Nano Genevieve Villaseñor, Strathmann Timothy J
Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
J Colloid Interface Sci. 2006 May 15;297(2):443-54. doi: 10.1016/j.jcis.2005.11.030. Epub 2005 Dec 9.
Ferrous iron is critical to a number of biogeochemical processes that occur in heterogeneous aquatic environments, including the abiotic reductive transformation of subsurface contaminants. The sorption of Fe(II) to ubiquitous soil minerals, particularly iron-free mineral phases, is not well understood. Colloidal TiO2, gamma-AlOOH, and gamma-Al2O2 were used as model hydrous oxides to investigate Fe(II) sorption to iron-free mineral surfaces. Rapid Fe(II) sorption during the first few hours is followed by a much slower uptake process that continues for extended periods (at least 30 days). For equivalent solution conditions, the extent of Fe(II) sorption decreases in the order TiO2 >gamma-Al2O3 >>gamma-AlOOH. Short-term equilibrium sorption data measured over a wide range of conditions (pH, ionic strength, Fe(II)-to-sorbent ratio) are well described by the diffuse double layer model. Fe(II) sorption to TiO2 is best described by a single-site model that considers formation of two surface complexes, SOFe+ and SOFeOH0. For gamma-AlOOH and gamma-Al2O3, sorption data are best described by a two-site model that considers formation of SOFe+ complexes at weak- and strong-binding surface sites. Accurate description of sorption data for higher Fe(II) concentrations at alkaline pH conditions requires the inclusion of a Fe(II) surface precipitation reaction in the model formulation. The presence of common groundwater constituents (calcium, sulfate, bicarbonate, or fulvic acid) had no significant effect on Fe(II) sorption. These results demonstrate that iron-free soil minerals can exert a significant influence on Fe(II) sorption and speciation in heterogeneous aquatic systems.
亚铁对非均相水生环境中发生的许多生物地球化学过程至关重要，包括地下污染物的非生物还原转化。Fe(II)对普遍存在的土壤矿物质，特别是无铁矿物相的吸附作用尚未得到充分了解。使用胶体TiO2、γ-AlOOH和γ-Al2O3作为模型水合氧化物来研究Fe(II)对无铁矿物表面的吸附。最初几个小时内Fe(II)的快速吸附之后是一个持续较长时间（至少30天）的慢得多的吸收过程。在相同的溶液条件下，Fe(II)的吸附程度按TiO2>γ-Al2O3>>γ-AlOOH的顺序降低。在广泛的条件（pH、离子强度、Fe(II)与吸附剂的比例）下测量的短期平衡吸附数据可以很好地用扩散双层模型来描述。Fe(II)对TiO2的吸附最好用一个单点位模型来描述该模型考虑了两种表面络合物SOFe+和SOFeOH0的形成。对于γ-AlOOH和γ-Al2O3，吸附数据最好用一个双点位模型来描述，该模型考虑了在弱结合和强结合表面位点形成SOFe+络合物。要准确描述碱性pH条件下较高Fe(II)浓度的吸附数据，需要在模型公式中纳入Fe(II)表面沉淀反应。常见的地下水成分（钙、硫酸盐、碳酸氢盐或富里酸）的存在对Fe(II)的吸附没有显著影响。这些结果表明，无铁土壤矿物质可以对非均相水生系统中Fe(II)的吸附和形态产生重大影响。
