CHARACTERIZATION OF ADSORBED LAYERS ON SULFIDE MINERALS BY PHOTOELECTRON-SPECTROSCOPY

The systems galena/2-mercaptobenzothiazole (MBT) and pyrite/MBT have b een studied using synchrotron radiation excited photoelectron spectros copy (SRXPS). The chemisorption of MBT and the multilayer formation of 2,2'-dithiobis-(benzothiazole) (BBTD) are evidenced by additional str uctures, observed beside the substrate signals, in the S2p-spectra of cleaved mineral surfaces after adsorption of MBT. The amount of the co mplex remains constant at concentrations as high as 10(-5) mol/L where as the amount of BBTD increases. From the dependence of the adsorbate intensities on the excitation energy the conclusion can be drawn that an overlayer of BBTD on a chemisorbed layer of MBT is formed. The very weak adsorption of MBT on pyrite in alkaline solutions may explain th e selective flotation of galena from pyrite in alkaline media.