Industry-friendly urea coating: by interlocking waste protein 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 has been developed through a scalable drum rotor method. Feathers have tensile strength as good as stainless steel, but lack quick and low cost processing. Hence acid hydrolysis followed by domestic microwave assisted thermal treatment has been developed, to our knowledge, for the first time to disperse the feathers into 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. The optimization of the hydrolysis led to tune the glass transition of feather microfiber to 70 °C, which causes 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 to uncoated urea. The feather microfiber, being recalcitrant and suited for sustained nutrient release in soil and the rice yield increases by ~ 15%. The chlorophyll analysis using SPAD value corroborates with the yield.