Department of Civil & Environmental Engineering, University of Houston , Houston, Texas 77004, United States.
Environ Sci Technol. 2015 Jan 6;49(1):292-300. doi: 10.1021/es504140k. Epub 2014 Dec 11.
Fe(III) hydroxide nanoparticles are an essential carrier for aqueous heavy metals. Particularly, iron hydroxide precipitation on mineral surfaces can immobilize aqueous heavy metals. Here, we used grazing-incidence small-angle X-ray scattering (GISAXS) to quantify nucleation and growth of iron hydroxide on quartz in 0.1 mM Fe(NO3)3 solution in the presence of Na(+), Cu(2+), Pb(2+), or Cr(3+) at pH = 3.7 ± 0.1. In 30 min, the average radii of gyration (R(g)) of particles on quartz grew from around 2 to 6 nm in the presence of Na(+) and Cu(2+). Interestingly, the particle sizes remained 3.3 ± 0.3 nm in the presence of Pb(2+), and few particles formed in the presence of Cr(3+). Quartz crystal microbalance dissipation (QCM-D) measurements showed that only Cr(3+) adsorbed onto quartz, while Cu(2+) and Pb(2+) did not. Cr(3+) adsorption changed the surface charge of quartz from negative to positive, thus inhibiting the precipitation of positively charged iron hydroxide on quartz. Masses and compositions of the precipitates were also quantified. This study provided new insights on interactions among quartz, iron hydroxide, and metal ions. Such information is helpful not only for environmental remediation but also for the doping design of iron oxide catalysts.
三价铁氢氧化物纳米颗粒是水相重金属的重要载体。特别是，矿物表面的氢氧化铁沉淀可以固定水相重金属。在这里，我们使用掠入射小角 X 射线散射（GISAXS）在 pH = 3.7 ± 0.1 的条件下，在 0.1 mM Fe(NO3)3 溶液中，定量研究了 Na(+)、Cu(2+)、Pb(2+) 和 Cr(3+)存在下石英上铁氢氧化物的成核和生长。在 30 分钟内，在 Na(+)和 Cu(2+)存在下，石英上颗粒的转动半径（R(g)）平均值从约 2nm 增加到 6nm。有趣的是，在 Pb(2+)存在下颗粒尺寸保持在 3.3 ± 0.3nm，而在 Cr(3+)存在下几乎没有颗粒形成。石英晶体微天平耗散（QCM-D）测量表明，只有 Cr(3+)被吸附到石英上，而 Cu(2+)和 Pb(2+)没有。Cr(3+)的吸附使石英的表面电荷从负变为正，从而抑制了带正电荷的铁氢氧化物在石英上的沉淀。还定量了沉淀物的质量和组成。本研究提供了有关石英、铁氢氧化物和金属离子之间相互作用的新见解。这些信息不仅有助于环境修复，而且有助于氧化铁催化剂的掺杂设计。
