However, there is also a loss of oxidation potential due to either recombination of
SO
• À
4
or scavenging of SO
• À
4
by ferrous ions (Fe
2+ ) as shown in the last two
reactions.
Chakma et al. have investigated sono-hybrid persulfate oxidation mechanism for
mineralization of textile dyes under different experimental conditions (Chakma et al.
2017). According to their studies, the binary activation method (US + UV) was
found to be the effective hybrid advanced oxidation process for degradation of Acid
Red B, an azo dye, as shown in Fig. 6.5 (Chakma et al. 2017). On the other hand,
when the persulfate was activated using three activators (US + UV + Fe
2+ ), the
TOC removal was reduced as compared to the process where the persulfate was
activated using US + UV. This could be due to the scavenging effect of free radicals
by the Fe
2+ ions.
Fig. 6.5 Total organic carbon (TOC) removal during degradation of Acid Red B dye using
different experimental conditions. Note: US ultrasound, MS mechanical stirring, 1A, US alone
(or sonolysis); 1B, [MS + UV], 1C: [MS + PS]; 2A, [US + PS]; 2B, [MS + PS + Fe
2+ ]; 2C,
[MS + PS + UV]; 3A, [US + PS + Fe
2+ ]; 3B, [US + PS + UV]; 3C, [MS + PS + Fe
2+ + UV]; 3D,
[US + PS + Fe
2+ + UV]. US ultrasound, MS mechanical stirring, PS persulfate, UV ultraviolet.
(Reprinted with permission of Elsevier from Chakma et al. 2017)
6 Degradation Mechanism of Pollutants Using Sono-hybrid Advanced Oxidation. . .
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