Dechlorination of tetrachloroethylene in water using stabilized nanoscale iron and palladized iron particles

Abstract

Chlorinated solvents such as tetrachloroethylene (PCE) in aquifers should be remediated due to their toxicity that limited the use of groundwater resources. Nanoscale zero-valent iron (NZVI) and palladized/iron (Pd/Fe) bimetallic particles were synthesized and employed to react with PCE in water to investigate its degradation behaviors. Batch tests were conducted in a 1 L serum bottle under airtight and anaerobic conditions with parameters of Pd mass contents, temperature, pH, and dispersant. The results showed that specific reaction rate constants (kSA) of 5 mg L−1 PCE degraded by metal particles at 30°C in the absence of dispersant enhanced with higher Pd mass contents on the Pd/Fe particles. Degradation rates of PCE increased as the reaction temperature was raised from 20 to 40°C. Carboxymethyl cellulose (CMC), a dispersant, enhanced the kSA values of NZVI and 1:100 Pd/Fe particles by a factor of about 33 and 4 at 30°C, respectively. The tests of pH control with buffer solution indicated that PCE degradation rates were promoted under acid and neutral conditions. Additionally, no chlorinated by-products were observed during the experimental period in each test. This study shows that effective dechlorination of PCE in water could be achieved by synthesized Pd/Fe and NZVI particles coupled with CMC dispersant.