreseeable future. For millennia, our society has been exploring and exploiting mineral deposits. Consequently, most of the easily exploitable high-grade deposits, which were of primary interest given their obvious technical and economic advantages, have already been depleted. For the future, the mining sector will have to efficiently produce metals and minerals from low-grade orebodies with complex mineralogical and microstructural properties -- these are generally referred to as complex orebodies. The exploitation of such complex orebodies carries significant technical risks. However, these risks may be reduced by applying modelling tools that are reliable and robust. In a broad sense, modelling techniques are already applied to estimate the resources and reserves contained in a deposit, and to evaluate the potential recovery (i.e., behaviour in comminution and separation processes) of these materials. This thesis focusses on the modelling of recovery processes, more specifically mineral separation processes, suited to complex ores. Despite recent developments in the fields of process mineralogy and geometallurgy, current mineral separation modelling methods do not fully incorporate the available information on ore complexity. While it is well known that the mineralogical and microstructural properties of individual particles control their process behaviour, currently widely applied modelling methods consider only distributions of bulk particle properties, which oftentimes require much simplification of the particle data available. Moreover, many of the methods used in industrial plant design and process modelling are based on the chemical composition of the samples, which is only a proxy for the mineralogical composition of the ores. A modelling method for mineral separation processes suited to complex ores should be particle-based, taking into consideration all quantifiable particle properties, and capable of estimating uncertainties. Moreover, to achieve a method generalizable to diverse mineral separation units (e.g., magnetic separation or flotation) with minimal human bias, strategies to independently weight the importance of different particle properties for the process(es) under investigation should be incorporated. This dissertation introduces a novel particle-based separation modelling method which fulfills these requirements. The core of the method consists of a least absolute shrinkage and selection operator-regularized (multinomial) logistic regression model trained with a balanced particle dataset. The required particle data are collected with scanning electron microscopy-based automated mineralogy systems. Ultimately, the method can quantify the recovery probability of individual particles, with minimal human input, considering the joint influence of particle shape, size, and modal and surface compositions, for any separation process. Three different case studies were modelled successfully using this new method, without the need for case-specific modifications: 1) the industrial recovery of pyrochlore from a carbonatite deposit with three froth flotation and one magnetic separation units, 2) the laboratory-scale magnetic separation of a complex skarn ore, and 3) the laboratory-scale separation of apatite from a sedimentary ore rich in carbonate minerals by flotation. Moreover, the generalization potential of the method was tested by predicting the process outcome of samples which had not been used in the model training phase, but came from the same geometallurgical domain of a specific ore deposit. In each of these cases, the method obtained high predictive accuracy. In addition to its predictive power, the new particle-based separation modelling method provides detailed insights into the influence of specific particle properties on processing behaviour. To name a couple, the influence of size on the recovery of different carbonate minerals by flotation in an industrial operation; and a comparison to traditional methodologies demonstrated the limitation of only considering particle liberation in process mineralogy studies -- the associated minerals should be evaluated, too. Finally, the potential application of the method to minimize the volume of test work required in metallurgical tests was showcased with a complex ore. The approach developed here provides a foundation for future developments, which can be used to optimize mineral separation processes based on particle properties. The opportunity exists to develop a similar approach to model the comminution of single particles and ultimately allow for the full prediction of the recovery potential of complex ores.:1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3 State-of-the-art in particle-based separation models . . . . . . . . . . . 11 1.4 Moving forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.4.1 Particle data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.4.2 Mathematical tools required for the particle-based separation model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 1.4.3 Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1.5 Structure of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2 The method and its application to industrial operations 23 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.2.1 Assumptions and limitations . . . . . . . . . . . . . . . . . . . . 26 2.2.2 Data structure and required pre-treatment . . . . . . . . . . . . 27 2.2.3 Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.3 Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.1 Artificial test cases . . . . . . . . . . . . . . . . . . . . . . . . . 31 2.3.2 Real case study . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2.4 Discussion and final considerations . . . . . . . . . . . . . . . . . . . . 39 3 The robustness of the method towards compositional variations of new feed samples 45 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3.2 Generalization potential of current Particle-based Separation Model (PSM) methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.3 Case study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.3.1 Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.3.2 Dry magnetic separation tests . . . . . . . . . . . . . . . . . . . 53 3.3.3 Sample characterization . . . . . . . . . . . . . . . . . . . . . . 53 3.3.4 Particle-based separation models . . . . . . . . . . . . . . . . . 54 3.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4 Flotation kinetics of individual particles 67 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.2.1 Data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.2.2 Cumulative recovery probability . . . . . . . . . . . . . . . . . . 72 4.2.3 Particle-based kinetic flotation model . . . . . . . . . . . . . . . 74 4.3 Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.3.1 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . 75 4.3.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 4.4 Discussion and final thoughts . . . . . . . . . . . . . . . . . . . . . . . 80 5 Conclusions and outlook 85 5.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 5.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Bibliography 89

In der Zusammenfassung der Tagung werden die behandelten Themen sowie wichtige Sprecher kurz vorgestellt. Themen sind Innovation im Bergbau, Nachhaltigkeit im Bergbau (New Climate Economy), Aufarbeitung von Halden und Tailings und Industrie 4.0 im chilenischen Bergbau sowie technologische Neuerungen. Wesentliche Kooperationsprojekte werden genannt. Das Deutsch-Chilenische Rohstoffforum wurde durch das „Kompetenzzentrum Bergbau und Rohstoffe“ der Deutsch-Chilenischen Industrie- und Handelskammer inhaltlich vorbereitet. / In the summary the topics of the meeting and important speakers are listed and shortly presented. Topics are the efficency of resources, environmental aspects, secondary mining and human resources in the mining industry of Chile. Technological innovations of the mining industry are also in the focus of the meeting. Some projects for cooperation are introduced. The German-Chilean Raw Materials Forum was organized by the „Kompetenzzentrum Bergbau und Rohstoffe“ of the Deutsch-Chilenische Industrie- und Handelskammer.

In der Zusammenfassung der Tagung werden die behandelten Themen sowie wichtige Sprecher kurz vorgestellt. Themen sind Innovation im Bergbau, Nachhaltigkeit im Bergbau (New Climate Economy), Aufarbeitung von Halden und Tailings und Industrie 4.0 im chilenischen Bergbau sowie technologische Neuerungen. Wesentliche Kooperationsprojekte werden genannt. Das Deutsch-Chilenische Rohstoffforum wurde durch das „Kompetenzzentrum Bergbau und Rohstoffe“ der Deutsch-Chilenischen Industrie- und Handelskammer inhaltlich vorbereitet. / In the summary the topics of the meeting and important speakers are listed and shortly presented. Topics are the efficency of resources, environmental aspects, secondary mining and human resources in the mining industry of Chile. Technological innovations of the mining industry are also in the focus of the meeting. Some projects for cooperation are introduced. The German-Chilean Raw Materials Forum was organized by the „Kompetenzzentrum Bergbau und Rohstoffe“ of the Deutsch-Chilenische Industrie- und Handelskammer.

In der Zusammenfassung der Tagung werden die behandelten Themen sowie wichtige Sprecher kurz vorgestellt. Themen sind Innovation im Bergbau, Nachhaltigkeit im Bergbau (New Climate Economy), Aufarbeitung von Halden und Tailings und Industrie 4.0 im chilenischen Bergbau sowie technologische Neuerungen. Wesentliche Kooperationsprojekte werden genannt. Das Deutsch-Chilenische Rohstoffforum wurde durch das „Kompetenzzentrum Bergbau und Rohstoffe“ der Deutsch-Chilenischen Industrie- und Handelskammer inhaltlich vorbereitet. / In the summary the topics of the meeting and important speakers are listed and shortly presented. Topics are the efficency of resources, environmental aspects, secondary mining and human resources in the mining industry of Chile. Technological innovations of the mining industry are also in the focus of the meeting. Some projects for cooperation are introduced. The German-Chilean Raw Materials Forum was organized by the „Kompetenzzentrum Bergbau und Rohstoffe“ of the Deutsch-Chilenische Industrie- und Handelskammer.