Fractionation of lignin using eco-friendly organic cosolvent and preparation of light-colored lignin micro-nanoparticles for sustainable natural sunscreens

The inherent challenges posed by lignin, such as its high heterogeneity, complex structure and dark color, have impeded its widespread high-value utilization. In the present study, a green cosolvent system comprising ethanol (EtOH) and dimethyl carbonate (DMC) was employed for the fractional separation of alkali lignin. Through careful manipulation of the solvent ratio, interactions between the solvents and lignin were effectively regulated, leading to the reduction of lignin heterogeneity and the isolation of lignin fractions with distinct properties. Notably, a high yield of up to 35.65% of lignin with desirable characteristics, including a light color, low molecular weight, and high hydroxyl groups content, was achieved. Furthermore, this specific lignin fraction exhibited enhanced UV absorption and antioxidative properties, rendering it highly suitable for potential applications in sun protection products. When incorporated as micro-nano particles, it exhibited great compatibility with hand creams and elevated their sun protection factor (SPF). This innovative approach not only presents a green and straightforward lignin fractionation process but also highlights the untapped potential of lignin in the realm of sun protection applications.