This work reports the synthesis, characterization, and photocatalytic performance of multifunctional spheres based on AgNP-doped TiO₂-Fe₃O₄ embedded in an alginate–chitosan biopolymeric matrix for the removal of organic contaminants from water. The composite powders exhibited a nanocrystalline structure composed of anatase TiO₂ (~20 nm) and magnetite (~25 nm), with homogeneously dispersed Ag nanoparticles, as observed by SEM. The spheres presented a mainly submicrometric particle size distribution (0.55–0.92 µm), favoring high surface area and colloidal stability. Under simulated solar irradiation, the material achieved efficient photocatalytic degradation of methylene blue, with a pseudo-first-order rate constant of 0.112 h⁻¹ and ~46% decolorization after 5 h. UV-Vis spectra showed progressive attenuation of the dye absorption band without accumulation of intermediates. Magnetic recovery tests confirmed rapid separation and reuse without performance loss. The enhanced activity is attributed to the synergistic interaction among plasmonic Ag, photocatalytic TiO₂, redox-active Fe₃O₄, and the adsorptive carbon–biopolymer matrix. The material exhibited strong antibacterial activity, achieving over 90% removal of fecal coliforms after 5 h of irradiation. Therefore, the developed AgNP-doped TiO₂-Fe₃O₄ spheres represent a sustainable, reusable, and efficient material for solar-assisted water sanitation.

This work reports the synthesis, characterization, and photocatalytic performance of mul-tifunctional spheres based on AgNPs-doped TiO2-Fe3O4 embedded in an alginate-chitosan biopolymeric matrix for the removal of organic contaminants from water. The composite powders exhibited a nanocrystalline structure composed of anatase TiO2 (~20 nm) and magnetite (~25 nm), with homogeneously dispersed Ag nanoparticles, as observed by SEM. The spheres presented a mainly submicrometric particle size distribution (0.55-0.92 µm), favoring high surface area and colloidal stability. Under simulated solar irradiation, the material achieved efficient photocatalytic degradation of methylene blue, with a pseu-do-first-order rate constant of 0.112 h⁻¹ and ~46 % decolorization after 5 h. UV-Vis spectra showed progressive attenuation of the dye absorption band without accumulation of in-termediates. The spheres also exhibited strong antibacterial activity, reaching 87 % reduc-tion of total coliforms and >93 % of fecal coliforms after 5 h of irradiation. Magnetic recov-ery tests confirmed rapid separation and reuse without performance loss. The enhanced activity is attributed to the synergistic interaction among plasmonic Ag, photocatalytic TiO2, redox-active Fe3O4, and the adsorptive carbon-biopolymer matrix. The material ex-hibited strong antibacterial activity, achieving over 90% removal of fecal coliforms after 5 h of irradiation Therefore, the developed AgNPs-doped TiO2-Fe3O4 spheres represent a sus-tainable, reusable and efficient material for solar-assisted water sanitation.