Abstract: The effective removal of silicon from iron-bearing silicate is a prerequisite condition in preparation of ultrapure iron concentrate. The effect of leaching time and pulp concentration on the removal of silicon in augite（a kind of iron-bearing silicate） leached by Aspergillus niger were studied by means of shaking flask leaching. In order to explore the leaching mechanism， minerals before and after leaching were characterized by scanning electron microscopy（SEM）， X-ray diffraction（XRD）， energy dispersion spectrum（EDS） and Fourier transform infrared spectroscopy（FTIR）. The results showed that with the leaching time increasing， the content of silicon in leaching solution increased at the beginning and then decreased. The maximum leaching rate is 10.68% at 13 days. With the increase of pulp concentration， the content of silicon in leaching solution increased at the beginning and then decreased. The best leaching effect was obtained when the pulp concentration was 10%， and the leaching rate was 6.01%. The analysis of leaching residue showed that the crystal structure of the augite was destroyed， which even collapsed during the process above. The O—H bond and the Si—O bond of the ore samples changed， which is attributed to the acid hydrolysis and complexation of Aspergillus niger metabolism， thereby reducing the crystallinity of the mineral， destroying the crystal structure and dissolving the ore components eventually.

Key words: Aspergillus niger, Augite, Shaking flask leaching, Organic acids, Extracellular polymers