title: A three-electrode column for Pd-catalytic oxidation of TCE in groundwater with automatic pH-regulation and resistance to reduced sulfur compound foiling.
abstract: A hybrid electrolysis and Pd-catalytic oxidation process is evaluated for degradation of trichloroethylene (TCE) in groundwater. A three-electrode, one anode and two cathodes, column is employed to automatically develop a low pH condition in the Pd vicinity and a neutral effluent. Simulated groundwater containing up to 5 mM bicarbonate can be acidified to below pH 4 in the Pd vicinity using a total of 60 mA with 20 mA passing through the third electrode. By packing 2 g of Pd/Al(2)O(3) pellets in the developed acidic region, the column efficiency for TCE oxidation in simulated groundwater (5.3 mg/L TCE) increases from 44 to 59 and 68% with increasing Fe(II) concentration from 0 to 5 and 10 mg/L, respectively. Different from Pd-catalytic hydrodechlorination under reducing conditions, this hybrid electrolysis and Pd-catalytic oxidation process is advantageous in controlling the fouling caused by reduced sulfur compounds (RSCs) because the in situ generated reactive oxidizing species, i.e., O(2), H(2)O(2) and OH, can oxidize RSCs to some extent. In particular, sulfite at concentrations less than 1 mM even greatly increases TCE oxidation by the production of SO(4)(•-), a strong oxidizing radical, and more OH.
authors.affiliation: State Key Lab of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China. yuansonghu622@hotmail.com
authors.forename: Songhu
authors.initials: S
authors.lastname: Yuan
authors.forename: Mingjie
authors.initials: M
authors.lastname: Chen
authors.forename: Xuhui
authors.initials: X
authors.lastname: Mao
authors.forename: Akram N
authors.initials: AN
authors.lastname: Alshawabkeh
mesh_terms: D002384:Catalysis; D004566:Electrodes; D060587:Groundwater / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D013457:Sulfur Compounds / Q000737:chemistry*; D014241:Trichloroethylene / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods
chemical_list: D013457:Sulfur Compounds; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D010165:Palladium