Degradation of Carbamazepine by Ozonation: Influence of pH and Mass Transfer on Water Quality Improvement for Sustainable Water Treatment

The presence of persistent pharmaceutical contaminants such as carbamazepine in aquatic environments represents a major challenge for sustainable water management and the long-term protection of water resources. Carbamazepine (CBZ) is a persistent pharmaceutical pollutant frequently detected in surface waters and poorly removed in conventional wastewater treatment plants. This study investigates the ozonation of CBZ (50.0 mg/L) under alkaline conditions (pH 10.0–14.0), focusing on the influence of pH and ozone mass transfer on oxidation kinetics and water-quality parameters. Ozonation was conducted at 25 °C using a high ozone dose (58.5 g Nm−3), achieving complete CBZ degradation within the first 10 min at all pH values. Marked differences in pH evolution were observed: solutions initially at pH 10.1 rapidly acidified to pH ≈ 4.0, whereas highly alkaline systems (pH > 13.0) remained stable. The most intense yellow coloration was observed at pH 14.0, followed by progressive removal. Turbidity remained low at pH 10.1 (<2.5 NTU) but increased at pH 12.0–13.0. Ozone mass-transfer behaviour revealed a transition from molecular-ozone-dominated oxidation to radical-dominated regimes at pH ≥ 12.0. Overall, ozonation proves highly efficient for CBZ removal, and the pH-dependent behaviour highlights the need to optimise oxidation conditions to improve water quality and minimise residual by-products, thereby supporting the development of more sustainable advanced treatment strategies for wastewater reuse and environmental protection.