Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Patent
1998-02-19
1999-09-14
Phasge, Arun S.
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
205687, 205688, 205703, 205746, 205747, 588210, 588227, C02F 146
Patent
active
059525428
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB96/02422 filed Oct. 3, 1996.
This invention relates to a method of oxidation and more particularly to a method of oxidation suitable for decomposing waste organic material and especially such waste organic material containing halogenated compounds.
Use of electrochemically regenerated Ag ions in the decomposition of organic waste matter is described in patent specification EP 0 297 738. Whilst that process is capable of use in the treatment of halogenated organic compounds, problems are created by the insolubility and consequent precipitation of resulting silver halides.
Use of an electrochemically regenerated higher valency oxide or salt of ruthenium, osmium, iridium, rhodium in the oxidative treatment of a substance such as polychlorinated biphenyl is described in patent specification GB 2 226 331.
The present invention is a development of GB 2 226 331, which development provides improvements in a number of respects in the method. Further, we have appreciated that the method has useful application in the destruction of halogenated organic compounds found in weapons materials and rocket fuels. The need to dispose of large stockpiles of such materials currently presents a major environmental problem. The presence in such materials of heteroatoms such as nitrogen, chlorine, phosphorus, arsenic and sulphur poses problems in the operation of the method of GB 2 226 331. It is an object of the present invention to overcome or ameliorate these problems.
According to the invention there is provided a method of oxidation of a substance by treatment with a metal oxide or salt the metal therof being in an initially higher valency state and reduced to a lower valency state during the oxidation reaction, the metal being selected from the group consisting of ruthenium, osmium, irridium and rhodium, wherein the metal oxide or salt after the oxidation reaction is continuously regenerated by means of an electrochemical cell including an anolyte comprising an aqueous solution containing an metal halide and the aforesaid metal oxide or salt, an aqueous catholyte and a cation exchange membrane separating the anolyte and catholyte, characterised in that, for the recovery of the ruthenium, osmium, iridium or rhodium and/or removal of heteroatoms such as nitrogen, chlorine, phosphorus, arsenic, or sulphur, feed of the substance for oxidation is stopped periodically or at the end of a batch treatment whilst operation of the electrochemical cell is continued until all of said metal in the cell which is to be recovered and which is in its lower valency state has been converted into its higher valency state and separated so that heteroatoms remaining are removable as a waste solution or recoverable by a separation process such as crystallisation or precipitation.
Where the metal is ruthenium, RuO.sub.4 is readily separated by volatilisation and absorption in an alkaline solution after all RuO.sub.2 in the cell to be recovered, either periodically or at the end of a batch treatment, has been electrochemically converted to RuO.sub.4.
Preferably the metal halide in the anolyte is an alkali metal halide and preferably the chloride.
We have now found that it is better to operate with the anolyte in a neutral or slightly acid solution which is preferably buffered with an inorganic salt such as phosphate.
Preferably the catholyte comprises an aqueous alkali solution and tendency for the acidity of the anolyte to rise during operation with corresponding increase in alkilinity of the catholyte is counteracted by a controlled feed of some catholvte into the anolyte.
This controlled feed of catholyte into the anolyte is conveniently used to scrub chlorine gas evolving from the anolyte. The quantity of the controlled feed of catholyte into the anolyte used for scrubbing can be adjusted so as to ensure all evolving chlorine gas is scrubbed out but not all of the evolving carbon dioxide. The evolution of carbon dioxide can then be used as an indication that the process is working.
It is also possible to use par
REFERENCES:
patent: 4752364 (1988-06-01), Dhooge
patent: 5855763 (1999-01-01), Conlin et al.
AEA Technology
Holt William H.
Phasge Arun S,.
LandOfFree
Method of oxidation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of oxidation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of oxidation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1511367