278
B. Gunawardana et al.
of the dissolved CP concentration were kept and utilized for the characterization of
the iron oxide phases formed and present during the reaction period using Raman
analysis.
12.2.3 Analysis
Quantification of CPs and its degradation products was carried out using the gas
chromatography–mass spectrometer (Shimadzu model GCMS-QP2010S, Japan)
(Gunawardana et al. 2018, 2019). A capillary column (ZEBRON ZB5-msi) with
the dimensions of 30 m L × 0.25 mm ID × 0.25 µm thickness was used for the
analysis. Selected ion monitoring (SIM) method was used with split mode injection
of two µl of the sample at a ratio of 80:1 for separation and quantification of parent
CP and degradation products. The carrier gas was high purity helium (1 ml/min),
injection temperature 250 °C, column temperature program: 70 °C for 2 minutes,
ramped at 5 °C minute
−1 to 200 °C and held for 2 minutes, and ramped at 10 °C min
−1
to 300 °C, and held for 5 minutes. A gas chromatograph (GC—SRI 8610C) with a
column (HayeSep Q 80/100, Alltech, 6
× 1/8
× 0.085
SS) coupled with a thermal
conductivity detector (TCD) was used for quantification of the amount of hydrogen gas accumulated in the headspace of batch reactors during the reaction period.
The operating conditions of the GC/TCD were: column temperature—24 °C; carrier
gas—N 2 with a 10 ml/min flow rate.
12.2.4 Solid-Phase Characterization
The specific surface area of the unmodified ZVI, acid-washed ZVI, and Ni/Fe
bimetallic particles were determined using the Brunauer–Emmett–Teller (BET) N 2
method and a Micromeritic Tristar 3000 (USA). The morphology, characteristics,
and elemental information on selected regions of the ZVI and Ni/Fe surfaces and the
presence of Ni on the Ni/Fe particle surface were obtained using FEI Quanta 200 F
environmental scanning electron microscope (ESEM) coupled with a SiLi (lithium
drifted) energy dispersive spectroscopy (EDS) (USA). A back-scattered detector was
used with a 20 kV beam potential to collect the images.
Raman spectroscopy (Renishaw Raman system 1000 spectrometer, Australia) was
used to identify (1) the specific iron oxides present on the Ni/Fe particles prior to
exposure to CP solutions and (2) the specific iron oxides formed on the Ni/Fe particles
post-exposure to CP solutions. Eight oxide phases typically present on iron surfaces
(akaganeite, maghemite, haematite, magnetite, lepidocrocite, goethite, feroxyhyte,
ferrihydrite) were considered, synthesized as the reference iron oxides (Cornell and
Schwertmann 2003), and characterized using Raman spectroscopy (Gunawardana
et al. 2018). A natural wustite mineral specimen was characterized by EDS and
Raman analysis and confirmed with the literature (Nadoll and Mauk 2011). During
B. Gunawardana et al.
of the dissolved CP concentration were kept and utilized for the characterization of
the iron oxide phases formed and present during the reaction period using Raman
analysis.
12.2.3 Analysis
Quantification of CPs and its degradation products was carried out using the gas
chromatography–mass spectrometer (Shimadzu model GCMS-QP2010S, Japan)
(Gunawardana et al. 2018, 2019). A capillary column (ZEBRON ZB5-msi) with
the dimensions of 30 m L × 0.25 mm ID × 0.25 µm thickness was used for the
analysis. Selected ion monitoring (SIM) method was used with split mode injection
of two µl of the sample at a ratio of 80:1 for separation and quantification of parent
CP and degradation products. The carrier gas was high purity helium (1 ml/min),
injection temperature 250 °C, column temperature program: 70 °C for 2 minutes,
ramped at 5 °C minute
−1 to 200 °C and held for 2 minutes, and ramped at 10 °C min
−1
to 300 °C, and held for 5 minutes. A gas chromatograph (GC—SRI 8610C) with a
column (HayeSep Q 80/100, Alltech, 6
× 1/8
× 0.085
SS) coupled with a thermal
conductivity detector (TCD) was used for quantification of the amount of hydrogen gas accumulated in the headspace of batch reactors during the reaction period.
The operating conditions of the GC/TCD were: column temperature—24 °C; carrier
gas—N 2 with a 10 ml/min flow rate.
12.2.4 Solid-Phase Characterization
The specific surface area of the unmodified ZVI, acid-washed ZVI, and Ni/Fe
bimetallic particles were determined using the Brunauer–Emmett–Teller (BET) N 2
method and a Micromeritic Tristar 3000 (USA). The morphology, characteristics,
and elemental information on selected regions of the ZVI and Ni/Fe surfaces and the
presence of Ni on the Ni/Fe particle surface were obtained using FEI Quanta 200 F
environmental scanning electron microscope (ESEM) coupled with a SiLi (lithium
drifted) energy dispersive spectroscopy (EDS) (USA). A back-scattered detector was
used with a 20 kV beam potential to collect the images.
Raman spectroscopy (Renishaw Raman system 1000 spectrometer, Australia) was
used to identify (1) the specific iron oxides present on the Ni/Fe particles prior to
exposure to CP solutions and (2) the specific iron oxides formed on the Ni/Fe particles
post-exposure to CP solutions. Eight oxide phases typically present on iron surfaces
(akaganeite, maghemite, haematite, magnetite, lepidocrocite, goethite, feroxyhyte,
ferrihydrite) were considered, synthesized as the reference iron oxides (Cornell and
Schwertmann 2003), and characterized using Raman spectroscopy (Gunawardana
et al. 2018). A natural wustite mineral specimen was characterized by EDS and
Raman analysis and confirmed with the literature (Nadoll and Mauk 2011). During