Effect of alkali surface dissolution in selective flotation of oxide minerals

In this study, a surface dissolution method by sodium hydroxide was used to improve the floatability of ilmenite in the presence of olivine-pyroxene and tremolite-clinochlore. The results of microflotation and UV-Vis indicated that the flotation recovery and collector adsorption of ilmenite are increased about 9.9% and 10.3% after surface dissolution at pH=6.3, respectively, while these parameters are decreased about 28.1% and 27.25% for olivine-pyroxene and 2.6% and 13.52% for tremolite-clinochlore, respectively. Also, the results of flotation showed that the recovery, grade and separation efficiency of ilmenite flotation from the aforementioned gangue minerals are improved after surface dissolution.It can be due to conversion of ferrous ions to ferric ones on the ilmenite surface and removing the iron, calcium and magnesium ions from the surface of gangue minerals. The IEP of all minerals are decreased after surface dissolution, but the Pzc value for ilmenite was increased in the presence of collector and pH=6.3 while it was decreased for two gangue minerals. These results are in good agreements with FTIR results. Also, changing in physicochemical properties of these mineral surfaces via surface dissolution was resulted in a selective adsorbtion of oleate ions on the surface of those minerals. After surface dissolution, floatability and selectivity of ilmenite from gangue minerals are increased in a wide range of pH.Finally, the results of ilmenite flotation from gangue minerals showed that the surface dissolution can improve the metallurgical parameters of ilmenite separation.