Synthesis and characterization of biomass lignin-based PVA super-absorbent hydrogel

The traditional polyvinyl alcohol composite hydrogel exhibited poor swelling and mechanical properties, which limited its application. To solve these issues, we use biomass lignin as raw material, PVA as matrix template and epichlorohydrin as cross-linker to prepare the Lignin-PVA super-absorbent hydrogels with the swelling ratio of up to 456 g/g under mild condition. When the lignin concentration was increased from vacancy to 5%, the swelling ratio of the Lignin-PVA hydrogels was increased from 92 g/g to 456 g/g. The lignin-based hydrogel synthesized by the higher molecular weight PVA showed better swelling performance. Softwood lignin, hardwood lignin and corncob lignin could also be used to fabricate the Lignin-PVA super-absorbent hydrogels with the swelling ratio of higher than 500 g/g. However, the optimum amount varied from different lignin types, which was related to the molecular weight and phenolic hydroxyl content of lignin. The structural mechanism of the Lignin-PVA hydrogel was proposed to clearly certify the enhancing role of lignin. The adsorption capacity of the Lignin-PVA hydrogel with respect to rhodamine 6G, crystal violet and methylene blue dyes was up to 196, 169 and 179 mg/g, respectively. The Lignin-PVA hydrogel presents great potential applications in the fields of soil water retention and seed cultivation in agriculture, and dye pollutant removal.