Industry-friendly urea coating by interlocking waste proteins and nanoparticles via a glass transition approach

Abstract

Sustainable agriculture seeks efficient fertilizers; hence, a stable urea coating using feather particles with zinc oxide nanoparticles as a reinforcing agent is developed through a scalable drum rotor method. Feathers have tensile strength as good as stainless steel, but they lack quick and low-cost processing methods. Hence, acid hydrolysis followed by domestic microwave-assisted thermal treatment is developed, to our knowledge, for the first time, to disperse the feathers into a free-flowing microfiber powder in 10 days. XPS analysis confirmed the formation of keratin–zinc complexes through ionic bonding with carboxyl groups, highlighting the reinforcing role of ZNPs. Optimization of the hydrolysis tuned the glass transition of the feather microfibers to 70 °C, which caused densification and membrane formation during the mild heat-facilitated drum rotor coating. The optimized feather microfiber to ZNPs ratio and subsequent rearrangement significantly enhanced the coating's hydrophobicity and raised the water contact angle to 126°. This densified structure also optimized the Young's modulus, fulfilling critical industrial requirements for stability and controlled release. Importantly, it drastically reduced nitrogen loss in soil, showing <15% leaching loss compared with uncoated urea. The feather microfiber, being recalcitrant and suited for sustained nutrient release in soil, increased the rice yield by ∼15%. The chlorophyll analysis using the SPAD value corroborates the yield.