The impact of pH on the process was evaluated by adjusting the initial cT of the sample to 100 mM and adjusting the pH to 3, 5, 7 or 10 with concentrated H2SO4 or NaOH pellets.
The solution was subjected to UVC/10 mM H2O2 treatment after evolution of CO2 ceased. As shown in Fig. 5, the COD removal was similar when the initial pH was 3 and 5.
For initial pH 7, the decrease in the COD removal was only noticeable after 2 h irradiation, whereas the effectiveness of the treatment was severely impaired when the initial pH was 10.
Thus the decrease in COD removal due to the presence of high concentrations of HCO3
/CO32 can be alleviated by operating at pH < 5. These results are consistent with those of Yonar et al. (2006) who found that pH 3 was optimal for the UVC/H2O2 process, but decrease in COD removal was pronounced only when the pH was greater than 5.