in electrochemical sensors or energy conversion devices. Some reports expose that
the electrocatalytic ability of carbon-based materials and metallic compounds can be
enhanced upon the use of PtNPs because it allows to have a higher surface area.
Also, it is important to mention that PtNPs are often supported on some material
because otherwise they might agglomerate [87, 88].
Consequently, the PtNPs supported in fluorine-doped tin oxide (FTO) has been
reported, and the use of the nanoparticles allows to increase the roughness, raise the
resistance and the stability, and lower the oxidation potential, which enhances the
catalytic performance of the electrode. This can be seen in the work published by
Ching et al. who showed that PtNPs/FTO degraded 79.3% and 89.1% of naproxen at
pH values of 4.6 and 3, respectively. Hence, a variation in the pH of the solution can
also help in improving the degradation efficiency [58]. In a more recent study
performed by Chang et al. the addition of MWCNTs to Pt on the FTO glass
increased this electrode efficiency toward ibuprofen removal due to a higher electric
conductivity and surface area for the adsorption and oxidation of ibuprofen [61].
4.5 Other Nanomaterials
Alumina nanoparticles (ANPs) are widely studied ceramic materials, because even
when they are nonconducting and cannot transfer electrons, they can be used as
catalysts or catalyst supports because they provide a high surface area that promotes
the adsorption of organics present in wastewater [89]. This property can be used to
concentrate organics that will be eletrooxidized. As an example, Tabeshnia et al.
reported that the incorporation of ANPs onto a glassy carbon electrode allowed to
obtain a better response for the voltammetric electrooxidation of selected NSAIDS:
diclofenac, mefenamic acid, and indomethacin, which were mainly attributed to a
higher adsorption surface [76].
Finally, as a summary of this chapter section, some examples of the nanomaterials
currently used in electrooxidation with their respective removal percentages are
shown in Table 3.
It is important to mention that the percentage of removal presented in this table
makes reference to the degradation of the mentioned pharmaceutical; however, its
oxidation generates other products that must be studied in order to determine if they
represent a toxic threat or if they can be further degraded due to the unspecific
chemical activity of hydroxyl radicals (Fig. 5).
For example, in the degradation of ibuprofen, several by-products have been
identified, particularly 1-(1-hydroxyethyl)-4-isobutyl-benzene, which has a toxic
effect on human erythrocytes; however, it was shown by Chang et al. that it can
be completely eliminated in 60 min using a PtRu-FTO electrode. However, it must be
kept in mind that larger amounts of reaction products are generated due to the higher
electrocatalytic ability of certain electrodes [61]. Other intermediates of reaction
include 4-isobutylacetophenone, 4
0 -(2-methylpropyl)-acetophenone, 4-isobutyl
phenol, and 4-ethylbenzaldehyde, whose structures can be seen in the next picture
[59, 66, 79].
Nanotechnologies for Removal of Nonsteroidal Anti-inflammatory Drug from. . .
293
the electrocatalytic ability of carbon-based materials and metallic compounds can be
enhanced upon the use of PtNPs because it allows to have a higher surface area.
Also, it is important to mention that PtNPs are often supported on some material
because otherwise they might agglomerate [87, 88].
Consequently, the PtNPs supported in fluorine-doped tin oxide (FTO) has been
reported, and the use of the nanoparticles allows to increase the roughness, raise the
resistance and the stability, and lower the oxidation potential, which enhances the
catalytic performance of the electrode. This can be seen in the work published by
Ching et al. who showed that PtNPs/FTO degraded 79.3% and 89.1% of naproxen at
pH values of 4.6 and 3, respectively. Hence, a variation in the pH of the solution can
also help in improving the degradation efficiency [58]. In a more recent study
performed by Chang et al. the addition of MWCNTs to Pt on the FTO glass
increased this electrode efficiency toward ibuprofen removal due to a higher electric
conductivity and surface area for the adsorption and oxidation of ibuprofen [61].
4.5 Other Nanomaterials
Alumina nanoparticles (ANPs) are widely studied ceramic materials, because even
when they are nonconducting and cannot transfer electrons, they can be used as
catalysts or catalyst supports because they provide a high surface area that promotes
the adsorption of organics present in wastewater [89]. This property can be used to
concentrate organics that will be eletrooxidized. As an example, Tabeshnia et al.
reported that the incorporation of ANPs onto a glassy carbon electrode allowed to
obtain a better response for the voltammetric electrooxidation of selected NSAIDS:
diclofenac, mefenamic acid, and indomethacin, which were mainly attributed to a
higher adsorption surface [76].
Finally, as a summary of this chapter section, some examples of the nanomaterials
currently used in electrooxidation with their respective removal percentages are
shown in Table 3.
It is important to mention that the percentage of removal presented in this table
makes reference to the degradation of the mentioned pharmaceutical; however, its
oxidation generates other products that must be studied in order to determine if they
represent a toxic threat or if they can be further degraded due to the unspecific
chemical activity of hydroxyl radicals (Fig. 5).
For example, in the degradation of ibuprofen, several by-products have been
identified, particularly 1-(1-hydroxyethyl)-4-isobutyl-benzene, which has a toxic
effect on human erythrocytes; however, it was shown by Chang et al. that it can
be completely eliminated in 60 min using a PtRu-FTO electrode. However, it must be
kept in mind that larger amounts of reaction products are generated due to the higher
electrocatalytic ability of certain electrodes [61]. Other intermediates of reaction
include 4-isobutylacetophenone, 4
0 -(2-methylpropyl)-acetophenone, 4-isobutyl
phenol, and 4-ethylbenzaldehyde, whose structures can be seen in the next picture
[59, 66, 79].
Nanotechnologies for Removal of Nonsteroidal Anti-inflammatory Drug from. . .
293