Acid production from sulfide minerals using hydrogen pet-oxide weathering

Sulfide mineral weathering is a major source of acid generation in mining e nvironments. Oxidation and hydrolysis reactions in soil and geologic materi al under earth surface conditions causes weathering of reduced sulfide mine rals resulting in liberation of weathering products including acid. Pyrite and marcasite are minerals common in mine environments that cause acid gene ration. Many other sulfide minerals are present in mining environments whic h may or may not form acid upon weathering. Characterization of complex min eral assemblages containing S compounds is therefore critically important t o pre-mine planning and postmine waste characterization. Despite the import ance of mineral weathering behavior, little is known about the acid generat ion characteristics of common sulfide and sulfate minerals. To assess the r esponse of common sulfide and sulfate minerals to oxidizing conditions, 13 minerals were subjected to treatment with 10% H2O2. The resulting leachate was analyzed for pH, electrical conductivity, S and titratable acidity. The sulfide minerals arsenopyrite, pyrite, chalcopyrite, pyrrhotite, marcasite and sphalerite demonstrated significantly elevated levels of titratable ac idity and are acid generating in contrast to galena, chalcocite and all the sulfates. The sulfate minerals barite, anhydrite, gypsum, anglesite and ja rosite were included in experimentation and were found not to form acid und er strongly oxidizing conditions. Remediation strategies for disturbed land s containing reduced S minerals must therefore consider not only the total quantity of sulfide minerals present, but the specific mineralogy of the S compounds. (C) 1999 Elsevier Science Ltd. All rights reserved.