CA1118210A - Process for separating iron from an organic extraction medium - Google Patents

Abstract

PROCESS FOR SEPARATING IRON FROM AN ORGANIC EXTRACTION MEDIUM

ABSTRACT

An organic extraction medium comprising a diluent and an extractant comprising a major part of alkyl phosphonic acid monoalkyl ester having alkyl group of C8 - C10, wherein iron is contained, is contacted with an alkali hydroxide solution or a mixture solution of alkali hydroxide and sucrose or the like, whereby iron is effectively separated from organic extraction medium. Iron may more effectively be removed therefrom by previously contacting the organic extraction medium with mineral acid to remove cobalt beforehand.

Description

~il8Z10 SPECIFICATION

PROCESS FOR SEPARATING IRON FROM AN ORGANIC EXTRACTION MEDIUM
.

BACKGROUND

The present invention relates to a process for treatment of an organic extraction medium for use of a liquid extraction process, especially to a process for separating iron from an organic extraction medium comprising a diluent and an ex-tractant which comprises a major par~ of alkyl phosphonic acid monoalkyl ester where the alkyl group is selected from those having 8 to 10 carbon atoms.
The liquid extraction process is employed to a selective extraction of some metals in hydrometallurgy. It should be considered in determining the extractant that the extractant is less soluble in an aqueous solution containing metal to be extracted and capable of selectively and effectively extract-ing the objective metal from the aqueous solution. The ex-tractant should be well soluble in the diluent since the extractant is diluted with the diluent when used as an organic ^

2~0 extraction medium.
Di - 2 -ethylhexyl phosphoric acid (D2HPA) is known as a cobal-t extractant which has a drawback that it is poorly capable o~ selective extraction between cobalt and nickel as follows: Cobalt will remain in the aqueous solution along with nickel when cobalt is extracted under restraining nickel from beïng extracted into the organic extraction medium. On the other hand, nickel will also be extracted into the organic extraction medium together with cobalt when cobalt is completely extracted from the aqueous solution. Thus, nickel and cobalt can not effectively be separated by liquid extraction in the prior art.
In contrast to the prior art, the present invention relates to a process wherein an organic extraction medium comprises alkyl phosphonic acid mono alkyl ester as an extractant comprising alkyl group having 8-10 carbon atoms.
A liquid which is obtained by dissolving said extractant in a diluent such as kerosene, mineral oil and the like is defined as an "organic extraction medium" hereinafter.
This organic extraction me~ium shows excellent extraction properties in selectively extracting cobalt from solutions containing cobalt and nickel such as leaching solution, process waste water and the like. An aqueous phase containing cobalt and nickel and the organic extraction medium is contacted each other by means of mixer settler, extraction tower, centrifugal extractor and the like, which plays as an antecedent stage to the process according to the present invention. An optical contact temperature ranges between 20 - 80C, and a volumetric ratio of the aqueous phase to the organic extraction medium ranges around 10 : 1 ru 1 : 10.
In the liquid extraction process, the organic extraction medium is used in recycle until its extraction properties deteriorate, while a small amount of iron present in the aqueous phase or iron dissolved from an apparatus will be accumulated in the organic extraction medium. It has turned out that such iron accumulation causes on the one hand a practical reduction in extraction capacity of cobalt cor-responding to an amount of the accumulated iron. On the other hand, it causes an extraordinary rise in its viscosity when an iron - containing organic extraction medium extracts cobalt, which makes a more serious drawback. This viscosity rise causes various difficulties and hindrances in the process such as pumping, mixing or piping, e.g. at valve point.
Therefore it is required for an extraction process using the organic extraction medium to remove the accumulated iron from the organic extraction medium in order to maintain steady extraction properties and capacity~

OBJECT OF THE PRESENT INVENTION

It is an object of the present invention to provide a novel process to separate iron from the organic extraction medium cap.l}~le ol sc:Lect:ively ex-trac~ing cobalt, :[t. is another object o the present invention to provide arl improvement in the extraction process wherein the organ.ic extractant may be reclaimed and recycled.

S~M~RY OF TElE INVEN~'ION

According to -the present invention, the organic extxac-tion medium is contacted with alkali hydroxide solution or a mixture solution o.E alkali hydroxide and monosaccharide, disacchar:ide, ployhydric al,co}lol and/or the like, The present invention provides a process for separating iron from an organic extraction medium comprising a diluent and an extractant comprises a major part of alkyl phosphonic acid mono alkyl ester represen-ted by a formula (I) :
o R - P - OEI ....................... (I) o where Rl and I~2 denote one or two alkyl g.roups selected :Erom alkyl group havi,ng 8 - 10 carbon atoms wherein said organic extractiorl meclium is colltactec~l w:ith an alkali hydroxide solutiorl .

Iron ent,e:red :rom the extraction medium into the alkaline aqueous solution -tellds to precipitate forming iron hydroxide which often causes difficulties in an operation, while the 1111~210 presense of saccharide or the like in the alkaline aqueous solution can effectively prevent the precipitation by chelate formation. Therefore, the present invention provides a process for separating iron from an organic extraction medium comprising a diluent and an extractant comprising a major part of alkyl phosphonic acid mono alkyl ester as defined by the formula (I) wherein said organic extraction me~ium is contacted with a mixture solution of alkali hydroxide and monosaccharide, disaccharide, polyhydric alcohol and/or the like.

It has turned out that the amount of cobalt remaining in the organic extraction medium affects iron separating efficiencies and the iron separation is accelerated by previously removing iron therefrom. Thus the present invention provides a process for separating iron from an organic extraction medium as defined hereinabove wherein said organic extraction medium is first contacted with mineral acid solution to remove cobalt therefrom then said organic extraction medium is contacted with an alkali hydroxide solution or a mixture solution of alkali hydroxide and monosaccharide, disaccharide, polyhydric alcohol and/or -the like.

i~l821~

BRIEF DESCRIPTION OF DRAWINGS

Figure graphically shows relations between chelating efficiencies and sucrose concentrations when a starting organic extraction medium of various iron contents is treated with a mixture solution of sodium hydroxide and sucrose.
Ordinate shows chelating efficiency of iron (%) as defined by (chelated iron concentration in a filtrate)/(iron con-centration in the starting organic extraction medium), abscissa showing sucrose concentrations in the mixture solution of alkali hydroxide and sucrose. Fach curve corresponds to an iron concentration in each starting organic extraction medium.

DETAILED DESCRIPTION

In the present invention, the organic extraction medium essentially consisting of alkyl phosphonic acid mono alkyl ester represented by the formula (I) is employed where Rl and R2 denote alkyl group having 8 - 10 carbon atoms. As Rl and R2, i.e. alkyl group having 8 - 10 carbon atoms one or two alkyl groups falling within following categories or a mixture thereof may be employed:

(as C8 alkyl group) 2 - ethyl -1 ~ hexyl, 4 - methyl - 1 - heptyl, 1 - octyl, 3 - ethyl -2 - methyl - 3 - pentyl group or the like;
(as Cg alkyl group) 3,5,5 - trimethyl - 3 - hexyl, 3 - ethyl - 5 - Inethyl. - 3 - hexyl, 1 - nonyl, 2 - methyl - 2 - ethyl group or the like;
(as C10 alkyl group) isodecyl, 1. - decyl., 4 - proyyl - 4 - heptyl., 5 -- methyl - 2 - isopropyl - 1 - hexyl,

3,7 - cdimctilyl - 1 - octyl, 3 - ethyl 3 -- oc-tyl group or t.he like.
Furthermore, o-ther known alkyl groups or derivatives thereof for Rl and R2 as defil-led by 8 - 10 carbon atoms and having similar chemical and physical properties 5uch as viscosi-ty, boiling point and extraction eapaei-ty and properties which are essential.ly dcfirlcd by -the carbon a-tom number may be employed as well. In the present invention, 2 - ethyl - 1 - hexyl, 3,5,5 - trimethyl - 3 - hexyl and/or isodeeyl group may be used for Rl and R2.

Thus said ext.rae-tant eomprises for instanee:
2 - ethyl - 1. - hexyl phosphonic aeid mono - 2 - ethyl - 1 - hexyl c-)stcr, 3,5,5 - trimctllyl - 3 - hcxyl.
phospholli.c acid mono - 3,5,5 - l:rimcthy:L -- 3 - hexyl este:r, isodecyl phosphonic acid monoisodecyl ester, 2 - e-thyl - 1 - hexyl phosphonic acid mono - 3,5,5 - -trime-thyl - 3 - hexyl ester, 2 - ethyl - 1. - hexyl phosyhoni.c acid monoisodccyl ester, 3,5,5 - trimethyl - 3 - hexyl yhosphonic acid monoisodecyl ester, and the like.
A mixture thereof may be used as well.

~1~8210 According to the present invention, an iron removal treatment is applied to the organic extraction medium when iron is accumula-ted up to an unfavourable concentration for practical operation (usually 1 ~ 2 g/~). If the iron accumulation reaches for instance 2 g/Q, then the practical extraction capacity for cobalt decrease by that correspond-ing amount or the more. Under such an lron accumulation, the viscosity of the organic extraction medium rises up to several hundreds to thousands centi Stokes when cobalt is extracted to a maximum extraction capacity. This viscosity rise on the one hand prevents the organic extraction medium from being smoothly pumped and piped through pipe lines and overloads mixer leaves, on the other hand greatly depress the extraction velocity, which is a still more serious polnt.
Thus the iron accumulation exceeding an allowable level causes various problems as mentioned hereinabove.

At the iron removal treatment, the organic extraction medium is partly or completely, if necessary, taken out of a liquid extraction system. The derived organic extraction medium is poured into a mixing tank together with an alkali hydroxide solution, being thoroughly mixed, then settled to a phase separation of the aqueous phase from the organic phase, thereafter the phase-separated organic extraction medium being recovered to complete the iron removal treat-ment. A room temperature for that treatment satisfies the lli8Z10 operation. A volumetric ratio between the organic extraction medium and the aqueous solution ("O/A ratio" hereinafter) need not be especially limited. However, a O/A ratio of around 1 is preferred for avoiding the organic phase from a contamination by precipitation.
A different reaction time is applied to the treatment according to mixability, O/A ratio and so on, at least two minutes reaction satisfying under a violent mixing. As alkali hydroxide sodium hydroxide, potassium hydroxide or the like may be employed.

Concerning concentrations of employed alkali hydroxide, the organic extraction medium does partly dissolve into the aqueous solution and an extraordinary poor iron removal efficiency is observed, when alkali hydroxide is less present than an amount necessary to react with the extractant. An iron removal efEiciency of 97.8 % or a higher efficiency may be achieved by keeping an alkali hydroxide concentration in the aqueous solution after the treatment to a value not less than 1~ g/Q. The iron removal efficiency is defined as follows:

A - B
x 100 (~) A
where A is iron in the organic extraction medium before treating, while B is iron therein after treating.

In some cases under a remain:ing alkyl hydroxicle concentration of about 16 g~ in -the aqueous solution af-ter the treatment, there is observed foaming at a surface, which would cause some difficul~ies to -the operation. This foaminc3 can be prevented by adcling salt such as sodium sulphate which is inert towards alkali hydroxide to the aqueous solu-tion at a salt concen-tra-tion of, e.g. 30 g/Q. A-t a remaining alkali hydroxide concentration of not less -than 50 g/~ in the aqueous solution af-ter the treatment, such foaming is not observed without -the addition of said salt.

The resultant organic extraction medium treated as above stays separated in two phases, and the ex-tractant turned into alkali salt such as sodium salt, which would sometime eause difficulties to the ope~ra-tion when these alkali salt is returned to the liquid extraction system. Therefore, the resultant organic ex-traction medium after the above treatment is preferably contaeted with a solution containincJ mineral aeid whereby alkali such as sodium in the resultant organie extraetion medium re-turns into the aqueous solution and the two~phased organie extraction medium re-turns to a single phase. Sulphuric acicl is preferably used as mineral acid at a eoneen-tra-tion enough to neutralize al}cali eontained in said resultant organic extraction medium. However, a sulphuric aeid eoneentration of not less than 100 g/~ is preferred in order to aehieve a high iron rernoval efficiency and to prevent a xe-extractioll of iron into the orgailic extractiorl medium since iron is usual.]y remaining therein as iron hydroxide or the like.

In the iron removal treatment process as hereinabove described, iron entered the aqueous solution from the organic extraction medium tends to precipitate to form iron hydroxide.
Generally, such a precipitation would often cause difficul-ties to the operation in the liquid-liquid reaction. There are an upper layer of the organic extraction medium and a lower layer of the aqueous solu-tion, the precipitation in the latter making some hinde:rnis to a solution taken out of a tank bottom.

According to -the present invention, it has turned out that an addition of monosaccharide, disacharide, polyhydric alcohols and/or the like to the alkali hydroxide solution can prevent the iron precipitati.on by chelate :Eormati.on of iron, iron get-ting into so].uble iron. Glucose, :Eructose, corn syrup, sucrose, molasses, solbitol, mannitol or a mixture thereof may be used as said monosaccharide, disaccharide, polyhydric al.cohol and/or the li]ce.

In the Iigure, there are shown results obtained from chelating -tests using an extractant essentially consisting of 2 - ethyl - 1 - hexyl phosphonic acid mono - 2 - ethyl - 1 , ~, 11~8210 - hexyl ester. In the figure there are shown relations between sucrose concentrations and chelating efficiencies which were obtained by a treatment of starting organic extraction medium having various iron concentrations with a mixture solution of sucrose and sodium hydroxide of a fixed sodium hydroxide concentration of 80 g/Q. It has been proved in the figure that a chelating efficiency not less than 80 ~ at a sucrose concentration of 60 g/Q, and that of about 100 ~ at a sucrose concentration of 100 g/Q can be achieved without being greatly affected by the iron concentration, provided the sodium hydroxide concentration is 80 g/Q. Here, the chelating efficiency is defined as a per cent of dissolved iron represented by a following formula:

chelated iron ion concentration (g/Q) in the solution ----- X 100 (~) iron ion concentration in the starting organic extraction medium A high chelating efficiency may be achieved by selecting an optimal sedium hydroxide concentration relevant to a lower sucrose concentration even when the sucrose concentra-tion is lower than 60 g/Q. The chelated iron as mentioned hereinabove denotcs iron in a filtrate which passed through No. 3 filter paper in the treatment.

The resultant organic extraction medium treated with a ...; ~
."~ .,, mixture solution of sodium hydroxide and sucrose or the like is also being phase-separated and contains a great deal of sodium. Thus, it is treated with mineral acid before it will the returned to the extraction system.

The starting organic extraction medium which is subjected to said treatment with alkali hydroxide or a mixture solution of alkali hydroxide and sucrose or the like is generally that after a stripping process, wherein however, there often remain other metal ions than iron due to an incomplete stripping. Provided cobalt ion remains, the iron removal efficiency is depressed by a great degree. In Table I, there are shown results obtained from iron removal wherein five various sample liquids which were prepared by adding 3.0 g/Q
of iron and 0.05 ~ 16 g/Q of cobalt to an organic extraction medium comprising 20 % by volume of 3,5,5 - trimethyl - 3 - hexyl phosphonic acid mono - 3,5,5 - trimethyl - 3 - hexyl ester and a balance of kerosene.

Table I

concentration before concentration after Sample No.treatment(g/Q) treatment (g/
Co Fe Fe . .. _ . ..
1 16.00 3.00 ' 2.00 2 1.00 " 0.18 0.082

4 0.05 " 0.009 .. . ~ . . .. ... ... . . . . . . . . .. . ... .. ... . . .

It has been proved by Table I that a higher cobalt concentra-tion provides a poorer iron removal efficiency~ The ~obalt concentration in the organic extraction medium should be maintained at a value not exceeding 0.05 g/Q for obtaining an iron ion concentration therein of not exc~eding 10 mg/Q.
Cobalt can be effectively removed by contacting with mineral acid having the same or a higher concentrati~n as ~r than that as employed in the stripping process, where for instance, a concentration not less than 50 g/Q for sulphuric acid is preferred.

In the followings, Examples are disclosed for a better illustration of the present invention and not for limitation thereto.

Example 1.
organic extraction medium comprising 22 ~ by volume of 2 - ethyl ~ 1 - hexyl phosphonic acid mono - 2 - ethy:L - 1 - hexyl ester and a balance of kerosene was ad~ixed with 0.64 g/Q of iron iOll. This organic extraction medium was contacted with sodium hydroxide solutions having concentrations as shown in Table II. In Sample No.5, 30 g/Q of sodium sulphate was previously added to prevent foaming. The contact treat-ments were carried out at a O/A ratio 1/1 where each 100 mQ
was shaken in a separatory funnel a-t a temperature of 25 C

for 5 minuts. After the treatment, the organl~ extraction ~ o~
r~
a~ ~ ~D
:> O ~ ~ r~ oo ~ 0 ~1 ~ a~
O E~ ~H
h (L) ~H
,t s, a,~
In ~ ~9 o

5~ ~ oo o o o a~ ~
~ o a3 ~ a~ O O O O O
O rJ 1~ ~1 ,1 ~ ~' 1-1 h a) ~ I
X a~
~ a~ a S~ O ~
O ~ o -l 41 0 ~ ~) o a) ~

H h ~ u~ o IS~ u ) irl o ~~1 4H O IJ ~ Itl 1-- 0 a) 1~3 a~ :~ ,:~, ~ , a~ co 1 ~. ~o ~ ~ ~:
a) v u~ 'In In 'O ~ X ~
J a) ~ ~1 " r~ ~ ~1 0 ~
au ~ a) ~1 ~I r 1 ~1 ~1 ~ O
~ ~_ O ~
a) O ~ D O
r~ c~ æ
a) o a) h ~ ~r o o o o ~OH a~
z a) ~1 Q

U~

. .

medium went separated into two phases. Average iron concentrations as shown in Table II were measured by analyzing test samples pipetted from each phase and then calculated in consideration of volume differences therebetween. In Sample Nos. 1 and 2, foaming was observed at a surface while in Sample Nos. 3 and 4 no foaming was observed. There was no foaming when NaOH concentration in the aqueous solution after the treatment was high. In Sample No. 5 to which sodium sulphate was previously added, there was no foaming.

Under a condition where sodium hydroxide hardly presents in the aqueous solution after the treatment (e.g. Sample Nos.
1 and 5), the organic extraction medium does not separate in two phases, and a very low iron removal efficiency was attained. On the contrary, iron was removed to a concentra-tion of 10 mg/Q which corresponds to an iron removal efficiency of more than 97.8 % in Example Nos. 2 - 4 where 16, 56 and 90 g/Q of sodium hydroxide were remaining in the aqueous solution after the treatment~

Example 2.
0.65 g/Q of iron ion was added to an organic extraction medium comprising 20 % by volume of 3,5,5 - trimethyl - 3 - hexyl ester no extractant ~Id a balance of kerosene. This organic extractant medium was treated with a sodium hydroxide solution having each concentration as shown in Table III.

.~, . ..

~ o\o ~ a) u~ 00 0 0 ,r~

;~ a ~ s~ ~
- ~

o:o ~ ~ o o o o o . ~ ~ u~
~ U . ~ ~
a~ ~ ~ o ~d o o s~
~ v o a) s~
H

= k ~ ` o 3 ~ .

^
~o ~
b aJI r~ o u~ ~ o .~J ~ O
~ ~1 ~1 ., ~
O ~
O ~ O O o o o 1~ 4-1 ~L) $ ~
a ~1 ~ r~

30 g/~Q oL sodium s~llphate was previously added to Sample No. 5 in order ~o preven-t foaming. The treatment was carried out similarly to Lxampl,e 1 and results are listed in Table III.
The results were similar to those for each Sample of Example 1, while in Sample Nos, 2 - ~ iron removal efficien-cies of not less than 98.0 O were a-ttained.

Example 3~
Organi,c extraction mediums asnumbered 1 ~ 4 were prepare,d each of which comprises 22 ~ of each extractant as follows and a ba:Lallce of kerosene:
No. 1 ; 2 - ethyl - 1 - hexyl phosphoric acid mono - 3,5,5 - trimethyl - 3 - hexyl ester, No. 2 ; 2 - ethyl - 1 - hexyl phosphonic acid mono-isodecyl ester, No. 3 ; 3,5,5 - tri,methyl - 3 - hexyl phosphonic acid mono--isodecyl ester, No. 4 ; isodecyl phosphonic acid mono isodecyl ester.
Each 0.65 g/Q of irorl:ion was adclccl Lo c~acll orglnic cxtrLIc-tion medium as ahove, each of which was t:llen -treated with a sodium hydroxide solution having a concentration of 80 g/~,.
Each treat:me~nt was carri,ed out similarly to that in Example 1.
Results for iron removal efficiencies are shown in Table IV.

~1 lii8ZiO

Table IV

organic extraction iron removal medium efficiency (%) 1 97 ! 80 2 98.10 3 98.00 4 97.85 Example 4 An organic extraction medium comprising 22% by volume of 2 - ethyl - 1 - hexyl phosphonic acid mono - 2 - ethyl hexyl ester, l.90 g/Q of iron ion, and a balance of kerosene was treated with five variant mixture solutions of sucrose and sodium hydroxide. The treatments were carried out in a similar manner to Example 1. Resultant iron removal efficiencies and chelating efficiencies are shown in Table V. In those~test~samples, the iron concentration reached utmost 28 mg/Q and good iron removal efficiencies exceeding 98 % were attained. Combinations of sucrose and sodium hydroxide in the aqueous solution after the treatment with ~ ..... . .
each concentration of 60 g/Q and 56 g/Q as well as 30 g/Q

and 16 g/Q proved high chelating efficiencies.

lil8~10 a\ u~ ~1 ~1 _I O
~ ~ X
_l ~ O u~
CO

CO ~ N
~ ~ ~ co o~ ao o~ co ~ a~
H ~ C~
~J
C ~1 ~ El N _I NO o~ ~D
O 0 00 ~ ~_) O O O O C:~
C~ _ ~J ~
C C ~ ~ o o o o o c~a ~ ~
O ~U ~-c ~ a ~ a O

~ 1~ a¦ O ~ "

~^ ~ o 'c ., ~ 91 '' ' ~ O ~ h ~ CO oo O
C~ o~ , ' ' ~ .
.. . C~ ~ ~ _ ~ ~ O O O O
U~

~ Z _I N ~ ~rIf) U~

. .

,: - . . . .

Example 5.
An organic extraction medium comprising 1.90 g/Q of iron and 22 % by volume of isodecyl phosphonic acid mono - 2 - ethyl hexyl ester was treated with five variank mixture solutions as shown in Table VI comprised of sucrose and sodium hydroxide. Each treatment was similar to that in Example 1. Resultant iron removal efficiencies and chelating efficiencies are listed in Table VI.
A ma~imum iron concentration in the organic extraction medium was utmost 29 mg/Q, and high iron removal efficiencies exceeding 98.5 % were achieved. Combinations of sucrose and sodium hydroxide in the aqueous solution after the treatment with each concentrat.ion of 60 g/Q and 56 g/Q as well as 30 g/Q and 16 g/Q exhibited high chelating efficien-cies.

~o o ~
rl Cl ~ CO OC;~ r-l ~ ~r~ r-l r~l tx:
r r r--l 11') c~ a ! r--l 1~'~ ~ CO
~1 a) Ll~ o o~ o ~ ~ ~o a~ ~ ~ oo G ~ ~ ~ a~
h a _~ ~
. 0~ 1:l a~ co ~ CO~D
~ 0 CI ~ ~ ~
0~ ~d ~ o o o o o ~0 ~ ~ O
a~
h ~ h O ~ -i ~ G~ X CJ ~
~ a) ~ ~
~ ~ O
(I) ~ ~_ o 1~ a~ o o:) N
e D ~1 ~;0 COa~ ~ c~

~ X ~ .~ r~ O
t~
~ a~
O ~

h U W W W ~D W
U~ O _~ U
rl ' ~ ~d u ~; ~ O O O O O
~d O h ~1 00 CO00 ~r (~
O~d -J
~1 ~ ~ ~.
O ~ Q) C~ rl ~n ,~
s~ ~ o o o o ~ bO
~q ~ .
o ~d Example 6r Five differerlt organic extraction medium samples comprising 20 % by volume of each extractant and a balance of kerosene as listed hereinbelow were prepared:

Organic extraction medium sample No. __ extractant 1 3,5,5 - tr;.methyl - 3 - hexyl phosphonic acid mono - 3,5,5 trimethyl - 3 - hexyl ester 2 isodecyl phosphonic acid mono - isodecyl ester 3 2 - ethyl - 1 - hexyl phosphonic acid mono - 2 - ethyl - 1 - hexyl ester 4 isodecyl phosphonic acid mono - 2 - ethyl - 1 - hexyl ester isodecyl phosphonic acid mono - 3,5,5 - trimethyl - 3 - hexyl ester.
.~

Each 2.00 g/Q of iron was admixed to each sample. Then each sample was treated with a mixture solution of 60 g/Q sucrose and 30 g/~ sodi.um hydroxicle ;.n a s:im:ilar marlner to that in ~xample 1. Resultant iron removal efficiencies and chelating efficiencies are shown in Table VII.

Table VII

organic extraction iron removal chelating medium efficiency _fficiency 1 98.73 93.60 2 98.78 93.58 3 98.88 93.81 4 98.81 93.70 98.82 93.72 Accordingly, a simple process for separating iron accumulated in the organic extraction medium comprising alkyl phosphonic acid mono alkyl ester therefrom has been developed in the present invention. Thus the deterioration of the organic extraction medium during the recycling use thereof and difficulties in the operation has been removed or eliminated. Fox a further reduction of iron concentration in the organic extraction medium up to a few mg/Q ~ 1 mg/o a recycling of the same treatment as hereinabove described in two or more times enables such a reduction.

~.

Claims (11)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A process for separating iron from an organic extraction medium comprising a diluent and an extractant comprising a major part of alkyl phosphonic acid mono alkyl ester represented by a formula:

where R1 and R2 denote alkyl group having 8 to 10 carbon atoms wherein said organic extraction medium is contacted with an alkali hydroxide solution.

2. A process as defined in Claim 1, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said R1 and R2 selected from a group consisting of:
2 - ethyl - 1 - hexyl, 4 - methyl - 1 - heptyl, 1 -octyl, 3 - ethyl - 2 - methyl - 3 - pentyl,3,5,5 -- trimethyl - 3.- hexyl, 3 - ethyl - 5 - methyl - 3 - hexyl, 1 - nonyl, 2 - methyl - 2 - octyl; isodecyl, 1 - decyl, 4 - propyl - 4 - heptyl, 5 - methyl - 2 - isopropyl - 1 - hexyl, 3,7 - dimethyl - 1 - octyl and 3 - ethyl - 3 - octyl group, or a mixture thereof is used as said extractant.

3. A process as defined in Claim 1, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said R1 and R2 selected from a group consisting of 2 - ethyl - 1 - hexyl, 3,5,5 - trimethyl - 3 - hexyl and isodecyl group or a mixture thereof is used as said extractant.

4. A process for separating iron from an organic extraction medium comprising a diluent and an extractant comprising a major part of alkyl phosphonic acid mono-alkyl ester represented by a formula:

Where R1 and R2 denote alkyl group having 8 to 10 carbon atoms wherein said organic extraction medium is contacted with a mixture solution of alkali hydroxide and mono-saccharide,disaccharide and/or polyhydric alcohol.

5. A process as defined in Claim 4, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said R1 and R2 selected from a group consisting of:

2 - ethyl - 1 - hexyl, 4 - methyl - 1 - heptyl, 1 - octyl, 3 - ethyl - 2 - methyl - 3 - pentyl,3,5,5 - trimethyl - 3 - hexyl, 3 - ethyl - 5 - methyl - 3 - hexyl, 1 - nonyl, 2 - methyl - 2 - octyl, isodecyl, 1 - decyl, 4 - propyl - 4 - heptyl, 5 - methyl - 2 - isopropyl - 1 - hexyl, 3,7 - dimethyl - 1 - octyl and 3 - ethyl - 3 - octyl group, or a mixture thereof is used as said extractant.

6. A process as defined in Claim 4, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said Rl and R2 selected from a group consisting of 2 - ethyl - 1 - hexyl, 3,5,5 - trimethyl - 3 - hexyl and isodecyl group or a mixture thereof is used as said extractant.

7. A process as defined in Claim 4, wherein glucose, fructose, corn syrup, sucrose, molasses, solbitol, mannitol or a mixture thereof is used as said monosaccharide, disaccharide and/or polyhydric alcohol.

8. A process for separating iron from an organic extraction medium comprising a diluent and an extractant comprising a major part of alkyl phosphonic acid mono alkyl ester represented by a formula Where R1 and R2 denote alkyl group having 8 to 10 carbon atoms wherein said organic extraction medium is first contacted with mineral acid solution to remove cobalt therefrom then contacted with an alkali hydroxide solution or a mixture solution of alkali hydroxide and monosaccharide, disaccharide and/or polyhydric alcohol.

9. A process as defined in Claim 8, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said RI and R2 selected from a group consisting of:
2 - ethyl - 1 - hexyl, 4 - methyl - 1 - heptyl, 1 - oatyl, 3 - ethyl - 2 - methyl - 3 - pentyl,3,5,5 - trimethyl - 3 - hexyl, 3 - ethyl - 5 - methyl - 3.
- hexyl, l - nonyl, 2 - methyl - 2 - octyl, isodecyl, 1 - decyl, 4 - propyl - 4 - heptyl, 5 - methyl - 2 - isopropyl - 1 - hexyl, 3,7 - dimethyl - 1 - octyl and 3 - ethyl - 3 - octyl group, or a mixture thereof is used as said extractant.

10. A process as defined in Claim 8, wherein alkyl phosphonic acid monoalkyl ester which comprises one or two alkyl groups for said R1 and R2 selected from a group consisting of 2 - ethyl - 1 - hexyl, 3,5,5 - trimethyl - 3 - hexyl and isodecyl group or a mixture thereof is used as said extractant.

11. A process as defined in Claim 8, wherein glucose, fructose, corn syrup, sucrose, molasses, solbitol, mannitol or a miture thereof is used as said monosaccharide, disaccharide and/or polyhydric alcohol.