Prevention of sulfide mineral leaching through covalent coating

The use of benzene-1,3-diamidoethanethiol as a covalent surface coating for the prevention of metal leaching was demonstrated with several sulfide minerals including cinnabar (HgS), pyrite (FeS2), chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), realgar (As4S4) and sphalerite (ZnS). The minerals were coated with sufficient H2BDT to bind the surface metals in a 1: 1 ratio. Leaching at pH 1, 3 and 7 was then conducted on both treated and untreated minerals. ICP and CVAFS (for mercury) analyses revealed that the coated minerals showed a dramatic reduction in metal leaching as compared to uncoated control samples. X-ray photoelectron spectroscopy indicated the formation of covalent bonds between the sulphur of the ligand and the metals from the minerals.