An extraction process for extracting ionic values from an aqueous solution containing same which comprises contacting the aqueous solution with an organic hydrophobic liquid extractant phase comprising an extractant for ions, the molecules of which extractant contain at least one hydrophobic group selected from cyclic phosphazene radicals, linear siloxane radicals, cyclic siloxane radicals, and three-dimensional siloxane radicals, and stripping resulting loaded extractant phase with an aqueous stripping liquid phase.

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 limit to the extent of chain lengthening 
which can in practice be carried out, because increase in the number of 
carbon atoms also increases the viscosity of the molecule and thus 
decreases the proportion or amount of amine which can be dissolved in a 
given volume of organic diluent, such as Escaid 100, to maintain 
acceptable phase disengagement properties after contacting the aqueous and 
organic phases. Furthermore, the increased chain length of the amine can 
also impair solubility in the organic phase, although branched chains are 
better than straight chains in this respect. With branched chain amines, 
care must be taken in positioning the amine groups if steric hindrance is 
to be avoided. 
There is thus a need to provide improved extractants of ionic values, 
particularly in the field of extractants of anions or acid values, for use 
in solvent extraction. 
The invention accordingly seeks to provide an improved extraction process 
for extracting ionic values, such as anions or acid values, from aqueous 
solutions thereof. 
According to the invention there is provided an extraction process for 
extracting ionic values from an aqueous solution containing same which 
comprises contacting the aqueous solution with an organic hydrophobic 
liquid extractant phase comprising an extractant for ions, the molecules 
of which extractant contain at least one hydrophobic group selected from 
cyclic phosphazene radicals, linear siloxane radicals, cyclic siloxane 
radicals, and three-dimensional siloxane radicals, and stripping resulting 
loaded extractant phase with an aqueous stripping liquid phase. 
In a preferred process according to the invention the extractant is an 
extractant for anions and comprises a cyclic phosphazene which is 
substituted by one or more non-water-solubilising substituents. Preferably 
the cyclic phosphazene comprises a cyclotriphosphazene or a 
cyclotetraphosphazene or a mixture thereof. Preferred phosphazenes are 
those of the formula: 
##STR1## 
or of the formula: 
##STR2## 
or a mixture thereof, wherein each of R.sub.1 to R.sub.8, independently of 
the others, is selected from halogen, alkyl, alkoxy, aryl, aryloxy, 
alkylthio, arylthio, --NR.sub.9 R.sub.10, alkoxyalkylene, 
alkoxyalkyleneoxy, --NHNR.sub.9 R.sub.10, --NR.sub.9 NHR.sub.10, 
arylalkyl, arylalkoxy, alkylthioalkylene, alkylthio alkyleneoxy, 
arylthioalkylene, R.sub.9 R.sub.10 N--alkylene, R.sub.9 R.sub.10 
N--alkyleneoxy, R.sub.9 R.sub.10 N--arylene, R.sub.9 R.sub.10 
N--aryleneoxy, and siloxanyl-alkylene radicals, or wherein at least one of 
the pairs of radicals R.sub.1 and R.sub.2, R.sub.3 and R.sub.4, and 
R.sub.5 and R.sub.6 together represent the atoms which are required to 
complete, together with the P-atom to which they are attached, a 5-, 6- or 
7-membered saturated or unsaturated, optionally substituted heterocyclic 
ring, wherein each of R.sub.9 and R.sub.10, independently of the other, is 
selected from hydrogen atoms, alkyl radicals and aryl radicals or R.sub.9 
and R.sub.10 together represent the atoms which are required, together 
with the N-atom to which they are attached, to form a 3-,4-,5-,6- or 
7-membered, saturated or unsaturated, optionally substituted heterocyclic 
ring, and wherein each of the aforementioned alkyl, alkoxy, alkylene, aryl 
and siloxanyl radicals may bear one or more non-water-solubilising 
substituents, provided that R.sub.1 to R.sub.10 are so selected that the 
compound of formula (I) or (II) is substantially water-insoluble. 
As examples of non-water-solubilising substituents there can be mentioned 
halogen, nitro, alkyl, alkoxy, alkylsulphonyl, alkoxycarbonyl, 
alkylcarbonyloxy, alkylcarbonyl, aryl, and cyano groups. By the term 
halogen we mean fluorine, chlorine, bromine and iodine. Chlorine is the 
preferred halogen substituent. Any alkyl groups present may contain for 
example from 1 to 20 carbon atoms or more, preferably 1 to 8 carbon atoms. 
Examples of suitable alkyl radicals include methyl, ethyl, n- and 
iso-propyl, n-, iso- or t-butyl, n-pentyl, n-hexyl, and n-heptyl radicals 
as well as homologues and isomers thereof. As examples of suitable aryl 
radicals there can be mentioned phenyl, p-tolyl, p-nitrophenyl, 
p-methoxyphenyl, p-bromophenyl, naphthyl-1 and naphthyl-2 and the like as 
well as the o- and m- isomers thereof. Ethyleneimino, N-morpholino-, 
N-piperidino and N-pyrryl radicals are examples of heterocyclic radicals 
of formula --NR.sub.9 R.sub.10. 
Excluded from consideration in the process of the invention are such 
compounds as hexakisethylcyclotriphosphazene, 
hexakisaminocyclotriphosphazene, hexakismethylaminocyclotriphosphazene, 
hexakisethylaminocyclotriphosphazene, 
hexakisdimethylaminocyclotriphosphazene, 
octakisethylcyclotetraphosphazene, octakisaminocyclotetraphosphazene, 
octakismethylaminocyclotetraphosphazene, 
octakisethylaminocyclotetraphosphazene, and 
octakisdimethylaminocyclotetraphosphazene, since these compounds are all 
too soluble in water to be useful in the process of the invention. 
Amongst preferred compounds of the formula (I) there can be mentioned those 
wherein at least one of the radicals R.sub.1 to R.sub.6 is an alkylamino 
radical and each of the remaining radicals R.sub.1 to R.sub.6, if any, is 
an alkyl group. Other preferred compounds of the formula (I) are those 
wherein at least one of the radicals R.sub.1 to R.sub.6 is a phenyl 
radical and each of the remaining radicals R.sub.1 to R.sub.6, if any, is 
an alkylamino radical. Compounds worthy of specific mention include 
hexakis-(n-butylamino)-cyclotriphosphazene, 
hexakis-(n-heptylamino)-cyclotriphosphazene and 
n-heptylaminopentaphenylcyclotriphosphazene. Examples of other compounds 
of the formula (I) and (II) will appear hereinafter. 
Amongst other preferred extractants suitable for use in the process of the 
invention are extractants for anions which comprise at least one primary, 
secondary or tertiary amino group linked by a divalent organic radical to 
a linear, cyclic or three-dimensional siloxane radical. Although the 
invention also contemplates the use of di-, tri- and polyamino substituted 
siloxanes, especially preferred are monoamino compounds of the formula 
A-X-B wherein A represents --NH.sub.2, --NHR', or --NR'R" wherein R' and 
R" each, independently of the other, represent an optionally substituted 
hydrocarbon radical or R' and R" together represent the atoms necessary, 
together with the N-atom to which they are attached, for forming an 
optionally substituted heterocyclic ring, X represents a divalent radical 
and B represents a three-dimensional siloxane radical or a radical of the 
formula 
##STR3## 
wherein each R, independently of the others, represents alkyl or phenyl, m 
and n each represent O or an integer and p represents an integer of from 1 
to about 6. Preferred groups R are methyl or ethyl groups. R' and R" may 
represent alkyl groups containing, for example 1 to 20 carbon atoms or 
more, especially 1 to 6 carbon atoms. Alternatively, when A represents 
-NR'R", R' and R" can together represent the atoms necessary, together 
with the N-atom to which they are attached, for forming an optionally 
substituted heterocycllic ring, such as N-morpholino, N-piperidyl, or the 
like. It is preferred that X represents an alkylene radical. 
The process of the invention can be carried out using conventional solvent 
extraction equipment, such as conventional mixer-settlers. Each of the 
extraction and stripping steps may be carried out in one or more stages, 
with co-current or, preferably, countercurrent flow between stages. In 
each of the extraction and stripping stages the aqueous:organic phase 
ratio by volume may vary within wide limits, e.g. from about 100:1 to 
about 1:100. However, since mass transfer is usually best effected at a 
phase ratio of between about 2:1 to about 1:2, it will often be necessary 
to recycle one of the phases within a particular stage from the settler to 
the mixer in order to promote favourable conditions for mass transfer 
within the mixer (e.g. about 1:1) despite a disparate feed rate ratio of 
the phases (e.g. about 50:1) to the mixer of that stage. Such recycle is 
conventional practice in solvent extraction and is usually known as 
"internal recycle". 
The process of the invention is applicable to the extraction of anions or 
acid values from aqueous solutions thereof. As examples of such processes 
there can be mentioned the treatment of bleed streams in electrolytic 
processes, the recovery of waste acid from plating baths, the reduction of 
acidity required in the course of the ilmenite process for the recovery of 
titanium dioxide as well as in the recovery of waste acid from the waste 
liquors therefrom, the treatment of acid and metal bearing wastes at low 
concentrations, the purification treatment of zinc electrolytes, 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. Besides extraction of acid 
values the extraction process of the invention can be used for extraction 
of metal-containing complex ions, such as uranium-containing complex 
anions and CoCl.sub.4 ", from aqueous solutions. 
The preparation of cyclotriphosphazenes of the formula (I) and 
cyclotetraphosphazenes of the formula (II) can be accomplished by known 
methods, for example by the methods outlined in the book 
"Phosphorus-Nitrogen Compounds" by H. R. Allcock, published by Academic 
Press, New York and London (1972) and in the references therein listed or 
by analogous methods. 
The preparation of the siloxane-containing extractants used in the process 
of the invention, for example those of the formula A-X-B wherein A, X and 
B are as defined above, can likewise be achieved by known methods, for 
example by the methods outlined in the book "Organosilicon Compounds" by 
C. Eaborn, published by Butterworths Scientific Publications, London 
(1960) and in the references therein listed, or by analogous methods. 
For example, the compound hexakis-(n-butylamino)-cyclotriphosphazene can be 
prepared by reaction of hexachlorocyclotriphosphazene with n-butylamine in 
benzene solutions. Preparation of the compound 
(n-heptylamino)-pentaphenylcyclotriphosphazene can be accomplished by 
treating dichlorophenylphosphine with chlorine gas to give 
tetrachlorophenylphosphine which is then heated with ammonium chloride in 
chlorobenzene to give 1,3,5-triphenyl-1,3,5-trichlorocyclotriphosphazene; 
this latter compound is then refluxed in dry benzene with aluminium 
chloride to form by the Friedel-Crafts reaction 
pentaphenylchlorocyclotriphosphazene, which in turn is reacted with 
n-heptylamine in benzene solution. In either case, in addition to the 
desired cyclic trimer, some cyclotetraphosphazenes may be produced as 
by-products. It is not necessary to purify the cyclotriphosphazenes to 
remove those by-products and in many cases it is satisfactory to use 
technical mixtures of cyclic phosphazenes rather than pure compounds. 
As an example of the preparation of an anion extractant containing a 
siloxane residue there can be mentioned the compound 
(4'-aminobutyl)-heptamethyltetrasiloxane. This can be prepared, for 
example, by reacting hydrido-heptamethylcyclotetrasiloxane with allyl 
cyanide in the presence of a catalytic amount of hexachloroplatinic acid 
and reducing the resulting 3'-cyanopropyl-heptamethylcyclotetrasiloxane 
with lithium aluminium hydride. It is of course well known that siloxane 
polymers tend to undergo "equilibration" upon heating particularly in the 
presence of acids or bases. Since the extractants themselves contain a 
basic group, the siloxane-containing materials contemplated for use in the 
process of the invention may undergo such equilibration, in which Si-O 
linkages are continuously broken and reformed until the system reaches an 
equilibrium condition at the thermodynamically most stable state, either 
during their formation or afterwards. Hence, although a particular 
extractant may nominally be assigned, for example, a cyclotetrasiloxane 
structure, it may in practice include linear siloxane radicals, 
three-dimensional siloxane radicals (e.g. radicals derived from siloxanes 
of the type discussed in Chapter 8 of the aforementioned book by Eaborn), 
and cyclic siloxane radicals containing 3 or more siloxane units. 
Besides the extractant the organic hydrophobic liquid extractant phase may 
also comprise an organic hydrophobic solvent. Typical solvents include 
hydrocarbons, more particularly paraffins, such as n-hexane, and aromatic 
solvents, such as benzene, toluene and xylene, and mixtures thereof. Other 
hydrophobic solvents, which can be used alone or in admixture with 
hydrocarbons, include esters, such as octyl acetate and ethyl butyrate and 
the like, chlorinated hydrocarbons, such as ethylene dichloride, carbon 
tetrachloride, chloroform, and the like, ethers, such as di-n-butyl ether, 
and mixtures thereof. Essentially any water-insoluble solvent can be used 
provided that the extractant has sufficient solubility therein. Preferred 
solvents include commercially available mixed hydrocarbon solvents such as 
Escaid 100 and the like. In certain cases it may be desirable to include a 
minor amount of a more polar solvent, such as a long chain alcohol, e.g. 
iso-decanol, in the solvent in order to improve its solubilising power for 
the extractant. 
Since siloxanes are generally very mobile liquids it is possible that by 
suitable tailoring of the siloxane moiety of the extractant molecule it 
may be unnecessary to utilise any solvent. 
The concentration of the extractant in the solvent (if any) is generally 
selected so as to give an organic hydrophobic liquid extractant phase of 
readily pumpable viscosity, whilst minimising the risk of precipitation of 
the extractant through variation in ambient temperature due to its 
solubility limit being exceeded. 
The aqueous stripping phase used in the process of the invention in many 
cases can be water. Alternatively there can be used an aqueous liquor 
containing a concentration of the ionic species to be stripped less than 
that which would be in equilibrium with the loaded organic phase to be 
stripped. 
The process of the invention can also be used for cationic, especially 
metal ion, extraction from aqueous solution. In this case the extractant 
is an extractant for metal ions and comprises at least one metal ion 
complexing group linked by means of a divalent radical to a hydrophobic 
group selected from linear siloxane radicals, cyclic siloxane radicals, 
and three-dimensional siloxane radicals. Although it is within the scope 
of the invention to utilise extractants containing two or more metal ion 
complexing groups, preferably the extractant comprises a compound of the 
formula E-Y-F wherein E represents a metal ion complexing group, Y 
represents a divalent organic radical and F represents a three-dimensional 
siloxane radical or a radical of the formular (III) or (IV) as defined 
above. In such compounds -Y- typically represents an alkylene radical 
containing, for example, 1 to about 20 carbon atoms or more. As examples 
of alkylene radicals there can be mentioned methylene, ethylene, butylene, 
and homologues thereof as well as isomers thereof. Extractants suitable 
for extraction of copper ions by the process of the invention include, for 
example compounds of the formula 
##STR4## 
wherein F represents a radical of the formula (III) or (IV), -Y- 
represents an alkylene radical, Z.sub.1 represents hydrogen or a 
non-water-solubilising substituent (as exemplified above), which 
preferably stands in ortho-position to the -OH group, and Z.sub.2 
represents an alkyl or cyclic aromatic radical which may bear one or more 
non-water-solubilising substituents (as exemplified above). Preferably 
Z.sub.1 represents hydrogen or chlorine. Z.sub.2 is preferably an 
optionally substituted phenyl radical or a (preferably branched) long 
chain alkyl radical containing, for example, at least four carbon atoms up 
to about 20 carbon atoms or more, such as a C.sub.8 to C.sub.12 alkyl 
radical, e.g. dodecyl. A specific example of a compound of this type is 
the compound of formula (V) wherein Z.sub.1 represents hydrogen, Z.sub.2 
represents phenyl, Y is 1,3-propylene and F is a 
heptamethylcyclotetrasiloxanyl radical (i.e. a radical of formula (III) 
wherein R is methyl and p is 2). 
When the extractant used in the process of the invention contains a 
siloxane (siloxanyl) radical, such radical is bound to the phosphazene 
group or to the amino or metal ion complexing group or groups by means of 
a divalent radical (such as optionally substituted alkylene, 
alkylene-oxy-alkylene or phenylene) attached to the siloxane (siloxanyl) 
radical by a silicon-carbon bond. Thus the term "siloxanyl radical" is 
used herein to designate a radical bound by means of a direct 
silicon-carbon bond (e.g. pentamethylcyclotrisiloxanyl) and radicals bound 
by means of a silicon-oxygen-carbon bond (i.e. siloxanyloxy groups) are 
excluded from consideration.

(FIGS. 1 to 3 are provided for comparison purposes only. HBCTP stands for 
hexakis-(n-butylamino)-cyclotriphosphazene, HHCTP for 
hexakis-(n-heptylamino)-cyclotriphosphazene, HPPCTP for 
n-heptylamino-pentaphenylcyclotriphosphazene, and BAHMCTS for 
(4-aminobutyl)-heptamethylcyclotetrasiloxane). 
Each of these distribution curves was obtained by the following procedure. 
Procedure for obtaining distribution curves 
Equal volumes (0.5 ml) of the unloaded organic phase and aqueous acid of 
known concentration were contacted and agitated for a few minutes one with 
another. After phase separation 0.1 ml aliquots of the acid loaded organic 
phase were diluted with 0.5 ml of ethanol and titrated versus 0.1 M 
caustic soda using thymol blue as indicator. A stream of nitrogen was 
passed through the solution during titration. The acid concentration in 
the aqueous raffinate was calculated by difference. From these results the 
distribution curves of FIGS. 1 to 10 were plotted. In plotting these 
curves "% loading" is defined such that 100% loading of the organic phase 
corresponds to an amine:acid ratio of 1:1, whilst a 200% loading 
corresponds to an amine:acid ratio of 1:2 etc. 
It will be noted from FIGS. 2 and 3 that, despite the fact that Alamine 336 
(trioctylamine) is a monoamine, organic phase loadings in excess of 100% 
can be achieved. It is postulated that, although up to 100% loading an 
organic phase containing a monoamine (A) extracts acid (HX) from aqueous 
solution by neutralisation according to the equation: 
EQU A+HX.fwdarw.AHX, 
further acid extraction can occur by an addition reaction: 
EQU AHX+HX.fwdarw.AHX.HX. 
Thus a monoamine, such as Alamine 336, can load to 100% by neutralisation 
but higher loadings can be achieved due to addition. A similar phenomenon 
can be noted from FIG. 10, in which the monoamine is 
(4-aminobutyl)-heptamethylcyclotetrasiloxane. A polyamine containing Z 
amino groups can load to (100.times.Z)% by neutralisation and possibly 
even higher by addition. 
Although different chemical species may be formed through neutralisation or 
addition this distinction is not necessarily apparent from the 
distribution curve which shows only the net overall extraction of acid. 
For example, if a diamine is loaded to more than 100%, it cannot be 
decided from the distribution curve whether this is due to (i) total 
neutralisation of a first amino group plus partial neutralisation of the 
second group, (ii) total neutralisation of a first amino group plus some 
addition but no neutralisation of the second amino group, or (iii) a 
situation somewhere between cases (i) and (ii) with total and partial 
neutralisation of both groups plus some addition. 
The distribution curves of FIGS. 1 to 10 can be used in the design of an 
extraction plant to operate using the process of the present invention. 
This is illustrated with reference to FIG. 11 of the accompanying 
drawings, which is the distribution curve of FIG. 4 on which have been 
superimposed the lines necessary for making the calculation. 
In FIG. 11 the loading step of the extraction process is accomplished in 
four theoretical stages (L1 to L4) by countercurrent extraction at an 
aqueous:organic phase ratio of 1:25 starting with an organic phase (i.e. 
5.03% w/v HBCTP in 10.2% v/v iso-decanol in toluene) that is loaded to 
0.06 M with H.sub.2 SO.sub.4 and with an aqueous phase that is 2.5 M is 
H.sub.2 SO.sub.4. The resulting loaded organic phase, after four 
theoretical stages, is loaded to 0.13 M with H.sub.2 SO.sub.4 and the 
aqueous raffinate is now 0.75 M in H.sub.2 SO.sub.4. Stripping is effected 
in four theoretical stages (S1 to S4) by countercurrent extraction against 
water at an aqueous:organic phase ratio of 1:21.43. The loaded organic 
phase is stripped from 0.13 M in H.sub.2 SO.sub.4 to 0.06 M in H.sub.2 
SO.sub.4, whilst the aqueous sulphuric acid solution from the fourth 
stripping stage is 1.5 M in H.sub.2 SO.sub. 4. It will be observed from 
FIG. 11 that the slope of the loading line A corresponds to the 
aqueous:organic phase ratio (v/v) used during loading, whilst that of 
stripping line B corresponds to the organic:aqueous phase ratio (v/v) used 
during stripping. 
The results of these and other calculations based upon the distribution 
curves of FIGS. 1, 5 and 7 are summarised below in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Calculation No. 
1 2 3 4 5 6 7 
FIG. No. 4 1 4 1 7 5 5 
Organic phase: 
HBCTP 
Alamine 336 
HBCTP 
Alamine 336 
HPPCTP 
HBCTP 
HBCTP 
Reagent 
Aqueous phase 
H.sub.2 SO.sub.4 
H.sub.2 SO.sub.4 
H.sub.2 SO.sub.4 
H.sub.2 SO.sub.4 
H.sub.2 SO.sub.4 
HCl HCl 
Loading: 
No. of theoretical 
4 4 7 6 6 3 5 
stages 
Aq./organic phase 
1:25 1:43.75 
1:28.13 
1:45 1:39.58 
1:50 1:60 
ratio (v/v) 
Initial org. loading 
0.06M 
0.08M 0.05M 
0.07M 0 0.12M 
0.14M 
Final org. loading 
0.13M 
0.12M 0.13M 
0.12M 0.06M 
0.16M 
0.19M 
Initial aq. concn. 
2.5M 2.5M 2.5M 2.5M 2.5M 3M 5.5M 
Final aq. concn. 
0.75M 
0.75M 0.25M 
0.25M 0.125M 
1M 2.5M 
Stripping: 
No. of theoretical 
4 5 8 12 8 4 3 
stages 
Aq./organic phase 
1:21.43 
1:37.5 1:18.75 
1:30 1:16.67 
1:31.25 
1.60 
ratio (v/v) 
Initial org. loading 
0.13M 
0.12M 0.13M 
0.12M 0.06M 
0.16M 
0.19M 
Final org. loading 
0.06M 
0.08M 0.05M 
0.07M 0 0.12M 
0.14M 
Initial aq. concn. 
0 0 0 0 0 0 0 
Final aq. conc. 
1.50M 
1.50M 1.50M 
1.50M 1M 1.25M 
3M 
__________________________________________________________________________ 
It will be apparent to those skilled in the art from the distribution 
curves of FIGS. 1 to 10 that a practical extraction plant cannot be 
designed that utilises Alamine 336 for stripping sulphuric acid from 
aqueous solutions thereof to give results comparable to those of 
Calculation No. 5, nor for stripping HCl from aqueous solution to give 
results comparable to those of Calculations Nos. 6 and 7. Hence the 
compounds HBCTP and HPPCTP can be used in situations where it is 
impracticable to use the known monoamine extractant, Alamine 336 
(trioctylamine). 
Furthermore it should be noted that, although the compound HPPCTP 
(n-heptylamino-pentaphenylcyclotriphosphazene) is a weak base, it can be 
essentially completely stripped of acid during the stripping step. This 
means that, for a given concentration of extractant in the organic phase, 
essentially all of the extractant can be loaded in a cyclic extraction 
process. When using a strong base such as Alamine 336 or HBCTP, however, 
it is impracticable to strip all of the acid from the organic phase during 
the stripping step. Hence only part of the theoretically available 
capacity of the extractant present in the organic phase can be loaded in 
the extraction step in a cyclic extraction process. 
Although the major component of the solvent used for preparing the 
distribution curves of FIGS. 4 to 10 (i.e. toluene) differs from that used 
for preparing the distribution curves of FIGS. 1 and 2 (i.e. Escaid 100), 
the close similarity between the curves of FIGS. 2 and 3 (which differ 
essentially only in the choice of solvent) indicates that the results of 
FIGS. 4 to 10 are directly comparable with those of FIGS. 1 to 3. Hence, 
when using Escaid 100 in place of toluene in preparing distribution curves 
with the bases used in FIGS. 4 to 10, similar results are obtained. 
Using a conventional laboratory scale mixersettler apparatus arranged to 
effect continuous countercurrent extraction in four stages at an 
aqueous/organic phase ratio of 1:25, a solution of the compound HBCTP of 
the type used in preparing the distribution curve of FIG. 4 is used to 
extract a 2.5 M H.sub.2 SO.sub.4 solution. The resulting loaded organic 
liquor is then stripped in the same apparatus with water at an 
aqueous/organic phase ratio of 1:21.43. Analysis of the loaded organic 
liquor, of the aqueous raffinate, of the stripped liquor, and of the 
aqueous liquor from the stripping step yields results which confirm the 
correctness of Calculation No. 1 within experimental limits. 
For use in a practical commercial extraction process the extractant phase 
is preferably so formulated that it is substantially insoluble in aqueous 
media. Preferably it is so formulated that less than about 20 p.p.m., and 
even more preferably less than about 10 p.p.m., of organic material 
dissolves in the aqueous phase from the extractant phase upon contact 
therewith. 
Further examples of compounds of the formula (I) are listed in Table 2. 
3 TABLE 2 
Compound No. R.sub.1 R.sub.2 R.sub.3 R.sub.4 R.sub.5 
R.sub.6 1 --CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.3 --NHPh 
2 --Ph --Cl --Ph --Cl --Ph --Cl 3 --Ph --Ph --Ph --Ph --Ph --Cl 4 --Ph 
--Ph --Ph --Ph --Ph --NH(CH.sub.2).sub.6 
CH.sub.3 5 --CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.3 
--NH(CH.sub.2).sub.6 CH.sub.3 6 --Ph --Br --Ph --Br --Ph --Br 7 --NHPh 
--NHPh --NHPh --NHPh --NHPh --NHPh 8 --CH.sub.3 --CH.sub.3 --CH.sub.3 
--CH.sub.3 --CH.sub.3 --NHCH.sub.2 CH.sub.2 NH.sub.2 9 --CH.sub.3 
--CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.3 --CH.sub.2 CH.sub.2 NH.sub.2 
10 --Ph --Ph --Ph --Ph --Ph --Ph 11 --Ph --NHCH.sub.3 --Ph --NHCH.sub.3 
--Ph --NHCH.sub.3 12 --Ph --NHCH.sub.3 --Ph --NHCH.sub.3 --NHCH.sub.3 
--NHCH.sub.3 13 --Ph --N(CH.sub.3).sub.2 --Ph --N(CH.sub.3).sub.2 --Ph 
--N(CH.sub.3).sub.2 14 --Ph --N(CH.sub.3).sub.2 --Ph --N(CH.sub.3).sub.2 
--N(CH.sub.3).sub.2 --N(CH.sub.3).sub.2 15 --Ph --Ph --Ph --Ph --Ph 
--NH.sub.2 16 o-phenylenedioxy o-phenylenedioxy o-phenylenedioxy 17 
1,8-naphthylenedioxy 1,8-naphthylenedioxy 1,8-naphthylenedioxy 18 --OPh 
--OPh --OPh --OPh --OPh --OPh 19 p-tolyloxy p-tolyloxy p-tolyloxy 
p-tolyloxy p-tolyloxy p-tolyloxy 20 --Ph --OCH.sub.2 CH.sub.2 NMe.sub.2 
--Ph --OCH.sub.2 CH.sub.2 NMe.sub.2 --Ph --OCH.sub.2 CH.sub.2 NMe.sub.2 
21 --SPh --SPh --SPh --SPh --SPh --SPh 22 --S--n-C.sub.4 H.sub.9 
--S--n-C.sub.4 H.sub.9 --S--n-C.sub.4 H.sub. 9 --S--n-C.sub.4 H.sub.9 
--S--n-C.sub.4 H.sub.9 --S--n-C.sub.4 H.sub.9 23 --CH.sub.3 --CH.sub.2 
Ph --CH.sub.3 --CH.sub.2 Ph --CH.sub.3 --CH.sub.2 Ph 24 --CH.sub.3 
p-C.sub. 6 H.sub.4 
--NH.sub.2 --CH.sub.3 p-C.sub. 6 H.sub.4 
--NH.sub.2 --CH.sub.3 
p-C.sub. 6 H.sub.4 --NH.sub.2 25 --SCH.sub.2 Ph --Ph --SCH.sub.2 Ph --Ph 
--SCH.sub.2 Ph --Ph 26 --Ph N--morpholino- --Ph N--morpholino- --Ph 
N--morpholino- 27 p-NO.sub.2 --C.sub.6 H.sub.4 -- --Br p-NO.sub.2 
--C.sub.6 H.sub.4 -- --Br p-NO.sub.2 C.sub.6 H.sub.4 -- --Br 28 --Ph 
--NH.sub.2 --Ph --NH.sub.2 --Ph --NH.sub.2 29 --Ph --NHNH.sub.2 --Ph 
--NHNH.sub.2 --Ph --NHNH.sub.2 30 --NHPh --CH.sub.2 CH.sub.2 OCOCH.sub.3 
--NHPh --CH.sub.2 CH.sub.2 OCOCH.sub.3 --NHPh --CH.sub.2 CH.sub.2 
OCOCH.sub.3 31 --OCH.sub. 2 CF.sub.3 --OCH.sub.2 CF.sub.3 --OCH.sub.2 
CF.sub.3 --OCH.sub.2 CF.sub.3 --OCH.sub.2 CF.sub.3 --OCH.sub.2 CF.sub.3 
32 p-tolylene-1,2-dithio p-tolylene-1,2-dithio p-tolylene-1,2-dithio 33 
naphthylene-2,3-dioxy naphthylene-2,3-dioxy naphthylene-2,3-dioxy 34 
--O--CH.sub.2 --CH.sub.2 --O-- --O--CH.sub.2 --CH.sub.2 
--O-- --O--CH.sub.2 --CH.sub.2 
--O-- 35 --S--C(.dbd.NH)--C(.dbd.NH)--S-- --S--C(.dbd.NH)--C(.dbd.NH)-- 
S-- --S--C(.dbd.NH)--C(.dbd.NH)--S-- 36 --Ph --N.dbd.(CH.sub.2).sub.2 
--Ph --N.dbd.(CH.sub.2).sub.2 --Ph --N.dbd.(CH.sub.2).sub.2 37 --F 
--N(CH.sub.3).sub.2 --F --N(CH.sub.3).sub.2 --F --N(CH.sub.3).sub.2 38 
--OCH.sub.2 CH.sub.3 --NHCH.sub.3 --OCH.sub.2 CH.sub.3 --NHCH.sub.3 
--OCH.sub.2 CH.sub.3 --NHCH.sub.3 39 --OCH.sub.2 CH.sub.2 
OMe --NHCH.sub.3 --OCH.sub.2 CH.sub.2 OMe --NHCH.sub.3 --OCH.sub.2 
CH.sub.2 OMe --NHCH.sub. 3 40 --CH.sub.2 CH.sub.2 OEt --NHCH.sub.3 
--CH.sub.2 CH.sub.2 OEt --NHCH.sub.3 --CH.sub.2 CH.sub.2 
OMe --NHCH.sub.3 41 --Ph --NHNHCH.sub.3 --Ph --NHNHCH.sub.3 --Ph 
--NHNHCH.sub.3 42 --Ph --N(CH.sub.3)NH.sub.2 --Ph --N(CH.sub.3)NH.sub.2 
--Ph --N(CH.sub.3)NH.sub.2 43 --OCH.sub.2 Ph --OCH.sub.2 Ph --OCH.sub.2 
Ph --OCH.sub.2 Ph --OCH.sub.2 Ph --OCH.sub.2 Ph 44 --CH.sub.2 CH.sub.2 
SMe --NHCH.sub.3 --CH.sub.2 CH.sub.2 SMe --NHCH.sub.3 --CH.sub.2 
CH.sub.2 SMe --NHCH.sub.3 45 --OCH.sub.2 CH.sub.2 SMe --OCH.sub.2 
CH.sub.2 SCH.sub.3 --OCH.sub.2 CH.sub.2 SMe --OCH.sub.2 CH.sub.2 
SCH.sub.3 --OCH.sub.2 CH.sub.2 SMe --OCH.sub.2 CH.sub.2 
SMe 46 --CH.sub.2 CH.sub.2 SPh --CH.sub.2 CH.sub.2 SPh --CH.sub.2 
CH.sub.2 SPh --CH.sub.2 CH.sub.2 SPh --CH.sub.2 CH.sub.2 SPh --CH.sub.2 
CH.sub.2 SPh 47 --CH.sub.3 --O--m-C.sub.6 H.sub.4 --NH.sub.2 --CH.sub.3 
--O--m-C.sub.6 H.sub.4 --NH.sub.2 --CH.sub.3 --O--m-C.sub.6 H.sub.4 
--NH.sub.2 48 --CH.sub.3 --NHCH.sub.3 --CH.sub.3 --NHCH.sub.3 --(CH.sub.2 
).sub.3 
Note: 
*Q = (4aminobutyl)-heptamethylcyclotetrasiloxanyl. 
Listed below in Table 3 are examples of compounds of the formula (II) 
TABLE 3 
__________________________________________________________________________ 
Compound 
No. R.sub.1 
R.sub.2 
R.sub.3 
R.sub.4 
R.sub.5 
R.sub.6 
R.sub.7 
R.sub.8 
__________________________________________________________________________ 
49 --CH.sub.3 
--NHPh 
CH.sub.3 
--NHPh 
--CH.sub.3 
NHPh --CH.sub.3 
--NHPh 
50 --CH.sub.3 
--CH.sub.3 
CH.sub.3 
--CH.sub.3 
--CH.sub.3 
--CH.sub.3 
--CH.sub.3 
--NH--n-C.sub.4 H.sub.9 
51 --Ph 
--NHCH.sub.3 
Ph --NHCH.sub.3 
--Ph 
--NHCH.sub.3 
--Ph 
--NHCH.sub.3 
52 --Ph 
--N(CH.sub.3).sub.2 
Ph --N(CH.sub.3).sub.2 
--Ph 
--N(CH.sub.3).sub.2 
--Ph 
--N(CH.sub.3).sub.2 
53 --Ph 
--NH.sub.2 
Ph --NH.sub.2 
--Ph 
--NH.sub.2 
--Ph 
--NH.sub.2 
__________________________________________________________________________ 
Using the methods outlined above distribution curves for the compounds 
listed in Tables 2 and 3 are readily obtainable. 
The invention is further illustrated in the following Examples in which 
concentrations are expressed in terms of anhydrous materials. 
EXAMPLE 1 
An organic hydrophobic liquid extractant phase was prepared containing 
5.02% w/v hexakis-(n-butylamino)-cyclotriphosphazene (HBCTP) dissolved in 
a mixed iso-decanol/toluene solvent containing 10.06% w/v iso-decanol. A 
uranium-containing aqueous feed solution was also prepared containing 44 
gpl ammonium sulphate, 1.18 gpl uranium and sufficient sulphuric acid to 
bring the pH of the solution to 1.04. 
Equal volumes of the two solutions were shaken together for about 5 minutes 
and then allowed to settle and separated. Analysis of the organic layer 
indicated that the uranium concentration therein was 0.87 gpl, whilst the 
uranium concentration of the aqueous layer was shown by analysis to be 
0.34 gpl. Thus, under the conditions used the distribution coefficient, 
i.e. equilibrium concentration of U in organic phase: equilibrium 
concentration of U in aqueous phase, was 2.56. 
Upon shaking the uranium-loaded organic layer with 5 times its volume of 80 
gpl aqueous sodium carbonate solution, essentially all the uranium was 
stripped from the organic phase into the aqueous stripping solution. 
The lean organic liquor from the stripping stage can be re-loaded with 
uranium by shaking with a fresh volume of the aqueous feed solution and 
re-stripped showing that the HBCTP extractant can be used repeatedly in a 
cyclic process. 
EXAMPLE 2 
A cobalt-containing aqueous feed solution was prepared containing 250 gpl 
free hydrochloric acid and 22.4 gpl cobalt. The same organic phase that 
was used in Example 1 was also used in this Example. 
Equal volumes of the solutions were shaken together for about 5 minutes and 
then allowed to settle and separated. Upon analysis it was shown that the 
equilibrium cobalt concentration was 4.1 gpl in the loaded organic phase 
and 18.3 gpl in the aqueous phase. The distribution coefficient under 
these conditions was 0.22. The cobalt loading of the HBCTP extractant in 
the organic phase was 87%. 
The cobalt-loaded organic phase was stripped by shaking with 10 times its 
volume of water. 
The lean organic liquor can be loaded again with cobalt by shaking with a 
fresh volume of the cobalt-containing aqueous feed solution and 
re-stripped again, thus showing that the HBCTP extractant can be used 
repeatedly in a cyclic process.