title: Iron anode mediated transformation of selenate in sand columns.
abstract: Removal of aqueous selenate by iron electrolysis is investigated using sand-packed column experiments under a flowing condition. An iron anode generates ferrous ions, while cathode produces hydroxide, thus producing ferrous hydroxide capable of reducing selenate to elemental selenium. Additionally, siderite could reduce selenate or selenite to elemental selenium. The removal rate of selenate is proportional to the contact time and the yield of ferrous hydroxide or ferrous carbonate. At a sequence of anode-cathode, the transformation of selenate mostly occurs in the zone after cathode. An operation of 48 h electrolysis finally transforms 82.2% of selenate at 0.2 mM of initial concentration, 1.8 m/day of seepage velocity and 1.26 mA/cm(2) of current density. A longer reactive zone after cathode slightly increases the reduction of selenate to 84.1%, in comparison with 82.2% of a shorter residence time in the reactive zone after cathode. With shorter electrode spacing (approximately 27% shorter), the transformation rate of selenate decreased to 73.5%; however, the specific electrical energy consumption was saved by 78%. A sequence of cathode-anode was ineffective in removing selenate because of the lack of reducing agent in the column. The results indicate that the electrochemical system might be effective in removing selenate in a single well.
authors.affiliation: Department of Environmental Engineering, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju, Republic of Korea. Electronic address: kbaek@jbnu.ac.kr.
authors.forename: Kitae
authors.initials: K
authors.lastname: Baek
authors.forename: Ali
authors.initials: A
authors.lastname: Ciblak
authors.forename: Xuhui
authors.initials: X
authors.lastname: Mao
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Kim
authors.forename: Akram
authors.initials: A
authors.lastname: Alshawabkeh
mesh_terms: D004560:Electricity; D055664:Electrochemical Techniques; D004566:Electrodes; D007501:Iron / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D064586:Selenic Acid / Q000302:isolation & purification*; D012822:Silicon Dioxide / Q000737:chemistry*; D013997:Time Factors
chemical_list: D012822:Silicon Dioxide; D007501:Iron; D064586:Selenic Acid
keywords: Chemical transformation; Ferrous hydroxide; Sand column; Selenium
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