Enhanced degradation of triclosan using aerated hydrodynamic cavitation: turbulence-based modelling and economic evaluation

Pharmaceutical and personal care product (PPCP)-contaminated wastewater, particularly with triclosan (TCS), poses a significant environmental concern due to TCS persistence, ecotoxicity, and endocrine-disrupting effects, necessitating the development of efficient and sustainable remediation technologies. In this study, the degradation of TCS using hydrodynamic cavitation coupled with air injection (aerated HC process) is investigated as a green and chemical-free treatment method for wastewater treatment. Initially, the optimum operating conditions of the standalone HC process were determined by varying the inlet pressure and flow rate, which were found to be 2.34 bar and 0.45 L/s, respectively, corresponding to the highest turbulence frequency level of 1041 s−1 and the lowest turbulent pressure −0.58 bar at the venturi throat, based on the turbulence model. Subsequently, upon introducing an air flow rate of 1.6 m³/h at the venturi throat, the aerated HC process achieved a TCS degradation efficiency of 79.89 ± 3.99%, with a synergistic index of 1.29 (compared to 71.54 ± 2.29% without air injection), confirming the enhanced performance due to air injection. The highest rate constant (0.073 min−1) was observed at pH 3, confirming that acidic conditions favour TCS degradation. Mechanistically, TCS degradation in the aerated HC process proceeds through both radical pathways, primarily mediated by hydroxyl radicals, and non-radical pathways such as thermal pyrolysis.