School of Environmental Science and Engineering, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong University of Technology, Guangzhou, 510006, China.
School of Environmental Science and Engineering, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong University of Technology, Guangzhou, 510006, China.
J Hazard Mater. 2020 Jun 15;392:122272. doi: 10.1016/j.jhazmat.2020.122272. Epub 2020 Feb 11.
The mobility of Cr(VI) in the environment is affected by the transformation of ferrihydrite (Fh) and ferrihydrite-humic acid co-precipitates (Fh-HA). However, the impacts of Fe(II)-induced transformation of Fh and Fh-HA on the mobility, speciation and partitioning of associated Cr(VI) remain unclear. In this study, the behaviors of adsorbed Cr(VI) during Fh and Fh-HA aging at 70 °C for 9 days (pH = 3.0 and 7.0) in the absence and presence of Fe(II) were studied. Results revealed that the main speciation of Cr(VI) after transformation was non-desorbable Cr and its formation involved the following pathways. Firstly, Fe(II) (0.2 and 2.0 mM) induced the transformation of Fh-HA to hematite and goethite, promoting the structural incorporation of adsorbed Cr into hematite and goethite via complexation. Secondly, under neutral condition (pH = 7.0), the low concentration of Fe(II) (0.2 mM) could not reduce completely Cr(VI) to Cr(III) and thus residual Cr(VI) was incorporated into the Cr(III)-Fe(III) co-precipitates. Thirdly, coprecipitated humic acid not only reduced Cr(VI) to Cr(III) via polysaccharide, but also formed complexes with incorporated Cr through carboxylic groups to sequester Cr. Our results demonstrate that Fe(II)-induced transformation of Fh-HA exerts major influences on associated Cr(VI) speciation and partitioning.
六价铬（Cr(VI)）在环境中的迁移性受针铁矿（Fh）和针铁矿-腐殖酸共沉淀物（Fh-HA）转化的影响。然而，Fe(II)诱导的 Fh 和 Fh-HA 转化对相关 Cr(VI)的迁移性、形态和分配的影响仍不清楚。在这项研究中，研究了在不存在和存在 Fe(II)的情况下，Fh 和 Fh-HA 在 70°C 下老化 9 天（pH 值分别为 3.0 和 7.0）过程中吸附 Cr(VI)的行为。结果表明，转化后 Cr(VI)的主要形态为不可解吸的 Cr，其形成涉及以下途径。首先，Fe(II)（0.2 和 2.0 mM）诱导 Fh-HA 向赤铁矿和针铁矿转化，通过络合作用促进吸附态 Cr 结构并入赤铁矿和针铁矿中。其次，在中性条件下（pH 值=7.0），低浓度的 Fe(II)（0.2 mM）不能将 Cr(VI)完全还原为 Cr(III)，因此残留的 Cr(VI)被并入 Cr(III)-Fe(III)共沉淀物中。第三，共沉淀的腐殖酸不仅通过多糖将 Cr(VI)还原为 Cr(III)，还通过羧酸基团与掺入的 Cr 形成配合物来螯合 Cr。我们的结果表明，Fh-HA 的 Fe(II)诱导转化对相关 Cr(VI)形态和分配有重大影响。
