Tai Yuan-Liang, Dempsey Brian A
Department of Civil and Environmental Engineering, The Pennsylvania State University, University Park, 212 Sackett Building, PA 16802, United States.
Water Res. 2009 Feb;43(2):546-52. doi: 10.1016/j.watres.2008.10.055. Epub 2008 Nov 27.
Fe(II)/Fe(III) oxide is an important redox couple in environmental systems. Recent studies have revealed unique characteristics of Fe(II)/Fe(III) oxide and reactions with oxidizing or reducing agents. Nitrite was used as an oxidizing agent in this study in order to probe details of these reactions and hydrous ferric oxide (HFO) was used as the Fe(III) oxide phase. Abiotic nitrite reduction is a significant global producer of nitric oxide (a catalyst for production of tropospheric ozone) and nitrous oxide (a greenhouse gas and contributor to stratospheric ozone depletion). All experiments were conducted at pH 6.8 using a strictly anoxic environment with mass-balance measurements for Fe(II). Oxidation of Fe(II) was negligible in the absence of HFO. The reaction was fast in the presence of HFO and was described by d[Fe(II)]/dt=-k(overall)[Fe(II)(diss)][Fe(II)(solid-bound)][NO(2)(-)] (k(overall)=2.59x10(-7)microM(-2)min(-1)) for Fe(II)/Fe(III) molar ratios less than 0.30. The reaction was inhibited for higher Fe(II)/HFO ratios. The concentration of solid-bound Fe(II) was constant after an initial equilibration period and the reaction stopped when dissolved Fe(II) was depleted even though substantial solid-bound Fe(II) and nitrite remained. The results regarding rate-dependence and conservation of solid-bound Fe(II) and inhibition of reaction at high Fe(II)/Fe(III) ratios were similar to our earlier results for the Fe(II)/HFO/O(2) system [Park, B., Dempsey, B.A., 2005. Heterogeneous oxidation of Fe(II) on ferric oxide at neutral pH and a low partial pressure of O(2). Environmental Science and Technology 39(17), 6494-6500.].
Fe(II)/Fe(III) 氧化物是环境系统中一种重要的氧化还原对。近期研究揭示了Fe(II)/Fe(III) 氧化物的独特特性以及与氧化剂或还原剂的反应。本研究中使用亚硝酸盐作为氧化剂以探究这些反应的细节，并使用水合氧化铁（HFO）作为Fe(III) 氧化物相。非生物亚硝酸盐还原是全球一氧化氮（对流层臭氧生成的催化剂）和氧化亚氮（一种温室气体且是平流层臭氧消耗的促成因素）的重要产生途径。所有实验均在pH 6.8下进行，采用严格的缺氧环境，并对Fe(II) 进行质量平衡测量。在没有HFO的情况下，Fe(II) 的氧化可忽略不计。在有HFO存在时反应很快，对于Fe(II)/Fe(III) 摩尔比小于0.30的情况，反应速率符合d[Fe(II)]/dt = -k(overall)[Fe(II)(溶解态)][Fe(II)(固相结合态)][NO₂⁻]（k(overall) = 2.59×10⁻⁷ μM⁻² min⁻¹）。对于更高的Fe(II)/HFO比值，反应受到抑制。经过初始平衡期后，固相结合态Fe(II) 的浓度保持恒定，并且当溶解态Fe(II) 耗尽时反应停止，尽管仍有大量固相结合态Fe(II) 和亚硝酸盐残留。关于反应速率依赖性、固相结合态Fe(II) 的守恒以及在高Fe(II)/Fe(III) 比值下反应受到抑制的结果与我们早期关于Fe(II)/HFO/O₂ 系统的结果相似[Park, B., Dempsey, B.A., 2005. 中性pH和低氧分压下Fe(II) 在氧化铁上的非均相氧化。《环境科学与技术》39(17), 6494 - 6500。]
