14.3.2 Clay
The usage of clay minerals as heterogeneous Fenton catalyst is a highly attractive
method, as it can exhibit higher catalytic property for the Fenton oxidation of organic
compounds. Clay minerals are low-cost promising materials for the fabrication of
reinforced catalysts with a high possibility of recovering the catalyst after the
treatment. Even though clay minerals contain iron and other cations, the low
concentration of iron in it can affect the heterogeneous Fenton degradation efficiency. The incorporation of iron into clays through pillaring and impregnation
seems to be a potential alternative for the preparation of heterogeneous catalyst
(Herney-Ramirez et al. 2010). It improved the catalytic properties of the clay
mineral, and the catalyst can be reused for several degradation cycles. Also, the
acid treatment of clay structures can eliminate the impurities present in its structure
and increase the surface area of the clay minerals (Ayodele 2013). The stability and
reusable potential of the prepared catalyst have a significant impact on the Fenton
process efficiency. Among the different clay minerals, montmorillonite, bentonite,
kaolinite, laponite, etc. are most commonly used as a heterogeneous Fenton catalyst.
Bentonite is a highly colloidal natural clay mineral belonging to the class of
smectites and is normally formed through volcanic ash weathering in the presence of
water (Gao et al. 2016; Nidheesh 2015). These clay minerals are smaller in size with
higher surface area and stability (Ma et al. 2018). A study conducted by Feng et al.
(2005) explored the degradation efficiency of bentonite clay-based iron
nanocomposite coated on the inner wall of photo-reactor and with suspended
nanocomposite catalyst for discoloration of orange II. Even though a decreased
decoloration rate was observed for the film catalyst because of a decreased specific
area, multiple experimental runs revealed that the coated catalyst has more stability
and diminished iron leaching than the suspended nanocomposite catalyst. In another
study, innovative photo-Fenton catalysts were prepared by arresting iron species on
bentonite plates by two distinct techniques and utilized for the degradation of
resorcinol (González-Bahamón et al. 2011). They have observed that the catalyst
prepared by forced hydrolysis of ferric nitrate on the bentonite plate shown an
enhanced activity due to an increased surface and high reusability potential. Ironsupported bentonite prepared by Gao et al. (2015) had shown a substantial increase
in the specific surface area of the catalyst and improved the adsorption performance
of the catalyst. Rhodamine B was completely removed due to the combined effects
of adsorption and degradation under visible light-emitting diode lamps at natural
pH 4.2, 0.25 g L
À1 and 12 mM H 2 O 2 concentration.
The synthetic clay mineral Laponite, made-up from natural inorganic mineral
sources, has received significant importance as a Fenton catalyst due to its unique
physical properties. As heterogeneous catalyst, laponite clay-based Fe
nanocomposite was studied for the discoloration and mineralization of reactive red
dye in the presence of hydrogen peroxide and ultraviolet light (Feng et al. 2003). The
higher surface area and total pore volume of the catalyst resulted in complete
discoloration of the compound at an optimal condition of 500 mg/L H 2 O 2 , 1.0 g of
14 Soil as Heterogeneous Fenton Catalyst for the Abatement of Organic Pollutants
525
The usage of clay minerals as heterogeneous Fenton catalyst is a highly attractive
method, as it can exhibit higher catalytic property for the Fenton oxidation of organic
compounds. Clay minerals are low-cost promising materials for the fabrication of
reinforced catalysts with a high possibility of recovering the catalyst after the
treatment. Even though clay minerals contain iron and other cations, the low
concentration of iron in it can affect the heterogeneous Fenton degradation efficiency. The incorporation of iron into clays through pillaring and impregnation
seems to be a potential alternative for the preparation of heterogeneous catalyst
(Herney-Ramirez et al. 2010). It improved the catalytic properties of the clay
mineral, and the catalyst can be reused for several degradation cycles. Also, the
acid treatment of clay structures can eliminate the impurities present in its structure
and increase the surface area of the clay minerals (Ayodele 2013). The stability and
reusable potential of the prepared catalyst have a significant impact on the Fenton
process efficiency. Among the different clay minerals, montmorillonite, bentonite,
kaolinite, laponite, etc. are most commonly used as a heterogeneous Fenton catalyst.
Bentonite is a highly colloidal natural clay mineral belonging to the class of
smectites and is normally formed through volcanic ash weathering in the presence of
water (Gao et al. 2016; Nidheesh 2015). These clay minerals are smaller in size with
higher surface area and stability (Ma et al. 2018). A study conducted by Feng et al.
(2005) explored the degradation efficiency of bentonite clay-based iron
nanocomposite coated on the inner wall of photo-reactor and with suspended
nanocomposite catalyst for discoloration of orange II. Even though a decreased
decoloration rate was observed for the film catalyst because of a decreased specific
area, multiple experimental runs revealed that the coated catalyst has more stability
and diminished iron leaching than the suspended nanocomposite catalyst. In another
study, innovative photo-Fenton catalysts were prepared by arresting iron species on
bentonite plates by two distinct techniques and utilized for the degradation of
resorcinol (González-Bahamón et al. 2011). They have observed that the catalyst
prepared by forced hydrolysis of ferric nitrate on the bentonite plate shown an
enhanced activity due to an increased surface and high reusability potential. Ironsupported bentonite prepared by Gao et al. (2015) had shown a substantial increase
in the specific surface area of the catalyst and improved the adsorption performance
of the catalyst. Rhodamine B was completely removed due to the combined effects
of adsorption and degradation under visible light-emitting diode lamps at natural
pH 4.2, 0.25 g L
À1 and 12 mM H 2 O 2 concentration.
The synthetic clay mineral Laponite, made-up from natural inorganic mineral
sources, has received significant importance as a Fenton catalyst due to its unique
physical properties. As heterogeneous catalyst, laponite clay-based Fe
nanocomposite was studied for the discoloration and mineralization of reactive red
dye in the presence of hydrogen peroxide and ultraviolet light (Feng et al. 2003). The
higher surface area and total pore volume of the catalyst resulted in complete
discoloration of the compound at an optimal condition of 500 mg/L H 2 O 2 , 1.0 g of
14 Soil as Heterogeneous Fenton Catalyst for the Abatement of Organic Pollutants
525