SE 4: Extraction Processes
SE 4:
Extraction Processes Part 1: Introduction 1. EXTRACTION PROCESSES Part 2: Metals Recovery from Scrap, Wastes and Effluents 1. INTRODUCTION 2. CATEGORIES OF METAL-CONTAINING SCRAP AND WASTE 2.1 General Categories 2.2 Metallic or Metal-based scrap 2.3 Non Metallic Wastes 2.4 Liquid Effluents 3. EXTRACTANTS AND EXTRACTION SYSTEMS 3.1 Chelating Agents 3.2 Acidic Extractants 3.3 Alkyl Amines 3.4 Solvating extractants 4. APPLICATION OF SOLVENT EXTRACTION TO THE TREATMENT OF SCRAPS,WASTES AND EFFLUENTS 4.1 General Considerations 4.2 Processes, In Operation and with Potential Application 4.2.1 Introduction 4.2.2 Metallic Scrap 4.2.3 Mixed Metallic and Non-Metallic Wastes 4.2.4 Non-Metallic Wastes 4.2.5 Liquid Effluent 4.3 New Developments 5. COMPARISON WITH OTHER PROCESSES 5.1 Introduction 5.2 Effluent Standards 5.3 Current Methods of Effluent Treatment 5.4 Recovery of Metals from Effluents 5.4.1 Liquid-Liquid Extraction 6. ECONOMIC CONSIDERATIONS IN THE USE OF LIQUID-LIQUID EXTRACTION 6.1 Introduction 6.2 Liquid-Liquid Extraction for Metals Recovery from Scrap and Waste 6.3 Effluent Treatment 7. ENVIRONMENTAL ASPECTS AND SOLVENT RECOVERY 7.1 Introduction 7.2 Solvent Loss 7.3 Solvent Recovery 7.4 Toxicological and Biological Effects 7.5 Biodegradability 8. CONCLUSIONS AND RECOMMENDATIONS 9. References Part 3: Metals Extraction: Theory and Practice of Complex Formation 1 INTRODUCTION 2. THEORY OF COMPLEX FORMATION 2.1 Complexing in Solution 2.1.1 Kinetics of Substitution 2.1.2 Thermodynamic Stability 2.2 Liquid-liquid Extraction 2.2.1 Chelating Agents and Acids 2.2.2 Neutral Donors 2.2.3 Amines 2.2.4 Synergism 2.2.5 Diluents and Modifiers 2.2.6 Experiments to determine the Equilibrium Data 2.3 Multistage extraction 2.3.1 Graphical and Mathematical Methods 2.3.2 Modelling 3. CRITERIA FOR EXTRACTANT CHOICE 4. INDUSTRIAL APPLICATIONS 4.1 General 4.2 Industrial Reagents 4.3 Metals 4.3.1 Copper 4.3.2 Cobalt and Nickel 4.3.3 Zinc 4.3.4 Uranium 4.3.5 Nuclear Fuel Reprocessing 4.3.6 Molybdenum 4.3.7 Platinum Metals 4.3.8 Rare Earths 4.3.9 Niobium and Tantalum 4.3.10 Other Metals - Transition Elements 4.3.11 Other metals - Non Transition Elements 5. FUTURE DEVELOPMENTS 5.1 New Reagents 5.2 New Processes 6 ABBREVIATIONS 7 GLOSSARY 8 REFERENCES | Part
1 Introduction Volume SE IV Part 1 Introduction. This part gives an overview of the volume and how to use it to best effect. The development in comparatively recent years of highly specific organic extractants capable of the recovery of metal values from low concentrations in aqueous liquors provides scope for the treatment of metallic ferrous effluents and wastes. Important differences exist, however, between recovery from primary ore and from waste streams, in terms of reagent selectivity and the greater sensitivity of waste treatment to economic considerations. Processes in current use and those in an advanced state of development are presented and discussed, alternative processes are compared and the relative economics are considered. The environmental aspects of effluent treatment for solvent recovery are discussed and the toxicity and biodegradability of solvents are also considered. Illustrative examples are given, and comparisons made between these and rival processes such as ion exchange, electrolytic treatment etc. Volume SE IV Part 3 Liquid-liquid extraction of metals: theory and practice of complex formation. Liquid-liquid extraction is finding ever-widening application for separation and purification of lower grade and more complex ores. Following the introduction about two decades ago of the LIX hydroxyoxime reagents for copper extraction, a wide range of extractants specific for a number of different metals is now available. This Part describes the mechanisms of metal extraction, the reagents available and criteria for their choice, and examples of industrial processes for metals extraction. The mechanism and rate of formation of a complex in the aqueous phase and its stability are discussed, as well as its subsequent distribution in two phase systems. The different types of extractant chelating agents, acids, neutral donors, amines and alkyl ammonium salts, are described and examples of their use given. The roles of synergism and of diluents and modifiers are briefly described and also the modelling of multistage solvent extraction processes. Criteria for solvent selection, presently available reagents and their structure are listed, together with manufacturers. Reactions of the more important industrially-used hydroxyoximes and phosphoric acid derivatives are described, as are processes for the extraction of various metals. These include commercial processes for copper, cobalt, nickel, zinc, uranium, molybdenum, niobium and tantalum, the platinum metals and the rare earths. The scope for the future development of hydrometallurgical extraction processes is reviewed. |