direction of overcoming the drawbacks associated with homogeneous Fenton catalyst have been conducted to develop solid materials with high catalytic activity. The
use of dynamic heterogeneous catalyst as a source for iron in the Fenton process can
control the sludge production, effectiveness at circumneutral pH, and the option to
recycle the iron promoter (Purceno et al. 2012). Immobilizing iron compounds on
various solid supports, such as carbon, zeolite, clay, alumina, etc., have been
comprehensively explored for the removal of organic pollutants (De Leon et al.
2013). This chapter briefly explains the use of different soil minerals as heterogeneous Fenton catalyst for toxicant degradation.
14.2 Heterogeneous Fenton Process
Classical Fenton process using ferrous ion is much efficient for the mineralization of
different organic pollutants. Pollutants, such as dyes (Xavier et al. 2015), pesticides
(Saini et al. 2016), phenol (Gümüş and Akbal 2016), sulfanilic acid azochromotrop
(Hassan et al. 2019), and amoxicillin (Verma and Haritash 2019), were effectively
decomposed via attack of hydroxyl radicals produced due to the reaction between
ferrous ions and hydrogen peroxide. This process is also found effective for the
treatment of real effluents generated from distillery (David et al. 2015), agro-food
industry (Leifeld et al. 2018), and textile industry (Cetinkaya et al. 2018) as well as
to treat turpentine processing wastewater (Huang et al. 2018), coke plant wastewater
(Razaviarani et al. 2019), triethyl phosphate wastewater (Yang et al. 2019), pharmaceutical wastewater (Changotra et al. 2019), and sulfide minerals processing
wastewater (Meng et al. 2019).
Generation of sludge after the treatment is one of the key limitations of the Fenton
process (Nidheesh 2015; Nidheesh and Gandhimathi 2012). The main reason behind
this sludge production is the rise in solution pH by Fenton reaction. Hydroxyl ion
generated in Fenton reaction results in an increase in solution pH. This elevated
solution pH reduces the concentration of ferrous and ferric ions in their ionic forms.
Ferric ions generated via Fenton reaction undergo complexation reactions. This
results in a reduction in ferrous regeneration and subsequent hydroxyl radical
generation. The concentration of ferrous ions required for the maximum pollutant
removal is on the scale of g/L (Nidheesh et al. 2013), and this higher concentration
leads to the increased sludge generation. Thus, conventional Fenton process removes
pollutants via degradation and the coagulation process.
Extended Fenton process, which utilizes external energy, is an option to reduce
the sludge production and to increase the pollutant abatement rate of conventional
Fenton process. The photo-Fenton process which uses energy in the form of light
(Clarizia et al. 2017; Rahim Pouran et al. 2015), electro-Fenton process with
electricity energy (Brillas et al. 2009; Nidheesh et al. 2018a, b), and ultrasoundbased sono-Fenton process (Nidheesh et al. 2013) found effective than conventional
Fenton process in terms of pollutant mineralization rate, reduced sludge production,
and minimized optimal iron concentration.
14 Soil as Heterogeneous Fenton Catalyst for the Abatement of Organic Pollutants
521
use of dynamic heterogeneous catalyst as a source for iron in the Fenton process can
control the sludge production, effectiveness at circumneutral pH, and the option to
recycle the iron promoter (Purceno et al. 2012). Immobilizing iron compounds on
various solid supports, such as carbon, zeolite, clay, alumina, etc., have been
comprehensively explored for the removal of organic pollutants (De Leon et al.
2013). This chapter briefly explains the use of different soil minerals as heterogeneous Fenton catalyst for toxicant degradation.
14.2 Heterogeneous Fenton Process
Classical Fenton process using ferrous ion is much efficient for the mineralization of
different organic pollutants. Pollutants, such as dyes (Xavier et al. 2015), pesticides
(Saini et al. 2016), phenol (Gümüş and Akbal 2016), sulfanilic acid azochromotrop
(Hassan et al. 2019), and amoxicillin (Verma and Haritash 2019), were effectively
decomposed via attack of hydroxyl radicals produced due to the reaction between
ferrous ions and hydrogen peroxide. This process is also found effective for the
treatment of real effluents generated from distillery (David et al. 2015), agro-food
industry (Leifeld et al. 2018), and textile industry (Cetinkaya et al. 2018) as well as
to treat turpentine processing wastewater (Huang et al. 2018), coke plant wastewater
(Razaviarani et al. 2019), triethyl phosphate wastewater (Yang et al. 2019), pharmaceutical wastewater (Changotra et al. 2019), and sulfide minerals processing
wastewater (Meng et al. 2019).
Generation of sludge after the treatment is one of the key limitations of the Fenton
process (Nidheesh 2015; Nidheesh and Gandhimathi 2012). The main reason behind
this sludge production is the rise in solution pH by Fenton reaction. Hydroxyl ion
generated in Fenton reaction results in an increase in solution pH. This elevated
solution pH reduces the concentration of ferrous and ferric ions in their ionic forms.
Ferric ions generated via Fenton reaction undergo complexation reactions. This
results in a reduction in ferrous regeneration and subsequent hydroxyl radical
generation. The concentration of ferrous ions required for the maximum pollutant
removal is on the scale of g/L (Nidheesh et al. 2013), and this higher concentration
leads to the increased sludge generation. Thus, conventional Fenton process removes
pollutants via degradation and the coagulation process.
Extended Fenton process, which utilizes external energy, is an option to reduce
the sludge production and to increase the pollutant abatement rate of conventional
Fenton process. The photo-Fenton process which uses energy in the form of light
(Clarizia et al. 2017; Rahim Pouran et al. 2015), electro-Fenton process with
electricity energy (Brillas et al. 2009; Nidheesh et al. 2018a, b), and ultrasoundbased sono-Fenton process (Nidheesh et al. 2013) found effective than conventional
Fenton process in terms of pollutant mineralization rate, reduced sludge production,
and minimized optimal iron concentration.
14 Soil as Heterogeneous Fenton Catalyst for the Abatement of Organic Pollutants
521