Electrocoagulation of colloidal biogenic selenium

Environ Sci Pollut Res Int. 2015 Feb;22(4):3127-37. doi: 10.1007/s11356-014-3592-2. Epub 2014 Sep 20.

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).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aluminum / chemistry
  • Colloids
  • Electrochemical Techniques
  • Electrodes
  • Iron / chemistry
  • Microscopy, Electron, Scanning
  • Pseudomonas fluorescens / metabolism*
  • Selenium / isolation & purification*
  • Selenium / metabolism
  • Wastewater / chemistry*
  • Water Pollutants, Chemical / chemistry
  • Water Pollutants, Chemical / isolation & purification*
  • Water Purification / methods*

Substances

  • Colloids
  • Waste Water
  • Water Pollutants, Chemical
  • Aluminum
  • Iron
  • Selenium