Quantitative NMR investigation on the low-temperature dissolution mechanism of chitin in NaOH/urea aqueous solution
The low-temperature dissolution mechanism of chitin in NaOH/urea aqueous solution has not been well established yet, especially at a temperature that lowers the crystallization temperature of both NaOH and urea. Using multiple nuclei (¹H, ¹⁵N and ²³Na) nuclear magnetic resonance (NMR) methods, we fi...
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Published in | Cellulose (London) Vol. 22; no. 4; pp. 2221 - 2229 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Dordrecht
Springer Netherlands
01.08.2015
Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | The low-temperature dissolution mechanism of chitin in NaOH/urea aqueous solution has not been well established yet, especially at a temperature that lowers the crystallization temperature of both NaOH and urea. Using multiple nuclei (¹H, ¹⁵N and ²³Na) nuclear magnetic resonance (NMR) methods, we find that the ternary NaOH/urea/D₂O system, different from the fully frozen binary NaOH–D₂O system, exhibits solid-liquid phase coexistence below −40 °C, and the residual liquid phase consists of certain concentrations of NaOH (10 wt%), urea (13 wt%) and D₂O at −40 °C. Our NMR results further demonstrate that chitin dissolves in the residual liquid phase (containing 5–10 wt% NaOH and 8–12 wt% urea) at low temperatures (−40 and −70 °C). An important role of urea is enhancing the low-temperature stability of NaOH aqueous solutions and then increasing the dissolution temperature range of chitin, thus providing an essential low-temperature liquid environment for chitin dissolution. |
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Bibliography: | http://dx.doi.org/10.1007/s10570-015-0667-2 |
ISSN: | 0969-0239 1572-882X |
DOI: | 10.1007/s10570-015-0667-2 |