1.IntroductionThere is significant interest in reducing the amount of metal sulfide oxidation in the environment. Exposure of mine waste containing metal sulfides, such as pyrite, to air and water leads to the formation of acid-mine drainage (AMD).1,2Research in our laboratories has been focused recently on the use of phospholipids to suppress pyrite oxidation. Specifically, it has been shown that phospholipids, containing two long hydrocarbon tails and one polar head group, adsorb readily on pyrite in an aqueous suspension and inhibit the oxidative decomposition of the mineral. At a solution pH of 2, the adsorption of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (23:2 Diyne PC), which has the general structure shown below,3While the mechanism by which the lipid inhibits pyrite oxidation is not borne out by experiment, research in our laboratories suggest that the formation of a protective lipid bilayer is perhaps an important aspect.4Such a lipid structure would include a hydrophobic pocket to inhibit the interaction of water with the pyrite surface. As we have reported in a series of contributions, water is a key reactant in the oxidation of pyrite.5–7Hence, the notion is that by creating a hydrophobic layer or partial layer on the pyrite surface, oxidation would be inhibited or at least suppressed. It is mentioned that the investigation of phospholipids as a oxidation suppression agent developed from an earlier observation in our laboratory that showed that phosphate adsorbed alone on pyrite decreased the extent of pyrite oxidation at relatively high pH (>4), but was readily removed at a pH near 2.6It was then hypothesized that the hydrophobic tail of a phospholipid might stabilize the adsorbed phosphate group, that would be expected to bind the lipid to the pyrite surface.In this contribution we extend our investigation of 23:2 Diyne PC as an adsorbed phase that inhibits pyrite oxidation. Prior studies have shown that the ultra-violet (UV) irradiation of this lipid,8which has diacetylene groups in its hydrocarbon tails, leads to cross linking and polymerization in circumstances where there is a favorable alignment of neighboring lipid molecule tails. The scientific hypothesis in our research is that the cross-linking (i.e., polymerization) will lead to further pyrite oxidation inhibition, relative to the unpolymerized lipid, by providing a significant barrier between the pyrite surface and reactant. To test this hypothesis aqueous batch experiments, which measure the extent of pyrite oxidation with and without lipid, are presented. For reference, it is interesting to note that polymerizable phospholipids have been actively studied because of their biological importance and are often used as models for biomembranes in biochemical research.9Such lipids also have applications as carriers for drugs,9biosensors,10,11artificial red cells12and other advanced biomaterials.13