گالن

In recent decades, the application of microorganisms and their products for the bioseparation of minerals, bioflotation, and bioflocculation, has been extensively recognized by researchers and industry. Considering several benefits of the bioseparation, in the current paper, a detailed review has been conducted on the bioseparation of galena from its most common accompanying minerals i.e. sphalerite, chalcopyrite, and pyrite using microorganisms and their extracellular products. Based on the findings, the bacterial cells of the Thiobacillus species have a good ability to depress and selectively flocculate galena, but the cells of the Polymyxa species have a lower ability. Therefore, they depress and flocculate most of the sulfide minerals present in the pulp. In addition, the adaptation of bacteria, especially polymyxa  species with galena and other minerals will increase extracellular secretions of protein or polysaccharides. Adapted Bacillus subtilis and Bacillus megatrium can separate galena. Due to the hydrophobic nature of extracellular proteins, their less absorption on the surface of galena compared to sphalerite, causes the second mineral to be floated and the galena to be depressed. On the other hand, adaptation leads to more protein secretion in the presence of galena compared to pyrite, which will cause galena to float and the second mineral to be depressed. Also, it can be said that the tendency of extracellular polysaccharides to adsorb on galena and the tendency of extracellular proteins to adsorb on sphalerite causes that when the mixture of these two minerals comes into contact with bacterial EPS, galena is usually depressed or flocculated and sphalerite floats to some extent.

Kooshk mine is one of the largest lead-zinc deposits in Iran. A high amount of pyrite and carbonaceous matter are two distinct characteristics of the Koosh deposit. Therefore, the competition between sphalerite, galena, and pyrite minerals and their selective separation in flotation is significant. In this research work, due to the low recovery of lead in the Kooshk flotation circuit, the possibility of pyrite depression and improvement of lead recovery by using various depressants was investigated. Pyrite and sphalerite depressants in galena flotation were used, such as sodium cyanide, sodium sulfite, sodium metabisulfite, iron sulfate, dextrin, Quebracho, SHQ (40% sodium silicate + 40% sodium phosphate + 20% Quebracho) and A3-3 (40% sodium silicate + 40% sodium metabisulfite + 20% aluminum sulfate). The results showed that each depressant, except dextrin, SHQ, and A3-3, significantly affected pyrite and sphalerite floatability, and lead recovery improved at some point during their consumption. Sodium cyanide, sodium metabisulfite, and sulfate iron showed the most effect in the depression of pyrite. In addition to sodium cyanide, the maximum pyrite & sphalerite depression and the maximum lead grade & recovery were obtained with the separate consumption of 600 g/t ferrous sulfate and 200 g/t sodium metabisulfite. Compared to other non-toxic depressants, iron sulfate, and sodium metabisulfite made pyrite and sphalerite depressants more effective and increased lead recovery by up to 8%.