Inhibition of pyrite oxidation by surface treatment

Pyrite samples were analyzed from two distinct locales with the intent of determining the extent of oxidative inhibition occurring in the presence of a passivating agent. Each sample was exposed to air and 9% H2O2 as oxidizing agents over specific time periods with and without the presence of an iron oxide layer on the pyritic surface. The samples were submitted to passivating agents which created reversible interactions protecting and altering the surface. The type of coating agent (acetyl acetone, humic acids, ammonium lignosulfonates, oxalic acid or sodium silicate) and the quality of the surface prior to oxidation were used to determine the effectiveness of the passivating agents. Hydrogen peroxide was utilized to provide a long-term overview of the results because of its harshness as an oxidizing agent. The air oxidation results are linked to the trend shown by the peroxide results and, in each sample type, the use of passivation (especially with pre-oxidation) proved to be effective. In the presence of peroxide with pre-oxidative treatment, the acetyl acetone was able to reduce oxidation by 53% in the NWT sample (22% in the K.C. sample) and sodium silicate reduced oxidation by 55% in the K.C. sample (42% in the NWT sample). (C) 1997 Elsevier Science B.V.