کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6436518 1637577 2015 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Copper sorption by the edge surfaces of synthetic birnessite nanoparticles
ترجمه فارسی عنوان
جذب مس توسط سطوح لبه نانوذرات خلوصتی مصنوعی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
چکیده انگلیسی


- The reactivity of the particle edges in nanoparticulate birnessite is investigated.
- EXAFS spectroscopy is used to elucidate the mechanism of copper sorption.
- Jahn-Teller distortion and polymerization limit copper adsorption at vacancies.
- Copper binds dominantly at edges as dimers or polynuclear surface species.

We investigated the sorption of Cu by δ-MnO2, an analog for natural birnessite (layer-type Mn oxide) that is characterized by randomly stacked and curled nanosheets, a low to moderate vacancy content, and variable amounts of layer and interlayer Mn3 +. The synthetic δ-MnO2 used in this study had a Na:Mn molar ratio of 0.13, an average manganese oxidation number (AMON) of 3.85 after reaction, a specific surface area of 254 m2 g− 1 and a particle size of 2-4 nm in the ab plane. The maximum surface excess (qmax) value at pH 6 estimated from sorption data of 0.72 (0.64-0.83, 95% confidence interval) mol Cu mol− 1 Mn far exceeded the nominal vacancy content for δ-MnO2 (ca. 6-11% mol vacancy mol− 1 Mn), thus implicating multiple binding sites for Cu. The large values of qmax and specific surface area of the mineral suggest a major role for surface sites at the particle edges relative to vacancy sites. The extended X-ray absorption fine structure (EXAFS) spectra from δ-MnO2 samples differ with respect to the EXAFS spectra for Cu(OH)2, CuO, and Cu3(CO3)2(OH)2 and Cu-sorbed by biogenic MnO2. The Cu K-edge EXAFS spectra show two second-shell peaks that can be modeled with Mn and Cu near-neighbors. Copper appears to bind dominantly at particle edges of δ-MnO2 as dimers or polynuclear surface species. This sorption mechanism is consistent with the moderate vacancy content of δ-MnO2 and explains the similarity in the EXAFS spectra from samples having surface loadings of 0.01 to 0.26 mol Cu mol− 1 Mn. The strong proclivity of Cu to bind on the edge surfaces of nanoparticulate birnessite leads to very large surface excesses of Cu without the formation of a discreet precipitate, making the surface sites at the particle edges the dominant sorption site for Cu.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Geology - Volume 396, 9 March 2015, Pages 196-207
نویسندگان
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