Phosphorous-doped TiO nanoparticles: synthesis, characterization, and visible photocatalytic evaluation on sulfamethazine degradation.

Mesoporous phosphorous-doped TiO (TP) with different wt% of P (0.5, 1.0, and 1.5) was synthetized by microwave-assisted sol-gel method. The obtained materials were characterized by XRD with cell parameters refinement approach, Raman, BET-specific surface area analysis, SEM, ICP-OES, UV-Vis with diffuse reflectance, photoluminescence, FTIR, and XPS. The photocatalytic activity under visible light was evaluated on the degradation of sulfamethazine (SMTZ) at pH 8. The characterization of the phosphorous materials (TP) showed that incorporation of P in the lattice of TiO stabilizes the anatase crystalline phase, even increasing the annealing temperature. The mesoporous P-doped materials showed higher surface area and lower average crystallite size, band gap, and particle size; besides, more intense bands attributed to O-H bond were observed by FTIR analysis compared with bare TiO. The P was substitutionally incorporated in the TiO lattice network as P replacing Ti to form Ti-O-P bonds and additionally present as PO on the TiO surface. All these characteristics explain the observed superior photocatalytic activity on degradation (100%) and mineralization (32%) of SMTZ under visible radiation by TP catalysts, especially for P-doped TiO 1.0 wt% calcined at 450 °C (TP1.0-450). Ammonium, nitrate, and sulfate ions released during the photocatalytic degradation were quantified by ion chromatography; the nitrogen and sulfur mass balance evidenced the partial mineralization of this recalcitrant molecule.