Comparative study on photooxidative treatment of diclofenac: Response surface and mechanistic modeling

The study evaluates the applicability of photooxidative processes for the degradation of diclofenac (DCF), frequently encountered pharmaceutical compound in water bodies. Response surface modeling (RSM) and mechanistic modeling (MM) were used to describe UV-C/H2O2 and UV-C/S2O82− processes. The influence of initial pH, oxidant concentration and type on the process effectiveness was assessed in terms of mineralization kinetics. The evaluation of process parameters significance, and their optimization within investigated range, was successfully performed by RSM. The predicted values deviated from the experimental results by 2.6%. It was found out that oxidant concentration and type are highly influential parameters. The both studied processes can be applied in relatively wide pH range due to its minor influence on mineralization kinetics. The simultaneous prediction of several process responses: DCF conversion, mineralization, oxidant consumption and pH changes were successfully achieved by MM. Predicted values deviated from the experimental data ≤1.5%. At determined optimal conditions for both processes, the treatment time required for complete DCF conversion and 90% mineralization by UV-C/S2O82− was 8 times lower in comparison to UV-C/H2O2 process.