Abstract
Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid-liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extractant, which takes place at the liquid-liquid interface experimentally and theoretically. Raman spectroscopy for the microflow reactor provided the concentration of boric acid after extraction, whereas density functional theory calculation showed the reaction energy profiles of the underlying chemical reactions. Calculation results suggested that H2O molecules from the aqueous phase promote extraction by enabling the formation of [BOH-HOH-HOC], a sufficiently stable, nonsteric structure, which stabilizes the transition state and facilitates boric acid esterification. Otherwise, this reaction cannot take place in standard conditions. Raman spectroscopy applied to the extraction process in a microflow reactor supported this conclusion experimentally. These results suggest that the extraction reaction at the liquid-liquid interface is mass transfer-limited. This can help the design of effective reactors to eliminate boron impurity from silica solution.
| Original language | English |
|---|---|
| Pages (from-to) | 10423-10429 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry C |
| Volume | 122 |
| Issue number | 19 |
| DOIs | |
| Publication status | Published - 2018 May 17 |
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ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Energy(all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
Cite this
Spectroscopic and Computational Analyses of Liquid-Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes. / Kunimoto, Masahiro; Bothe, Dieter; Tamura, Risa; Oyanagi, Takahiro; Fukunaka, Yasuhiro; Nakai, Hiromi; Homma, Takayuki.
In: Journal of Physical Chemistry C, Vol. 122, No. 19, 17.05.2018, p. 10423-10429.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Spectroscopic and Computational Analyses of Liquid-Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes
AU - Kunimoto, Masahiro
AU - Bothe, Dieter
AU - Tamura, Risa
AU - Oyanagi, Takahiro
AU - Fukunaka, Yasuhiro
AU - Nakai, Hiromi
AU - Homma, Takayuki
PY - 2018/5/17
Y1 - 2018/5/17
N2 - Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid-liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extractant, which takes place at the liquid-liquid interface experimentally and theoretically. Raman spectroscopy for the microflow reactor provided the concentration of boric acid after extraction, whereas density functional theory calculation showed the reaction energy profiles of the underlying chemical reactions. Calculation results suggested that H2O molecules from the aqueous phase promote extraction by enabling the formation of [BOH-HOH-HOC], a sufficiently stable, nonsteric structure, which stabilizes the transition state and facilitates boric acid esterification. Otherwise, this reaction cannot take place in standard conditions. Raman spectroscopy applied to the extraction process in a microflow reactor supported this conclusion experimentally. These results suggest that the extraction reaction at the liquid-liquid interface is mass transfer-limited. This can help the design of effective reactors to eliminate boron impurity from silica solution.
AB - Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid-liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extractant, which takes place at the liquid-liquid interface experimentally and theoretically. Raman spectroscopy for the microflow reactor provided the concentration of boric acid after extraction, whereas density functional theory calculation showed the reaction energy profiles of the underlying chemical reactions. Calculation results suggested that H2O molecules from the aqueous phase promote extraction by enabling the formation of [BOH-HOH-HOC], a sufficiently stable, nonsteric structure, which stabilizes the transition state and facilitates boric acid esterification. Otherwise, this reaction cannot take place in standard conditions. Raman spectroscopy applied to the extraction process in a microflow reactor supported this conclusion experimentally. These results suggest that the extraction reaction at the liquid-liquid interface is mass transfer-limited. This can help the design of effective reactors to eliminate boron impurity from silica solution.
UR - http://www.scopus.com/inward/record.url?scp=85047475773&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85047475773&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.8b01086
DO - 10.1021/acs.jpcc.8b01086
M3 - Article
AN - SCOPUS:85047475773
VL - 122
SP - 10423
EP - 10429
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 19
ER -