Homogeneous and Heterogeneous (Fex, Cr1-x)(OH)3 Precipitation: Implications for Cr Sequestration
Homogeneous and Heterogeneous (Fex, Cr1-x)(OH)3 Precipitation: Implications for Cr Sequestration
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DOI：
10.1021/acs.est.5b04319
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发表时间：
2016-02-16
影响因子：
11.4
通讯作者：
Hu, Yandi
中科院分区：
文献类型：
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作者：
Dai, Chong;Zuo, Xiaobing;Hu, Yandi
（Fe，Cr）（OH）（3）纳米颗粒的形成决定了水溶液中Cr在许多水环境中的命运。使用小角X射线散射，在pH = 3.7 +/-0.2下，从含有0- 0.25mM Cr（III）的0.1mM Fe（III）溶液中定量溶液中和石英上的（Fe，Cr）（OH）（3）纳米颗粒的沉淀速率。Cr（III）/Fe（III）浓度比控制了（Fe-x，Cr 1-x）（OH）（3）沉淀的化学组成（x）、溶液相对于沉淀的过饱和度和石英表面电荷。因此，水溶液中Cr（III）/Fe（III）的比例通过不同的机制影响（Fe-x，Cr 1-x）（OH）（3）的均匀（在溶液中）和非均匀（在石英上）沉淀速率。还研究了沉淀物中Cr（III）的螯合机理。在具有高含水Cr（III）/Fe（III）比率的溶液中，发生Cr（III）在沉淀物上的表面富集，导致溶液中的颗粒生长较慢。从0-0.1 mM Cr（III）的溶液中，石英上的颗粒在1 h内从2 nm生长到4 nm。有趣的是，从0.25 mM Cr（III）的溶液中，在石英上形成了两种不同尺寸（2和6 nm）的颗粒，并且它们的尺寸在整个反应过程中保持不变。我们的研究为（Fe-x，Cr 1-x）（OH）（3）纳米颗粒的均匀和非均匀沉淀提供了新的见解，这有助于确定Cr在水环境中的归宿。
The formation of (Fe, Cr)(OH)(3) nanoparticles determines the fate of aqueous Cr in many aquatic environments. Using small-angle X-ray scattering, precipitation rates of (Fe, Cr)(OH)(3) nanoparticles in solution and on quartz were quantified from 0.1 mM Fe(III) solutions containing 0-0.25 mM Cr(III) at pH = 3.7 +/- 0.2. Concentration ratio of aqueous Cr(III)/Fe(III) controlled the chemical composition (x) of (Fe-x, Cr1-x)(OH)(3) precipitates, solutions' supersaturation with respect to precipitates, and the surface charge of quartz. Therefore, the aqueous Cr(III)/Fe(III) ratio affected homogeneous (in solution) and heterogeneous (on quartz) precipitation rates of (Fe-x, Cr1-x)(OH)(3) through different mechanisms. The sequestration mechanisms of Cr(III) in precipitates were also investigated. In solutions with high aqueous Cr(III)/Fe(III) ratios, surface enrichment of Cr(III) on the precipitates occurred, resulting in slower particle growth in solutions. From solutions with 0-0.1 mM Cr(III), the particles on quartz grew from 2 to 4 nm within 1 h. Interestingly, from solution with 0.25 mM Cr(III), particles of two distinct sizes (2 and 6 nm) formed on quartz, and their sizes remained unchanged throughout the reaction. Our study provided new insights on homogeneous and heterogeneous precipitation of (Fe-x, Cr1-x)(OH)(3) nanoparticles, which can help determine the fate of Cr in aquatic environments.