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.

Sulphur is one of the waste elements in coal material which is in two forms, organic and inorganic. The amount of sulphur more than acceptable quantity in coal concentration affects the environment and coke characteristics. The quality of steel is depended on the quantity of sulphur in coke. High sulphur in entering materials to the steel furnace causes inferior steel. Also, sulphur in heat coal makes SO2 gas which has negative environmental effects. Different chemical, physical and biological techniques are investigated for removing sulphur from coal. In recent years, new method for desulfurization from coal is expressed with improving biotechnology and microbial mining. In this research, feasibility study of depyritization from Tabas coal using bioflotation method in laboratory scale was considered. In these tests, Pyrite in coal pulp depressed with desulfurization bacteria. To carry out bio flotation tests, a sample from C1 seam (Tabas, Parvadeh Mine, no.2) was used. After comminuting and screening, the coal material less than 500 micron was used as flotation feed. AThiobacillus ferrooxidansbacterium was obtained from the biotechnology laboratory at Sarcheshme Copper Mine. Thiobacillus ferrooxidans was cultured in 9K medium. Bio flotation tests were carrying out in Denver flotation cell and the important parameters such as pulp density, particle size, bacterial density and interaction time were optimized. Final results indicated that by using the mentioned method, the pyritic and total sulphur were decreased about %62 and %35, respectively.

Tabas coal possesses favorable plastometric properties that make it suitable for use in metallurgical industries as coking coal. However, its high sulfur content, which stands at approximately 2%, poses a significant environmental pollution risk. Additionally, reducing ash content to below 10% is a critical objective of this study to prevent a decline in coal's thermal efficiency in the metallurgical industries. This research work investigates the removal of sulfur and ash from Tabas coal samples using the biological methods including bioflotation and bioleaching. Initially, a combination of mesophilic bacteria including Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, and Leptosprillium ferrooxidans were employed in the bioflotation method to detain pyrite sulfur in the Tabas coal samples. The highest reduction percentages of pyrite sulfur and ash were equal to 62% and 54.18%, respectively. In the next stage, bioleaching experiments were conducted, the effect of the test time, percentage of bacteria by volume, percentage of coal solids, and absence of bacteria on the amount of sulfur and ash removal was investigated. The test time emerged as the most critical factor. The best sulfur removal was achieved using bioleaching, with a maximum removal of 72.43%, observed for the PE coal sample. Bioflotation also achieved significant sulfur removal, with a maximum removal of 61% observed for the same sample. On the other hand, the best ash removal was achieved using bioflotation, with a maximum removal of 68.98% observed for the PE coal sample, and a maximum removal of 69.34% observed for the B4B2 coal sample using bioleaching. Finally, this research work conducted a comparison of biological methods to determine the amount of sulfur and ash reduction achieved. The results showed that both bioleaching and bioflotation were effective for coal desulfurization and ash removal, with bioleaching performing slightly better for sulfur removal and bioflotation performing slightly better for ash removal.