Neutralization Potential Determination of Siderite (FeCO₃) Using Selected Oxidants

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 Fe2+ and hydrolysis of Fe3+) 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 with the standard USEPA method. However, oxidation with H2O2 produced variable results depending on 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 most closely represent those intermediate products 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.

Mn- and Fe-carbonate rich layers in Meso-Cenozoic shales as proxies of environmental conditions: A case study from the southern Apennine, Italy

“…The dominant peak of FeCO 3 and MnCO 3 are weakly shifted, suggesting Fe partially substituted by Mg, and Mn partially substituted by Ca. These results are comparable with other previous studies on Mn-rich sediments (e.g., Middelburg et al, 1987;Glasby and Schulz, 1999;Haney et al, 2006).…”

Nitrite Reduction by Siderite

“…Past studies have documented the important role of O 2 in siderite oxidation. Resulting oxidation products include ferrihydrite (Duckworth and Martin, 2004), lepidocrocite, and goethite (Senkayi et al, 1986;Frisbee and Hossner, 1995;Haney et al, 2006). Our results show that NO 2 − can function as an oxidant of siderite under anoxic conditions and produce lepidocrocite as the primary mineral, which coexisted with goethite ( Fig.…”

“…Siderite [FeCO 3(s) ] is a common Fe(II) mineral produced as a result of secondary precipitation during microbial Fe(III) reduction under anoxic conditions (Coleman et al, 1993;Fredrickson et al, 1998;Zachara et al, 1998;Williams et al, 2005). Siderite has been shown to control Fe(II) solubility in anoxic sediments (Suess, 1979;Postma, 1982), rice paddy soil (Ratering and Schnell, 2000), subsoil peat horizons in close association with plant material (McMillan and Schwertmann, 1998), and coal overburden (Frisbee and Hossner, 1995;Haney et al,2006). Oxidants for FeCO 3(s) include O 2 (Frisbee and Hossner, 1995;Duckworth and Martin, 2004), Cr(VI) (Wilkin et al, 2005), H 2 O 2 (Jambor et al, 2003), and KMnO 4 (Haney et al, 2006).…”

Comparison of static and mineralogical ARD prediction methods in the Nordic environment

“…The ABA method has some disadvantages. Some carbonate minerals containing iron, particularly siderite (FeCO 3 ), do not necessarily contribute to neutralisation (Lawrence and Wang 1997 ; Haney et al 2006 ). The method does not take into account the reactive non-carbonate minerals that may contribute to acid neutralisation, e.g.…”