BaTiO3/ZnO nanocomposite photocatalysts for enhanced degradation of mixed antibiotics and dyes

Composite photocatalysts were developed from hydrothermally synthesized barium titanate (BaTiO 3 , BTO) and zinc oxide (ZnO), combined by ultrasonic mixing in ethanol followed by calcination, and applied to remove a quaternary mixture of persistent pollutants in wastewater (ciprofloxacin (CIP), tetracycline (TC), methylene blue (MB), and methyl orange (MO)) in a heterogeneous photocatalysis process. These BTO/ZnO composites deliver substantially higher pollutant-degradation performance than pristine BTO in single-pollutant tests under UV irradiation, with the largest gains observed for the antibiotics (up to about 3.5-fold for tetracycline); for the two dyes, the composites approach but do not exceed the activity of pure ZnO. In multiple-pollutant tests, they show good repeatability across four runs, following pseudo-first-order kinetics. Structural, optical, and surface characterizations indicate that the composites consist of distinct BTO and ZnO phases in intimate contact, forming a heterojunction. Control experiments show that pollutant removal is dominated by photocatalysis rather than adsorption or direct photolysis, and scavenger tests identify photogenerated holes as the dominant reactive species, with hydroxyl radicals secondary and superoxide radicals minor. This work demonstrates that BTO/ZnO composites are effective for the photocatalytic removal of mixed antibiotics and dyes and provides a basis for designing semiconductor heterojunctions for multi-component wastewater treatment.