Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Organic
Patent
1996-11-05
1999-01-05
Phasge, Arun S.
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Organic
205742, 588204, 588210, 588227, 210702, 204263, 204275, C02F 1461
Patent
active
058557636
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB95/01186 filed May 24, 1995.
The invention relates to a method and apparatus for the electrochemical oxidation of matter and has particular application in the decomposition of waste material comprising organic compounds which contain sulphur, nitrogen and/or halogen and which may or may not be contaminated with inorganic or radioactive material.
Patent specification EP 0 297 738 describes a method and apparatus for electrochemical treatment of organic waste matter using an aqueous electrolyte comprising nitric acid and containing silver ions as an electrochemically regenerable primary oxidising species. Operated at a temperature between 50.degree. C. and 90.degree. C., the cell is particularly effective in decomposing organic waste matter. This occurs to a significant extent via secondary oxidising species produced by reaction in this temperature range of Ag(II) ions with water, a reaction which would otherwise have been regarded as parasitic because it would have been expected to reduce the efficiency of the cell for oxidising the organic matter.
Nitric acid electrolyte is advantageous for a number of applications such as when radioactive materials are being treated to destroy their organic content because many waste treatment systems already in place for dealing with radioactive materials are configured to handle aqueous waste containing nitric acid. The volatility of the acid is advantageous in such applications because it can be distilled and recovered, thereby reducing waste volumes for disposal.
Examples of use of the apparatus and method for decomposition of organic matter which is to be disposed of are described in EP 0 297 738, the disclosure of which is imported by reference herein. Forms of organic waste which have assumed importance in recent years are explosive material and chemical weapons required to be destroyed, for example, under International Treaty arrangements. The method and apparatus described in EP 0 297 738 provides a safe and effective route for disposal of such material. However, the presence of certain elements in the waste matter, particularly within complex organic components can present a problem requiring special treatment if continued efficient operation of the cell is to be maintained. In this context, the problem of phosphorus is mentioned briefly in EP 0 297 738.
We have also found that such problems arise as a consequence of the presence in the waste matter of sulphur, nitrogen and halogens. These problems and that of recovery of silver are addressed in accordance with the present invention by a modification of the method and apparatus described in EP 0 297 738.
The present invention provides, in one of its aspects, a method of treating waste matter comprising organic matter which method comprises the steps of subjecting aqueous electrolyte to an electric potential within an electrochemical cell, said electrolyte comprising nitric acid and containing ions of silver which act as an electrochemically regenerable primary oxidizing species, adding the waste matter to the electrolyte continuously or periodically, the waste matter being thereby decomposed by an oxidation process in which the primary oxidizing species is reduced, said reduced primary oxidizing species being regenerated by said electric potential, and an element selected from the group consisting of sulphur, nitrogen, chlorine, bromine or iodine and mixtures thereof containing in the waste matter accumulating in the electrolyte, withdrawing a portions the electrolyte continuously or periodically from the cell, passing the portion of electrolyte to apparatus comprising at least one reaction vessel in combination with at least one solid/liquid separator, treating the portion of withdrawn electrolyte to a precipitation, crystallization and/or distillation process to remove an element selected from the group consisting of sulphur, nitrogen, chlorine, bromine or iodine and mixtures thereof, and returning to the electrochemical cell the treated electrolyte from which said element or
REFERENCES:
patent: 4869794 (1989-09-01), Koehly et al.
patent: 4874485 (1989-10-01), Steele
patent: 4939256 (1990-07-01), Takamatsu et al.
patent: 5516972 (1996-05-01), Farmer et al.
Conlin Iain
Steele David Frame
Warren Nigel Desmond Evan
AEA Technology PLC
Hinds William R.
Holt William H.
Phasge Arun S,.
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