title: Electrochemical transformation of trichloroethylene in aqueous solution by electrode polarity reversal.
abstract: Electrode polarity reversal is evaluated for electrochemical transformation of trichloroethylene (TCE) in aqueous solution using flow-through reactors with mixed metal oxide electrodes and Pd catalyst. The study tests the hypothesis that optimizing electrode polarity reversal will generate H2O2 in Pd presence in the system. The effect of polarity reversal frequency, duration of the polarity reversal intervals, current intensity and TCE concentration on TCE removal rate and removal mechanism were evaluated. TCE removal efficiencies under 6 cycles h(-1) were similar in the presence of Pd catalyst (50.3%) and without Pd catalyst (49.8%), indicating that Pd has limited impact on TCE degradation under these conditions. The overall removal efficacies after 60 min treatment under polarity reversal frequencies of 6, 10, 15, 30 and 90 cycles h(-1) were 50.3%, 56.3%, 69.3%, 34.7% and 23.4%, respectively. Increasing the frequency of polarity reversal increases TCE removal as long as sufficient charge is produced during each cycle for the reaction at the electrode. Electrode polarity reversal shifts oxidation/reduction and reduction/oxidation sequences in the system. The optimized polarity reversal frequency (15 cycles h(-1) at 60 mA) enables two reaction zones formation where reduction/oxidation occurs at each electrode surface.
authors.affiliation: Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA.
authors.forename: Ljiljana
authors.initials: L
authors.lastname: Rajic
authors.affiliation: Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA.
authors.forename: Noushin
authors.initials: N
authors.lastname: Fallahpour
authors.affiliation: Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA; State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Songhu
authors.initials: S
authors.lastname: Yuan
authors.affiliation: Civil and Environmental Engineering Department, Northeastern University, Boston, MA 02115, USA. Electronic address: aalsha@coe.neu.edu.
authors.forename: Akram N
authors.initials: AN
authors.lastname: Alshawabkeh
mesh_terms: D002384:Catalysis; D055664:Electrochemical Techniques / Q000379:methods*; D006861:Hydrogen Peroxide / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D014241:Trichloroethylene / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D014874:Water Pollutants, Chemical; D014867:Water; D014241:Trichloroethylene; D010165:Palladium; D006861:Hydrogen Peroxide
keywords: Electrochemical; Groundwater; Polarity reversal; Trichloroethylene