Extractants

Details Extractants Extractants

1980-05-21

1983-01-25

Cintins, Ivars C.

Liquid purification or separation

Processes

Liquid/liquid solvent or colloidal extraction or diffusing...

B01D 1104

Patent

active

043702376

DESCRIPTION:

BRIEF SUMMARY
This invention relates to extractants which can be used in liquid systems for extracting ionic values, e.g. metal values or acid values, into an organic phase from an aqueous phase.
Many industrial processes involve the selective extraction of certain components from an aqueous to an organic phase using a suitably chosen extractant in the organic phase, followed by regeneration of the extractant and release of the extracted components.
An example of such a process concerns the recovery of copper from impure copper-bearing materials. It has, for example, been proposed to utilise solvent extraction using a selective organic extractant for copper, such as one of those known under the trade name Lix (e.g. Lix 64 N), typically an oxime-containing hydrocarbon modified by adjacent hydroxyl groups, to extract copper values from an aqueous copper sulphate-containing leach liquor. The copper sulphate is back-extracted from the organic extract with aqueous sulphuric acid to give an aqueous acidic copper sulphate solution, which itself is subjected to a further solvent extraction, using a selective organic extractant for the acid values, preferably an amine such as trioctylamine (a form of which is available under the trade name Alamine 336) in a solvent such as a mixed aromatic/aliphatic type kerosene (commercially available as Escaid 100).
Other industrial processes which may involve the extraction of acids with an organic extractant include the treatment of bleed streams in electrolytic processes, the recovery of waste acid from plating baths, the ilmenite process for the recovery of titanium dioxide, the recovery of magnesium and magnesia from sea-water, the treatment of acid and metal bearing wastes at low concentrations, the purification treatment of zinc electrolytes, the control of acid concentration in solvent extraction plants, the treatment of acid wastes from pickle liquor baths, and the control of acid concentration in electro-winning acid concentration controls where sulphur dioxide is injected into electro-winning cells.
The extractants used in such processes have problems leading to low efficiency in use. Thus, if for example, one considers the use of amine extractants for extracting acid values from an aqueous solution containing, inter alia, acid values or salts of acids, as for example for extraction of acid values from acidic copper sulphate solutions, a material such as trioctylamine can be used as extractant in an organic diluent, preferably with the addition of a minor amount of an alcohol such as iso-decanol. Trioctylamine has only a single amino group per extractant molecule. However, it is often necessary, to remove from the aqueous phase relatively large quantities of acid values in the organic flow, per cycle. It is desirable therefore to have an extractant with high carrying capacity defined as: acid extraction per cycle extractant weight per cycle.
This carrying capacity may be increased by increasing the number of amine groups per extractant molecule, to form a diamine or polyamine. Such materials are well known and widely used in polymer industries, an example being 1,6-diaminohexane used in nylon production. In the absence of steric hindrance between adjacent amino groups, such diamines and polyamines will form salts with acids in the usual manner, a diamine extracting two molecules of a monobasic acid, and a triamine three molecules of the same acid, etc. Thus the carrying capacity of a diamine is approximately twice that of a monoamine on a weight for weight basis, where the monoamine contains the same number of carbon atoms.
However the problem of providing a high carrying capacity cannot be solved simply by increasing the number of amine groups. Diamines and polyamines have greater solubility in aqueous liquors than mono-amines. In general the greater the number of amine groups present, the more hydrophilic is the amine molecule. This hydrophilicity can to a certain extent be offset by lengthening the hydrocarbon chain to restore adequate water insolubility. However, there is a lim

REFERENCES:
patent: 3666446 (1972-05-01), Cook et al.

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