This work explores the novelty of achieving high photocatalytic efficiency and remarkable bactericidal activity with Al₂O₃-TiO₂ coatings on perforated 304 stainless steel (SS) substrates, placed transversely along an airlift reactor of 0.980 L for wastewater treatment under visible light irradiation. The Al₂O₃-TiO₂ coatings achieved methylene blue and total organic carbon (TOC) concentration reductions of 97.3 and 96.51%, respectively, in a wastewater sample with heterogeneous photocatalsis. The Al₂O₃-TiO₂ coatings resulted in a 33.30% reduction in total and fecal coliforms and a remarkable 94.23% decrease in Salmonella spp. in the wastewater sample. XRD confirmed the TiO₂ anatase–rutile phases and Al₂O₃ α-γ phases in the coating. The particle size distribution ranges from 100 to 500 nm, and the coating surface was homogeneous without cracks confirmed using SEM and AFM, respectively. The roughness and thickness of the coatings were 85 ± 5 nm and 250 ± 50 nm, respectively.

Hydroxyapatite (HAp) nanoparticles with a homogeneous rod morphology were successfully synthesized using the hydrothermal method. The powders were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The antibacterial and dermal irritation analyses of the samples were performed and discussed. The use of cationic and anionic surfactants, namely, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), respectively, at a low concentration (2.5 mol%) modified the length/diameter (L/D) ratio of the HAp rods. Structural characterizations of hydroxyapatite synthesized without surfactant (HA), with 2.5 and 5 mol% of SDS (SDS− and SDS+, respectively), and with 2.5 and 5 mol% of CTAB (CTAB− and CTAB+, respectively) revealed well-crystallized samples in the hexagonal phase. The CTAB− sample presented antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, Streptococcus anginosus, Staphylococcus aureus, Micrococcus luteus, and Klebsiella pneumoniae, suggesting that antimicrobial susceptibility was promoted by the bacterial nature and the use of the surfactant. Dermal irritation showed no clinical signs of disease in rabbits during the study, where there was neither erythema nor necrosis at the inoculation sites.