Unraveling Lignin's Color Puzzle: From Chromophore Origins to Advanced Decolorization Strategies

ABSTRACT Lignin, as one of the most abundant natural aromatic polymers, holds significant promise for high‐value applications; however, its inherent dark coloration poses a major constraint for such uses. In this review, we systematically examine the key factors contributing to lignin's color, with a focus on structural alterations during extraction, the formation of chromophores, and the influence of molecular weight and morphology. We then provide a comprehensive overview of current decolorization strategies, including oxidative bleaching, hydroxyl shielding modification, physical methods, and biomass fractionation techniques. This review offers a detailed summary of both the mechanisms underlying lignin coloration and recent advances in decolorization, thereby providing valuable guidance for the optimization of whitening processes and facilitating the advanced utilization of lignin.