464
S. Das et al.
With this regards natural magnetic mineral pyrrhotite photocatalyst was explored
and tailored by thermal treatment (Aramendía et al. 2008). Natural pyrrhotite always
occurred with impurities corresponding to mineral phases like pyrite (FeS 2 ), a semiconductor mineral. A pure pyrrhotite sample is a mixture of phases of pyrrhotite-6
T (Fe 1−x S, PDF 29-0725)and pyrite (FeS 2 , PDF 42-1340). A broad absorption band
in the range of 300–800 nm could be observed in case of pyrrhotite, a sign of being
active in both UV and visible light ranges.
The photocatalytic activity of treated pyrrhotite was assessed by photocatalytic
inactivation of E. coli K-12 under visible light. With the best activity conferred
by the pyrrhotite calcined at 600°C, where the PCD rate was nearly three times
higher than that of untreated pyrrhotite. The X-ray diffraction spectra specified
the mineral phase of calcined pyrrhotite was altered to mixed crystallite phases
of hematite-pyrite (Fe 2 O 3 –FeS 2 ) composite. So, the escalation in PCD performance
could be attributed to the formation of Z-scheme photocatalysis system composed
of hematite and pyrite which guarantees better electron–hole separation efficiency
and the bactericidal efficiency (Wang et al. 2008).
3 Challenges Associated with Photocatalysis
Throughout the entire lesson, we have been talking about the utility of photocatalytic reaction in various forms of bactericidal and photocatalytic efficiency. The
advantages generally include (Saravanan et al. 2017).
(i) Photocatalysis is a renewable alternative for the energy and cost-intensive conventional treatment methods (adsorption on activated carbon and synthetic
resins, ultrafiltration, reverse osmosis, chemical coagulants, ion-exchange
methods, and membranes), with remediation efficiency throughout the day
time in presence of just sunlight and atmospheric oxygen and water.
(ii) Photocatalysis transfer the pollutants from one phase to nontoxic by-products
and secondary wastes unlike conventional treatment measures.
(iii) The photocatalytic process can be applied to various kinds of hazardous
organic, inorganic, and microbial contaminants present in waste water matrix.
(iv) It is a reaction that requires mild conditions, lesser time, and chemical input.
(v) Its versatility can be useful for hydrogen generation, gaseous and aqueous phase
treatments as well for solid-phase treatments moderately.
The limitation of photocatalysis relies on its interfacial charge separation and
charge transfer and delayed recombination of the charge carriers in the form of
electron and holes. These are the key factors controlling the photocatalytic efficiency.
Despite a steady development in the use of photocatalyst technologies in recent
years, some primary scientific questions must be answered before it can be widely
applied and its considerable benefits can be properly exploited.
As per the challenges are concerned, light availability and applicability in multiple
geographical locations seem to be the greatest challenge. Proficient photocatalytic
S. Das et al.
With this regards natural magnetic mineral pyrrhotite photocatalyst was explored
and tailored by thermal treatment (Aramendía et al. 2008). Natural pyrrhotite always
occurred with impurities corresponding to mineral phases like pyrite (FeS 2 ), a semiconductor mineral. A pure pyrrhotite sample is a mixture of phases of pyrrhotite-6
T (Fe 1−x S, PDF 29-0725)and pyrite (FeS 2 , PDF 42-1340). A broad absorption band
in the range of 300–800 nm could be observed in case of pyrrhotite, a sign of being
active in both UV and visible light ranges.
The photocatalytic activity of treated pyrrhotite was assessed by photocatalytic
inactivation of E. coli K-12 under visible light. With the best activity conferred
by the pyrrhotite calcined at 600°C, where the PCD rate was nearly three times
higher than that of untreated pyrrhotite. The X-ray diffraction spectra specified
the mineral phase of calcined pyrrhotite was altered to mixed crystallite phases
of hematite-pyrite (Fe 2 O 3 –FeS 2 ) composite. So, the escalation in PCD performance
could be attributed to the formation of Z-scheme photocatalysis system composed
of hematite and pyrite which guarantees better electron–hole separation efficiency
and the bactericidal efficiency (Wang et al. 2008).
3 Challenges Associated with Photocatalysis
Throughout the entire lesson, we have been talking about the utility of photocatalytic reaction in various forms of bactericidal and photocatalytic efficiency. The
advantages generally include (Saravanan et al. 2017).
(i) Photocatalysis is a renewable alternative for the energy and cost-intensive conventional treatment methods (adsorption on activated carbon and synthetic
resins, ultrafiltration, reverse osmosis, chemical coagulants, ion-exchange
methods, and membranes), with remediation efficiency throughout the day
time in presence of just sunlight and atmospheric oxygen and water.
(ii) Photocatalysis transfer the pollutants from one phase to nontoxic by-products
and secondary wastes unlike conventional treatment measures.
(iii) The photocatalytic process can be applied to various kinds of hazardous
organic, inorganic, and microbial contaminants present in waste water matrix.
(iv) It is a reaction that requires mild conditions, lesser time, and chemical input.
(v) Its versatility can be useful for hydrogen generation, gaseous and aqueous phase
treatments as well for solid-phase treatments moderately.
The limitation of photocatalysis relies on its interfacial charge separation and
charge transfer and delayed recombination of the charge carriers in the form of
electron and holes. These are the key factors controlling the photocatalytic efficiency.
Despite a steady development in the use of photocatalyst technologies in recent
years, some primary scientific questions must be answered before it can be widely
applied and its considerable benefits can be properly exploited.
As per the challenges are concerned, light availability and applicability in multiple
geographical locations seem to be the greatest challenge. Proficient photocatalytic