14.2.2 Laboratory Tests
Laboratory-scale tests were carried out on real groundwater from two different
localities in the Czech Republic, where a pilot field ex situ and in situ application
of ferrates was planned. During these experiments, the removal of selected contaminants was studied. Water from locality A was strongly contaminated with chlorinated ethenes (CEs)—total value of CEs (ΣCEs) ranged from 60 to 70 mg/L. Water
from locality B was contaminated mainly with benzene, toluene, ethylbenzene, and
xylenes (BTEX). The aim of these experiments was to verify and compare the
efficiency of ferrates in combination with hydrogen peroxide under various conditions in order to find the most effective method for the pilot application.
During the batch tests, 1000 mL reagent bottles were used. Two parallel sets, each
containing six reagent bottles, were prepared. The bottles were labeled sp. 1–6. The
first set (labeled A) was prepared with water from locality A, the second set (labeled
B) was prepared with water from locality B. Both sets included various combinations
of reagents for possible applications. Each of the bottles represented one type of a
sample prepared as follows:
sp. 1 Ferrates (0.5 g/L) + pH adjustment % 3 + H 2 O 2 (5 mL/L),
sp. 2 Ferrates (0.5 g/L) + H 2 O 2 (5 mL/L),
sp. 3 Ferrates (0.5 g/L) + pH adjustment % 3,
sp. 4 Only a dose of ferrates (0.5 g/L),
sp. 5 Only a dose of H 2 O 2 (5 mL/L),
sp. 6 Blank
The dose of commercial ferrates was set to 0.5 g/L, which corresponds to the
doses of Fe(VI) commonly used for laboratory tests (Prucek et al. 2013). Ferrates
were dosed in a powder form and applied directly to the reagent bottle with
contaminated groundwater. The bottles were closed and their contents were vigorously mixed with a magnetic stirrer for 30 minutes. Subsequently, the following
steps in the selected samples were taken: pH adjustment by 50% H 2 SO 4 (sp. 1 and 3)
and application of 5 mL hydrogen peroxide (sp. 1, 2, and 5). The closed bottles with
the prepared water samples were put on an orbital shaker and were shaken intensively at regular 6-hour intervals for 5 min. Due to the effervescence of the samples
(mainly sp. 1 and 2), the lids of the bottles were opened at regular intervals to release
accumulated gases. 100 mL of each water sample was collected for analysis after
24, 48, 96, and 168 h and each sample was filtered through a filter paper to remove
sludge before analytical sample treatment. The content of contaminants in the
samples was analyzed with headspace gas chromatography/mass spectrometry in
accredited laboratories. All samples were processed within 24 h of the collection.
318
P. Lacina and M. Hegedüs
Laboratory-scale tests were carried out on real groundwater from two different
localities in the Czech Republic, where a pilot field ex situ and in situ application
of ferrates was planned. During these experiments, the removal of selected contaminants was studied. Water from locality A was strongly contaminated with chlorinated ethenes (CEs)—total value of CEs (ΣCEs) ranged from 60 to 70 mg/L. Water
from locality B was contaminated mainly with benzene, toluene, ethylbenzene, and
xylenes (BTEX). The aim of these experiments was to verify and compare the
efficiency of ferrates in combination with hydrogen peroxide under various conditions in order to find the most effective method for the pilot application.
During the batch tests, 1000 mL reagent bottles were used. Two parallel sets, each
containing six reagent bottles, were prepared. The bottles were labeled sp. 1–6. The
first set (labeled A) was prepared with water from locality A, the second set (labeled
B) was prepared with water from locality B. Both sets included various combinations
of reagents for possible applications. Each of the bottles represented one type of a
sample prepared as follows:
sp. 1 Ferrates (0.5 g/L) + pH adjustment % 3 + H 2 O 2 (5 mL/L),
sp. 2 Ferrates (0.5 g/L) + H 2 O 2 (5 mL/L),
sp. 3 Ferrates (0.5 g/L) + pH adjustment % 3,
sp. 4 Only a dose of ferrates (0.5 g/L),
sp. 5 Only a dose of H 2 O 2 (5 mL/L),
sp. 6 Blank
The dose of commercial ferrates was set to 0.5 g/L, which corresponds to the
doses of Fe(VI) commonly used for laboratory tests (Prucek et al. 2013). Ferrates
were dosed in a powder form and applied directly to the reagent bottle with
contaminated groundwater. The bottles were closed and their contents were vigorously mixed with a magnetic stirrer for 30 minutes. Subsequently, the following
steps in the selected samples were taken: pH adjustment by 50% H 2 SO 4 (sp. 1 and 3)
and application of 5 mL hydrogen peroxide (sp. 1, 2, and 5). The closed bottles with
the prepared water samples were put on an orbital shaker and were shaken intensively at regular 6-hour intervals for 5 min. Due to the effervescence of the samples
(mainly sp. 1 and 2), the lids of the bottles were opened at regular intervals to release
accumulated gases. 100 mL of each water sample was collected for analysis after
24, 48, 96, and 168 h and each sample was filtered through a filter paper to remove
sludge before analytical sample treatment. The content of contaminants in the
samples was analyzed with headspace gas chromatography/mass spectrometry in
accredited laboratories. All samples were processed within 24 h of the collection.
318
P. Lacina and M. Hegedüs