Fremgangsmåde til behandling af saltlageopløsning og afløbsvand

1375129 Treating alkaline effluents electrolytically; diaphragm cells AE & CI Ltd 20 June 1973 [26 June 1972] 29242/73 Heading C7B An aqueous alkaline effluent containing NaOH and ionic oxychlorine compounds is supplied to the cathode compartment of a diaphragm cell and electrolyzed to reduce to the oxychlorine ions (e.g. ClO- and ClO 2 -) to Cl- and OH- at the cathode while recovering Cl 2 from the anode and withdrawing NaOH solution from the catholyte. The anolyte may be brine or the effluent described above, and is preferably acidified, e.g. to pH 4 using HCl. Electrolysis may be conducted so that hydrogen evolution at the cathode just occurs, indicating all reducible oxychlorine ions are being reduced. A diaphragm cell useful in the above process comprises PVC woven diaphragm 25 separating anolyte and catholyte compartments 17, 18. The cathode 14 is of Fe, or steel and the anode 15 is of graphite or Ti coated with Pt, Pd, Rh, Ru or Ir. Inlets and outlets for the various solutions/ products are provided as shown, together with thermometers 16 and a pH probe 23. Inlet 22 is for acid to adjust the anolyte pH An alternative embodiment Fig. 2 (not shown) comprises a central catholyte compartment with outer anolyte compartments, the cathodes comprising mild steel mesh covered on their anolyte sides with woven PVC.