title: Effects of the electrode arrangements on reductive dechlorination of trichloroethylene in an electro-enhanced iron wall.
abstract: This study examined the factors that influence the reductive dechlorination of trichloroethylene (TCE) when direct current is externally supplied to a laboratory scale iron wall. Experimental results indicated that an anode electrode was placed in contact with the iron filling near the inlet of the column, and then a cathode was located on the top of the column. Excellent TCE degradation efficiency was displayed. The surface of the iron particles was acid-washed by H+, owing to water oxidation around the anode, and large quantities of Fe2+ were produced as a reductant which enhanced the TCE degradation, due to iron corrosion caused by the supply of external electrons. The cathode should be placed in sand fill atop the iron filling in order to avoid the formation of iron (hydr) oxide precipitates on the surface of the iron particles when the pH increases as a result of the release of OH+ around the cathode. Due to more H+ being released, which benefited the acid-washing of the iron filling, the TCE removal efficiency increased from 32% to 100% when the electric potential increased to 60V. However, black precipitates of iron (hydr) oxide were observed coated on the iron surface, causing the blocking of pores in the iron wall with the increase in the electric potential application. The efficiency of TCE degradation was almost equal regardless of groundwater velocity when direct current was applied to the iron wall. Based on observations of TCE degradation during long-term operations, the TCE removal efficiency in the effluent reached 100% after seven days of operation and maintained this high level after 25 days of operation. Thus, iron wall by electroremediation displayed excellent potential for development in long-term operations.
authors.affiliation: Graduate Institute of Environmental Engineering, National Central University, Chungli, Taiwan 32001, ROC.
authors.forename: C C
authors.initials: CC
authors.lastname: Liu
authors.forename: S F
authors.initials: SF
authors.lastname: Liau
authors.forename: D H
authors.initials: DH
authors.lastname: Tseng
mesh_terms: D001673:Biodegradation, Environmental; D002713:Chlorine / Q000737:chemistry / Q000302:isolation & purification*; D004563:Electrochemistry; D004566:Electrodes; D004572:Electrolysis; D004573:Electrolytes; D005290:Ferric Compounds / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D013997:Time Factors; D014241:Trichloroethylene / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014881:Water Supply
chemical_list: D004573:Electrolytes; D005290:Ferric Compounds; C000499:ferric oxide; D014241:Trichloroethylene; D002713:Chlorine; D007501:Iron