12 Chlorophenols Dechlorination Water Treatment Using …
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12.2.2 Experimental Procedure
Batch experiments were performed using Wheaton amber vials (30 ml) under identical experimental settings and anoxic conditions over the 25 day reaction period.
Individual stock solution of PCP, 2,3,4,6-TeCP, 2,4,6-TCP, and 2,4-DCP (5000 mg/L)
was prepared using ethyl acetate. Each CP was added and tested as a single compound
in each vial. The initial concentration of each CP introduced to the batch reactors
was 5 mg/L. This was equivalent to 19 µM of PCP, 22 µM of 2,3,4,6-TeCP, 25 µM
of 2,4,6-TCP, and 31 µM of 2,4-DCP being initially introduced and available in each
system before reaction with Ni/Fe bimetal. In each batch reactor, 1.00 (±0. 01) g
of Ni/Fe and 10 ml DW were added and 10 µl of the respective CP stock solution
was spiked. The high purity O 2 -free N 2 gas was used as the headspace gas and the
batch reactors were continuously purged with high purity O 2 -free N 2 gas during the
addition of deoxygenated water, CP stock solution, and during setting up the batch
experiments to keep the reactors under anoxic conditions. The batch reactors were
immediately sealed with aluminium caps with PTFE/silicone septa after the addition
of respective CP solution and continuously agitated at 100 rpm on a rotary shaker at
23 (±1) °C until each sampling time. The control vials were prepared in a similar
procedure without the addition of Ni/Fe bimetal particles. Duplicate experiments
were conducted. At every sampling time over 25 days reaction duration, the pH of
the reaction solution was monitored. At each sampling time, four reactors with Ni/Fe
and two control vials without Ni/Fe were used for analyses.
The remaining concentration of parent CPs and the corresponding degradation
products (Total CP concentration) as well as the aqueous concentrations of the parent
CPs (dissolved CP concentration) in each reactor was determined at each sampling
time using separate vials. A liquid–liquid extraction method with acid modification
was used to extract the CPs from the Ni/Fe solids and the reaction solutions (Gunawardana et al. 2018; Kim and Carraway 2000). The total concentrations, which is the
dissolved plus incorporated concentration of parent CPs and its degradation products,
were determined after extracting the Ni/Fe bimetal/water mixture with ethyl acetate
and concentrated HCl. In order to measure the concentration of total CP and degradation products, ethyl acetate (5 ml) was added to each batch reactor (containing the
reaction solution and Ni/Fe particles). The mixture was continuously agitated for
30 minutes on a rotary shaker at 100 rpm, and then 1 ml concentrated HCl was added
and the mixture was agitated for another ten minutes (Kim and Carraway 2000).
The aqueous concentration (i.e. dissolved) of the parent CPs was determined after
extracting the filtered reaction solutions with ethyl acetate and concentrated HCl. For
the quantification of dissolved CPs in the solution, aqueous solution (9 ml) filtered
by 0.2 µm regenerated cellulose (RC) membrane filters was used to along with the
liquid–liquid extraction procedure using ethyl acetate/HCl as explained above for
the quantification of total CP concentrations. After the liquid–liquid extraction procedure, 1.5 ml of the ethyl acetate layer was extracted, filtered (0.2 µm RC) and then
stored in GC/MS autosampler vials for CPs and degradation product analysis. The
solid contents (Ni/Fe particles) from the batch reactors sacrificed for quantification
277
12.2.2 Experimental Procedure
Batch experiments were performed using Wheaton amber vials (30 ml) under identical experimental settings and anoxic conditions over the 25 day reaction period.
Individual stock solution of PCP, 2,3,4,6-TeCP, 2,4,6-TCP, and 2,4-DCP (5000 mg/L)
was prepared using ethyl acetate. Each CP was added and tested as a single compound
in each vial. The initial concentration of each CP introduced to the batch reactors
was 5 mg/L. This was equivalent to 19 µM of PCP, 22 µM of 2,3,4,6-TeCP, 25 µM
of 2,4,6-TCP, and 31 µM of 2,4-DCP being initially introduced and available in each
system before reaction with Ni/Fe bimetal. In each batch reactor, 1.00 (±0. 01) g
of Ni/Fe and 10 ml DW were added and 10 µl of the respective CP stock solution
was spiked. The high purity O 2 -free N 2 gas was used as the headspace gas and the
batch reactors were continuously purged with high purity O 2 -free N 2 gas during the
addition of deoxygenated water, CP stock solution, and during setting up the batch
experiments to keep the reactors under anoxic conditions. The batch reactors were
immediately sealed with aluminium caps with PTFE/silicone septa after the addition
of respective CP solution and continuously agitated at 100 rpm on a rotary shaker at
23 (±1) °C until each sampling time. The control vials were prepared in a similar
procedure without the addition of Ni/Fe bimetal particles. Duplicate experiments
were conducted. At every sampling time over 25 days reaction duration, the pH of
the reaction solution was monitored. At each sampling time, four reactors with Ni/Fe
and two control vials without Ni/Fe were used for analyses.
The remaining concentration of parent CPs and the corresponding degradation
products (Total CP concentration) as well as the aqueous concentrations of the parent
CPs (dissolved CP concentration) in each reactor was determined at each sampling
time using separate vials. A liquid–liquid extraction method with acid modification
was used to extract the CPs from the Ni/Fe solids and the reaction solutions (Gunawardana et al. 2018; Kim and Carraway 2000). The total concentrations, which is the
dissolved plus incorporated concentration of parent CPs and its degradation products,
were determined after extracting the Ni/Fe bimetal/water mixture with ethyl acetate
and concentrated HCl. In order to measure the concentration of total CP and degradation products, ethyl acetate (5 ml) was added to each batch reactor (containing the
reaction solution and Ni/Fe particles). The mixture was continuously agitated for
30 minutes on a rotary shaker at 100 rpm, and then 1 ml concentrated HCl was added
and the mixture was agitated for another ten minutes (Kim and Carraway 2000).
The aqueous concentration (i.e. dissolved) of the parent CPs was determined after
extracting the filtered reaction solutions with ethyl acetate and concentrated HCl. For
the quantification of dissolved CPs in the solution, aqueous solution (9 ml) filtered
by 0.2 µm regenerated cellulose (RC) membrane filters was used to along with the
liquid–liquid extraction procedure using ethyl acetate/HCl as explained above for
the quantification of total CP concentrations. After the liquid–liquid extraction procedure, 1.5 ml of the ethyl acetate layer was extracted, filtered (0.2 µm RC) and then
stored in GC/MS autosampler vials for CPs and degradation product analysis. The
solid contents (Ni/Fe particles) from the batch reactors sacrificed for quantification