Color characteristics of microlignin

In recent years, more and more attention has been paid to the lignin utilizations and researchers are doing their best to convert lignin into value-added industrial products. The dark color of technical lignin is an inherent recognition and it has become an obstacle in the development of color-dependent utilizations of lignin. In this chapter, the color characteristics of lignin were introduced. Chromophores and auxochromes were identified and summarized. The methods used for the evaluation of the color of lignin were collected and compared. The relationship between the color of lignin and its chemical structure and micromorphology was illustrated. The traditional and newly emerged lignin color reduction methods and related color reduction mechanisms were described. Current color-dependent hotspots, such as lignin-based sunscreens, dyestuff dispersants and inks, were collected and introduced. At last, the development direction of color-dependent utilization of lignin was proposed.