Valorization of citrus processing waste into high-performance bionanomaterials: green synthesis, biomedicine, and environmental remediation.

The global citrus industry generates millions of tons of citrus processing waste (CPW), composed primarily of peel, pulp, and seeds. This agro-industrial byproduct represents both an environmental challenge and a valuable feedstock for sustainable nanotechnology. This review explores green synthesis approaches for transforming CPW, rich in bioactive compounds such as flavonoids, essential oils, and pectin, into high-performance bionanomaterials. Emphasis is placed on their biomedical applications, including antimicrobial formulations, wound healing agents, and nanocarriers for drug delivery, as well as their use in environmental remediation and catalysis. In contrast to earlier reviews, this work highlights recent progress in eco-friendly synthesis techniques (e.g., microwave-assisted, biological, and hydrothermal methods) while addressing challenges related to scalability, reproducibility, and bioavailability. The review also frames CPW valorization within the broader context of circular economy models and the UN Sustainable Development Goals. By offering a critical synthesis of current knowledge and identification of key knowledge gaps, this work aims to support future research and industrial translation in green nanotechnology.