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Topics in Current Chemistry (2020) 378:29
hydroxyl radicals as well as the form of the pollutant in the medium. A detailed
study on the degradation of trichloroacetic acid using a UV/TiO 2 /US combined
process revealed that the maximum extent of degradation for the combined process largely depended on the pH and the speciation of the parent compound [97].
In all cases, however, SPC degradation was always showing better efficacy than
sonolysis or photolysis alone. A study performed by Tabasideh et al. [71] on the
degradation of diazinon showed that maximum degradation using the SPC process with iron-doped TiO 2 was obtained under acidic conditions (pH 5.5), while
a much lower degradation was observed in strongly alkaline conditions (pH 9.5).
These authors also noted that the effect of pH was dominant in the case of photocatalytic oxidation alone and less significant in the case of SPC oxidation (see
Fig. 14).
Catalyst loading also plays a major role in determining the efficacy of SPC
oxidation. For example, Tabasideh et al. [71] studied the effect of catalyst loading
over the range of 0.2–0.6 g/L and reported that optimum catalyst loading did exist
at 0.4 g/L. These authors reported that significantly higher loading of the catalyst
interfered with both the passage of ultrasonic energy and the transmission of light
energy, resulting in detrimental effects. In addition, the negative effect of catalyst
loading beyond the optimum was more dominant in the case of only sonocatalytic
oxidation as compared to SPC oxidation [71] (see Fig. 15).
Several studies have also focussed on the effect of doping of the catalyst on
SPC processes. Reddy et al. [81] studied various iron loadings and reported that
96% degradation of naphthol-blue-black dye was observed at the optimum loading. Multi-walled carbon nanotubes (CNTs) deposited with Fe–TiO 2 under both
visible and UV light showed enhanced formation of reactive radicals and prevention of electron–hole recombination, with sonophotocatalysis giving the better results [98]. These results show that the use of doping or composites definitely helps in enhancing catalyst activity as compared to bare forms of the oxide
catalyst.
Fig. 14 Data for the effect of pH on the degradation of diazinon in presence of Fe-doped TiO 2 using
photocatalytic (a), sonocatalytic (b) and SPC (c) treatment approaches. Data reproduced from Tabasideh
et al. [71]
97
Reprinted from the journal
Topics in Current Chemistry (2020) 378:29
hydroxyl radicals as well as the form of the pollutant in the medium. A detailed
study on the degradation of trichloroacetic acid using a UV/TiO 2 /US combined
process revealed that the maximum extent of degradation for the combined process largely depended on the pH and the speciation of the parent compound [97].
In all cases, however, SPC degradation was always showing better efficacy than
sonolysis or photolysis alone. A study performed by Tabasideh et al. [71] on the
degradation of diazinon showed that maximum degradation using the SPC process with iron-doped TiO 2 was obtained under acidic conditions (pH 5.5), while
a much lower degradation was observed in strongly alkaline conditions (pH 9.5).
These authors also noted that the effect of pH was dominant in the case of photocatalytic oxidation alone and less significant in the case of SPC oxidation (see
Fig. 14).
Catalyst loading also plays a major role in determining the efficacy of SPC
oxidation. For example, Tabasideh et al. [71] studied the effect of catalyst loading
over the range of 0.2–0.6 g/L and reported that optimum catalyst loading did exist
at 0.4 g/L. These authors reported that significantly higher loading of the catalyst
interfered with both the passage of ultrasonic energy and the transmission of light
energy, resulting in detrimental effects. In addition, the negative effect of catalyst
loading beyond the optimum was more dominant in the case of only sonocatalytic
oxidation as compared to SPC oxidation [71] (see Fig. 15).
Several studies have also focussed on the effect of doping of the catalyst on
SPC processes. Reddy et al. [81] studied various iron loadings and reported that
96% degradation of naphthol-blue-black dye was observed at the optimum loading. Multi-walled carbon nanotubes (CNTs) deposited with Fe–TiO 2 under both
visible and UV light showed enhanced formation of reactive radicals and prevention of electron–hole recombination, with sonophotocatalysis giving the better results [98]. These results show that the use of doping or composites definitely helps in enhancing catalyst activity as compared to bare forms of the oxide
catalyst.
Fig. 14 Data for the effect of pH on the degradation of diazinon in presence of Fe-doped TiO 2 using
photocatalytic (a), sonocatalytic (b) and SPC (c) treatment approaches. Data reproduced from Tabasideh
et al. [71]
97
Reprinted from the journal