302
S. B. Jaffri and K. S. Ahmad
6 Silver: A Nano-biotechnological Tool
for Eco-detoxification
6.1 Nano-photocatalytic Potential
Hydrospheric contamination arising from the indiscriminate dumping of waste materials into water bodies has been following an increasing trend. In this regard, different
pollutants in an untreated form are being dumped into waterbodies partly by the
dint of non-existence of treatment plants at industrial and partly due to the lack of
resources of industries to bear the capital and operational costs of treatment plants.
In any case, waterbodies are being harmed. Organic dyes have been one of such
pollutant groups that are used in a multitude of industries and are being dumped
regularly. Such coloring agents are being accumulated into the hydrospheric zones
leading to eutrophication, alleviation in the re-oxygenation potential and imparting
severe harm toward the aquatic biota by becoming an obstacle in hindering the
solar light infiltration in waterbody (Jaffri and Ahmad 2017, 2018; Dasgupta et al.
2020). Such pollutants are usually persistent organic pollutants (POPs) and are not
easier targets for microbial degradation in addition to showing poor percentages
of removal by costly physical and chemical methods such as flocculation, adsorptive, ultra-filtration, redox treatments, electrochemical, and electro-coagulation. In
this regard, the photo-catalysis-based environmental detoxification with NPs has
been proven to be an effective method signifying a facile and cost-effective mode.
Nano-photocatalytic degradation has been marked by a rapid oxidative rate, no toxic
compounds releases and driven by sunlight without requiring complex machinery
and other operational requirements (Noman et al. 2020).
AgNPs synthesized by microbial route is an effective nano-biotechnological tool
that has been employed for photo-catalysis of various dyes shown in Table 2 achieving
impressive aromatization percentages. The underlying mechanism responsible for
the effective nano-photocatalytic degradation percentages with AgNPs is due to
the adsorptive interaction established between the organic dyes and AgNPs acting
as an adsorbent with positive ions for the negatively charged dye molecules to be
attached on it (Jiang et al. 2005; Jaffri and Ahmad 2020b). In a recent study, AgNPs
were synthesized using microbial precursors—Bacillus subtilis (SJ 15) having been
isolated from the pedospheric samples for the photo-catalysis of thiazine dye known
as methylene blue which is known for causing a number of health issues (Roshmi
et al. 2017). Impressive detoxification rates obtained for AgNPs based assay can be
ascribed to the adsorption as well the decomposition phenomenon. The incidence
of solar light on reaction mixture of methylene blue dye and AgNPs triggers the
photocatalytic process due to the excitation of the surface plasmon resonance, i.e.,
vacillations of charge density having an ability of the propagation at the interfacial
region of metallic and dielectric intermediate (García 2011). AgNPs synthesized
from Bacillus subtilis (SJ 15) displayed an effective removal of methylene blue in
4 h with the yield reaching up to 18 ± 0.3% for AgNPs taken, i.e., 20 mg L
−1 . In a
S. B. Jaffri and K. S. Ahmad
6 Silver: A Nano-biotechnological Tool
for Eco-detoxification
6.1 Nano-photocatalytic Potential
Hydrospheric contamination arising from the indiscriminate dumping of waste materials into water bodies has been following an increasing trend. In this regard, different
pollutants in an untreated form are being dumped into waterbodies partly by the
dint of non-existence of treatment plants at industrial and partly due to the lack of
resources of industries to bear the capital and operational costs of treatment plants.
In any case, waterbodies are being harmed. Organic dyes have been one of such
pollutant groups that are used in a multitude of industries and are being dumped
regularly. Such coloring agents are being accumulated into the hydrospheric zones
leading to eutrophication, alleviation in the re-oxygenation potential and imparting
severe harm toward the aquatic biota by becoming an obstacle in hindering the
solar light infiltration in waterbody (Jaffri and Ahmad 2017, 2018; Dasgupta et al.
2020). Such pollutants are usually persistent organic pollutants (POPs) and are not
easier targets for microbial degradation in addition to showing poor percentages
of removal by costly physical and chemical methods such as flocculation, adsorptive, ultra-filtration, redox treatments, electrochemical, and electro-coagulation. In
this regard, the photo-catalysis-based environmental detoxification with NPs has
been proven to be an effective method signifying a facile and cost-effective mode.
Nano-photocatalytic degradation has been marked by a rapid oxidative rate, no toxic
compounds releases and driven by sunlight without requiring complex machinery
and other operational requirements (Noman et al. 2020).
AgNPs synthesized by microbial route is an effective nano-biotechnological tool
that has been employed for photo-catalysis of various dyes shown in Table 2 achieving
impressive aromatization percentages. The underlying mechanism responsible for
the effective nano-photocatalytic degradation percentages with AgNPs is due to
the adsorptive interaction established between the organic dyes and AgNPs acting
as an adsorbent with positive ions for the negatively charged dye molecules to be
attached on it (Jiang et al. 2005; Jaffri and Ahmad 2020b). In a recent study, AgNPs
were synthesized using microbial precursors—Bacillus subtilis (SJ 15) having been
isolated from the pedospheric samples for the photo-catalysis of thiazine dye known
as methylene blue which is known for causing a number of health issues (Roshmi
et al. 2017). Impressive detoxification rates obtained for AgNPs based assay can be
ascribed to the adsorption as well the decomposition phenomenon. The incidence
of solar light on reaction mixture of methylene blue dye and AgNPs triggers the
photocatalytic process due to the excitation of the surface plasmon resonance, i.e.,
vacillations of charge density having an ability of the propagation at the interfacial
region of metallic and dielectric intermediate (García 2011). AgNPs synthesized
from Bacillus subtilis (SJ 15) displayed an effective removal of methylene blue in
4 h with the yield reaching up to 18 ± 0.3% for AgNPs taken, i.e., 20 mg L
−1 . In a