However, large-scale utilization of ferrates seems to be less effective than it was
previously expected. The pilot studies show big deviances from the results obtained
in laboratories. The main drawbacks of their application are as follows:
• they show strong oxidation properties only in acidic environment (lowering the
pH value will lead to an increase in the salt content in groundwater)
• under these conditions, they are highly unstable (high amount of ferrates is
needed for full remediation)
• in strongly polluted waters, they deteriorate quickly failing to show significant
removal efficiency of contaminants
Thus, their efficiency may strongly vary depending on the conditions given by the
treated groundwater/wastewater. Their inappropriate application to real waters may
end up in a failure. Therefore, there is an ongoing need to consider the suitability of
their use or consider their possible combination with other agents (e.g., hydrogen
peroxide) to achieve favorable results. It is worth mentioning that a practical
application of ferrates should also be preceded by laboratory experiments conducted
on particular waters in order to verify the suitability of the proposed process.
The presented research reports on a comprehensive practically oriented study on
applications of ferrates in combination with hydrogen peroxide in order to enhance
their removal efficiency in remediation of a contaminated real water. On the basis of
previously obtained results from laboratory experiments, a field pilot application was
realized as an ex situ experiment and subsequently as in situ large-scale remediation
in areas of two different industrial factories in the Czech Republic.
14.2 Methods
14.2.1 Materials and Chemicals
Commercial ferrates, ENVIFER, were obtained from NANO IRON, s.r.o. (Czech
Republic) in a powder form. It contained iron in high oxidation states as K 3 Fe
V O 4 a
K 2 Fe
VI
O 4 (total content of Fe 18.4 mass%; content of Fe
V 57 Æ 3 mol%; content of
Fe
VI < 3 mol%; content of K 2 O from production 19 Æ 3 mass%). After the product
was dissolved in water, Fe
V was disproportionate to Fe
VI and Fe
III (Kokarovtseva
et al. 1972; Kolář et al. 2015). The Fe
VI
/Fe
V ratio in water was roughly 0.81. One
gram of ENVIFER dissolved in water, thus creating approximately 85 mg of Fe
VI
.
Other used chemicals were as follows: technical hydrogen peroxide 35% (OQEMA,
s.r.o., Czech Republic) and sulfuric acid (Chromservis s.r.o., Czech Republic).
14 Field Study V: Combined Oxidation Technology Using Ferrates (Fe
IV–VI
). . .
317
previously expected. The pilot studies show big deviances from the results obtained
in laboratories. The main drawbacks of their application are as follows:
• they show strong oxidation properties only in acidic environment (lowering the
pH value will lead to an increase in the salt content in groundwater)
• under these conditions, they are highly unstable (high amount of ferrates is
needed for full remediation)
• in strongly polluted waters, they deteriorate quickly failing to show significant
removal efficiency of contaminants
Thus, their efficiency may strongly vary depending on the conditions given by the
treated groundwater/wastewater. Their inappropriate application to real waters may
end up in a failure. Therefore, there is an ongoing need to consider the suitability of
their use or consider their possible combination with other agents (e.g., hydrogen
peroxide) to achieve favorable results. It is worth mentioning that a practical
application of ferrates should also be preceded by laboratory experiments conducted
on particular waters in order to verify the suitability of the proposed process.
The presented research reports on a comprehensive practically oriented study on
applications of ferrates in combination with hydrogen peroxide in order to enhance
their removal efficiency in remediation of a contaminated real water. On the basis of
previously obtained results from laboratory experiments, a field pilot application was
realized as an ex situ experiment and subsequently as in situ large-scale remediation
in areas of two different industrial factories in the Czech Republic.
14.2 Methods
14.2.1 Materials and Chemicals
Commercial ferrates, ENVIFER, were obtained from NANO IRON, s.r.o. (Czech
Republic) in a powder form. It contained iron in high oxidation states as K 3 Fe
V O 4 a
K 2 Fe
VI
O 4 (total content of Fe 18.4 mass%; content of Fe
V 57 Æ 3 mol%; content of
Fe
VI < 3 mol%; content of K 2 O from production 19 Æ 3 mass%). After the product
was dissolved in water, Fe
V was disproportionate to Fe
VI and Fe
III (Kokarovtseva
et al. 1972; Kolář et al. 2015). The Fe
VI
/Fe
V ratio in water was roughly 0.81. One
gram of ENVIFER dissolved in water, thus creating approximately 85 mg of Fe
VI
.
Other used chemicals were as follows: technical hydrogen peroxide 35% (OQEMA,
s.r.o., Czech Republic) and sulfuric acid (Chromservis s.r.o., Czech Republic).
14 Field Study V: Combined Oxidation Technology Using Ferrates (Fe
IV–VI
). . .
317