Pyrite oxidation inhibition in coal waste by PO4 and H2O2pH-buffered pretreatment
Titel:
Pyrite oxidation inhibition in coal waste by PO4 and H2O2pH-buffered pretreatment
Auteur:
Evangelou, V.P.
Verschenen in:
International journal of mining, reclamation and environment
Paginering:
Jaargang 10 (1996) nr. 3 pagina's 135-142
Jaar:
1996
Inhoud:
Pyrite is coal waste is initially oxidized by atmospheric O2, releasing acidity and Fe2+. At pH around 3, Fe2+ is rapidly oxidized by T. ferrooxidans to Fe3+ which oxidizes pyrite at a much faster rate than O2. Commonly, the approach used to prevent pyrite oxidation in the field involves the use of limestone. This approach, however, has a short span of effectiveness. The objective of this study was to demonstrate that pyrite oxidation inhibition (in the absence or presence of coal waste) may take place when a pyritic sample is pre-treated with a solution of H2O2plus sodium acetate (NaAQ) with or without phosphate (PO4 buffered at pH around 5. This objective was tested by pre-treating pyrite (with or without coal waste) with the above pretreatment solution in a chromatographic column with a 1 cm i.d. and a flow rate of 0.5 ml min-1. When the pretreatment solution reached pyrite surfaces, H2O2 oxidized the surface portion of pyrite and released Fe3+ so that FePO4 or Fe-OOH precipitated and formed a coating on pyritic surfaces. This laboratory-scale study demonstrated that the iron phosphate or Fe-OOH coating could be established with a solution composed of 10-4 to 10-2 mol L-1 KH2PO4 (or without phosphate in the case of Fe-OOH coating), 0.159 mol L-1 H2O2, and greater than 0.01 mol L-1 NaAC at approximately pH 5. The percent of pyrite consumed for creating these coatings ranged from 5-10%. The FePO4 or Fe-OOH coating on pyrite surfaces was shown to inhibit pyrite oxidation in the presence/absence of coal waste. However, formation of Fe-OOH coating required a greater portion of pyrite to be consumed and appeared to be less effective in inhibiting pyrite oxidation than the phosphate coating. The process requires testing under field conditions.
Tijdschrift beschrijving