The root bark extract of the Maerua oblongifolia plant in the green synthesis of titanium dioxide nanoparticles (TiO₂ NPs) for photocatalytic degradation of toxic pollutants and antibacterial activities was implemented in this study. The root bark extract served as a novel capping and reducing agent for the first time. Characterization of the TiO₂ NPs was conducted by using visual observation, ultraviolet visible spectrometry (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques, confirming their successful synthesis. The TiO₂ NPs exhibited maximum absorbance at 323 nm and an average particle size of 19.58 nm; the conjugations and existences of Ti-O and OH vibrational bands were revealed by the FTIR spectrum. The photocatalytic activities of the TiO₂ NPs were investigated by using solar irradiation as an energy source for aqueous solutions of methyl orange (MO) and methylene blue (MB) dyes. The TiO₂ NPs showed strong photocatalytic activities by degrading 97.23% MB and 91.8% MO under optimized conditions. Degradation behavior was investigated by isotherms and kinetics models, with the Langmuir isotherms (R²: 0.996, 0.979) and Langmuir–Hinshelwood (R²: 0.998, 0.997) highest correlation coefficients for MB and MO, respectively. Moreover, the antibacterial efficacy of the green-synthesized TiO₂ NPs and the results indicated higher antibacterial activities on Gram-negative bacteria (27 ± 0.52).

The worst of the COVID-19 (coronavirus disease 2019) pandemic may be over, but its impact continues to be felt worldwide. During the outbreak, medical regu