A density functional theory investigation of oxalate and Fe(II) adsorption onto the (010) goethite surface with implications for ligand- and reduction-promoted dissolution
A density functional theory investigation of oxalate and Fe(II) adsorption onto the (010) goethite surface with implications for ligand- and reduction-promoted dissolution
复制标题
DOI：
10.1016/j.chemgeo.2016.08.010
复制
发表时间：
2017-08
期刊：
影响因子：
3.9
通讯作者：
J. Kubicki;D. Tunega;S. Kraemer
中科院分区：
文献类型：
--
作者：
J. Kubicki;D. Tunega;S. Kraemer
草酸是自然环境中一种重要的生物产物。去质子化的形式，草酸盐，是占主导地位的水溶液中的circumneutral pH条件下，是一个强配体的Fe（III）。草酸盐对Fe（III）的高亲和力意味着Fe（III）-草酸盐表面和水性络合物是常见的，并且可以导致配体增强的溶解。Fe（II）在针铁矿（α-FeOOH）上的吸附增强了溶解-重结晶反应。针铁矿（010）面是这种环境关键的氢氧化铁相上更常见和反应性更强的表面之一。因此，本研究模型的草酸盐和Fe（II）的（010）面针铁矿上的单独和协调的吸附，以测试配体促进和还原溶解的协同效应。周期性和集群密度泛函理论（DFT）的能量最小化进行，以确定各种配置的结构，振动频率和能量。通过与红外光谱的比较，验证了草酸根的吸附机理。讨论了草酸盐和Fe（II）在配体促进针铁矿还原溶解中的潜在作用。
Oxalic acid is an important, biologically-produced species in the natural environment. The deprotonated form, oxalate, is dominant in aqueous solutions under circumneutral pH conditions and is a strong ligand for Fe(III). The high affinity of oxalate for Fe(III) means that Fe(III)-oxalate surface and aqueous complexes are common and can lead to ligand-enhanced dissolution. Fe(II) adsorption onto goethite (α-FeOOH) has been shown to enhance dissolution-recrystallization reactions. The goethite (010) face is one of the more common and reactive surfaces on this environmentally critical Fe-hydroxide phase. Hence, this study models both separate and coordinated adsorption of oxalate and Fe(II) onto the (010) face of goethite in order to test for synergistic effects of ligand-promoted and reductive dissolution. Periodic and cluster density functional theory (DFT) energy minimizations were performed to determine the structure, vibrational frequencies and energies of various configurations. The adsorption mechanism of oxalate is verified via comparison to observed IR spectra. The potential roles of oxalate and Fe(II) in ligand-enhanced reductive dissolution of goethite are discussed.