Influence of chemical and biogenic leaching on surface area and particle size of laterite ore

Currently there is a decline in the world’s nickel sulfide deposits, which are the main source of this metal. Due to the fact, that more than 70% of nickel reserves are in the form of oxide ores, more attention is nowadays paid on laterites. Leaching processes using different organic acids are widely described in the literature, but there is a lack of works linking influence of leaching process with the surface area and particle size distribution. Therefore, the main aim of this study was to examine how citric acid produced by microorganisms and citric acid added as chemical affected the specific surface and particle size distribution of mineral particles. The laterite ore was obtained from Szklary deposit, Poland. This study also compared the effect of chemical citric acid and filtrate after cultivation of Aspergillus niger on nickel extraction. It was observed that higher nickel recovery correspond to higher surface area of particles. The highest yield of nickel extraction was observed for a citric acid concentration of 1 mol/dm3 (67%). The specific surface area after leaching was 159 m2/g. An analysis of particle size distribution showed increase in the median particle size of particles after leaching with citric acid. It may suggest that dissolution of Polish laterites follows a shrinking core-shrinking particle model.