Aerogels Based on Silicon Dioxide and Lignosulfonate

Currently, there is considerable interest in the synthesis of aerogels based on natural polymers. The use of biopolymers is due to their physical and chemical properties, availability, non-toxicity, and the renewable nature of the raw materials needed for their production. These characteristics are possessed by lignosulfonates – sulfonates of the natural biopolymer lignin, formed as a result of sulfite (bisulfite) delignification of wood. Composite aerogel materials attract special attention by combining the properties of both organic and inorganic components. The incorporation of biopolymers into the matrix of nanocomposite aerogels can improve their consumer properties. The aim of this work has been the synthesis of aerogels based on silicon dioxide and sodium lignosulfonate, the study of gelation in the “sodium lignosulfonate – silicon dioxide” system and the assessment of the influence of synthesis conditions on the formation of the structure of aerogel materials based on them. Hydrogels based on components of various chemical natures of sodium lignosulfonate and silicon dioxide, have been obtained by sol-gel synthesis. It has been shown that strong elastic gels are formed at silicon dioxide concentrations above 175 g/l. It has been established that modification of sodium lignosulfonates with silicon dioxide leads to particle aggregation and an increase in their size. Aerogel materials based on sodium lignosulfonate and silicon dioxide, obtained at different molar ratios of componets (the mass fraction of lignosulfonate in the system), have a developed inner surface, the specific surface area is 250...452 m2/g, the total pore volume varies from 0.84 to 2.00 cm3/g. It has been shown that with an increase in the mass fraction of lignosulfonate in the system, the textural characteristics of synthesized composite aerogel materials change: an increase in the specific surface area and pore volume of the obtained materials is observed. With a sodium lignosulfonate content of 6…25 % in the system, the specific surface area of composite aerogels is 250…325 m2/g; with an increase in the proportion of sodium lignosulfonate in the system to 33...50 %, it reaches 357…452 m2/g. The synthesized materials can be used as sorbents, sensor devices, and catalyst carriers.