Extraction of Glyoxylic Acid Stabilized Lignin from Lignocellulosic Biomass for a Natural Sunscreen Additive

Natural lignin has been considered a promising additive for ultraviolet (UV) protection cosmetics applications. Nevertheless, its potential application in cosmetics production is impeded by its inherent dark coloration due to structural damage incurred during the industrial lignin extraction process. In this study, glyoxylic acid (GA) was used to prevent lignin condensation during lignin extraction using an acid recycled hydrotrope (p-toluenesulfonic acid, p-TsOH). Further processing of the GA stabilized lignin yielded lignin nanospheres (LNPs) for a natural sunscreen additive. Incorporating 3% and 4% LNPs into a baseline SPF10 commercial sunscreen resulted in lignin-based sunscreen with SPF values of 37.2 ± 2.55 and 58.74 ± 2.14, respectively. These exceeded the SPF levels observed in commercial sunscreens with SPF30 and SPF50. Furthermore, the pretreated cellulose residue was utilized in the production of pulp fibers for papermaking. It was observed that the ring crush strength index of the paper, achieved by incorporating 15 wt % fibers into softwood pulp, reached a notable value of 2.98 ± 0.10 N·m/g. The tear index and tensile index of the produced paper, augmented with a 5 wt % addition of fibers, were as high as 4.77 ± 0.41 mN·m2/g and 9.49 ± 0.27 N·m/g, respectively. Therefore, a new strategy for stabilized lignin extraction and lignocellulose biomass valorization was proposed in this study.