uptake of micropollutant. This exogenous hydrogen peroxide release in the rhizosphere was found maximum at 12 days and resulted in Fenton reactions in the
presence of laterite soil. The authors observed a decrease in hydrogen peroxide
concentration with time and are credited to the utilization of hydrogen peroxide in
Fenton reactions. Thus, about 35.34% of acetaminophen was removed with the
action of hydroxyl radicals. A total of 60–64% of acetaminophen removal was
occurred in the combined process, and it is also due to adsorption, microbial
degradation, and byproduct transformation other than the plant uptake and Fenton
reactions.
Reusability of the catalyst is a significant factor which should be considered for
the real-field implementation of the heterogeneous Fenton process. Laterite is found
highly reusable as reported by Khataee and Pakdehi (2014) and Kamagate et al.
(2018). Fluoroquinolone antibiotics removal efficacy of the heterogeneous photoFenton process was 94% and 70%, respectively, at pH 3 and 6.5. A slight reduction
in efficiency was observed after the first recycling. The efficacy of the photo-Fenton
process to mineralize fluoroquinolone antibiotics was found 72% and 50% at pH 3
and 6.5, respectively. This efficiency remains the same after five cycles. Very low
iron release from laterite was observed by Kamagate et al. (2018). This is also an
important characteristic of a reusable heterogeneous catalyst.
Calcination is an option to improve the catalytic activity of every solid catalyst.
Kpinsoton and co-workers (Kpinsoton et al. 2018) tested the changes in morphology
and the catalytic activity of laterite with calcination. The authors did the calcination
at 400, 600, and 800
C and tested its performance for the Fenton oxidation of
methylene blue. Hematite and goethite are the chief iron oxides present in the laterite
and are embedded in kaolinite and quartz frameworks. Calcination at 400
C resulted
in the shrinkage in surface area of laterite significantly due to the transformation of
goethite (which was previously associated with kaolinite) to hematite crystals.
Further calcination process at 600 C resulted in the formation of “amorphous meta
kaolin matrix containing mainly surface defectively crystalized hematite
nanophases” (Kpinsoton et al. 2018). This calcined laterite exhibits highest Fenton
catalytic activity with 99% of methylene blue removal after 100 min of reaction.
Synthesis of iron nanoparticles from laterite and its utilization in the heterogeneous Fenton process is an interesting area, recently proposed by Prof. Manu and his
groups (Sangami and Manu 2019). The researchers prepared iron nanoparticles
using laterite and Tectona Grandis extract and used it for the degradation of
herbicide mixture (Sangami and Manu 2019). The mixture contains 3.5 mg/L
ametryn, 94 mg/L dicamba, and 25 mg/L 2,4-D, and the authors found complete
mineralization of the herbicide mixture within 135 min of heterogeneous Fenton
oxidation with 430 mg/L of hydrogen peroxide and 25.29 mg/L of catalyst at pH 5.
In similar way, iron nanoparticles prepared from laterite soil and eucalyptus leaves
extract are able to remove ametryn completely from water medium (Sangami and
Manu 2019).
524
A. V. Karim et al.
presence of laterite soil. The authors observed a decrease in hydrogen peroxide
concentration with time and are credited to the utilization of hydrogen peroxide in
Fenton reactions. Thus, about 35.34% of acetaminophen was removed with the
action of hydroxyl radicals. A total of 60–64% of acetaminophen removal was
occurred in the combined process, and it is also due to adsorption, microbial
degradation, and byproduct transformation other than the plant uptake and Fenton
reactions.
Reusability of the catalyst is a significant factor which should be considered for
the real-field implementation of the heterogeneous Fenton process. Laterite is found
highly reusable as reported by Khataee and Pakdehi (2014) and Kamagate et al.
(2018). Fluoroquinolone antibiotics removal efficacy of the heterogeneous photoFenton process was 94% and 70%, respectively, at pH 3 and 6.5. A slight reduction
in efficiency was observed after the first recycling. The efficacy of the photo-Fenton
process to mineralize fluoroquinolone antibiotics was found 72% and 50% at pH 3
and 6.5, respectively. This efficiency remains the same after five cycles. Very low
iron release from laterite was observed by Kamagate et al. (2018). This is also an
important characteristic of a reusable heterogeneous catalyst.
Calcination is an option to improve the catalytic activity of every solid catalyst.
Kpinsoton and co-workers (Kpinsoton et al. 2018) tested the changes in morphology
and the catalytic activity of laterite with calcination. The authors did the calcination
at 400, 600, and 800
C and tested its performance for the Fenton oxidation of
methylene blue. Hematite and goethite are the chief iron oxides present in the laterite
and are embedded in kaolinite and quartz frameworks. Calcination at 400
C resulted
in the shrinkage in surface area of laterite significantly due to the transformation of
goethite (which was previously associated with kaolinite) to hematite crystals.
Further calcination process at 600 C resulted in the formation of “amorphous meta
kaolin matrix containing mainly surface defectively crystalized hematite
nanophases” (Kpinsoton et al. 2018). This calcined laterite exhibits highest Fenton
catalytic activity with 99% of methylene blue removal after 100 min of reaction.
Synthesis of iron nanoparticles from laterite and its utilization in the heterogeneous Fenton process is an interesting area, recently proposed by Prof. Manu and his
groups (Sangami and Manu 2019). The researchers prepared iron nanoparticles
using laterite and Tectona Grandis extract and used it for the degradation of
herbicide mixture (Sangami and Manu 2019). The mixture contains 3.5 mg/L
ametryn, 94 mg/L dicamba, and 25 mg/L 2,4-D, and the authors found complete
mineralization of the herbicide mixture within 135 min of heterogeneous Fenton
oxidation with 430 mg/L of hydrogen peroxide and 25.29 mg/L of catalyst at pH 5.
In similar way, iron nanoparticles prepared from laterite soil and eucalyptus leaves
extract are able to remove ametryn completely from water medium (Sangami and
Manu 2019).
524
A. V. Karim et al.