Evaluation of Performance of Hybrid Photolysis-DCMD and Photocatalysis-DCMD Systems Utilizing UV-C Radiation for Removal of Diclofenac Sodium Salt From Water

The removal of a non-steroidal anti-inflammatory drug (NSAID) diclofenac sodium salt (DCF, C₁₄H₁₀Cl₂NNaO₂) from water in two hybrid systems coupling photolysis or photocatalysis with direct contact membrane distillation (DCMD) is presented. A UV-C germicidal lamp was used as a source of irradiation. The initial concentration of DCF was in the range of 0.005-0.15 mmol/dm³ and the TiO₂ Aeroxide® P25 loading (hybrid photocatalysis-DCMD) ranged from 0.05 to 0.4 g/dm³. Regardless of the applied hybrid system and the initial concentration of DCF, the model drug was completely decomposed within 4h of irradiation or less. Mineralization was less efficient than photodecomposition. In case of the hybrid photolysis-DCMD process the efficiency of TOC degradation after 5h of irradiation ranged from 27.3-48.7% depending on the DCF initial concentration. The addition of TiO₂ allowed to improve the efficiency of TOC removal. The highest degradation rate was obtained at 0.3 gTiO₂/dm³. During the process conducted with the lowest DCF initial concentrations (0.005-0.025 mmol/dm³) a complete mineralization was obtained. However, when higher initial amounts of DCF were used (0.05-0.15 mmol/dm³), the efficiency of TOC degradation was in the range of 82.5-85%. The quality of distillate was high regardless of the system: DCF was not detected, TOC concentration did not exceeded 0.7 mg/dm³ (1.9 mg/dm³ in permeate) and conductivity was lower than 1.6 μS/cm.