Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Radioactive metal
Patent
1996-01-31
1998-05-12
Mai, Ngoclan
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Radioactive metal
423 8, 210634, 405128, 134 2, 134 251, 976DIG392, 976DIG376, C01G 5600
Patent
active
057500819
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the solvent extraction of metal containing species.
Solvent extraction of metal containing species is used in a variety of analytical and industrial applications particularly in the chemical engineering and waste treatment fields. For example, hazardous radioactive and non-radioactive species present in a solid or liquid medium may be extracted into a solvent system and subsequently isolated and disposed of or recycled as appropriate.
A known technique which has been used for solvent extraction of metal containing species is supercritical fluid extraction (SFE). This technique is reported in a number of papers for example: Johnson, D M; McNally, M E P Anal. Chem. 1963, 65, 1462; Lin, Yuehe; Brauer, R D; Laintz, K E; Wai, C M Anal. Chem. 1993, 65, 2549; and Hedrick, J L; Mulcahey, L J Taylor L T, In "Supercritical Fluid Technology--Theoretical and Applied Approaches to Analytical Chemistry", Bright F V and McNally M E, Eds.; ACS Symposium Series 488; Amer. Chem. Soc., Washington, D.C., 1991, p 206-220. In SFE the extractant solvent comprises a supercritical fluid such as carbon dioxide together with a complexant or chelant which serves to dissolve the metal species by forming a soluble complex.
According to the present invention there is provided a method of extracting metal species from a metal species containing medium which comprises contacting the medium with an extractant solvent which comprises a supercritical fluid and a complexant for solubilising metal species in the said medium and also a conditioning agent for changing the oxidation state of the metal species.
The conditioning agent may comprise an oxidising agent or a reducing agent and is present to assist dissolution of the metal species in the complexant by changing the oxidation state of the metal species. The presence of the conditioning agent thereby beneficially increases the efficiency of the solvent system in dissolving the metal species.
Where the conditioning agent is an oxidising agent it may be selected from a peroxide such as H.sub.2 O.sub.2, a perchlorate such as NaClO.sub.3, oxygen, ozone and potassium permanganate or a plurality of oxidising species.
Where the conditioning agent is a reducing agent it may be selected from hydrogen, hydrazine or a solution containing an oxidisable metal species such as Fe.sup.++ or Cu.sup.+, or a plurality of reducing species.
The medium from which metal species is desired to be removed by the method according to the present invention may be a solid or liquid medium. Where the medium is a solid it may comprise a particulate material such as soil, sludge, an industrial process residue, an industrial process slag or the like. The metal species may be contained on the surface of the particles and/or bound within the particles. The medium could alternatively be a material to be decontaminated, eg a metal or concrete structure, waste building materials such as rubble or contaminated waste materials such as rubber, plastics or textiles materials. Where the medium is a liquid it may for example comprise a process solvent or an industrial effluent stream.
The method of the present invention may for example be employed to analyse the concentration of metal species of interest in liquid or solid samples. For example, when analysing for the presence of contaminants it may be desirable to produce a stock solution which is subsequently divided into multiple samples for different analyses.
The present invention may alternatively be employed to decontaminate surfaces contaminated with radioactive or non-radioactive toxic heavy metal species.
The present invention may for instance be employed for soil clean-up for land remediation purposes.
The present invention may alternatively be employed in processes which employ conventional solvent extraction, eg dissolution of actinides in reprocessing of irradiated nuclear fuel or dissolution of uranium in the refinement treatment of uranium ores.
The metal species to be extracted by the method of the present invention may comprise radioa
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patent: 5322644 (1994-06-01), Dunn et al.
patent: 5356538 (1994-10-01), Wai et al.
British Nuclear Fuels PLC
Mai Ngoclan
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