Impact of Weak Organic Acids as Coagulants on Tailoring the Properties of Cellulose Aerogel Beads.

Abstract

Tailoring the properties of cellulose aerogel beads was investigated in the present study by using weak organic acids as coagulants. Three different weak acids were specifically chosen, acetic acid, lactic acid and citric acid. For comparative studies, a strong acid, hydrochloric acid was examined. The production of aerogel beads by conventional dropping technique was controlled and optimized for weak acids. Aerogels were characterized by density analyses, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. In common, all the aerogel beads showed interconnected nanofibrillar network, high specific surface area, high pore volume, high porosity and meso- and macroporous structure. In particular, when the weakest acid (acetic acid) was used as coagulant in the regeneration bath, the lowest shrinkage was observed. As a result, the cellulose aerogel beads produced from acetic acid showed the highest values of specific surface area (423 m2 g-1) and pore volume (3.6 cm3 g-1). The porous structure can be tuned by the choice of regeneration bath, which has either strong acid or a high concentration of weak acid. The aerogel beads were pure and showed cellulose II crystallinity. Hence this study paves an alternative path way to tailor the properties of cellulose aerogel beads.