Processing hard rock lithium

The focus of this thesis project has been on recovering lithium from its mineral ores, primarily being from spodumene. The general process for recovering lithium has been to begin with a roast to improve the dissolution rate of lithium ions. This occurs by expanding the crystal structure from an alpha to beta-spodumene form. However, this initial roast contributes a significant energy expense in processing the ore. This project has aimed at finding an alternative, less expensive pre-treatment for recovering lithium from spodumene ores. The attempt has been to use a caustic leach within an autoclave at an elevated pressure of 40 bar and moderate temperatures of 150 to 250°C. A 0.01M acid digestion followed at temperature of 50°C for 12 hours. The obtained results were from Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and X-Ray Diffraction, which indicated a very poor extraction. The x-ray peaks did however indicate a potential change in crystal structure. Overall, the experiment remained as a work in progress with the identification of newly formed x-ray peaks still being required. Solid residue analysis has also been helpful in providing a conclusive account of the mineral elements. There were three sections covered in this study. The first phase has involved preparing a comprehensive literature review to give a general overview of the lithium industry. The literature review is located within Appendix A. The second phase was then to develop a planned laboratory procedure, while covering an adequate risk assessment and budgetary proposal. These planning activities are within the Program of Study that is located within Appendix B. The final phase was then to apply the practical autoclave leaching experiments on mineral samples. The body of this thesis contains the laboratory report, which presents the applied procedure and the analysis of results. The main intention was to identify efficiencies, reduce costs and provide more an effective lithium recovery option, for commercial use. The literature review has targeted the world’s lithium resources along with the various technologies that exist for its extraction from primary and secondary deposits. The acid leaching, alkaline, ion-exchange, pressure leaching, bioleaching and chlorination processes have been examined for processing the primary mineral ores of spodumene, lepidolite, amblygonite, petalite, zinnwaldite and clays. Brine resources; have also been explored with its extraction process techniques of adsorption, precipitation and ion exchange through solvent extraction. The secondary resource of recycling lithium ion batteries (LIBs) have then evaluated as an alternative source and explained in detail. This has involved an initial pre-treatment of the spent LIBs, acid leaching of the metals and recovery of the lithium and by-product compounds from the leach liquors. The suitable recycling processes to handle the varying compositions of available batteries have also contributed. Another secondary resource has been lithium’s presence in seawater; however, this source has been ignored as an uneconomical supply due to its very low concentration. Overall, the key industrial extraction procedures were critically examined with reference to various journal articles and patents. The essential objective has been to provide a detailed description of the available lithium recovery techniques that are applied to the various reserves. The second phase was to complete a program of study. This involved outlining the project objectives, intended materials and equipment items. The identification of potential health and safety aspects were include with major risks examined. This involved an overview of the toxicity of materials and potential hazards within the laboratory workplace and a risk assessment with control measures being completed. The intended experimental procedure was then outlined which targeted the operation of the autoclave equipment, the sulphuric acid process and the caustic treatment options. A laboratory plan was developed to optimise several testing parameters for an autoclave leach. This plan involved adjusting the leaching reagents, their concentration, the temperature, pulp density, grind size and ore variability. The remainder of the program of study then budgeted and scheduling the activities and expected outcomes. Overall, this second section was a planning procedure to determine the direction of the project. The final phase was then to complete the practical laboratory procedures and an analysis of the obtained results. Once completed, this developed a laboratory report that is the body of this thesis article. This section introduces the reasons for the intended procedure, lists the actual materials and method applied before evaluating the results. Major changes to the laboratory plan were identified, before focusing attention on presenting and discussing the results. Overall, the planned variation of leaching conditions has been replaced. A variation of caustic leaching reagents were instead implemented at varying temperatures, with the solid residues then being treated with a secondary acid wash. The conclusion section then summarizes the results and suggests any further testing recommendations. The literature review and program of study have been placed in Appendix A and B due to a word limitation within the body of this article. As such, the body only contains the final laboratory report