CLOSE to 20% 150 - Northeastern Universityamong substances most commonly found at US EPA Superfund...

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Bipolar

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33%/67%

Problem. Once released to the environment, chlorinated organic compounds (COCs) like

trichloroethylene (TCE) have a tendency to cause or contribute to widespread groundwater

contamination due to a unique combination of physical and chemical properties. TCE is

among substances most commonly found at US EPA Superfund sites.

northeastern.edu/protect }

Puerto Rico Testsite for Exploring Contamination Threats SRP Center

This program is supported by Award Number P42ES017198 from

the National Institute of Environmental Health Sciences.

Puerto Rico

CLOSE to

20%

of Preterm Births

MORE than

150 Contaminated Sites

Prof. Akram Alshawabkeh: email: aalsha@coe.neu.edu

Ljiljana Rajic, PhD; email: l.rajic@neu.edu

A THREE ELECTRODE SYSTEM FOR ELECTROCHEMICAL

TRANSFORMATION OF TRICHLOROETHYLENE IN

GROUNDWATER Ljiljana Rajic, Roya Nazari, Noushin Fallahpour, Akram N. Alshawabkeh

Civil and Environmental Engineering Department, Northeastern University, Boston, MA, 02115, USA

Proposed Solution. Due to the fast and effective processes, electrocatalytic reduction of

COCs in groundwater has gained interest. The main removal mechanism is

hydrodechlorination (HDC). To improve the reduction mechanism in mixed electrolyte

electrochemical cells, an iron anode can be used.

Limitations. The use of an iron anode in the undivided electrochemical cell eliminates the

competition between the oxygen (that is produced at the inert anodes) and contaminants for

the reduction at the cathode but may cause precipitation and an increase in pH.

Improvement. Using an additional anode of inert material with an iron anode (a three

electrode system) will create conditions to control precipitation and maintain natural pH

value of the groundwater.

Compared to the 2 electrode system, the 30 mA /30 mA ratio

doubled TCE removal efficiency without any significant change

in pH and with a decrease in precipitation by 20% (Figure 1). By

reducing precipitation, less cathode surface is covered by the

particles thus leaving it available for TCE reduction.

Further, we found that increased current intensity to 90 mA and

120 mA, improved TCE removal compared to 60 mA by 12% and

13% (Figure 2), and reduced precipitation formation by 30% and

42%, respectively. However, the higher currents caused an

increase of pH to 11.

The results of this study show that optimization of

anode→anode→cathode arrangement overcome the drawbacks

of the use of a single iron anode and increases the removal rate

of TCE. This process will allow implementation of an efficient,

solar-powered and practical electrochemical system for in situ

treatment of contaminated groundwater.

RESULTS

Experimental setup:

Anode (E1): Mesh Ti/MMO

Anode (E2): Perforated cast iron

Cathode (E3): Iron foam

Current intensity: 60 mA

Flow velocity: 3 mL min-1

Inter-electrode distance: 2.5 cm

Solution: 0.172 g L-1 CaSO4;

0.413 g L-1 NaHCO3; 5.3 mg L-1 TCE

Treatment duration: 180 min

Current Split

(Ti/MMO/Cast Iron anode)

Current Intensity

(mA)

Bipolar 60

50%/50% 30, 60, 90, 120

33%/67% 60

Tested Variables

Figure 1. TCE decay during experiments with different

current split ratios under 60 mA

Figure 2. TCE decay during experiments with different current

intensities under 50%/50% split ratio