northeastern.edu/protect

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Puerto Rico Testsite for Exploring Contamination Threats

This program is supported by Award Number P42ES017198 from the

National Institute of Environmental Health Sciences.

Puerto Rico

Approaching

20%

of preterm births

MORE than

150 Superfund Sites

CLOSE to

20%

of Preterm Births

MORE than

150 Contaminated Sites

Hydrochlorination of TCE by Pd and H2 produced from a copper foam cathode in a circulated electrolytic column at high flowrate

Noushin Fallahpour1, 1Civil and Environmental Engineering Department, Northeastern University, 400 Snell Engineering, 360 Huntington Avenue, Boston, MA 02115 Songhu Yuan1,2 , 2State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Road, Wuhan, 430074, P. R. China.

Akram N. Alshawabkeh1,* , *To whom correspondence should be addressed. Email: aalsha@coe.neu.edu (A. Alshawabkeh).

Trichloroethylene (TCE) is a man-made chlorinated hydrocarbon, which is

moderately soluble in water and widely used in many industrial processes.

Due to the specific structure of TCE, it is most likely to accept electrons being

reduced. Thus, the rational of using Pd- catalytic hydrodechlorination using

cathodic H2 and high flow rate can be used. We investigated the influence of

high flow rate and current intensity in a circulated system on TCE removal,

precipitate formation and clogging prevention. Clogging by precipitates

formation is a main problem challenging field application when using iron

anode.

INTRODUCTION

RESULTS

In order to evaluate the performance of various electrode configurations for remediating TCE in

ground water in a circulated electrolytic system, four different strategies were applied to find

out how different factors such as the amount of palladium, flow rate, current, and types of

electrodes can affect the removal efficiency of the system.

Set (1): MMO anode and MMO cathode with 20 g Pd/Al2O3, (500-250-125-62mA),1 L/min

Set (2): Cast iron anode and MMO cathode, 20 g Pd/Al2O3, (500-250-125-62 mA), 1 L/min

Set (3): Cast iron anode and copper foam cathode 20 g Pd/Al2O3, (250-125-62 mA), 1 L/min

Set (4): Cast iron anode and copper foam cathode without Pd/Al2O3, (250-125-62mA), 1 L/min

EXPERIMENTS CONCLUSION

• Pd surface acts as a collector of hydrogen gas produced via water reduction on the

cathode leading to the hydrogen radicals formation. Based on these series of

experiments, the best design for Pd-catalytic dechlorination of TCE would be the

arrangement includes iron anode, MMO cathode, and palladium due to high

removal efficacy attained (96, 92, 88, and 73 % when the current is 500, 250, 125,

and 62 mA, respectively) and less precipitates formation.

• Although the results show the effectiveness of two-electrode configuration with

iron anode, the amount of precipitation is limiting as it may cause clogging and

prevent the clean up process.

• Comparing a high flow rate system with a low flow rate one (1 mL/min) under

the same condition results in the same removal efficacy whereas the amount of

precipitation was higher when lower flow rate applied. This result suggests that

under high flow rate system more precipitates can be flushed out. Also, it is

evident that applying lower current intensity reduces the amount of precipitation.

Flowrate:1L/min-TCEinitialConc.:5mg/L

Current(mA)

Precipitation(mg)

Efficiency(%)

Anode:IronCathode:MMOCatalyst:Pd

500 2390 96

250 1264 92125 700 88

62 381 73

Anode:IronCathode:Copper

Catalyst:Pd

250 1101 96

125 756 88

62 419 84

Anode:Iron

Cathode:CopperCatalyst:NoPd

250 945 40

125 830 35

62 419.5 40

Table.1- Considering the effect of current on remediation efficiency

and the amount of precipitation under various electrode configuration

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200

No

rma

lize

d T

CE

Co

nce

ntr

ati

on

Time (min)

MMO Anode

Iron Anode

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200

No

rma

lize

d T

CE

Co

nce

ntr

ati

on

Time (min)

500 mA 250 mA 125 mA 62 mA

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200

No

rma

lize

d T

CE

Co

nce

ntr

ati

on

Time (min)

250 mA

125 mA

62 mA

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 20 40 60 80 100 120 140 160 180 200

No

rma

lize

d T

CE

Co

nce

ntr

ati

on

Time (min)

250 mA

125 mA

62 mA

Fig.1 Effect of anode type on TCE degradation under the conditions of 500 mA

current and 1 L/min flow rate. This is a two-electrode design which both include

MMO cathode and palladium pellets.

Fig.2 Decay of the aqueous TCE concentration in the effluent under different

currents. Curves refer to iron anode-MMO cathode with Pd pellets.

Fig.3 Decay of the aqueous TCE concentration in the effluent under different

currents. Curves refer to iron anode and copper cathode including Pd pellets.

Fig.4 Decay of the aqueous TCE concentration in the effluent under different

currents. Curves refer to iron anode and copper cathode without Pd pellets.

Fe2+ + 2OH- ⟶ Fe(OH)2 ↓