Pine Needle Biochar–Supported Ag/TiO₂/Mg(OH)₂ Nanocomposites for Photocatalysis and Biomedical Remediation

This study reports the hydrothermal synthesis of silver-anchored binary (PNBC–Ag/TiO₂, PNBC–Ag/Mg(OH)₂) and ternary (PNBC–Ag/TiO₂/Mg(OH)₂) nanocomposites using activated biochar (PNBC) derived from dead pine needles as a sustainable support. Structural, optical and surface analyses using XRD, FTIR, XPS, FESEM/HRTEM, and UV–Vis DRS confirmed the successful integration of Ag, TiO₂, and Mg(OH)₂ within the biochar matrix, producing nanocrystalline composites with improved light-absorption properties. The ternary nanocomposite demonstrated superior photocatalytic performance, achieving 98.4% degradation of crystal violet and 93.7% degradation of methyl orange in 27 and 45 min, respectively. The nanocomposite also exhibited significant antimicrobial activity against S. marcescens, E. faecalis, and T. asperellum, cytotoxicity studies revealed selective anticancer activity toward HeLa cells (GI₅₀ = 16.08 µg mL⁻¹ with significantly lower toxicity to normal fibroblast cells (GI₅₀ = 94.09 µg mL⁻¹). The enhanced performance is attributed to the synergistic interaction of Ag, TiO₂, and Mg(OH)₂ supported on pine-needle-derived biochar, providing a sustainable multifunctional nanoplatform for photocatalytic and biomedical remediation applications.