Based on the results it was concluded that the

The percentage of PNP degradation by the dual-pulse US-EC coupling process was investigated under different initial pH values. The relationship between the degradation percentage and the initial pH values was shown in Fig. 5. It was found that the initial pH values of the solution had a great impact on degradation with the pulsed process and the degradation percentage was higher in a more acidic solution. When the pH value changed from 3 to 7, the degradation percentage decreased. The results matched that the oxidation of organic compounds was more favorable in acidic media using DSA electrodes, owing to the lower pH values diminishing the oxygen evolution reaction, which in favor of organic LCL161 oxidation [25]. On the other hand, when the pH value changed from 7 to 9, the degradation percentage increased. An increase in pH to alkaline media would result in an increase in the speciation. When the electron cloud density on adjacent-contrapuntal position increased with the pH, the electrophilic attack of OH became easier, resulting in a higher PNP removal rate [26]. At pH above 9, more free radicals scavengers might exist and lead to a decrease in the amount of OH radicals, which ultimately led to the decrease of the degradation rate at pH 11 [27]. However, some authors reported that the degradation efficiency was increased in alkaline media [28]. As a result, the impact of initial pH values on the dual-pulse US-EC coupling process might strongly rely on the characteristics of the investigated organics and the supporting electrolyte [29]. In this test, the maximum degradation efficiency was observed at pH = 3, thus pH = 3 can be chosen as an optimal pH value of this process.