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Potential Microencapsulation of Pyrite by Artificial Inducement of Ferric Phosphate Coatings
Author(s) -
Evangelou V. P.
Publication year - 1995
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1995.00472425002400030021x
Subject(s) - pyrite , leaching (pedology) , ferric , chemistry , oxidizing agent , phosphate , iron phosphate , coating , inorganic chemistry , hydrogen peroxide , sulfur , mineralogy , chemical engineering , geology , organic chemistry , soil science , engineering , soil water
Pyrite in mining waste is initially oxidized by the atmospheric O 2 , releasing acidity and Fe 2+ . At a pH below 3.5, Fe 2+ is rapidly reoxidixed by Thiobacillus ferrooxidans to Fe 3+ , which oxidizes pyrite at a much faster rate than O 2 . Commonly, the approach used in preventing pyrite oxidation in the field involves the use of limestone. This approach, however, has a short span of effectiveness because the surfaces of pyrite particles in mining waste are still exposed to the atmospheric O 2 after treatment. The objective of this study was to examine the feasibility in controlling pyrite oxidation by creating an FePO 4 coating on pyrite surfaces to block access of the atmospheric O 2 to pyritic surfaces. The coating methodology involved leaching pyrite using a chromatographic column with a 1 cm i.d. and a flow rate of 0.5 mL min −1 at 40°C with a PO 4 solution containing hydrogen peroxide (H 2 O 2 ); when this solution reached pyrite surfaces, H 2 O 2 oxidized the surface portion of pyrite and released Fe 3+ so that Fe phosphate precipitated and formed a passive coating on pyritic surfaces. This laboratory‐scale study demonstrated that Fe phosphate coatings on pyritic surfaces could be established with a solution containing as low as 10 −4 tool L −1 phosphate and 0.03 mol L −1 H 2 O 2 and that the FePO 4 phosphate coating could effectively protect pyrite from oxidizing further.