Systematic design, optimization, and comparative photocatalytic performance of FeVTiOx, FeCrTiOx, and FeCrVTiOx multi-metal titania catalysts for bromocresol green degradation

The photocatalytic degradation of Bromocresol Green dye was systematically investigated over FeVTiO x , FeCrTiO x , and FeCrVTiO x catalysts using batch reactor experiments. The effects of pH, irradiation time, and initial dye concentration were evaluated, with photodegradation efficiency (PDE) as the main response. Among the studied catalysts, FeCrTiO x exhibited superior photocatalytic performance, achieving rapid degradation under acidic conditions. The optimization of the process parameters was carried out using Response Surface Methodology based on a Face-Centered Central Composite Design. The results indicated that pH is the most influential parameter, followed by initial dye concentration, while irradiation time showed a secondary effect. The quadratic model demonstrated good agreement with experimental data, with statistical parameters of R 2 = 0.99, confirming the adequacy and reliability of the model. The optimal operating region was identified at intermediate pH values, moderate irradiation times (≈ 25–35 min), and low initial dye concentrations, where near-complete decolorization was achieved. The predicted optimal conditions were experimentally validated, showing good agreement between predicted and observed PDE values. Additionally, radical scavenging experiments revealed that hydroxyl radicals and superoxide radicals are the dominant reactive species in the photocatalytic process. The FeCrTiO x catalyst demonstrated high efficiency, stability, and reliable performance, highlighting its potential for practical wastewater treatment applications.