Film unit assembly
Electrolytic cell utilizing pretreated semi-permeable membranes Patent #: 4124477
ApplicationNo. 06/038812 filed on 05/14/1979
US Classes:205/514, Utilizing cell having three or more compartments or units204/263, With feeding and/or withdrawal means204/266, Gas withdrawal205/525Electrode bonded diaphragm or membrane
ExaminersPrimary: Andrews, R. L.
Attorney, Agent or Firm
International ClassesC25B 1/00 (20060101)
C25B 9/08 (20060101)
C25B 1/46 (20060101)
C25B 9/06 (20060101)
AbstractThe invention describes a pressurized, three compartment membrane cell for the electrolyzing aqueous alkali metal halides at low cell voltages and with high cathodic current efficiencies. Unitary electrode-electrolyte structures, in the form electrochemically active electrodes physically bonded to ion transporting permselective membranes divide the cell into anode, cathode and buffer compartments. The buffer compartment feed is pressurized to maintain at a positive pressure differential with respect to the anode and cathode compartment feeds. The flexible unitary electrode-membrane electrolytes are forced outwardly against electronically conductive anode and cathode current collectors to provide uniform, constant and controllable contact between the bonded electrodes and thereby minimizing ohmic losses. A three compartment cell operated in this fashion not only minimizes the voltage required to electrolyze the halide solution, but also increases the cathodic current efficiency at high caustic concentrations by providing multiple hydroxide rejection stages in a single cell process. The improvement in cathodic current efficiency is realized by forming a lower caustic concentration in the buffer compartment than in the cathode compartment thereby reducing backmigration of OH- ions into the anode compartment.