Bacteria as Flotation Reagents for the Flotation of a Dolomitic Phosphate Rock
The mineralogical characteristics of two Florida dolomitic phosphates were investigated by microscopic analysis, liberation degree analysis, and BET surface area measurement. The growth of two bacteria Mycobacteria phlei and Bacillus licheniformis JF-2, and study on some of their properties in aqueous solutions were conducted through electrokinetics, contact angle, and surface tension measurements. The experimental work on the micro flotation of pure apatite and dolomite and flotation of the real Florida dolomitic phosphate pebble samples were also conducted using bacteria as both collector and depressant in anionic collector flotation. The results of the investigations and experiments indicated that apatite in the phosphate pebble samples has good liberation from other minerals and a very large surface area, which is the major reason for high reagent consumption and low flotation selectivity. The cell walls of both M.phlei and B.licheniformis JF-2 include very active biosurfactants, which can remarkably reduce the surface tension of the suspensions and increase the contact angle of minerals they adsorb onto in aqueous solution. The results of experiments indicate that M.phlei was markedly adsorbed on the dolomite and apatite surfaces. The bacterium demonstrated more affinity towards dolomite than apatite, and that B.licheniformis JF-2 has even more affinity than M.phlei for adhesion onto dolomite. Flotation tests revealed that both bacteria act as a depressant of dolomite during phosphate flotation using anionic collectors. A flotation concentrate less than 1% MgO content can be obtained from Florida phosphate pebble flotation.