Precipitation of Hemicelluloses from DMSO/Water Mixtures Using Carbon Dioxide as an Antisolvent

Emmerich Haimer,Martin Wendland,Thomas Rosenau,Antje Potthast,Falk Liebner

doi:10.1155/2008/826974

Emmerich Haimer, Martin Wendland + Show 3 more

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https://doi.org/10.1155/2008/826974

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Abstract

Supercritical antisolvent precipitation is a relatively recent technology which can be used for controlled preparation of polymer particles from solutions. This is done by the addition of an antisolvent to a polymer solution causing supersaturation of the polymer, especially under supercritical conditions. The particle size of the precipitates can be adjusted mainly by the rate of supersaturation. Spherical xylan or mannan particles having a narrow particle size distribution were precipitated from hemicellulose solutions in dimethyl‐sulfoxide (DMSO) or DMSO/water mixtures by carbon dioxide as an antisolvent. By depending on the type of hemicellulose, the DMSO/H2O ratio, and the precipitation conditions such as pressure and temperature, the resulting particle size can be adjusted within a wide range from less than 0.1 to more than 5 μm. Nano‐ and microstructured native xylans and mannans as obtained can be used in many applications such as encapsulation of active compounds, slow release agents, or chromatographic separation materials.

Highlights

Biopolymers as renewable raw materials are currently attracting enormous interest
Spherical xylan or mannan particles having a narrow particle size distribution were precipitated from hemicellulose solutions in dimethyl-sulfoxide (DMSO) or DMSO/water mixtures by carbon dioxide as an antisolvent
With increasing CO2 content and after crossing the binodial, the homogeneous solution splits into a solvent/CO2 phase and a liquid phase which is rich in DMSO and hemicellulose

Summary

INTRODUCTION

Biopolymers as renewable raw materials are currently attracting enormous interest. Hemicelluloses represent an important percentage amongst these classes of natural compounds. With increasing CO2 content and after crossing the binodial, the homogeneous solution splits into a solvent/CO2 phase (point A) and a liquid phase which is rich in DMSO and hemicellulose (point A’). Continued addition of CO2 to point D leads to supersaturation in the polymer-rich liquid phase (point B’) and precipitation of hemicellulose particles. Increasing pressure and temperature beyond the critical values of the solvent/antisolvent mixture causes complete miscibility of the solvent with CO2. Precipitation under these conditions is no longer influenced by any mass transfer resistance. We would like to communicate the first results of antisolvent precipitation of hemicelluloses from solutions containing DMSO as the principal solvent. The controlled preparation of xylan and mannan particles was successful for both batch mode and semicontinuous mode

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSION