Diclofenac (DCF) as a non-steroidal pharmaceutical has been detected in aquatic samples more than other compounds due to its high consumption and limited biodegradability. In this study, ultrasound waves were applied along with an advanced nano-Fenton process (US/ANF) to remove DCF, and subsequently, the synergistic effect was determined. Before that, the efficiency of the US and ANF processes was separately studied. The central composite design was used as one of the most applicable responses surface method techniques to determine the main and interactive effect of the factors influencing DCF removal efficiency in US/ANF. The mean DCF removal efficiency under different operational conditions and at the time of 1-10 min was obtained to be about 4%, 83%, and 95% for the US, ANF, and US/ANF, respectively. Quadratic regression equations for two frequencies of US were developed using multiple regression analysis involving main, quadratic, and interaction effects. The optimum condition for DCF removal was obtained at time of 8.17 min, H/F of 10.5 and DCF concentration of 10.12 at 130 kHz US frequency. The synergy index values showed a slight synergistic effect for US/ANF (1.1). Although the synergistic effect of US/ANF is not very remarkable, it can be considered as a quick and efficient process for the removal of DCF from wastewater with a significant amount of mineralization.
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