Stepwise extraction, functionalization, and composite formation of lignin and silica from rice husk: Synthesis and characterization

Abstract

This study presents a novel approach for the stepwise extraction of lignin and silica from rice husk, followed by the synthesis of a silica-lignin hybrid composite. The rice husk was first processed to obtain rice husk ash (RHA), from which lignin and silica were sequentially extracted using alkali and acidic treatments. Lignin was isolated by acidification of the filtrate, while silica was recovered by neutralizing the remaining solution and calcining the precipitate. The silica was functionalized with amino groups via reaction with 3-aminopropyltriethoxysilane (APTES) to enhance its compatibility with lignin. The lignin-silica composite was synthesized by oxidizing the lignin with sodium periodate, followed by the addition of the amino-functionalized silica, which led to electrostatic interactions between the two components. The composite was characterized using UV-Vis, FTIR, SEM, EDX, and TGA techniques, confirming successful hybridization of lignin and silica. The obtained results indicate that the composite exhibited unique structural and thermal properties, demonstrating potential applications in areas such as adsorption, catalysis, and material science. This study provides a sustainable method for valorizing rice husk waste into high-value hybrid materials.