Influence of the Nature of the Crosslinking Agent on the Structure and Properties of the Organic Xerogels Obtained from Cedar Bark Tannins

Objective: To synthesize organic xerogels from Siberian cedar bark tannins and study the effect of different crosslinking agents (formaldehyde, furfuryl alcohol, glutaraldehyde) on their properties. Methods: Xerogels were prepared by sol-gel condensation and characterized using density measurements, FT-IR, BET analysis, SEM, and TGA. Methylene blue sorption was tested. Results and Discussion: The crosslinking agent defined the gel structure. The tannin-furfuryl alcohol (T/FA) xerogel was microporous and dense (0.348 g/cm3), while tannin-formaldehyde (T/F) and tannin-glutaric (T/G) xerogels were meso/macroporous with low density (~0.07 g/cm3). T/FA was the most thermally stable (onset decomposition at 282°C). The T/F xerogel showed the highest methylene blue sorption capacity (107 mg/g). Conclusions: Cedar bark tannins are a promising raw material for producing xerogels. The crosslinking agent type allows control over the porosity, density, thermal stability, and sorption properties of the final material.