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.