Remarks on recent developments in the chemical oxido-reduction reaction used in treat the wastewater

The first role of these reactions can be emphasized in the biological oxidation of the compounds that appear in water from the rotting process, but it also requires the presence of microorganisms. A second important role of redox reactions for waste water treatment is to convert pollutants into compounds that are less toxic or even harmless. Oxidation of inorganic substances such as: hexavalent chromium, cyanide can be possible by resorting to the energized oxidizing agents such as sodium metabisulfite or sodium hypochlorite. We experimentally tried to treat waste water from electroplating plants that have a high content of hexavalent chromium by using IC 14D system. First of all, the hexavalent chromium was reduced to trivalent chromium by using the sodium metabisulphite as oxidizing agent. Secondly, the trivalent chromium was removed by passing it into a precipitated Cr(OH)3 in an alkaline medium. After sedimentation, the slurry was removed, water thus treated may be discharged in any effluent. (C) 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures.