- As far as the oxidation and mineralisation of recalcitrant organic
contaminants in water and wastewater are concerned, the combination of ozone, appropriate photocatalyst(s), optimum
design and optimised conditions will lead to higher degradation, removal rates and efficiencies compared to using ozonation and photocatalysis separately. The synergistic effects of
this combination have been observed in many cases and are primarily attributed to the intensive generation of highly oxidative
and non-selective reagents (such as hydroxyl radicals) in the
oxidation medium of photocatalytic ozonation.
- The high mineralisation rates of nearly all model pollutants in
water by photocatalytic ozonation, and the simplicity of this
process, make it an excellent alternative to other oxidation
treatment methods.
- In addition to choosing a suitable photocatalyst, a proper irradiation source and an optimum ozone concentration for photocatalytic ozonation treatments, developing new operative designs
for oxidation reactors, where these factors are combined and
utilised together, is important. An effective reactor design could
considerably stimulate the synergistic effects and benefits of
photocatalytic ozonation systems.
- Much like other successful technologies, in order to move this
treatment method from the lab to commercial utilisation, more
attention should be focused on the immobilisation of photocatalyst particles onto inert substrates, as slurry applications of
photocatalytic ozonation are not economically justifiable, due
to the additional high costs of photocatalyst filtration after
treatment. Fortunately, photocatalytic ozonation can moderate
the relatively poor mass transfer properties of immobilised
photocatalysts in photocatalytic treatments.
- In most reported cases, increasing the concentration of pollutant(s) and ozone led to an increased oxidation rate by photocatalytic ozonation. However, an optimal ozone concentration
must be applied to reach an optimal specific ozone consumption and for synergy between photocatalysis and ozonation to
occur.
- The structure, properties and concentration of applied photocatalyst play a significant role in the oxidation efficiency of photocatalytic ozonation. Using shorter wavelengths and increasing
the light intensity of the irradiation source usually led to
increased oxidation rates. However, employing photocatalysts
able to absorb natural sunlight and moving towards visible
wavelengths can significantly reduce cost.
- Most published studies indicated acidic pH being preferred for
photocatalytic ozonation treatments due to higher oxidation
and mineralisation efficiencies.
- The presence of chemical substances in the oxidation medium
of photocatalytic ozonation systems can either promote or inhibit the oxidation process.
- As far as the oxidation and mineralisation of recalcitrant organic
contaminants in water and wastewater are concerned, the combination of ozone, appropriate photocatalyst(s), optimum
design and optimised conditions will lead to higher degradation, removal rates and efficiencies compared to using ozonation and photocatalysis separately. The synergistic effects of
this combination have been observed in many cases and are primarily attributed to the intensive generation of highly oxidative
and non-selective reagents (such as hydroxyl radicals) in the
oxidation medium of photocatalytic ozonation.
- The high mineralisation rates of nearly all model pollutants in
water by photocatalytic ozonation, and the simplicity of this
process, make it an excellent alternative to other oxidation
treatment methods.
- In addition to choosing a suitable photocatalyst, a proper irradiation source and an optimum ozone concentration for photocatalytic ozonation treatments, developing new operative designs
for oxidation reactors, where these factors are combined and
utilised together, is important. An effective reactor design could
considerably stimulate the synergistic effects and benefits of
photocatalytic ozonation systems.
- Much like other successful technologies, in order to move this
treatment method from the lab to commercial utilisation, more
attention should be focused on the immobilisation of photocatalyst particles onto inert substrates, as slurry applications of
photocatalytic ozonation are not economically justifiable, due
to the additional high costs of photocatalyst filtration after
treatment. Fortunately, photocatalytic ozonation can moderate
the relatively poor mass transfer properties of immobilised
photocatalysts in photocatalytic treatments.
- In most reported cases, increasing the concentration of pollutant(s) and ozone led to an increased oxidation rate by photocatalytic ozonation. However, an optimal ozone concentration
must be applied to reach an optimal specific ozone consumption and for synergy between photocatalysis and ozonation to
occur.
- The structure, properties and concentration of applied photocatalyst play a significant role in the oxidation efficiency of photocatalytic ozonation. Using shorter wavelengths and increasing
the light intensity of the irradiation source usually led to
increased oxidation rates. However, employing photocatalysts
able to absorb natural sunlight and moving towards visible
wavelengths can significantly reduce cost.
- Most published studies indicated acidic pH being preferred for
photocatalytic ozonation treatments due to higher oxidation
and mineralisation efficiencies.
- The presence of chemical substances in the oxidation medium
of photocatalytic ozonation systems can either promote or inhibit the oxidation process.
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