Adsorption of phospholipids on pyrite and their effect on surface oxidation

Pyrite, FeS2, oxidation in nature has severe environmental implications. The adsorption of two-tail phospholipids on polycrystalline pyrite was investigated as a means to suppress the oxidation chemistry. Attenuated total reflection Fourier transform infrared spectroscopy suggested that the binding of long-chain, two-tail lipids, such as L-alpha-phosphatidylcholine, hydrogenated (egg, chicken) lipid and 1,2-bis-(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine occurred primarily through the phosphate group of the lipid headgroup. The adsorption of this type of lipid on pyrite resulted in a strong suppression of the oxidation of the mineral under oxic conditions down to a pH of 1.0. No such oxidation suppression was experimentally observed when 1,2-dipropionoyl-sn-glycero-3-phosphocholine, a short-chain, two-tailed lipid, was used to form an adsorbed phase. The difference in the oxidation suppression efficacy suggested that the length of the hydrophobic tail is an important attribute in this regard. Experimental observations suggested that the long-chain, two-tail lipids formed structures on the pyrite surface that were at least in part thicker than a bilayer structure.