Facile preparation of monolithic κ-carrageenan aerogels

Abstract

Carrageenans are a group of naturally available anionic polysaccharides having sulfate functional groups. Due to their renewable source, ease of production, biodegradability, presence of anionic sulfate functional groups and gelling nature1, open porous materials of carrageenan may draw good attention in many applications like other polysaccharides e.g., calcium alginate, chitosan and cellulose aerogels2. Aerogels based on polysaccharides containing cationic or anionic functional groups are in great demand because they could be used as host for applications where high chemical affinity to guest atoms/molecules is essential. It is demonstrated in the literatures that carrageenan can give good chelating effect to minerals and nanoparticles in composite structures3-6. Our interest is to prepare monolithic form of κ-carrageenan aerogel. Aerogels of κ-carrageenan were successfully synthesized and their properties were investigated by envelope density analyzer, scanning electron microscopy and N2 adsorption-desorption analysis. The concentrations of κ-carrageenan were varied between 0.5 and 3 wt %. Aerogels showed volume shrinkage, 55-65 %, depending upon the concentration of κ-carrageenan. The envelope density was in the range between 42-160 kg.m-3. For all concentrations, the specific surface area of aerogels was about 225 m2.g-1. The interconnected fibrillar structures of aerogel and fibre thickness were characterized by scanning electron microscope. The pore size distribution was observed to be broad, ranging from meso- to macroporous.