CA1086076A

CA1086076A - Process for the elimination of accumulated iron in organic phases of fluid-fluid extraction that contain di-2-ethyl-hexyl phosphoric acid

Info

Publication number: CA1086076A
Application number: CA262,782A
Authority: CA
Inventors: Jose Manuel Regife Vega; Angel Luis Redondo Abad; Eduardo Diaz Nogueira
Original assignee: Individual
Current assignee: Individual
Priority date: 1975-10-06
Filing date: 1976-10-05
Publication date: 1980-09-23
Also published as: BR7606683A; PT65683A; PL107319B1; AU1843376A; IL50629A0; FI762829A; SE7610999L; AU512317B2; PT65683B; DE2645130A1; MX144484A; FR2327199A1; ZA765992B; SU712025A3; JPS6026049B2; IT1068260B; ES441536A1; RO72871A; JPS5289566A

Abstract

ABSTRACT

A process is disclosed for the elimination of accumulated iron in the organic phase of a fluid-fluid extraction that contains di-2-ethyl-hexyl phosphoric acid. This process involves treating said organic phase with an aqueous acidic solution of chloride ions, subsequently extracting the iron with an anionic ion exchanger leaving the di-2-ethyl-hexyl phosphoric acid iron-free for subsequent re-use, and regenerating the anionic exchanger by treatment with water to provide a relatively concentrated aqueous ferric chloride solution.
Di-2-ethyl-hexyl phosphoric acid is used commercially as a cationic exchanger in the extraction of hexavalent uranium from sulfate solutions, in the separation of uranium and vanadium, in the separation and purification of rare earths, in the separation of cobalt and nickel, and in many other such applications.

Description

6~76 Di~2-ethyl-hcxyl phosplloric acid i5 UsO(:I commercially as a cationic oxchal1gcr in tho extraction of hcxaval(3nt uranium from sulrate solutions~ in thc scparation of uranium and vanaclium, in tl--c scparatior and purification of rarc earths, in thc separation of coba]t and nickcl, in the extraction of beryllium from sul~ate solutions, in the separation o-~ zinc, iron, manganese, and cobalt, in the extraction o~ zinc, and in many other applications that are in the course of development.

In all these proc¢sses the fluids processed as aqueous feed usually contain various ionic impurities, one of the most common being iron. The affinity of di-2-ethyl-hexyl phosphoric acid for iron is so high that even in very low concentrations it is extracted quantitatively forming a complex that p~lymerizes in the organic phase, reaching molecular polymerization weights of the order of 2,000. This phenomenon, in time, produces a marked decrease o~ the load capacity oÇ the cationic exchanger as well as a considerable increase in viscosity in the organic phase that makes dif-ficult and even prevents its utilization as an extraction agent in a very large number of possible applications It is well known that there are two possible processes to eliminate ., .; . .
iron from these organic phases The first consists in washing it with a strong alka1ine solution of hydroxide or sodium carl~onate. This treatment achieves thc rupture of the the polymer forming ferric hydroxide/sodium salt of di-2-ethyl-l1exyl phosphorio acid. The presence of the precipitate of ferric hydroxide in the aqueous sta~e and the high degree of disassociation of the sodium salt frorrl the acid causes the carrying alony and the solubility of the di-2-ethyl-hoxyl phosphoric acid to bo so high that thcy malce its application on an industrial scale prohibitive economically speaking.

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~~ The second process consists in washing it with an aqueous solution of 6M hydrochloric acid. This treatment also achieves the rupture of the polymer by the formation of the anionic complex from the ferric ion in a chloride medium, C~4Fe , that displaces the cationic exchange between the F ions of the organic stage and the H ions of the aqueous stage. This process is not very attractive from the economic point of view because of the high consumption of acid necessary.
In this second process the consumption of hydrochloric acid is determined by the balance existing between the two phases during the treatment with respect to the ferric ion, which makes it necessary to purify the acid aqueous solution when a given concentration of iron is reached but which always represents an insignificant fraction of the acid equivalents utilized so that the consumption of acid normally represents from 10 to 20 times the stochiometry of the iron.
The subject of the present invention is a proce~ss for the elimination of iron accumulated in the organic stages that contain di-2-ethyl-hexyl phosphoric acid by means of an acid aqueous ` 20 solution containing chloride ions and the subsequent treatment o-the regeneration liquid in order, by means of the elimination of the iron, to reuse it.
In one particular aspect the present invention provides in a process for the removal of iron from an iron contaminated cll-2-ethyl-he~yl phosphoric acid containing organic phase of n Eluid-fluid extraction process, the steps of directly con~acting said iron contaminated di-2-ethyl-hexyl phosphoric nc:ld containing organic phase with a regeneration fluid comprising an acidic aqueous solution containing chloride ``- 30 , ~ -2-;' ' :

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- ions to effect cationic exchange of ferric ions and yield a : regenerated di-2-ethyl-hexyl phosphoric acid containing : organic phase and an iron containing regeneration fluid phase, contacting the iron containing regeneration fluid phase with an anionic ion exchanger containing organic phase to extract the iron from the iron containing regeneration fluid phase, treating the anionic ion exchanger containing organic phase containing extracted iron with water and recovering iron in the form of a relatively concentrated : 10 aqueous solution of ferric chloride.
. The process that is the subject of the present invention therefore consists of three stages:
In the first stage the organic phase containing di-2-ethyl-; hexyl phosphoric acid "poisoned" by iron is placed in contact ..
with an acid solution containing chloride ions in concentrations , such as produce the exchange of ~1+ ions for ~e+ ions between the aqueous phase and the organic phase, achieving the "regeneration" of the organic phase.
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The sc~cond ';t;~CJC consists oE tlle oxtr~ction of tl,c iron c-~r~t.~ c~l in the rccJeneration ~lui~l of tho proc~din~3 sta~e by mcans of its contact with an or~anic solution containin~3 an anionic ion exchan~or in such a way that the rc~eneration liquid i5 rcutilized in thc first st.l~3c after the replacement of the stochiometric hydrochloric acid equivalcnt to the iron eliminated.

The third stage consists of the re-extraction of the iron from the organic phase containing the anionic exchanger proceeding from the preeeding stage by means of its contaet with water, so that this or~anie stage, free from ironJis reeycled for reutilization in the second stage.

In brief, the iron passes from the or~anic phase eontaining the <li-2-ethyl-hexyl phosphoric acid to the wa~;er by means of two intermediate vehieles: an acid solution of chloride ions and an organie solution of an anionie exehan~er, the whole of the proeess which is the subject of this invention produeing only the eonsumption of hydroehloric acid ecluivalent to the iron eliminated and the quantityof water necessary to evacuate from b the system the ferric ions eliminated.

In the first stage, or the regeneration stage, the reaction ~nechanism is one of eationic exehange and in a simplified ~orm it may be represented by the following equilibrium:

R Fe() 3Rt (aq) ~ ~ICl ~ (aq) ~ 3 RH(o) ~C14Fe (aq) RH bein~ the di-2-ethyl-hexyl phosphorie aeid Thus, in prineiple, the re~eneration reagent may be any mixture of an inorganie mineral aeid and a sol~lblo choride, hydrochloric aeid bein~ preferable from the practical point o-f vi~w, alone or mixed Wit}l sodium chloride or calcium ehloridc, nnd sulfurie :Irid with -odium rhloride ~ .
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, ~8G(~76 The optimum conccntr~tions of thcse roagcnts in tho rcgcllcr~ g liquid obviously dcpcnd c n the concentration of di-2-cthyl-hcxyl pllosphoric - ;~cid in the organic pl-aso and on the lcvcl of rcsidual iron that is sc ugllt in the applic~tion in question.
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For a concentration that is widcly util ized of 10% v/v ; in kerosene, the optimum environment of concentration of hydrochloric acid in the regenerating liquid is found between 4 and 6 molar.

,~ The regeneration of the di-2-ethyl-hexyl phosphoric acid may be carried out in any extraction equipment with solvents and preferably in sedimentator_mixers. This type of apparatus is that which was used in '. our tests continuously.
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The time required for agitation or contact n order to attain the equilibrium depends on the concentrations in the organic and aqueous phases ~` and on the degre.e of agitation, In any case it waS less than 10 minutes, values of less than 3 minutes predominating.
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The separation of phases does not offer any difficulty.
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In a single contact between the re~enerating reagent in the form of hydrochloric acid 5.5 M and the organic phase with di-2-ethyl-hexyl ~,- , phosphoric acid 10% v/v, with appropriate regulation of the ~'atio of the flows of both, the elimination of the latter was achieved plus 90~o of tho iron, an organic phase resulting that contains iron in quantities of less than 150 mg/l, l` The temperature compatible with the process varies betwocn 10 `h and 50 C.

The concontrations of D2EHPA in the organic phasc may vary - between 1% and 50% v/v.
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~86~76 5 Tllo conccntrat;ons of clllori~le ion in the rcgoncr~lting r~{lgcnt may vary froln 0~1 to 12 M, tho bost results being obtainccl in tho erlvironmcnt of ~ 0 to 6 0 M.

Another aim of the process of the present invcntion is thc elimination of iron from thc aqueous reagent used in thc re~cneration of the di-2-ethyl-llexyl phosphoric acid for the purpose of utilizing it again.
:, In order to extract the iron in the second cycle, an organic phase is employed constituted by three components: an extraction agent, a modifi er and a diluting agent.
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The extraction agent belongs to the amino groups, and may be primary, secondary, or tertiary, or on a basis of quaternary ammonium with long alkylic chains, only slightly soluble in water and with a molecular weight superior to ~00 The second component of the organic phase - modifier - has the purpose of facilitating the separation of phases during extraction. Alcchols of from 8 to 14 carbons give the desired results.

The third component or the diluting agent serves as the carrier of the other two reagents and causcs the viscosity of the medium to decrease A hydrocarbon may be used or mixtures of hydrocarbons such a5 those obtained in the fractionating process in the distillation of petroleum.
`:~ The fixing of the iron on the extraction agent is ba5ed on the ~act that this element forms in solutions of ehloride ion the ehlorinized comple x o~ an anionie nature, Cl~Fe, in aeeordance with the equilibrium:

~ICl ~ Fe3~ Cl Fe~
The extraetion of the iron i5 earried out by an ionie exchange .
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., mcchallismJ bctwccn thc cl-loriclo oF th¢ aminatcd compouncl ancl tl)c ion complex of the iron. For thc case oF secondary aminc chloride, (R2H2NCl), the equilibrium may bc reprcserlted by the following eq~lation:

R2NH2Cl ~ C14Fe , > R2NH2Clq.Fe ~ Cl .. .
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The displacement oF this reaction towards the right - the direction of extraction _ to the extent that it is made by the conccntrations of Fe ~
and Cl , on all the latter~ which intervenes in the constant of formation of the anionic complex of the iron.
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The extraction of iron may be carried out in any extraction equipment with solvents, preferably in sedimentator-mixers This type of apparatus is that which has been used continuously in our tests.

The time required for agitation or contact in order to attain equilibrium depends on the concentrations in the organic and aqueous phases and on the degree of agitation. In any case it was lèss than 10 minutes, values of from between 2 and 5 minutes being predominant.

YVhen there is a modifier in the organic phase the separation of phases does not present any difficulty.

In a sin~le contact between the organic phase containing the aminc c~nd the regenerating reagent, appropriately regulating the ratio of the llow of both, an climination was achieved of more than 95% oF the iron From tho latter, an aclueous cxtract resulted with a concentration of iron inFerior to ~0 mg/l - ~ . .
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Thc tcmpcraturc compatil)lc witll thc proccss varics bctwccn 10 and 50 C.
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- Thc concentrations of amine in the organic phasc may vary l~twecn 1,and 50%, and thc concentration of aliphatic alcohol fr~m 0 to 25%
depending on the concentration of iron and chlorides in thc regenerating reagent .. . .
~, - The re-extraction of iron from the organic phase that contains the amine is carried out with waterJ being based on the disassociation of the anionic complex of iron ~14Fe in the absence of chloride ions.
Depending on the !ratios of the flows of the organic phase and water, more or less concentrated solutions of ferric chloride may be obtained as well as a greater or less discharge of the organic phase.
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After re-extraction, the organic phase is practically free of iron, SO that it is re-utilized in the process.

Losses of regenerating reagent (hydrochloric acid) using this method are reduced to the stochiometric consumption corresponcling to the iron plus the small amount of purifying necessary to maintain the balance of ~;ater in the system, This method may also be used for regenerating the di-2-ethyl-hexyl phosphoric acid of other ions that form anionic complexes in chloride cnvironments such as: chrome, aluminium, etc.
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The invention is illustrated by means Or a number of exarnples that are not limitative, and in order to facilitate the interpretation a drawingi~ is also attached.

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Ex~lrnr>l~ N 1 An illustrative examplo is given bclow, which is not limitative, of thc rcgcncration of the D2E~IPA. An organic pllase is establislled whose eom,oosition is the following:

D2EHPA : 10% v/v Petroleum (CAMPSA) : 90% v/v This organic phase ;s charged with iron to a concentration of 0. 338 g/l . In what follo~Ars the above~mentioned organic phase is subjected to a contact, in a single stage, with a solution of hydrochloric acid 5.9M. The ratio . of the flot~s in those the organic phase to/ Of aqueous phase was 10.

The results were the following:
- Iron in the organic phase : 0.110 g/l - Iron in the aqueous phase : 2.19 g/l Example N 2 A new demonstrative and non limitative example is given in what follows .. in whieh all the coneentrations of the regenerating reagent that have been enumerated may be used to regenerate the D2EHPA.

The organie phase has a eomposition the same as that utilized in example N 1.

The eoneentrations of iron in the organie phase, the eoncentrations of re~eneratin~ reagent and th6~: ratio . of the flows in the or~anic phase to those of aqueous phase are tho following:

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Tcst ~rganic phasc r:egcnor;lt;ng solution Ral;io Or f]ows qFc/l Cl~ M/lorclonic/~q-leous 1 0. 240 s . 0 30

2 0, 240 5 . 0 20

3 0 . 338 5, 0 10 0~338 5.0 5 0.2~0 ~.0 5 6 0.338 3,9 S
7 0, 338 3 . 0 10 Both phases were subjected to a contact in a single sta~e, the following results being produced:

Test Organic resultantAqueous resu.ltent gFe/l qFe/l 0. 110 3.57 2 0,090 2.60 3 0, 055 2 . 45 0. 068 1 . 37 0.120 ~,23 6 0 . 063 1 . 34 7 0. 190 1.48 '~ .
Ex~mple N 3 , . .
Another demonstrative and non-l;mitative example is given below in which all the compositions of the regenerating reagent enumerated :l` may be used in order to regenerate the D2EHPA.
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'-' ' Th¢ organ;c phase has a cornposition the same as that utilized in tho preceding examples.

Tho concentrations of iron in the organic phase, the cornposition of the rcgen~ratin~ solution and the ratio of flows in the organic phase to those o~ the aqucous pllase are thc following:

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~i~ Rc~cncrant solution Tcst Or~1anic pln~s~ I</l Ratio of flows ~FC/I CIH ClMa SO~H2 Or(~anic/aqucous .~. . .. . ... . .
1 O. 338 5.0 1.0 ~ 10 2 0.338 ~.0 1.1 ~ 15 3 0.240 ~.0 1.1 ~ 20

4 0.338 2.9 2.2 - 10 0.338 2.0 3.3 _ 1n 6 0.338 2.0 2.0 2.0 10 Both phases were sub~ected to a contact in a single stage, the following results being produced:

Test Organic resultant Aqueous resultant __ ~Fe/l _ ~Fe/l _ 1 ' O. 098 2, 3~
2 O. 115 3.~0 3 0.095 2.70 ~ , 0.115 2.2 O, 165 1.6~
6 0,123 2,13 Example N 4 A non~limitative illustrative example is given below of the elimination of iron from the liquid for regeneration of D2EHPA. The composition of the organic phase is the following:
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~' Amberlite - LA-2 (commercial secondary amine) 15%
Isodecanol ........... ,.,.. ,,.. ,... ~........... 6%
, Petroleum C~PSA) ... , 79%
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~; The above-mcntioned organic phase was then subjected t,o a !''`~ contact, in a sin~le sta~e, with the regenereration effluent from thcD2EHPA.
'' The organic stage char~ed with iron was re-extracted with water in one , ~ .

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The concentrati~ns of iron in the effluent fram the regeneration and the ratio of flows in ~he organic phase to those in the aqueous phase .
in extraction an~ re-extraction are the following:
Regenerant solution Ratio of flows Ratio of flows Test gFe/l extraction re-extraction crgam c/aqueous organic/aqueous 1 3.24 1.80 7O20 2 3.04 0~67 3.23 3 3.20 1.25 5.59 4 3.48 2.54 10.06 2.6g 1.98 10.23 6 2.97 2.50 17.12 The results were the ~ollowingO
Test Aqueous ex~ract. Organic extract. Aqeuous re-extract. Orangic ~e-extract _gFe/l ~Fe/l gFe/l ~Fe~l , 1 0.20 1.81 12.20 0,12 2 0.63 3.77 11.60 0.18 3 0.43 2.79 12.40 0.58 4 0.20 1,47 13.00 0.18 ; 5 0.08 2.54 13.50 1,22 6 0.27 2,53 18.50 1.~5 Exampi~ NQ 5 This exa~ple sums up the results of the regeneration o DZEHPA
~; and o the elimination of iron rom the effluent from regeneration, carried out continuously on the scale oE a pilot study, The stages of the process ar2 identified with Roman numerals and the main flows are identified in the Figure wi-th arabic numerals.
In these tests the prooess consists of the follow1ng s~ages:
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Rc~cneration o~ D2EI-IPA
Extraction witll LA-2 II
. Re-extr~ction with w~t~r III

An organic extract was available proceeding from a previous extraction stage. The or~anic extract had the followinc~ composition:
Iron 0 . 29 g/l Zinc 0 . 26 g/l ClH Acids < 0.5 g/l The regeneration reagent utilized was a solution of hydrochloric acid with a concentration of 4.9 M/l.

;~ A summary is given below of the flows and compositions of th;~
- ~- main flows of the process, which flows are detailed on the sheet of drawings attached to this memorandum.
- N" Flow . . . Flow Composition in g/l Identlflcatlon ,, . ~ f~ll l Figure m~ n ~e ~.n :~: 1 Organic feed (D2EHPA) 1119 0.29 0.26 0.5 ' 2 Or~anic extract1119 0.08 0.013 0.5 3 Regenerant solution 114 0.014 1.70 161.0 4 Regeneration effluent 114 2.00 3.40 161.0 .`. l 5 Re-extracted org~nic -~ . phase (LA-2) 224 0.0~0 1.20 .: 6 Charged organic phase 224 1.10 2.20 7 Rc-extraction water 46 ;~/; ' 8 Aqueous extract 46 5.50 4.20 4.00 . ~ , , .
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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a process for the removal of iron from an iron contaminated di-2-ethyl-hexyl phosphoric acid containing organic phase of a fluid-fluid extraction process, the steps of directly contacting said iron contaminated di-2-ethyl-hexyl phosphoric acid containing organic phase with a regeneration fluid comprising an acidic aqueous solution containing chloride ions to effect cationic exchange of ferric ions and yield a regenerated di-2-ethyl-hexyl phosphoric acid containing organic phase and an iron containing regeneration fluid phase, contacting the iron containing regeneration fluid phase with an anionic ion exchanger containing organic phase to extract the iron from the iron containing regeneration fluid phase, treating the anionic ion exchanger containing organic phase containing extracted iron with water and recovering iron in the form of a relatively concentrated aqueous solution of ferric chloride.

2. A process according to Claim 1, wherein said regeneration fluid is an aqueous solution of an inorganic mineral acid and a compatible soluble chloride.

3. A process according to Claim 2, wherein the inorganic mineral acid is selected from the group consisting of hydrochloric acid and sulfuric acid and wherein the compatible soluble chloride is selected from the group consisting of sodium chloride and calcium chloride.

4. A process according to Claims 1, 2 or 3, in which the chloride ion concentration of the regeneration fluid is in the range of from 3 to 9 molar.

5. A process according to Claims 1, 2 or 3, in which the chloride ion concentration of the regeneration fluid is in the range of from 4 to 6 molar.

6. A process according to Claims 1, 2 or 3, in which the acid concentration of the regeneration fluid is in the range of from 2 to 6 normal.

7. A process according to Claims 1, 2 or 3, in which the acid concentration of the regeneration fluid is in the range of from 4 to 6 normal.

8. A process according to Claim 1, in which the anionic ion exchanger containing organic phase is comprised of a solution of at least one member selected from the group consisting of primary amines, secondary amines, tertiary amines and long alkyl chain quaternary ammonium compounds in an aliphatic alcohol of from 8 to 14 carbon atoms and a hydrocarbon diluting agent.

9. A process according to Claim 8, in which the amine concentration in the anionic ion exchanger containing organic phase is in the range of 5 to 50%.

10. A process according to Claims 8 or 9, in which the aliphatic alcohol concentration in the anionic ion exchanger containing organic phase is in the range of from 0 to 25%.

11. A process according to Claims 1, 2 or 8, in which the water used to treat the anionic ion exchanger containing organic phase containing extracted iron is in a form selected from the group consisting of dilute aqueous saline solutions and dilute aqueous acidic solutions.