Method for selectively leaching scandium and sodium from bayer red mud

The invention mainly belongs to the technical field of pyrogenic process-hydrometallurgy and particularly relates to a method for selectively leaching scandium and sodium from bayer red mud. By the adoption of the method, the scandium, a rare and expensive metallic element, and sodium high in content can be leached from the red mud, and separation of the scandium and the iron element in the red mud can also be achieved. According to the method, based on the occurrence form of the scandium in the red mud, the bayer red mud is evenly mixed with concentrated sulfuric acid, after low-temperature sulphating is conducted, medium-temperature calcinating is conducted, and escaping sulfur trioxide and sulfur dioxide or sulfuric acid are recycled during sulphating and medium-temperature calcinating; and after sulfate impurities are decomposed, a washing liquor rich in the scandium and the sodium and low in iron content is obtained through water leaching. The washing liquor, prepared through the method, rich in the scandium and the sodium and low in iron content provides absolute advantages for the follow-up steps of ion exchange and solvent extraction and re-extraction; and after solid-liquid separation, the obtained leaching residues high in iron content and low in sodium content can be used as a building material or a raw material of blast furnace iron making. Besides, the sulfuric acid used as the reagent in the method can be recycled and reused, and therefore no new pollution is generated.