During ferrihydrite precipitation, metal ions can be sequestered in it to form impurity-bearing ferrihydrite (IBF). Using grazing-incidence small-angle X-ray scattering (GISAXS), heterogeneous precipitation/deposition of pure and IBF nanoparticles on quartz (SiO₂) and corundum (Al₂O₃) was quantified in 0.1 mM Fe³⁺ solutions in the absence and presence of 1 mM Mn²⁺ or Al³⁺ (pH = 3.8 ± 0.1). The impurity ions (Mn and Al) greatly affected ferrihydrite nanoparticle precipitation/deposition on substrates. On SiO₂, ferrihydrite nanoparticle precipitation/deposition was promoted in the presence of Mn but was inhibited in the presence of Al. On Al₂O₃, Mn- and Al-bearing ferrihydrite nanoparticle precipitation/deposition was slower than for pure ferrihydrite. Compared with on SiO₂, pure and IBF nanoparticle precipitation/deposition on Al₂O₃ was significantly inhibited. To understand the mechanisms, interactions among impurity ions, substrates, and precipitates were explored. Surface enrichment of Mn and Al on precipitates was found to increase the zeta potential of ferrihydrite nanoparticles. The changes in surface charges of the precipitates and substrates affected heterogeneous IBF precipitation/deposition significantly. The rates and mechanisms of heterogeneous IBF precipitation/deposition provided here can help predict pollutant transport and design catalyst synthesis.

中文翻译：

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含杂质的水铁矿纳米颗粒在石英和刚玉上的沉淀/沉积†

在三水铁矿沉淀过程中，金属离子可以螯合在其中，形成含杂质的三水铁矿（IBF）。使用掠入射小角度X射线散射（GISAXS），在不存在的情况下，在0.1 mM Fe ³⁺溶液中定量分析了纯的和IBF纳米颗粒在石英（SiO ₂）和刚玉（Al ₂ O ₃）上的异质沉淀/沉积。并存在1 mM Mn ²⁺或Al ³⁺（pH = 3.8±0.1）。杂质离子（Mn和Al）极大地影响了水铁矿纳米颗粒在基材上的沉淀/沉积。在SiO _2上，锰的存在促进了水铁矿纳米颗粒的沉淀/沉积，而铝的存在则抑制了铁水合物纳米颗粒的沉淀/沉积。在Al _2上含O ₃，Mn和Al的铁水合物纳米颗粒的沉淀/沉积速度比纯铁水合物慢。与SiO ₂相比，Al ₂ O ₃上纯净和IBF纳米颗粒的沉淀/沉积受到明显抑制。为了理解机理，探索了杂质离子，底物和沉淀物之间的相互作用。发现沉淀物上的Mn和Al表面富集会增加水铁矿纳米颗粒的Zeta电位。沉淀物和底物表面电荷的变化显着影响了异质IBF沉淀/沉积。此处提供的异质IBF沉淀/沉积的速率和机理可以帮助预测污染物的迁移并设计催化剂的合成。