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).
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Lucian C. Staicu, Eric D. Van Hullebusch, Piet N. L. Lens, Elizabeth A. H. Pilon-Smits, Mehmet A. Oturan. Electrocoagulation of colloidal biogenic selenium. Environmental Science and Pollution Research, Springer Verlag, 2015, 22 (4), http://link.springer.com/article/10.1007/s11356-014-3592-2. ⟨10.1007/s11356-014-3592-2⟩. ⟨hal-01066500⟩

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