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ARS Home » Research » Publications at this Location » Publication #181327
Title: NEUTRALIZATION POTENTIAL DETERMINATION OF SIDERITE (FECO3) USING SELECTED OXIDANTS

Author
item HANEY, E - STATE OF TX-RR COMMISSION
item Haney, Richard
item HOSSNER, L - TEXAS A&M UNIV
item WHITE, G - TEXAS A&M UNIV

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2005
Publication Date: 5/15/2006
Citation: Haney, E.B., Haney, R.L., Hossner, L.R., White, G.N. 2006. Neutralization potential determination of siderite (FeCO3) using selected oxidants. Journal of Environmental Quality. 35:871-879.

Interpretive Summary: Siderite (FeCO3) is commonly found in reclaimed soil and, when present, can cause interference in the determination of neutralization potential (NP) which effects soil pH. Since the value of the soil after reclamation is largely determined by soil pH, it is important to accurately test the soil pH. Many methods were tested and it was found that bubbling oxygen through the soil was best suited to remove the siderite and offer an accurate soil pH measurement.

Technical Abstract: Siderite (FeCO3) is commonly found in coal overburden and, when present, can cause interference in the determination of neutralization potential (NP). Under acidic testing conditions, FeCO3 reacts to neutralize acid, which contributes to the NP. However, continued weathering of FeCO3 (oxidation of Fe**2+ and hydrolysis of Fe**3+) produces a neutral to slightly acidic solution. The effects of hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and O2 on the laboratory measurement of NP of siderite samples taken from overburden were examined. All oxidation treatments lowered the NP values of the siderite samples as compared to the standard EPA method. However, oxidation with H2O2 produced variable results depending upon the amount of H2O2 added. Neutralization potential values obtained after oxidation treatments were highly correlated with Mn concentration. Reaction products (i.e., 2-line ferrihydrite) of siderite samples with H2O2 and KMnO4 were not representative of natural siderite weathering. Oxidation with O2 produced the lowest NP values for siderite samples. The reaction products produced by oxidation with O2 represent those formed when siderite is exposed to atmospheric weathering conditions. Oxidation with O2 also proved to be the most reproducible method for accurately assessing NP when siderite is present in overburden samples.