1 3
Topics in Current Chemistry (2020) 378:6
By adding H 2 O 2 , a larger variety of pollutants have been degraded than in the case
of pure photocatalysis using ferrites (Table 4). In the first case, Sannino et al. [30]
employed LaFeO 3 for the removal of acetic acid. Only 60% depletion in 300 min
was obtained for the best case. Then CoFe 2 O 4 ferrite was used to oxidize methylene
blue, with almost complete oxidation in 75 min of reaction [22]. Gao et al. [102]
employed mesoporous CuFe 2 O 4 ferrite for the elimination of sulfonamides in water.
The antibiotic conversion was 31% within 180 min, but no mineralization data was
available. Samoila et al. [103] evidenced differences between pristine NiFeO 4 and
NiFeO 4 substituted with La
3+
, Sm
3+
, Gd
3+
or Dy
3+
cations. The undoped material
afforded 30% of Orange II azo dye decolorization vs. around 90% in 30 min with
the La-substituted catalyst. Recently, a mixed strategy has been the employment of
a co-catalyst with H 2 O 2 [92]. The heterojunction of CuS/BiFeO 3 was exploited for
alachlor degradation. The combined mechanism in the presence of H 2 O 2 led to 90%
of pesticide removal in 1 h of reaction.
Several efforts have been made to intensify the reactivity of ferrite materials in
water in simultaneous application of advanced oxidation processes (AOPs). In this
sense, the addition of H 2 O 2 to the reaction media was not enough to improve substantially the activity. Lately, research has moved towards the material modification
taking into account the composition of a ferrite and its ability to exchange A or B
cation and so to tune its catalytic properties. In this scenario, the latest trend has been
the doping of the materials with transition metals [31, 43, 95, 104, 105]. Zn x Fe 3–x O 4
materials were synthesized by a soft chemical route by Mandal et al. [95]. This magnetic catalyst was employed for the degradation of Acid Blue 113 and also for antimicrobial purposes. The pristine and modified ferrites showed very good photoactivity when H 2 O 2 was added in the reaction media. The ferrites were quite stable
after eight cycles of reaction and their magnetic properties allowed recovery after
each sequential run. Around the same time, Soltani and Lee [31] obtained BiFeO 3
substituted by barium via sol–gel method. The ratio of substitution of Bi 1–x Ba x FeO 3
was between 0.03 and 0.12. The experimental results indicate that the increase of Ba
until 12% affected the redox cycle and provoked oxygen vacancies that significantly
enhanced the toluene degradation under pure visible light.
In 2018, Cu-doped LaFeO 3 was obtained by Phan et al. [104]. The catalysts were
employed for the decoloration of dye, in this case methyl orange. The best reactivity
resulted from the catalyst with 15% copper. The authors attributed this improvement
to the fact that it generates much more HO· than pristine LaFeO 3 . This behaviour
was associated with an enhancement of the H 2 O 2 decomposition by the two metals,
Cu and Fe, which provoke additional reactions, as well as an improvement of the
availability of Fe(II) at the surface. The greater generation of HO· was corroborated
by electron spin resonance (ESR) technique. In the same way, Co-doped MgFe 2 O 4
was synthesized from saprolite laterite ore [43]. The low addition of Co (ca. 1%)
greatly improved the activity; 97% of the dye was degraded and 68% of TOC mineralized after 180 min. The authors pointed out a synergistic effect between photocatalysis and heterogeneous photo-Fenton mechanism with this stable catalyst. The
measurement of the iron leached into the solution showed that the activity was associated with the surface iron of the catalyst and not the iron in homogeneous solution.
Besides this, the ferrite lost 10% of activity during its reuse.
129
Reprinted from the journal
Topics in Current Chemistry (2020) 378:6
By adding H 2 O 2 , a larger variety of pollutants have been degraded than in the case
of pure photocatalysis using ferrites (Table 4). In the first case, Sannino et al. [30]
employed LaFeO 3 for the removal of acetic acid. Only 60% depletion in 300 min
was obtained for the best case. Then CoFe 2 O 4 ferrite was used to oxidize methylene
blue, with almost complete oxidation in 75 min of reaction [22]. Gao et al. [102]
employed mesoporous CuFe 2 O 4 ferrite for the elimination of sulfonamides in water.
The antibiotic conversion was 31% within 180 min, but no mineralization data was
available. Samoila et al. [103] evidenced differences between pristine NiFeO 4 and
NiFeO 4 substituted with La
3+
, Sm
3+
, Gd
3+
or Dy
3+
cations. The undoped material
afforded 30% of Orange II azo dye decolorization vs. around 90% in 30 min with
the La-substituted catalyst. Recently, a mixed strategy has been the employment of
a co-catalyst with H 2 O 2 [92]. The heterojunction of CuS/BiFeO 3 was exploited for
alachlor degradation. The combined mechanism in the presence of H 2 O 2 led to 90%
of pesticide removal in 1 h of reaction.
Several efforts have been made to intensify the reactivity of ferrite materials in
water in simultaneous application of advanced oxidation processes (AOPs). In this
sense, the addition of H 2 O 2 to the reaction media was not enough to improve substantially the activity. Lately, research has moved towards the material modification
taking into account the composition of a ferrite and its ability to exchange A or B
cation and so to tune its catalytic properties. In this scenario, the latest trend has been
the doping of the materials with transition metals [31, 43, 95, 104, 105]. Zn x Fe 3–x O 4
materials were synthesized by a soft chemical route by Mandal et al. [95]. This magnetic catalyst was employed for the degradation of Acid Blue 113 and also for antimicrobial purposes. The pristine and modified ferrites showed very good photoactivity when H 2 O 2 was added in the reaction media. The ferrites were quite stable
after eight cycles of reaction and their magnetic properties allowed recovery after
each sequential run. Around the same time, Soltani and Lee [31] obtained BiFeO 3
substituted by barium via sol–gel method. The ratio of substitution of Bi 1–x Ba x FeO 3
was between 0.03 and 0.12. The experimental results indicate that the increase of Ba
until 12% affected the redox cycle and provoked oxygen vacancies that significantly
enhanced the toluene degradation under pure visible light.
In 2018, Cu-doped LaFeO 3 was obtained by Phan et al. [104]. The catalysts were
employed for the decoloration of dye, in this case methyl orange. The best reactivity
resulted from the catalyst with 15% copper. The authors attributed this improvement
to the fact that it generates much more HO· than pristine LaFeO 3 . This behaviour
was associated with an enhancement of the H 2 O 2 decomposition by the two metals,
Cu and Fe, which provoke additional reactions, as well as an improvement of the
availability of Fe(II) at the surface. The greater generation of HO· was corroborated
by electron spin resonance (ESR) technique. In the same way, Co-doped MgFe 2 O 4
was synthesized from saprolite laterite ore [43]. The low addition of Co (ca. 1%)
greatly improved the activity; 97% of the dye was degraded and 68% of TOC mineralized after 180 min. The authors pointed out a synergistic effect between photocatalysis and heterogeneous photo-Fenton mechanism with this stable catalyst. The
measurement of the iron leached into the solution showed that the activity was associated with the surface iron of the catalyst and not the iron in homogeneous solution.
Besides this, the ferrite lost 10% of activity during its reuse.
129
Reprinted from the journal