Återvinning av kritiska råmaterial från gruvavfall med hjälp av hydrometallurgiska processer

Abstract

Recycling of critical materials from mining waste by using hydrometallurgical processes– a study that investigates the potential of organic acids as leaching agents for boron, lithium and copper. During the coming years, the need for critical and strategical elements, such as boron, lithi um and copper, is expected to increase rapidly. From this, it follows that the importance of extracting a larger part of elements from mining waste also heightens. A traditional method for material recovery is through leaching with inorganic acids, which leads to environmentally harmful emissions. If such leaching can be done with organic acids, that do not lead to such emissions, it would be beneficial for both the industry and the environment. The aim of this work is to develop an effective method for the leaching of boron, lithium and copper from mi ning waste using organic acids as leaching agents. The ambition is to achieve equal leaching yields using organic acids as opposed to inorganic, through a process compatible with the in dustry. To achive the aim, leaching of three different mining wastes, containing boron, lithium and 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 these acids were all evaluated. The leaching of boron, lithium and copper, similar or higher leaching yields were obtained with organic acid as with inorganic acid leaching. For boron leaching, a yield of around 100 % was reached in several leaching conditions with oxalic acid during two hours. For lithium leaching, a yield of around 100 % was reached with oxalic acid, but after four hours. For copper, the highest leaching yield achieved was around 45 %, and this was done with Na-EDTA. The advantageous results achieved for boron and lithium leaching provides a good reason to continue exploring the possibility to implement these leaching conditions on an industrial scale. To make a continued scientific work on an industrial scale applicable for copper leaching, a higher leaching yield must be attained.