Evaluation of the production of lignin-containing cellulose nanofibrils with high whiteness for blocking UV light

Abstract

Lignin is a natural polymer that could absorb ultraviolet (UV) light, making it a potential material for anti-UV applications. The dark color and the low emulsion stability, however, greatly hinder the extended application of lignin in various areas such as sunscreens. To address this concern, the colorless lignin-containing cellulose nanofibrils (LCNFs) with different lignin content was prepared through a sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, hydrogen peroxide (H₂O₂) decolorization, and high-pressure homogenization. The obtained LCNFs were characterized in terms of chemical composition, whiteness, morphology, and lignin content. The results indicated that the preparation process not only largely preserved lignin, but also maintained the structure of cellulose. Moreover, the UV blocking property of the prepared white LCNFs was determined by blending into a cream. The rates of UV blocking and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging were measured to be 94.7% and 23.1%, respectively, which were comparable to that of the commercial sunscreen products. The results demonstrated that LCNFs with high whiteness could be efficiently prepared and have great potential to be applied in the anti-UV industry.