1 3
Topics in Current Chemistry (2020) 378:6
The last technique employed for the synthesis of ferrite as photocatalysts for water
treatment is the autocombustion route as performed by Patil et al. [88]. In this case,
the authors got ZnFe 2 O 4 by using sugar cane as fuel. The resulting material showed
a bandgap value of 2.8 eV and was used for two objectives: as photocatalyst for dye
removal and for antibacterial purposes. The data indicated that complete removal
of mixed dyes after 150 min was achieved as well as good inhibition of Escherichia
coli, Staphylococcus aureus and Pseudomonas aeruginosa. ZnFe 2 O 4 showed good
reusability over a minimum of four cycles.
However, the perovskite specific surface areas are usually quite low and, in most
cases, the activity can be limited by this parameter. In order to increase the activity,
they have been immobilized on different supports like montmorillonite and active carbon. A few works have been developed in this sense. It is worth highlighting the works
of Peng et al. [29] and Roonasi and Mazinani [89]. In the former, LaFeO 3 was deposited on montmorillonite and employed to oxidize rhodamine B in water [29]. The
composite photoactivity was higher than that of pristine LaFeO 3 , which was associated with adsorption onto the surface. They got complete degradation of rhodamine B
in 75 min, but the main drawback was that the total organic carbon (TOC) evolution
was not followed during the time course of the photoreactions. Roonasi and Mazinani
[89] supported barium ferrite on active carbon for the discoloration of dyes in water.
When comparing the unsupported ferrite with the supported one, data showed that the
photoactivity improved when adding active carbon owing to a synergetic effect.
Other strategies have been developed to improve the activity, too. Among them,
coupling semiconductors in heterojunctions has gained importance. In this context,
it is worth highlighting the employment of LaFeO 3 /SnS 2 , LaFeO 3 /AgBr, BiFeO 3 /
BiOI and Ag 3 PO 4 -CoFe 2 O 4 -GO, the last one with a double improvement by the
addition of an adsorbent. In the first case, LaFeO 3 was obtained by a hydrothermal
method and was well dispersed in SnS 2 nanosheets [40]. Better activity than pristine
LaFeO 3 was observed for tetracycline oxidation. In parallel, Song et al. [90] obtained
a LaFeO 3 /AgBr composite, used for rhodamine B removal. They got a faster movement of charges with the 10% LaFeO 3 /AgBr. In these two cases, the enhancement
of the photoactivity could be ascribed to the prevalence of Z-scheme mechanism
of charge transfer. The synthesis of a BiFeO 3 /BiOI composite by wet impregnation
was carried out by Malathi et al. [91]. The authors designed a photocatalyst that was
quite active and stable after several runs. The 2% BiFeO 3 /BiOI afforded the maximum activity for complete rhodamine B depletion within the first 60 min of reaction
and after three sequential cycles of reaction. The good activity was related to the
efficient charge separation of photoinduced hole–electron pairs by transferring the
electrons from the BiOI to BiFeO 3 surface [91]. Finally, the last work with composites was performed by Zielinska-Jurek et al. [26]. In this case, the role of ferrites was
to provide a magnetic core to a TiO 2 /SiO 2 -coated material for recovery purpose after
application. Figure 8 shows the high-angle annular dark-field (HAADF) images of
the catalyst for illustration.
The last recently reported strategy deals with the partial substitution of cations in
the ferrite structure. A few works have developed this method thus far. Jamil et al.
synthesized a BaFe 1–x Cu x O 3–δ material [38], the group of Rashmi et al. prepared
125
Reprinted from the journal
Topics in Current Chemistry (2020) 378:6
The last technique employed for the synthesis of ferrite as photocatalysts for water
treatment is the autocombustion route as performed by Patil et al. [88]. In this case,
the authors got ZnFe 2 O 4 by using sugar cane as fuel. The resulting material showed
a bandgap value of 2.8 eV and was used for two objectives: as photocatalyst for dye
removal and for antibacterial purposes. The data indicated that complete removal
of mixed dyes after 150 min was achieved as well as good inhibition of Escherichia
coli, Staphylococcus aureus and Pseudomonas aeruginosa. ZnFe 2 O 4 showed good
reusability over a minimum of four cycles.
However, the perovskite specific surface areas are usually quite low and, in most
cases, the activity can be limited by this parameter. In order to increase the activity,
they have been immobilized on different supports like montmorillonite and active carbon. A few works have been developed in this sense. It is worth highlighting the works
of Peng et al. [29] and Roonasi and Mazinani [89]. In the former, LaFeO 3 was deposited on montmorillonite and employed to oxidize rhodamine B in water [29]. The
composite photoactivity was higher than that of pristine LaFeO 3 , which was associated with adsorption onto the surface. They got complete degradation of rhodamine B
in 75 min, but the main drawback was that the total organic carbon (TOC) evolution
was not followed during the time course of the photoreactions. Roonasi and Mazinani
[89] supported barium ferrite on active carbon for the discoloration of dyes in water.
When comparing the unsupported ferrite with the supported one, data showed that the
photoactivity improved when adding active carbon owing to a synergetic effect.
Other strategies have been developed to improve the activity, too. Among them,
coupling semiconductors in heterojunctions has gained importance. In this context,
it is worth highlighting the employment of LaFeO 3 /SnS 2 , LaFeO 3 /AgBr, BiFeO 3 /
BiOI and Ag 3 PO 4 -CoFe 2 O 4 -GO, the last one with a double improvement by the
addition of an adsorbent. In the first case, LaFeO 3 was obtained by a hydrothermal
method and was well dispersed in SnS 2 nanosheets [40]. Better activity than pristine
LaFeO 3 was observed for tetracycline oxidation. In parallel, Song et al. [90] obtained
a LaFeO 3 /AgBr composite, used for rhodamine B removal. They got a faster movement of charges with the 10% LaFeO 3 /AgBr. In these two cases, the enhancement
of the photoactivity could be ascribed to the prevalence of Z-scheme mechanism
of charge transfer. The synthesis of a BiFeO 3 /BiOI composite by wet impregnation
was carried out by Malathi et al. [91]. The authors designed a photocatalyst that was
quite active and stable after several runs. The 2% BiFeO 3 /BiOI afforded the maximum activity for complete rhodamine B depletion within the first 60 min of reaction
and after three sequential cycles of reaction. The good activity was related to the
efficient charge separation of photoinduced hole–electron pairs by transferring the
electrons from the BiOI to BiFeO 3 surface [91]. Finally, the last work with composites was performed by Zielinska-Jurek et al. [26]. In this case, the role of ferrites was
to provide a magnetic core to a TiO 2 /SiO 2 -coated material for recovery purpose after
application. Figure 8 shows the high-angle annular dark-field (HAADF) images of
the catalyst for illustration.
The last recently reported strategy deals with the partial substitution of cations in
the ferrite structure. A few works have developed this method thus far. Jamil et al.
synthesized a BaFe 1–x Cu x O 3–δ material [38], the group of Rashmi et al. prepared
125
Reprinted from the journal