Abstract:At present, HF-H2SO4 mixed acid system is widely used to extract niobium and tantalum from ores in order to improve leaching rate of niobium and tantalum and reduce discharge of fluoride slag. Based on columbite ore occurrence characteristics of China and applying columbite ore rich in cassiterite as raw material, phase, structure and morphology of columbite were detected through XRD and SEM observation before and after acid leaching. EDS analysis were used to analyze micro zone elements for minerals and change of surface macrostructure and surface element content before and after acid leaching. XPS was used to analyze changes of chemical valence and bond state of each element on surface of columbite before and after acid leaching, as well as changes of component content of each element. Combined with ICP results, surface structure changes of columbite under different acid leaching conditions and dissolution mechanism caused by structural changes were studied. The results show that cassiterite does not react with sulfuric acid and remains in tailings. Niobium is more soluble in minerals than tantalum.