Alkaline Delignification of Tropical Hardwoods: A promising Approach for Sustainable Material Development

Abstract Wood delignification is a promising approach for developing sustainable materials from tropical hardwoods. This study investigated the uniformity and efficiency of partial alkaline delignification of three commercially important tropical hardwoods (Andiroba, Sande, and Choiba) using a mixed aqueous solution of sodium hydroxide and sodium sulfite (NaOH/Na 2 SO 3 ) as a pretreatment for densification. The effects and distribution of the solution under the influence of the anatomical features of each hardwood were analyzed using FT-IR, optical microscopy, and SEM. The process resulted in the partial removal of lignin and hemicellulose in varying proportions between the center and ends of the wood. This reduction in lignin and hemicellulose content led to a decrease in MOE, MOR, and hardness of the delignified wood. Additionally, the results suggest that sodium accumulation in the wood structure may also modify its mechanical properties. The relationship between the chemical treatment and the anatomical characteristics of the wood species was found to influence delignification, which in turn affected the effectiveness of densification and subsequent compression. The findings of this study suggest that alkaline delignification is a promising approach for developing new materials from tropical hardwoods, but further research is needed to optimize the process and minimize the negative impact on mechanical properties.