The effects of carboxylic acid addition on hydrofluoric acid autoclave leaching of a ferrocolumbite

The effects of adding carboxylic acid to the leaching media upon the extraction of niobium and tantalum from a ferrocolumbite are studied. Leaching tests were carried out with a pressure reactor in hydrofluoric and carboxylic acids media. Comparative experiments were performed modifying the following variables: temperature, hydrofluoric acid concentration, solid/liquid ratio and carboxylic acid type and concentration. agents and products have been characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS), X-ray fluorescence (XRF), X-ray diffraction (XRD), and surface area (BET) measurement. sults obtained show an increase in the niobium and tantalum dissolution when carboxylic acids such as oxalic and tartaric acids are added to the reaction media. The addition of tartaric acid also increases the iron and manganese recovery. The addition of oxalic acid decreases the extraction of manganese, while the extraction of iron is almost nonexistent under certain conditions due to the formation of an insoluble compound that remains in the residue. Results of the residue analysis by XRD show the formation of a new crystalline structure when oxalic acid is used. In experiments with other carboxylic acids such as formic and citric acids, no significant changes in the recovery are observed.