Återvinning av kritiska råmaterial från gruvavfall med hjälp av hydrometallurgiska processer

Sammanfattning

Recycling of critical materials from mining waste by using hydrometallurgical processes– astudy that investigates the potential of organic acids as leaching agents for boron, lithium andcopper.During the coming years, the need for critical and strategical elements, such as boron, lithium and copper, is expected to increase rapidly. From this, it follows that the importance ofextracting a larger part of elements from mining waste also heightens. A traditional methodfor material recovery is through leaching with inorganic acids, which leads to environmentallyharmful emissions. If such leaching can be done with organic acids, that do not lead to suchemissions, it would be beneficial for both the industry and the environment. The aim of thiswork is to develop an effective method for the leaching of boron, lithium and copper from mining waste using organic acids as leaching agents. The ambition is to achieve equal leachingyields using organic acids as opposed to inorganic, through a process compatible with the industry. To achive the aim, leaching of three different mining wastes, containing boron, lithiumand copper respectivly, was carried out using organic acids. Leaching efficiency of Na-EDTA,oxalic, acetic and formic acid as leachant was investigated. The impact of acid concentration,temperature, leaching time, solid to liquid ratio and the addition of hydrogen peroxide for theseacids were all evaluated. The leaching of boron, lithium and copper, similar or higher leachingyields were obtained with organic acid as with inorganic acid leaching. For boron leaching, ayield of around 100 % was reached in several leaching conditions with oxalic acid during twohours. For lithium leaching, a yield of around 100 % was reached with oxalic acid, but afterfour hours. For copper, the highest leaching yield achieved was around 45 %, and this was donewith Na-EDTA. The advantageous results achieved for boron and lithium leaching provides agood reason to continue exploring the possibility to implement these leaching conditions on anindustrial scale. To make a continued scientific work on an industrial scale applicable for copperleaching, a higher leaching yield must be attained.