Adsorption and photocatalysis of escitalopram: Kinetics, catalyst loading, and matrix effects

This study investigates the removal of the antidepressant escitalopram (ESC) from aqueous environments using TiO 2 (P25) photocatalysis. Adsorption studies conducted in the dark revealed that the process follows the Langmuir isotherm model indicating monolayer coverage on homogeneous surface. A significant solid-effect was observed where increasing the catalyst concentration from 0.3 to 1.0 g/L resulted in a decrease in the maximum specific adsorption capacity (Q max ) from 209 to 48 µmol/g. Photocatalytic experiments demonstrated that ESC is recalcitrant to direct UV photolysis whereas TiO 2 -mediated photocatalysis achieved approx. 50% removal in ultrapure water within 180 min. The initial degradation rates (V 0 ) followed Langmuir-Hinshelwood kinetic, reaching a plateau at higher catalyst loadings due to light-shielding effects. Application of the process to a real wastewater matrix (COD = 30 mg/L) showed a reduction in efficiency to 27% removal, attributed to competitive adsorption and radical scavenging by organic matter and inorganic ions. These findings highlight the potential of TiO 2 (P25) for treating neuroactive micropollutants while underscoring the necessity of optimizing catalyst concentration for complex aqueous matrices.