-Al2O3 and a retention time of 4.3 min. Slow catalyst deactivation was reversed by treatment with a dilute sodium hypochlorite solution. The presence of high concentrations of H2CO3, HCO3-, CO32-, SO42-, and Cl- did not adversely affect catalyst activity. TCE conversion increased 30% upon increasing the solution pH from 4.3 to 11. The presence of 87 mg/L SO32- or 0.4 mg/L HS- caused rapid catalyst deactivation, presumably due to chemisorption to active sites. Dilute sodium hypochlorite solutions regenerated catalysts deactivated by HS- and SO32-. Sulfate-reducing bacteria that developed in natural groundwater amended with H2 deactivated the catalyst, but activity was restored after flushing with a dilute sodium hypochlorite solution. TCE conversion remained stable between 20 and 28% during a 63-day experiment using natural groundwater and periodic (4-7-day intervals) 90-min pulses of a dilute sodium hypochlorite solution. " />
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PD-CATALYZED TCE DECHLORINATION IN GROUNDWATER: SOLUTE EFFECTS, BIOLOGICAL CONTROL, AND OXIDATIVE CATALYST REGENERATION. (R825421)
Citation:
Lowry, G. V. AND M. Reinhard. PD-CATALYZED TCE DECHLORINATION IN GROUNDWATER: SOLUTE EFFECTS, BIOLOGICAL CONTROL, AND OXIDATIVE CATALYST REGENERATION. (R825421). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 34(15):3217-3223, (2000).
Description:
The performance of a Pd-on-src="/ncer/pubs/images/gamma.gif">-Al2O3 catalyst for
dechlorination of trichloroethylene (TCE) was evaluated in synthetic and real
groundwater. Low initial TCE conversions were used to provide maximum
sensitivity to changes in catalyst activity. TCE conversions of >24% were
maintained in DI water for 60 days using 0.5 g of 1% (w/w) Pd-on-src="/ncer/pubs/images/gamma.gif">-Al2O3 and a retention
time of 4.3 min. Slow catalyst deactivation was reversed by treatment with a
dilute sodium hypochlorite solution. The presence of high concentrations of
H2CO3, HCO3-,
CO32-, SO42-,
and Cl- did not adversely affect catalyst activity. TCE conversion
increased 30% upon increasing the solution pH from 4.3 to 11. The presence of 87
mg/L SO32- or 0.4 mg/L HS- caused
rapid catalyst deactivation, presumably due to chemisorption to active sites.
Dilute sodium hypochlorite solutions regenerated catalysts deactivated by
HS- and SO32-. Sulfate-reducing
bacteria that developed in natural groundwater amended with H2
deactivated the catalyst, but activity was restored after flushing with a dilute
sodium hypochlorite solution. TCE conversion remained stable between 20 and 28%
during a 63-day experiment using natural groundwater and periodic (4-7-day
intervals) 90-min pulses of a dilute sodium hypochlorite solution.