compartment and the compartments are connected directly to a gas chromatograph to
determine the products of decay. This setup enables to confirm the above-mentioned
processes during DC and nZVI application in aquifer.
The laboratory test focused on the demonstration and quantification of the
increased reactivity caused by the addition of the DC electric field for
dehalogenation of water contaminated by chlorinated hydrocarbons. For testing
the groundwater from sites contaminated by chlorinated ethenes, namely PCE
(concentration of 1586 mg/L); TCE (866 mg/L); and 1,2-cis-DCE (583 mg/L),
two types of nZVI were selected—commercial products NANOFER STAR
(NANO IRON, Czech Republic) and STAR_DC (NANO IRON, Czech Republic).
STAR_DC is a product developed especially for applications of nZVI enhanced by
the DC electric field. It mainly consists of nZVI with about 3–5% of magnetite, the
specific surface is higher than 10 m
2 /g and it is used without any surface
modification.
The laboratory experiments were run in simple reactors under various conditions
of the nZVI and DC combinations and there was also a reactor without any nZVI and
electricity in order to observe tightness of the reactors and natural degradation rate of
each contaminant (control). The experiments were run for 24 days with sampling
after 1, 3, 8, 14, and 24 days. The DC unit (type Velleman PS1503SB) generated 5 V
voltage field in the reactor. In frame of this laboratory reactor tests, there were six
separate reactors in the following configuration:
• Control: observation of experimental error and possible uncertainties (volatility
of volatile organic compounds—VOCs, manipulation with samples, natural
degradation, etc.);
• Control + DC: observation of DC effect alone
• STAR 0.3 g/L: nZVI NANOFER STAR, concentration 0.3 g/L;
• STAR 0.3 g/L + DC: nZVI NANOFER STAR, concentration 0.3 g/L enhanced by
DC electric field;
• STAR_DC 0.8 g/L: composite material STAR_DC, concentration 0.8 g/L;
• STAR_DC 0.8 g/L + DC: composite material STAR_DC, concentration 0.8 g/L
enhanced by DC electric field.
During the laboratory tests with Aargau groundwater, a strong reductive effect of
direct electric current was observed. Added value of the DC electric field to the ClE
reduction is shown in each of the three pairs of reactors—with or without DC
application. The results from the reactor with a NANOFER STAR concentration
of 0.3 g/L and without DC showed very similar courses to the results from the
Control. The reductive effect of NANOFER_DC in a concentration of 0.8 g/L is also
rather weak. Twentyfour days after the nZVI application, there was only 50% of ClE
in the total reduction (Fig. 4.12).
Efficiency of the ClE reduction in reactors with DC enhancement was far better
than without DC. Actually, the reductive potential when only DC was used without
nZVI was better than in the experiments with nZVI but without DC. The highest
degradation potential was documented in the reactor with 0.8 g/L STAR_DC
enhanced by DC, where, after 3 days from the application, no TCE and DCE and
4 Combination of Electrokinetics and nZVI Remediation
77
determine the products of decay. This setup enables to confirm the above-mentioned
processes during DC and nZVI application in aquifer.
The laboratory test focused on the demonstration and quantification of the
increased reactivity caused by the addition of the DC electric field for
dehalogenation of water contaminated by chlorinated hydrocarbons. For testing
the groundwater from sites contaminated by chlorinated ethenes, namely PCE
(concentration of 1586 mg/L); TCE (866 mg/L); and 1,2-cis-DCE (583 mg/L),
two types of nZVI were selected—commercial products NANOFER STAR
(NANO IRON, Czech Republic) and STAR_DC (NANO IRON, Czech Republic).
STAR_DC is a product developed especially for applications of nZVI enhanced by
the DC electric field. It mainly consists of nZVI with about 3–5% of magnetite, the
specific surface is higher than 10 m
2 /g and it is used without any surface
modification.
The laboratory experiments were run in simple reactors under various conditions
of the nZVI and DC combinations and there was also a reactor without any nZVI and
electricity in order to observe tightness of the reactors and natural degradation rate of
each contaminant (control). The experiments were run for 24 days with sampling
after 1, 3, 8, 14, and 24 days. The DC unit (type Velleman PS1503SB) generated 5 V
voltage field in the reactor. In frame of this laboratory reactor tests, there were six
separate reactors in the following configuration:
• Control: observation of experimental error and possible uncertainties (volatility
of volatile organic compounds—VOCs, manipulation with samples, natural
degradation, etc.);
• Control + DC: observation of DC effect alone
• STAR 0.3 g/L: nZVI NANOFER STAR, concentration 0.3 g/L;
• STAR 0.3 g/L + DC: nZVI NANOFER STAR, concentration 0.3 g/L enhanced by
DC electric field;
• STAR_DC 0.8 g/L: composite material STAR_DC, concentration 0.8 g/L;
• STAR_DC 0.8 g/L + DC: composite material STAR_DC, concentration 0.8 g/L
enhanced by DC electric field.
During the laboratory tests with Aargau groundwater, a strong reductive effect of
direct electric current was observed. Added value of the DC electric field to the ClE
reduction is shown in each of the three pairs of reactors—with or without DC
application. The results from the reactor with a NANOFER STAR concentration
of 0.3 g/L and without DC showed very similar courses to the results from the
Control. The reductive effect of NANOFER_DC in a concentration of 0.8 g/L is also
rather weak. Twentyfour days after the nZVI application, there was only 50% of ClE
in the total reduction (Fig. 4.12).
Efficiency of the ClE reduction in reactors with DC enhancement was far better
than without DC. Actually, the reductive potential when only DC was used without
nZVI was better than in the experiments with nZVI but without DC. The highest
degradation potential was documented in the reactor with 0.8 g/L STAR_DC
enhanced by DC, where, after 3 days from the application, no TCE and DCE and
4 Combination of Electrokinetics and nZVI Remediation
77