Green synthesis of hydroxyapatite from biogenic and waste-derived precursors: a bibliometric and systematic analysis of trends, strategies, and applications

Resumo

This study presents a comprehensive bibliometric and qualitative analysis of the scientific literature on the green synthesis of hydroxyapatite (HAp) derived from biogenic and waste-based precursors. The dataset was retrieved from the Scopus database and analyzed using a structured workflow, including screening, eligibility assessment, and bibliometric mapping. The results reveal a consistent growth in scientific production, particularly after 2023, indicating the increasing relevance of sustainable synthesis strategies. Geographic analysis highlights a strong concentration of research in emerging economies, especially in Asia. Keyword and co-occurrence analyses demonstrate that the field is structured around four main domains: green synthesis approaches, material development, physicochemical characterization, and application-driven research. The most influential studies emphasize the use of calcium-rich waste materials, bio-mediated synthesis routes, and the development of hybrid and multifunctional systems. Furthermore, the qualitative analysis evaluates the underlying physicochemical and kinetic mechanisms of these green pathways, demonstrating how alternative synthesis methods operate as efficient crystal engineering strategies. Additionally, HAp-based materials are increasingly applied in both biomedical and environmental contexts, including bone tissue engineering and pollutant removal. Despite these advances, challenges remain regarding reproducibility, standardization, and scalability of green synthesis methods. Overall, this study provides a structured and integrative overview of the field, identifying key trends, research gaps, and future directions toward more sustainable and high-performance HAp-based materials.