Electrochemical detoxification of waste water without additives using solid polymer electrolyte (SPE) technology

Ion exchange membranes as solid polymer electrolytes (SPE) facilitate the electrochemical detoxification of waste water without addition of supporting electrolyte. Cation exchange membranes as H+ ion conductors or anion exchange membranes as OH- ion conductors were used in combination with different electrode materials. A variety of cell configurations were investigated which differ in the direction of the electro-osmotic stream (EOS). This is a characteristical property of SPE technology, caused by the solvation shells of the ions during their migration through the membrane. Dependent on cell configuration mass transfer at the electrodes can be hindered or enhanced by EOS. In the latter case it is appropriate to increase EOS by preparation of Nafion(R) membranes in order to decrease energy consumption per m(3) waste water. Using a perforated membrane, which operates in this case only as ion conducting solid polymer electrolyte but not as cell separator, flow rates through the cell can be adjusted independent of the EOS and a further decrease of energy consumption is possible. The best results were obtained using anodic oxidation followed by cathodic reduction: 2-chlorophenol as example compound was destroyed almost completely and more than 80% of the chlorine was mineralized to chloride ions. By-products were detected in very low amounts, less than the remaining traces of 2-chlorophenol.