期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 50, 期 4, 页码 1741-1749出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.5b04319
关键词
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资金
- University of Houston
- U.S. Department of Energy, Office of Science, Office of Basic Energy Science [DE-AC02-06CH11357]
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.
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