Influence of agricultural residues on the formation of TiO2 phases: Real-time in situ X-ray diffraction monitoring in a reaction chamber

This study investigates the influence of agricultural residues on the structural evolution of titanium dioxide (TiO 2 ) synthesized through a green route using rice husk (C1), sugarcane bagasse (C2), and coconut husk (C3) ashes. Real-time in situ X-ray diffraction (XRD) was employed to monitor phase transitions during controlled heating up to 900 °C, enabling quantitative tracking of anatase–rutile transformation and crystallite growth by Rietveld refinement. At 800 °C, pure TiO 2 was predominantly rutile (≈94.3%) with only ≈5.7% anatase, whereas C1–TiO 2 and C2–TiO 2 retained ~50% anatase (49.7% and 51.0%, respectively), and C3–TiO 2 remained anatase-rich (70.1%) due to concurrent formation of priderite (27.8%) and ramsdellite (1.6%). The incorporation of siliceous ashes (C1 and C2) delayed rutile nucleation and reduced crystallite coarsening, indicating that SiO 2 and mineral components hinder atomic diffusion and stabilize anatase at higher temperatures. In contrast, coconut ash (C3) promoted the formation of secondary titanate phases (priderite and ramsdellite), leading to distinct multiphase kinetics. These results demonstrate that the chemical nature of agro-industrial ashes can be used to modulate TiO 2 microstructure and phase stability. The findings provide a quantitative framework for engineering sustainable TiO 2 materials, where the choice of agricultural residue enables control over anatase retention or rutile formation, with direct implications for photocatalytic and surface-active applications. • Sustainable valorization of agro-residues (rice, sugarcane, coconut) as TiO₂ structure modifiers. • Real-time in situ XRD tracks anatase→rutile transformation up to 900 °C with quantitative Rietveld analysis. • SiO₂-rich ashes delay rutile nucleation and suppress crystallite coarsening, stabilizing anatase at higher T. • K-rich coconut ash redirects crystallization to priderite/ramsdellite, enabling tunable multiphase TiO₂. • Provides actionable, sustainable calcination parameters to engineer TiO₂ phase composition for green applications.