Effect of sodium chloride on bioleaching of sulfidic ores by mesophilic acidophilic iron-oxidizing bacteria and moderately thermophilic iron/sulfur-oxidizing bacteria

摘要

In bio-hydrometallurgical operations, besides the challenge with regard to chloride ion, several studies found that chloride could enhance the bacterial leaching of metal sulfides. This study was undertaken to compare the effect of chloride on bacterial growth, iron oxidation activity and bioleaching performance of iron oxidizers at mesophilic and moderate thermophilic temperatures. Sulfobacillus thermosulfidooxidans and Leptospirillum ferriphilum were used for the investigation. The exposure to elevated NaCl concentration affected cell growth and eventual iron oxidation rate in both strains. Sb. thermosulfidooxidans showed better tolerance to NaCl than L. ferriphilum. The minimum inhibitory concentrations of NaCl were 325 mM and 525 mM for L. ferriphilum and Sb. thermosulfidooxidans, respectively. Bioleaching of chalcopyrite and sphalerite-containing ores were studied. For copper-containing sulfide minerals, bioleaching by Sb. thermosulfidooxidans in the presence of 200 mM was similar to bioleaching performance in the absent of NaCl. However, in the presence of NaCl, bioleaching by L. ferriphilum reduced by 50 %. For zinc-containing ores, bioleaching by L. ferriphilum and Sb. thermosulfidooxidans were compared. It is found that NaCl inhibited significantly bioleaching by L. ferriphilum and Sb. thermosulfidooxidans.