Strategic Lignin Fractionation: Sustainable Encapsulation and Controlled Release of Pelargonic Acid

Abstract Interest in bio-based herbicides, such as pelargonic acid (PA), a naturally occurring fatty acid with rapid post-emergent herbicidal activity, has increased in response to the growing demand for sustainable and effective weed-control strategies. However, its practical application remains constrained by high volatility, photodegradation, and limited residual activity. In this study, kraft lignin (KL) was fractionated using aqueous acetic acid at defined concentrations (30%, 40%, and 50%) to obtain well-characterized fractions (KL30, KL40, and KL50). These fractions were subsequently used to synthesize lignin nanoparticles encapsulating PA via antisolvent precipitation. The resulting formulations were systematically characterized for their structural, colloidal, and thermal properties, as well as photostability, release kinetics, and herbicidal performance. Among the tested systems, KL30-based nanoparticles demonstrated high encapsulation efficiency, enhanced resistance to ultraviolet C radiation, and sustained colloidal stability. Post-emergence bioassays using Lolium multiflorum and Amaranthus viridis demonstrated that KL30_1PA induced rapid and severe phytotoxicity effects like those of commercial formulations while also maintaining low cytotoxicity toward mammalian cells. These findings demonstrate that rational lignin fractionation improves nanoparticle design and supports the development of scalable, effective, and environmentally sustainable agrochemical delivery systems for PA.