Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
  • B01D61/44—Ion-selective electrodialysis

Definitions

• a fixing agent e.g., sodium, ammonium or potassium thiosulfate.
• fixer baths include fixer baths, bleach-fixes and monobaths (developer and fixer in the same solution).
• the hypo containing solution is passed through the compartment with the cathode electrode upon which the silver is deposited as silver metal.
• the second compartment contains the anode electrode, and through this flows a receiving solution.
• the semipermeable membrane is an anionic membrane permeable to halide ions but impermeable to cationic species and multiply charged anions.
• the receiving solution is an aqueous solution preferably dilute and containing a species which can be oxidized providing a driving force for the transfer of halide across the membrane.
• Such a solution could be one containing a soluble ferrous salt, sulfite, or stannous salt or other common reducing agent which can be oxidized at the surface of the anode.
• the receiving solution which is eventually discarded should preferably contain innocuous materials such as ferrous sulfate, sodium sulfite, ascorbic acid or sugar-type derivatives of ascorbic acid and the stereoisomers and diastereoisomers of these acids.
• the derivatives of ascorbic acid useful in the practice of this invention are disclosed in U.S. appl. Ser. No. 391,507, filed concurrently with this application, attorney's docket No. 28,426.
• the wash water may be passed through the anode chamber as the receiving solution.
• EXAMPLE An electrodialysis cell of the following description was used in this example.
• a semipermeable membrane (Ionics l l l-BZL1065) separated the cell into two chambers, one chamber containing the anode and the other chamber, the cathode. Two openings were provided for each chamber as inlet and outlet passages for liquid streams. The flow of the fixer solution was directed into the cathode chamber, and the receiving solution was directed into the anode chamber.
• a receiving solution comprising FeSO, 0.] Molar 1 liter was passed through the anode chamber.
• the silver measured in the hypo solution was 0.038 M.
• the Br in the receiving solution was measured to be 0.051 Molar.
• the data indicate that 0.062 Moles Ag was removed from solution (62%) and 0.051 Moles Br transferred to the receiving solution (51%) from the hypo containing bath.
• the receiving solution in the practice of this invention must, as previously indicate, contain an oxidizable species in the solution.
• the oxidizable species must also be an electrode active oxidizable species which means that the species is capable of having the oxidation reaction (electron transfer) occur at an electrode.
• the ascorbic acid materials useful in the practice of this invention as oxidizable species are ascorbic acid, its sugar-type derivatives and stereoisomers and diastereoisomers of the acid and its derivatives.
• the ascorbic acids, including the sugar-type derivatives of ascorbic acid as well as ascorbic acid, may be represented by the generic structural formula:
• a power source connected to the anode and cathq ode, passing an aqueous solution of an electrode active oxidizable species through the anode chamher. and with the power source applying a voltage differential across the anode and cathode.
• oxidizable species is selected from a soluble ferrous salt, soluble sulfite, soluble stannous salts, ascorbic acid, or derivatives of ascorbic acid.

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• Engineering & Computer Science (AREA)
• Water Supply & Treatment (AREA)
• Health & Medical Sciences (AREA)
• Urology & Nephrology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

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Cited By (9)

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Citations (2)

• 1973
  • 1973-08-24 US US391509A patent/US3925175A/en not_active Expired - Lifetime

Patent Citations (2)

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