Facile tuning of hydrogel properties for efficient water removal from biodiesel: An assessment of alkaline hydrolysis and drying techniques

Polymeric hydrogels are a promising new technology for dehydrating fuels. This study critically analyzes the effects of hydrolysis post-treatment and drying methods (oven-drying and freeze-drying) on polyacrylamide hydrogels for removing diluted water from biodiesel. The materials were characterized using FTIR, TGA, SEM, DVS, compressive strength, and swelling degree analyses. The water diffusion profiles during swelling were observed using an innovative method described in this study. Hydrolysis improved the hydrophilicity of the hydrogel, increasing the swelling degree from 33–37 g.g−1 to 987–1,095 g.g−1, and doubling the water absorption from biodiesel. Freeze-drying benefited the kinetics of water uptake. Using hydrolyzed polyacrylamide hydrogel, the water content in biodiesel decreased from 1497 ppm to 978 ppm in just 30 min. Within 72 h, 49% of the water was removed from the biofuel. This demonstrates the efficiency of hydrogel systems, which could become a competitive alternative to traditional fuel desiccants, removing even traces of moisture.