title: Electrocoagulation of colloidal biogenic selenium.
abstract: Colloidal elemental selenium (Se(0)) adversely affects membrane separation processes and aquatic ecosystems. As a solution to this problem, we investigated for the first time the removal potential of Se(0) by electrocoagulation process. Colloidal Se(0) was produced by a strain of Pseudomonas fluorescens and showed limited gravitational settling. Therefore, iron (Fe) and aluminum (Al) sacrificial electrodes were used in a batch reactor under galvanostatic conditions. The best Se(0) turbidity removal (97 %) was achieved using iron electrodes at 200 mA. Aluminum electrodes removed 96 % of colloidal Se(0) only at a higher current intensity (300 mA). At the best Se(0) removal efficiency, electrocoagulation using Fe electrode removed 93 % of the Se concentration, whereas with Al electrodes the Se removal efficiency reached only 54 %. Due to the less compact nature of the Al flocs, the Se-Al sediment was three times more voluminous than the Se-Fe sediment. The toxicity characteristic leaching procedure (TCLP) test showed that the Fe-Se sediment released Se below the regulatory level (1 mg L(-1)), whereas the Se concentration leached from the Al-Se sediment exceeded the limit by about 20 times. This might be related to the mineralogical nature of the sediments. Electron scanning micrographs showed Fe-Se sediments with a reticular structure, whereas the Al-Se sediments lacked an organized structure. Overall, the results obtained showed that the use of Fe electrodes as soluble anode in electrocoagulation constitutes a better option than Al electrodes for the electrochemical sedimentation of colloidal Se(0).
authors.affiliation: Department of Environmental Engineering and Water Technology, UNESCO-IHE Institute for Water Education, 2601 DA, Delft, The Netherlands.
authors.forename: Lucian C
authors.initials: LC
authors.lastname: Staicu
authors.forename: Eric D
authors.initials: ED
authors.lastname: van Hullebusch
authors.forename: Piet N L
authors.initials: PN
authors.lastname: Lens
authors.forename: Elizabeth A H
authors.initials: EA
authors.lastname: Pilon-Smits
authors.forename: Mehmet A
authors.initials: MA
authors.lastname: Oturan
mesh_terms: D000535:Aluminum / Q000737:chemistry; D003102:Colloids; D055664:Electrochemical Techniques; D004566:Electrodes; D007501:Iron / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D011551:Pseudomonas fluorescens / Q000378:metabolism*; D012643:Selenium / Q000302:isolation & purification* / Q000378:metabolism; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D000535:Aluminum; D003102:Colloids; D007501:Iron; D012643:Selenium; D062065:Wastewater; D014874:Water Pollutants, Chemical