Evaluation of performance of hybrid photolysis-DCMD and photocatalysis-DCMD systems utilizing UV-C radiation for removal of diclofenac sodium salt from water

Abstract

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 4 h of irradiation or less. Mineralization was less efficient than photodecomposition. In case of the hybrid photolysis-DCMD process the efficiency of TOC degradation after 5 h 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.