Novel microorganism for selective separation of coal from pyrite and ash. Final report

Abstract

In keeping with the main objective of the project, the separation of fine coal from ash and pyrite was conducted using a microorganism Mycobacterium phlei (M. phlei). The surface hydrophobicity and surface charge ofMycobacterium phlei and it's sonicated products (extracellular soluble fractions) were established using contact angle and electrophoretic measurements.Mycobacterium phlei was highly hydrophobic and point-of-zero charge was around pH 2. The hydrophobic character and negative surface charge of the microorganism above pH 2 were due to the presence of excessive fatty groups at the surface and corresponding carboxylate groups. In addition, soluble fractions derived from the cell exhibited the presence of varying amounts of fatty acids ranging from C,, -C,, carbon chain and phosphate groups.The surface chemistry analyses of coal, coal-pyrite, mineral pyrite and quartz were conducted. The adhesion of Mycobacterium phlei onto coal, coaliii .. ..e..,,-pyrite and quartz was measured as a function of pH and Mycobacterium phlei concentration. It was noticed that Mycobacterium phlei selectively attached to hydrophobic coal particles and did not attach to hydrophilic mineral fractions.Adhesion was strongly dependent on pH and maximum adhesion was observed in an acidic pH range of 3-4.On the basis of the detailed surface chemistry analysis, adhesion and contact angle measurements, a series of flocculation and flotation experiments were conducted. The experimental results showed that Mycobacterium phlei was an excellent flotation collector and flocculating agent. However, the soluble fkaction derived from Mycobacterium phlei by sonication was a better flotation collector and flocculating agent for fine coal than whole cells of Mycobacterium phlei. In order to selectively separate the coal-Myco bacterium phlei entities, a modified floc-flotation technique was used. At an optimized experimental condition, more than 70 percent pyritic sulfur and 60 percent of ash could be rejected with a combustible (clean coal) recovery of 90 percent. During this investigation, it was established that Mycobacterium phlei and more importantly it's sonication products had a strong potential to be used for selective flocculation and separation of fine coal from associated mineral matters.. . . The impurities occurring in coal may be classified broadly into those that form ash and those that contribute sulfur. From the standpoint of coal cleaning, both the ash-forming and the sulfur-containing impurities may be subdivided into two categories -inherent and extraneous. The inherent impurities are inseparably combined with the coal. The extraneous impurities are segregated and can be eliminated by the available cleaning methods.Sulfur occurs in coal in three different forms. It is present in organic compounds as part of the coal substance, as sulfides, generally pyrite or marcasite, and as sulfate. The amount of organic sulfur normally is not over 3%.The sulfates, mainly calcium and iron, rarely exceed a few hundredths...

Algal Lipids as Biocollector for Recovery of Coal from Fine Coal Waste by Froth Flotation

“…The addition of a collector is required for improving the coal floatability. Much research has focussed on suitable collectors for fine coal flotation [15][16][17][18]. Standard fuel oil or kerosene is the most commonly used coal flotation reagent.…”