with a slight increase in the basal spacing from d 001 ¼ 1.26 (Na–Mt) to 1.53 nm (Fe–
Mt). The Fenton process was efficient for phenol removal using Fe–Mt as a catalyst
under visible light irradiation, and the process had two-stage pseudo-first-order
kinetics. The overall reaction had a higher degradation rate even when it was only
irradiated with visible light for the first 40 min period. Further investigation confirmed that the irradiation increased the presence of certain intermediates. Among
them, 1, 4-benzoquinone, hydroquinone, and catechol all enhanced the Fenton
reaction rates. Either catechol or hydroquinone was added to the Fenton system
with Fe–Mt/H 2 O 2 with or without visible light irradiation, and they both accelerated
phenol degradation because catechol and hydroquinone are capable of reductively
and effectively transforming Fe
3+ into Fe
2+ . The concentrations of dissolved total Fe
increased with the increase in the oxalic acid concentration, which can strongly
chelate Fe
3+ . Hence, iron was released from Fe–Mt, and reductive transformation
played an important role in promoting the Fenton reaction process for phenol
removal.
11.2.4 Porous Carrier
Bossmann et al. investigated the heterogeneous photoenhanced Fenton oxidation of
PVA and found that contrary to the homogeneous reaction mechanism [16], the
degradation of PVA using the system zeolite Y/Fe
3+ /H 2 O 2 generates low molecular
weight reaction products because DOC removal remains incomplete after 120 min
reaction. In addition, they confirmed that Fe
3+ does not form complexes with PVA
and its oxidation products. Most likely, the Fe
3+ remains bound inside the zeolite Y
framework. However, it should be noted that a heterogeneous catalyst for photoFenton reaction with a high efficiency as well as an acceptable cost has not been fully
established. Hence, there is no doubt that to develop such a catalyst has not only
academic significance but also industrial applications.
Photo-Fenton-like processes using two types of Fe-zeolites (Fe-ZSM5 and
Fe-Beta) as heterogeneous catalysts were carried out in order to treat contaminated
effluents with organic compounds at neutral pH [17]. It was proved that light (solar
and artificial) improves significantly the DOC removal in this kind of processes. A
possible contribution by homogeneous photo-Fenton reaction catalyzed by the iron
leached during the reaction was insignificant. This study also proves that the
catalytic activity of Fe-zeolites is improved by photo-Fenton-like processes using
solar light in a pilot plant equipped with compound parabolic collectors.
A novel α-FeOOH/mesoporous carbon (α-FeOOH/MesoC) composite prepared
by in situ crystallization of adsorbed ferric ions within carboxyl functionalized
mesoporous carbon was developed as a novel visible light-assisted heterogeneous
Fenton-like catalyst [18]. The visible light active α-FeOOH nanocrystals were
encapsulated in the mesoporous frameworks accompanying with surface attached
large α-FeOOH microcrystals via CÀOÀFe bonding. Assisting with visible light
irradiation on α-FeOOH/MesoC, the mineralization efficiency increased owing to
11.2 Heterogeneous Photo-Fenton Reaction
263
Mt). The Fenton process was efficient for phenol removal using Fe–Mt as a catalyst
under visible light irradiation, and the process had two-stage pseudo-first-order
kinetics. The overall reaction had a higher degradation rate even when it was only
irradiated with visible light for the first 40 min period. Further investigation confirmed that the irradiation increased the presence of certain intermediates. Among
them, 1, 4-benzoquinone, hydroquinone, and catechol all enhanced the Fenton
reaction rates. Either catechol or hydroquinone was added to the Fenton system
with Fe–Mt/H 2 O 2 with or without visible light irradiation, and they both accelerated
phenol degradation because catechol and hydroquinone are capable of reductively
and effectively transforming Fe
3+ into Fe
2+ . The concentrations of dissolved total Fe
increased with the increase in the oxalic acid concentration, which can strongly
chelate Fe
3+ . Hence, iron was released from Fe–Mt, and reductive transformation
played an important role in promoting the Fenton reaction process for phenol
removal.
11.2.4 Porous Carrier
Bossmann et al. investigated the heterogeneous photoenhanced Fenton oxidation of
PVA and found that contrary to the homogeneous reaction mechanism [16], the
degradation of PVA using the system zeolite Y/Fe
3+ /H 2 O 2 generates low molecular
weight reaction products because DOC removal remains incomplete after 120 min
reaction. In addition, they confirmed that Fe
3+ does not form complexes with PVA
and its oxidation products. Most likely, the Fe
3+ remains bound inside the zeolite Y
framework. However, it should be noted that a heterogeneous catalyst for photoFenton reaction with a high efficiency as well as an acceptable cost has not been fully
established. Hence, there is no doubt that to develop such a catalyst has not only
academic significance but also industrial applications.
Photo-Fenton-like processes using two types of Fe-zeolites (Fe-ZSM5 and
Fe-Beta) as heterogeneous catalysts were carried out in order to treat contaminated
effluents with organic compounds at neutral pH [17]. It was proved that light (solar
and artificial) improves significantly the DOC removal in this kind of processes. A
possible contribution by homogeneous photo-Fenton reaction catalyzed by the iron
leached during the reaction was insignificant. This study also proves that the
catalytic activity of Fe-zeolites is improved by photo-Fenton-like processes using
solar light in a pilot plant equipped with compound parabolic collectors.
A novel α-FeOOH/mesoporous carbon (α-FeOOH/MesoC) composite prepared
by in situ crystallization of adsorbed ferric ions within carboxyl functionalized
mesoporous carbon was developed as a novel visible light-assisted heterogeneous
Fenton-like catalyst [18]. The visible light active α-FeOOH nanocrystals were
encapsulated in the mesoporous frameworks accompanying with surface attached
large α-FeOOH microcrystals via CÀOÀFe bonding. Assisting with visible light
irradiation on α-FeOOH/MesoC, the mineralization efficiency increased owing to
11.2 Heterogeneous Photo-Fenton Reaction
263