CA1095689A - Simultaneous extraction and recovery of uranium and vanadium from wet process acids - Google Patents
Simultaneous extraction and recovery of uranium and vanadium from wet process acidsInfo
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- CA1095689A CA1095689A CA281,522A CA281522A CA1095689A CA 1095689 A CA1095689 A CA 1095689A CA 281522 A CA281522 A CA 281522A CA 1095689 A CA1095689 A CA 1095689A
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- uranium
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for the simultaneous coextraction of uranium and vanadium from an aqueous acidic solution containing the same comprising contacting said aqueous acidic solution with an organic phase comprising a mixture of (a) an alkyl sub-stituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound, and (c) an organic diluent whereby the uranium and vanadium are coextracted into the organic phase and thereafter recovering the uranium and vanadium from the organic phase.
A process for the simultaneous coextraction of uranium and vanadium from an aqueous acidic solution containing the same comprising contacting said aqueous acidic solution with an organic phase comprising a mixture of (a) an alkyl sub-stituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound, and (c) an organic diluent whereby the uranium and vanadium are coextracted into the organic phase and thereafter recovering the uranium and vanadium from the organic phase.
Description
i6~
The present invention relates to a process for the simultaneous recovery of uranium and vanadium from an acidic solution.
Phosphoric acid generally is produced commercially by one of two methods. One method generally is called the "furnace"method, and the other generally is referred to as the "wet process" method. In the wet process method of producing phosphoric acid, phosphate rock is contacted with a mineral acid such as sulfuric acid. Most phosphate rock contal~ns~metal compounds in varying amounts. In many cases, these metal compounds are dissolved from the phosphate rock and appear in the wet process acid as contaminants. Vanadium and uranium compounds are among those dissolved from the phosphate rock, particularly when the rock is of the type comparable to that from the so-called western deposits of the States of Idaho, Wyoming, Utah and Montana in the United States.
Vanadium, however, is an undesirable component of wet process phosphoric acid in that it prevents the use of the phosphoric acid in making animal feed supplements, as the amount of vanadium must be kept at a low level in such animal feed supplements. Similarly, uranium is undesirable in such feed supplements.
On the other hand, vanadium and uranium are valuable materials and wet process phophoric acid can be an important source of these materials. Therefore, a process for the simultaneous recovery of vanadium and uranium from wet process ~k ,, phosphoric acid provides an important benefit, in that the vanadium and uranium are converted from undesirable contami-nants to valuable by-products.
There have been many attempts made in the past to recover vanadium from wet process acid. One such process involves addition of a soluble ferrocyanide compound to the acid to precipitate the vanadium. Other such processes in-volve extraction of the acid with an organic extractant for the vanadium. The organic extractant can be isopropyl ether, an alphahydroxy oxime or certain neutral organophosphorus compounds.
Further, there have been several processes developed for recovering uranium fro~ wet process acids derived from eastern United States phosphate deposits. Typical of such uranium recovery processes are those using, as an extractant, a mixture of a dialkyl phosphoric acid and a neutral organo-phosphorus compound.
Furthermore, there is a process for the simultaneous coextraction of uranium and vanadium from wet process phos-phoric aci~d ut~ in~ as~aune~tractant, a mixture of dialkyl phosphoric acld,t ~ lkylphosphine oxide and an organic diluent.
That process has resulted in the successful coextraction of up to approximately 82 percent of the vanadium and approximately 88 percent of the uranium present in the wet process acid.
It has now been discovered that an organic solvent comprising a mixture of (a) an alkyl substituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound and l O g 5 6 8 9 -(c) an organic diluent will effectively coextract up to approximately 99 percent of the uranium and approximately 83 percent of the vanadium present in wet process acids while utilizing extractant concentrations lower than heretofore possible. This improved extraction capability results in a significantly lower volume of solvent required to effect uranium and vanadium recovery from wetprocess acids. Thus, the new extractant composition provides a more economical process in that (1) smaller processing equipment is required;
The present invention relates to a process for the simultaneous recovery of uranium and vanadium from an acidic solution.
Phosphoric acid generally is produced commercially by one of two methods. One method generally is called the "furnace"method, and the other generally is referred to as the "wet process" method. In the wet process method of producing phosphoric acid, phosphate rock is contacted with a mineral acid such as sulfuric acid. Most phosphate rock contal~ns~metal compounds in varying amounts. In many cases, these metal compounds are dissolved from the phosphate rock and appear in the wet process acid as contaminants. Vanadium and uranium compounds are among those dissolved from the phosphate rock, particularly when the rock is of the type comparable to that from the so-called western deposits of the States of Idaho, Wyoming, Utah and Montana in the United States.
Vanadium, however, is an undesirable component of wet process phosphoric acid in that it prevents the use of the phosphoric acid in making animal feed supplements, as the amount of vanadium must be kept at a low level in such animal feed supplements. Similarly, uranium is undesirable in such feed supplements.
On the other hand, vanadium and uranium are valuable materials and wet process phophoric acid can be an important source of these materials. Therefore, a process for the simultaneous recovery of vanadium and uranium from wet process ~k ,, phosphoric acid provides an important benefit, in that the vanadium and uranium are converted from undesirable contami-nants to valuable by-products.
There have been many attempts made in the past to recover vanadium from wet process acid. One such process involves addition of a soluble ferrocyanide compound to the acid to precipitate the vanadium. Other such processes in-volve extraction of the acid with an organic extractant for the vanadium. The organic extractant can be isopropyl ether, an alphahydroxy oxime or certain neutral organophosphorus compounds.
Further, there have been several processes developed for recovering uranium fro~ wet process acids derived from eastern United States phosphate deposits. Typical of such uranium recovery processes are those using, as an extractant, a mixture of a dialkyl phosphoric acid and a neutral organo-phosphorus compound.
Furthermore, there is a process for the simultaneous coextraction of uranium and vanadium from wet process phos-phoric aci~d ut~ in~ as~aune~tractant, a mixture of dialkyl phosphoric acld,t ~ lkylphosphine oxide and an organic diluent.
That process has resulted in the successful coextraction of up to approximately 82 percent of the vanadium and approximately 88 percent of the uranium present in the wet process acid.
It has now been discovered that an organic solvent comprising a mixture of (a) an alkyl substituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound and l O g 5 6 8 9 -(c) an organic diluent will effectively coextract up to approximately 99 percent of the uranium and approximately 83 percent of the vanadium present in wet process acids while utilizing extractant concentrations lower than heretofore possible. This improved extraction capability results in a significantly lower volume of solvent required to effect uranium and vanadium recovery from wetprocess acids. Thus, the new extractant composition provides a more economical process in that (1) smaller processing equipment is required;
(2) smaller solvent inventories are required and (3) lower extractant concentrations can be used to e~`fect the recovery operations.
~roadly, the present invention provides a process for the simultaneous coextraction of uranium and vanadium from acidic solutions. In practicing the process, the aqueous acidic solution containing uranium and vanadium values first is treated with an oxidant to oxidize the uranium to the hexavalent oxidation state(VI) and the vanadium to the pentavalent oxidation state(V).
The oxidized aqueous acidic solution then is contacted with an organic solvent comprising a mixture of (a) an alkyl substituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound and (c) an organic diluent. The molar ratio of alkyl substituted diaryl phosphoric acid to trialkyl-phosphine oxide compound is within the range of from about 1:10 to about 1.5:1, with a preferred range of from about 1:8 to about 1:1 and an especially preferred range of from about 1:3 to about 4:5. It has been found that by utilizing such ratios, substantial quantities of uranium and vanadium are coextracted into the organic phase.
X
. . .
The loaded organic phase is separated from the aqueous phase. Thereafter, the uranium and vanadium are stripped from the l~aded organic phase with, for example, solutions of an aqueous base or reducing agents.
According to a preferred embodiment, the vanadium is preferentially stripped from the loaded organic phase utilizing a base such as, for example, sodium hydroxide, and controlling the addition of the stripping solution so that the equilibrium pH is about 5.5 Subsequently, the uranium can be stripped from the organic phase by an aqueous basic sol~ut1on such as sodium carbonate, for example.
Speciflcally the present invention provides a process for the ~imultaneous recovery of uranium(VI) and va~adium(V~ from an aqueous acidic solution containing the same which comprises:
contacting said sblution in the presence of at least about 0.25 mole fluoride per mole vanadium with an organic extractant phase comprising (a) a substantially water-immiscible organic diluent:
(b) an ~ substituted diaryl phosphoric acid having the formula ON
Rl--O--P=O
where R] and R2 represent aryl radicals at least one of which is substituted with an alkyl group and the total number of carbon atoms in the alkyl substituted diaryl phosphoric acid is at least 13 and !C) a trialkylphosphine oxide having the formula R
R ~ P=O
R"
where R, R' and R" are àlkyl radicals, whereby the uranium and vanadium are preferentially coextracted into the organic phase and, recovering the uranium and vanadium containing organic phase- the alkyl substituted diaryl phosphoric acid and trialkylphosphine oxide~being present in the organic extractant p~ase in an amount sufficient to provide a molar ratio of alkyl substituted diar~l phos-phoric acid- to trialkylphosphine oxide ~f from 1:8 to 1:1.
R, R' and R" each are organic saturated hydrocarbon radicals containing from 4 to 14 carbons. Mixtures of compounds having the general formula as defined above also may be used.
Exemplary alkyl radicals of the above formula are .
the butyl, amyl, hexyl and octyl radicals.
In addition to the tertiary phosphine oxides, it is to be understood that within the scope of the claime~
invention the corresponding oxonium salts are also contem-plat-d- As examFles of such o~onium salts ~y bé~
.
l~9S68~
mentioned tri-n-octylphosphinoxonium bisulfate, tri-n-octylphosphinoxonium phosphate and tri-n-butylphosphinoxo-nium nitrate. These salts are typically prepared by con-tacting an organic solution of a phosphine oxide with an aqueous solution of the appropriate acid.
According to a preferred embodiment of the present invention,the trialkylphosphine oxide compounds are those wherein R, R' and R" are a~l radicals of from 6 to 12 carbon atoms.
An especially preferred trialkylphosphine oxide compuond according to the present invention is tri-n-octylphosphine oxide.
Examples of applicable alkylaryl groups include 2-ethylhexylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, -~
n-octylphenyl, nonylphenyl, dodecylphenyl and the like.
A preferred group ~f alkyl substituted diaryl phosphoric acids are those containing from about 16 to 36 carbon atoms. EKamples of such acids include butylphenyl-phenyl phosphoric acid, butylphenyl-octylphenyl phosphoric acid, didodecylphenyl phosphoric acid and dioctylphenyl phosphoric acid. An especially preferred acid is dioctylphenyl phosphoric acid.
In accordance with the present process, the trialkyl-phosphine oxide compound and the alkyl substituted diaryl phosphoric acid are dissolved in a water-immiscible organ-ic diluent prior to contacting the same with the aqueous acidic solution containing the uranium and vanadium.
., . ~ , .
The term Iwater-immiscible organic diluent" as used here-in refers to an organic material normally liquid at am-bient temperatures which may be substantially, but not necessarily entirely, insoluble in water. The preferred organic diluents for the process of the present invention are hydrocarbons. Examples of suitable hydrocarbon sol-vents include isooctane, kerosene, and the li~e. Solvents which contain functional groups can also be employed pro-viding that the functional groups do not adversely affect the extraction. Particularly good results are obtainable when the organic diluent is a substantially nonreducing diluent with respect to oxidation by the vanadium(V) present.
The amount of organic extractant phase to be used for most efficient extraction is from about O.I5~to ~'bout ~O;~imes the volume of acid solution to be treated. Parti-cularly good results have been obtained with an organic to aqueous ratio of from about 0.5:1.to about 1.5:1. The ratio of organic phase to aqueous acid phase to be used is dependent upon the concentration of extractants in the organic phase, the temperature at which the extraction is performed, the contact time~ between the two phases and the amount o~ vanadium(~) in the acid solution. The concentra-tion of trial~ylphosphine oxide in the organic phase may range from about 0.05 molar to about 0.5 molar. An espec-ially preferred range is from about 0.1 to about 0.3 molar.
The amount of alkyl substituted diaryl phosphoric acid lo9S689 present in the organic phase may be determined based on the desired ~atio of trialkylphosphine oxide compound to alkyl substituted diaryl phosphor~c acid. The molar ratio of alkyl substituted diaryl phosphoric acid to trialkylphosphine oxide may vary from about 1:10 to about 1.5:1. the especially preferred range being from about 1;3 to about 4:5.
The proces.s of the present ~nvention is applicable to any aqueous acidic solution containing uranium and vanadium. The instant process is particularly applica- -ble to wet process -9=
:
,,~, 1~)95689 phosphoric acid obtained from the western phosphate deposits which contain significant quantities of both uranium and vanadium.
It has been found in the practice of this invention that fluoride must be present in the aqueous acidic solution in order for the complexing agents of the present invention to properly complex the vanadium(V3. Although the exact theory of the complex is not known, it is believed that the fluoride is complexed with vanadium(V) and the complexing agent. The amount of fluoride present in the mixture preferably is at least about 0.25 moles per mole of vanadium present, although a large excess of fluoride does not harm the extraction. ~luoride is a natural component of wet process phosphoric acid and thexefore wet process phosphoric acid is particularly suited to the extraction process of the present invention.
- Prior to contacting the aqueous acidic solution with the organic extractant mixture, the aqueous solution is treated, if necessary, with an oxidizing agent to make certain that the vanadium contained therein is in the pentavalent oxidation state(V) and the uranium is in the hexavalent oxidation state~VI). When the vanadium and uranium are not present as vanadium(V) and uranium~VI), the extraction process with the solvent extractants of the ` present invention is not satisfactory as vanadium and uranium in the lower oxidation states do not form a complex with the extractants contemplated in the scope of the invention.
~)95t~89 The aqueous acidic solution may be oxidized by any known method such as, for example, with sodium chlorate, manganese dio~ide, ozone, and the like. The oxidizer should be added in an amount sufficient to provide at least the stoichiometric requirements for oxidation o, all the vanadium to vanadium~V) and uranium to uranium(VI). ~en there are other oxidizable species present in the aqueous acidic solution, such as are found in wet process acid, for example, it is desirable to provide an excess of the stoichiometric requirements of the oxidizer. This being necessary, of course, to insure that substantially all the uranium and vanadium values present are oxidized.
The process of the present invention may be practiced within a temperature range of from about 20C to about 80~C
with a temperature of about 35C to about 55C being preferred.
^ It has been found that the contact time between the organic phase and the acid phase is an important variable to consider when extracting vanadium from acidic solutions.
~onger contact times result in increased vanadium extraction.
In practice, contact times of from about 1 minute to about 60 minutes are satisfactory with about 5 minutes to about 30 minutes per contact being especially preferred at temperatures of from about 40C to about 50C. The extraction may be performed on a batch basis or a continuous basis, such as in a continuous countexcurrent multi-stage extraction system.
In the process of the present invention, the organic phase is contacted with an aqueous acidic solution containing .109S6~9 ranium and vanadium, at least a major portion of the vanadium and ura~ lues being in the pentavalent and hexavalent oxidation states respectively, whereby the uranium and vanadium are simultaneously coextracted in the organic phase. The loaded organic phase may be stripped by conven-tional methods; for example, the loaded organic phase may be contacted with an aqueous solution of sodium carbonate, ammonium carbonate or similar base at a pH above about 8.~ -to simultaneously strip both the vanadium and uranium values contained therein.
According to a preferred embodiment of the invention, the vanadium can be stripped from the organic extract phase, free from the uranium. In this embodiment the loaded organic phase is contacted with an aqueous sodium hydroxide, sodium carbonate or other suitable basic stripping solution under-carefully controlled conditions so that the equilibrium pH
of the resulting mixture does not exceed about 6. However, the equilibrium pH may rise to about 8.4 without causing an adverse effect. It has been discovered that by such control of the equilibrium pH that vanadium is pre~erentially stripped from the loaded organic phase. Particularly good results have been obtained when the addition of a stripping solution is controiled such that the equilibrium pH is from about 5.5 to about 6Ø Under such conditions, substantially all the vana~ium is stripped from the loaded organic phase with less than about 1 part per million of U308 being removed.
Thus, stripping with an aqueou~ sodium hydroxide or similar , ' - ~a -.... ,_ . . . . . . . .
1~95689 solution at a controlled pH results in the preferential removal of only the ~anadium values. The remaining uranium loaded organic can be processed by ~nown me~hods for the subsequent removal of the uranium values. For example, the uranium loaded organic phase can be stripp~d with an aqueous solution of sodium carbonate, ammonium carbonate or similar base at a pH above about 8.4.
Suitable aqueous base strip solutions may contain any one of a number of alkali metal hydroxides, carbonates or mixtures thereof. Ammonium hydroxide can be used but is not as desirable for stripping vanadium as the alkali metal hydroxides or carbonates as it will also cause the formation of solid precipitates during the stripping process.
Stripping may be accomplished in a batch or continuous operation. A preferred method utilizes a multi-stage countercurrent stripping process.
The foregoing description and the following specific examples are for the purpose of illustration and are not to be considered as limiting the scope of the invention, reference being had to the appended claims for this purpose~
EXAMPLE I
This example demonstrates, in a one stage extraction, the effect of varying the molarity of the trialkylphosphine oxide compound and alkyl substituted diaryl phosphoric acid in the organic phase as well as the effect of ~arying the~
ratio of trialkylphosphine oxide compound to alkyl substituted diaryl phosphoric acid.
~395ti~3g In a single stage extraction, a separatory funnel mounted in a wrist shaker is utilized. The aqueous acidic solution is an oxidized wet process phorphoric acid (WPA) obtained from a western phosphate deposit and containing 1.53 ~rams per liter vanadium as V2O5 and 0.148 grams per liter uranium as U3O8. The organic extractant phase is a kerosene diluent containing various quantities of tri-n-octylphosphine oxide (TOPO) and dioctylphenyl phosphoric acid (DOPPA) as set forth in Table I below. The separatory funnel contains a portion of the organic extractant solution and is contacted with the oxidized wet process phosphoric acid~ The organic to aqueous ratio is maintained at 1 and the extractions are conducted at 50C with a 20 minute mix time. After the extraction, the aqueous phase is analyzed to determine the percent vanadium and uranium remaining therein. The results are set forth in Table I below.
Further, Table I also shows the percent of V2O5 and V3O8 extracted.
.
TABLE I
SIMULTANEOUS EXTRACTION OF VANADIUl AND
URANIUM FROM OXIDIZED WPA BY VARIOUS
MOLE RA~IOS OF DOPPA AND TOPOi ~
Solvent CompositionAnalysis, g/l ~ Per Cent Molarity A~ueous PhaseExtracted : TOPO DOPPA ,V205U30aV205 U30a 0.2 0.1 0.71 0.05846.~60.8 0.2 0.15 1.07 0.04830.167.6 0.2 0.2 1.42 0.0457.269.6 0.2 0.3 1.42 0.0367.275.7 0.3 0.15 0.59 0.03961.473.6 0.25 0.125 0.620.05259.5 64.g 0.20 0.0 0.31 -0.1~279.74.1 0.0 - 0.2 1.~4 0.1365.9 8.1 ~ -.
`~ ~
.
' :,` ~ `
-- ~ _ 56~39 From the results set forth in Table I, it will ~e seen that the optimum simultaneous coextraction of uranium and vanadium occurs when the molar ratio of alkyl substituted diaryl phosphoric acid to trialkylphosphin~ oxide is about 0.5. The exact concentration utilized depends on the con-centration of vanadium in the solution to be processed and on the relative economic value of~ the two metals compared with the total costs of the recovery process.
EXAMPLE II
This example more fully demonstrates the simultaneous coextraction capability of this invention.
In a four-stage extraction process, four separatory funnels mounted in wrist shakers are utilized. The aqueous acidic solution is WPA obtained from a western phosphate i deposit containing 1.53 grams per liter vanadium as V2O5 and 0.148 grams per liter uranium as U3O8. The organic extractant phase is a kerosene diluent containing 0.25M tri-n-octyl-phosphine oxide (ToPOj and 0.125M dioctylphenyl phosphoric acid (DOPPA). Each of the four separatory funnels contains a portion of the organic extractant solution and is contacted serially with the WPA. The organic to aqueous ratio is maintained at 1 and the extractions are conducted at 50C
with a 20 minute mix time per stage. Af ter each extraction stage, the aqueous phase is analyzed to determine the percent vanadium and uranium remaining therein. The results are set forth in Table II below.
.
~ 5689 TABLE II
.
SERIAL SIMULTANEOUS EXTRACTIONS OF
VANADIUM AND URANIUM FROM OXIDIZED ~PA BY
'''' O.125M DOPPA AND 0.25M TOPO SO~VENT - .
- .
Extraction Stage' Analysis, g/l Cumulative Percent '' ' # ''' ~ ~ ~queou's Phase ' EXtract'ed ' V20~' UaOa V20~i U30~
' 1 ' 0'.57 '0.050 , 62.7 66.2 .
2 , 0.38 0.01575.2 '89.9 . 3 . 0.28 0.00581.7 96.6 " ' 4 0.26 0.00183.0 99.3 ': , .: , .
.
, , ' ~ , 1'7 , . . , .
" 1~;)~35689 EXAMPLE III
This example illustrates the preferential separation of vanadium from a vanadium-uranium loaded extractant organic phase.
A sample of organic extract phase loaded with vanadium and uranium is prepared containing 0.25M tri-n-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid ~DOPPA) in kerosene loaded with 2.61 grams per liter V2O5 and 0.175 grams per liter U3O8.
The sample is scrubbed with water in a two-stage process. It has been found that an initial water scrub removes some of the impurities tha~ are coextracted from WPA, such as phosphoric acid and hydrofluoric acid. The removal of such impurities reduces the amount of sodium carbonate or other base required to strip the uranium and vanadiwm from the loaded extractant. The sample of loaded organic is serially contacted with an equal amount of water placed in separatory funnels mounted on a wrist action ~; shaker and agitated for 5 minutes at a temperature of 50C.
: . .
;~ Following the water scrub, a sample of the aqueous phase of each stage i8 obtained and analyzed. The analyses are set forth in Table III below.
: : : . . . .
.
, ~ , ' , -; ~ ~ ' s ' , ' ' --~ ~og5689 TABLE III
WATER SCRUBBING OF VANADIUM
AND URANIUM LOADED
0.125M DOPPA and 0.25 TOPO SOLVENT
Scrub Stage Analysis of Scrub Analysis o~ Scrubbed Water, g/l__ _ Or~anic Phase, g/l VzOs U~O~ ~'. V20, U30~
1 ' 0.17 . ~0.001 2 0.07 ~.001 2.32 0.175 , .
, ~ ' . ' - .
.
~ ~ , ' ~ - ' . ' Iq ' ~.
lOg5689 The results set for~h in Table III clearly show that ~;ubstantially no uranium and little vanadium is removed by water scrubbing.
The water scrubbed organic extract phase preferen-tially is stripped of its vanadium content u~ilizing the following procedure. In the first stage, the water scrubbed loaded oxganic extract phase is placed in a beaker equipped with a stirrer. A sufficient volume of an aqueous sodium carbonate strip solution is slowly added to the beaker to provide an equilibrium pH of about 6Ø The contents of the bea~er then are stirred for 5 minutes at 50C, following which the aqueous strip solution containing the vanadium is removed from the beaker. That solution and the remaining organic extract phase both are analyzed. The results are set forth in Table IV below. In the second stage of strip-ping, the remaining organic extract phase is contacted with a further solution of sodium carbonàte in an amount sufficient to proYide an equilibrium pH of 8.4. The mixture is stirred for 5 minutes at 50C, following which the aqueous strip solution containing residual vanadium is recovered. That -solution and the then remaining organic phase are analyzed.
The resu1ts are set forth iA ~ahle IV below.
'' `' - . ' .
.
, ' , - ~
, ' TABL~ IV
SELECTIVE STRIPPING OF VANADIUM
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA AND 0`.25M TOPO SOL~'ENT
, Analysis of Va~adium- I
. Containing StripAnalysis of Stripped Stage No. -Solution, ~/l Organic Phase, g/l ~ ~ .
.
' ~ Og ' U308 ~_ ' ~20!1 U308 0 -- -- -- 2.32 0.17~
1 2.14 <0.001 6.0 0.17 0.182 2 0.06 <0.001 8.4 ~0.05 0.18 .
.
: ~ : , ` ' : :: "
'~ ; ~ ' . , , ': . ' ' ' ' ' '~ J
_, ~ _ ... , _., .. . , - , . , .... , E~.~3 i~)95689 The results as set forth in Table IV clearly demon-strate that the vanadium is recovered substantially free of uranium. Less than 0.001 grams per liter lranium are found with the vanadium. The uranium subsequently is recovered from the vanadium strippea extractant by contacting it with a sufficient amount of an aqueous base solution to ma;ntain the equilibrium pH above about 8.4.
Alternatively, both the uranium and vanadium may be stripped by a reducing agent in acid solution, or the uranium alone may be stripped by a reducing agent in acid solution or by high concentration of phosphoric or hydrofluoric acid.
For example, the vanadium stripped organic extract phase is stripped of its uranium utilizing the following procedure.
The uranium loaded organic is contacted with an equal amount of alternate stripping agent aqueous solution placed in separatory funnels mounted on a wrist-action shaker and agitated for S minutes at a temperature of 50C. The organic and aqueous phases are separated and the organic phase is analyzed. The results of these tests are set forth in Table V below.
~ '. ' ' .
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TABLE V
SINGLE S~AOE S~RIPPING OF URANIUM FROM
VANADIUM STRIPPED-URANIUM LOADED
0.125M DOPPA AND 0.25M TOPO SOLVEN'r -Stripping Agent Analysis of Stripped (In H20) Organic Phase, ~5/1 : ' _ NONE 0.184 85% H P04 0 . 009 *12M H3Po4 0.028 20% H~ 0 . ollo *Containing 2 g/l iron(II) ~ .
~:
~ 23 -: : , , , -1~)95ti89 ~
SUPPLE~ENTARY DISCLOSURE
It is stated in the principal disclosure that stripping with an aqueous sodium hydroxide or similar solution at a control-led pH results in the preferential removal of only the vanadium values and that the remaining uranium loaded organic phase can be processed for the subsequent removal of the uranium values.
Alternatively, the uranium loaded organic phase can be stripped with an aqueous acidic solution of phosphoric acid or hydrofluoric acid. A preferred form of aqueous acidic stripping is obtained through addition of a reducing agent to the acidic solution which is capable of reducing uranium to the tetravalent state.
In alternate embodiments, both the vanadium and uran- ~;
ium can be stripped from the organic extract phase by means of a reducing agent. Selection of an appropriate reducing agent and process conditions provide a means by which the vanadium and uraniu= can be simultaneously stripped from the loaded organic phase into the same aqueous medium or sequentially into the same or different aqueous media.
In one alternate embodiment, vanadium and uranium are simultaneously stripped from the loaded organic phase with a phos-phoric acid solution containing a reducing agent, such a8 ferrous iron, in such an amount so as to reduce the vanadium to a mixture ~; of trivalent and tetravalent states while reducing the uranium to the tetravalent state.
In another alternate embodiment, the amount of reducing agent is controlled such that only vanadium is reduced and strip-ped from the loaded organic phase and the uranium remains primar-ily in the hexavalent state. To produce high concentrations of vanadium in the stripping solution by this technique, it is de-sirable to wash the stripped organic phase in a counter-current fashion with the stripping medium makeup solution prior to ad-,^,, 1 \ ~ss~s~
dition of the reducing agent to the solution.
In yet another alternate embodiment, vanadium can be selectively stripped from the loaded organic phase through use of a reducing agent in an aqueous stripping solution which is not capable of complexing tetravalent uranium. Such non-complexing aqueous stripping solutions include sulfuric acid.
When using ferrous iron as the reducing agent in the sulfuric acid stripping solution, the reduction and stripping of van-adium is essentially complete while virtually no uranium is stripped from the loaded organic phase. The uranium then can be stripped by any of the previously described methods.
An additional means of selectively stripping van-adium from the loaded organic phase is with strong nitric acid solutions, which may also contain additional nitrate salts. While it is not fully understood, it is believed the selective stripping results from the high affinity of the alkylphosphine oxide component of the organic phase for nitric acid.
Stripping by the above procedures may be accomplished in a batch or continuous operation. A preferred method util-izes a multi-stage countercurrent stripping process.
In addition, the process of the present invention has been found to remove certain other impurities from wet process phosphoric acid. These include yttrium, iron, zinc, bromine and possibly trace amounts of other metallic compon-ents. This purification is seen as a valuable side effect of the present process and provides the additional benefit of allowing the recovery of other by-products of economic worth such as yttrium, The following additional Examples are for the pur-pose of illustrating the inventlon.
- 25 _ ~95689 EXAMPLE IV
This example illustrates the preferential separation of vanadium from a vanadium-uranium loaded extractant organic phase using an aqueous acidic stripping solution containing a reducing agent.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illustrated in Example III. The water scrubbed organic extract phase contains 0.25M tri~n-octylphosphine oxide (TOPO) and 0.125M
dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 1.0 grams per liter V2O~ and 0.081 grams per liter The water scrubbed organic extract phase preferentially is stripped of its vanadium content utilizing the follo~ing procedure. The sample is contacted with an equal volume of a sulfuric acid solution containing ferrous iron placed in a separatory funnel mounted on a wrist-action shaker ~ and a~itated for 5 minutes at a temperature of 50C. Follow-: ing the agi.tation, the organic and aqueous phases are : separated and the aqueous phase is analysed. The results ~ of this test are set forth in Table VI belQw~
~ ~ .
A -;26 _ ~ogs~9 TABLE VI
SELECTIVE STRIPPING OF VANADIUM FROM
VANADIUM AND URlhNIUM LOADED
0 125M DOPPA - 0.25M TOPO SOLVENT
Analysis of Vanadium Analysis o .and Uranium Loaded Resultant Strip Stripping_Agent Organic Phase, g/l Solution, g/l ~725 U308 V205 U30B
5 vol. % H2SO4* 1.0 0.081 0.76 0.0019 ; *containing 9 g/l iron II
; ~ , .
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~ .
~ ' ` - 27 ~
.
~0~5689 The results as set forth in Table VII clearly demon-strate that the vanadium is recovered substantially free o~ uranium. Less than 0.002 grams per liter uranium are found with the vanadium.
EXAMPLE V
This example illustrates the preferential separation of vanadium from a vanadium uranium loaded extractant organic phase using aqueous nitric acid solutions.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illu-strated in Example III. The water scru~bed organic extract phase contains 0.25M tri-n-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 1.0 grams per liter V205 and 0.~81 grams per liter U308.
The water scrubbed organic extract phase preferentially is stripped o~ its vanadium content utilizing the following procedure. Samples are contacted with an equal volume of a nitric acid solution placed in separatory ~unnels mounted on a wrist-action shaker and agitated ~or 5 minutes at a temperature of 50C. Following the agitation, the organic and aqueous phases are separated and the aqueous phase is anal~zed. The re9ults of these tests are set forth in able VII below.
.
, ~ ~ - 28 _ lOgS689 TABLE VI I
SELECTIVE STRIPPING OF VANADIUM FROM
VANADIUM AND URANIUM LOADED
0 .12 5M DOPPA_-- 0 . 2 5M TOPO _SOLVENT
Analysis of Vanadium Analysis of and Uranium Loaded Resultant Strip Stripping Agent Org~anic Phase, g/l Solution, g/l_ V2O, U3O8 V205 U30tl 0.5M HNO3 1.0 0.081 0.24 <0.0005 0 . 5~1 HNO 3 +
3M NH4NO3 1.0 0.081 0.37 <0.0005 1. OM FINO3 1. 0 0 . 081 0 . 40 <0 . 0005 I :
,: :
- ~ , ' :
-_ 29 _ c ., ~
1~95689 The results set forth in Table VII clearly demonstratethat the vanadium is recovered substantially free of uranium.
Further, the data show that nitric acid solutions supple-mented with additional nitrate salts and stronger nitric acid solutions improve vanadium stripping.
EX~PLE VI
This example illustrates simultaneous aqueous acidic solution stripping of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illu-strated in Example III. The water scrubbed organic extract phase contains 0.25M tr~-n-octylphosphine oxide (TOPO) and 0.25M dioctylphenyl phosphoric acid (DOPPA) in ~erosene loaded with 1.0 grams per liter V2Og and ~.081 grams per liter U30~.
The water scrubbed organic extract phase simultaneously is stripped of its vanadium and uranium by utilizing the following procedure. Samples are contacted with equal volumes o~ aqueous acidic solutions placed in separatory funnels mounted on a wrist-action sha~er and agitated for 5 minutes at a temperature of 50C. Following the agitation, the organic and a~ueous phases are separatea and the aqueous phase is analyzed. The results of these tests are set forth in Table VTI below.
~ . .
' - 30 -A
~95689 TABLE VIII
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA - 0.25~1 TOPO SOLVENT
Analysis of Vanadium Analysis of ` and Ura~iurn Loaded Resultant Strip Stripping Agent Organic Phase, ~ Solution, g/l V205 U308 ~25 U30EI
~50~ H3PO4 1.0 0.081 0.49 0.091*
~ ~ 70% H3PO4 1.0 0.081 0.49 0.078 - ~ ~ 85~ H3PO4 1.0 0.081 0.49 0.062 24% HF 1.0 0.081 0.94 0.087*
: : *value is within the experimental accuracy of the fluorometric analysis empioyed : :~ : :
.
' - 31,-A
1095~9 The results as set forth in Ta~le VIII clearly demon-strate the ability to simultaneously recover substantial amounts of vanadium and uranium from a loaaed organic extract phase.
EX~ ~LE VII
This example illustrates simultaneous aqueous acidic solution stripping of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
~ sample of organic extract phase loaded with vanadium and uranium is prepared containing 0.25M tri-_-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid ~DOPPA) in kerosene loaded with 3.60 grams per liter V205 and 0.0~3 grams per liter U 30 8 ~
The loaded organic phase is stripped by contacting with an equal volume of an aqueous acidic solution placed in a separatory funnel mounted on a wrist-action shaker and agitated for 5 minutes at a temperature of 50C. Following the agitation, the organic and aqueous phases are separated and the aqueous phase is analyzed. The results of these tests are set f o eh in ~able IX below.
.
.
~' , 1C~95689 TABLE IX
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FRO~I VANADIUM AND URANIUM LOADED
0.125~1 DOPPA - 0.25M TOPO SOLVENT _ ; Analysis of Vanadium Analysis o and Uranium Loaded Resultant Strip Stripping Agent Organlc Phase, g/l Solution, g/l V2O j U3OB V20~ U3OB
8~% H3PO4; 3 . 60 0 . 073 0 . 82 0 . 076*
24% HF 3.60 0.073 3.51 0.066 *value is withi..n the experimental accuracy o~ the fluorometric analysis e~ployed .
~ .
,. j :
- 33. -:
Al . :
109568~
The results set forth in Table IX demonstrate an abilityto simultaneously strip vanadium and uranium from the loaded organic phase.
EXAMP~E VIII
This example illustrates the simultaneous aqueous acidic solution stripping of vanadium and uranium ~rom a vanadium-uranium loaded extractant organic phase.
A sample of organic extractant phase loaded with vanadium and uranium is prepared and scrubbed with water as illustrated in Example III. The water scrubbed organic extract phase contains 0.25M tri-n-octylphosphine oxide (TOPO~ and 0.125M
dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 0.49 grams per liter V2O5 and 0.090 grams pe~ liter U30a-The water scrubbed organic extract phase simultaneously is stripped of its vanadium and uranium by utilizing the following procedure. Samples are contacted with equal volumes of aqueous acidic solutions containing a reducing agent placed in separatory funnels moun~ed on a wrist-action shaker and agitated for 5 minu-tes at a temperature of 50C.
Following the agitation, the organic and aqueous phases are separated and the aqueous phase is analyzed. The results of these tests are set rorth in Table X, below-.
.
. - 34 -~' lOgS689 TABLE X
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA ~ 0.25M TOPO SOLVENT
.
Analysis of Vanadium Analysis of and Uranium Containing Resultant Strip Stripping Agent* Organic Phase, g/l Solution, g~l V2Og U3Oa V2O5 U3O8 50~ H3PO4 0.49 0.090 0.49 0.064 70% H3PO4 0.49 0.090 0.54** 0.093**
85% H3PO4 0.49 0 090 0 54** 0 094**
*containing 2 g/l iron II
**value is within the experimental accuracy of the fluorometric analysis employed . ~
~ ' .
:: :
.
;
' .
_ 35 -~ .l5'J
The results set forth in .able X demonstrate the ability to simultaneously strip substantial amounts of vanadium and uranium from the loaded organic phase.
EXAMPLE IX
This example illustrates individual preferential stripping and separation of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
~ n organic phase containing 0.~M tri-n-octylphosphine oxide (TOPO) and 0.2M dioctylphenyl phosphoric acid (DOPPA) in kerosene continuously is loaded with vanadium and uranium in a small multistaged extraction module. The loaded organic extract phase then enters a multistage stripping module.
Vanadium stripping and separation is accomplished in the first stage of the stripping module using a controlled volume of phosphoric acid solution that contains sufficient reducing agent to provide the stoichiometric quantity required to reduce the vanadium (V) content of the organic phase to the quadravalent state. This permits the preferential separation of vanadium and allows only a small quantity of the uranium to be stripped. The aqueous phase resulting from the stripping is quite rich in vanadium~ The vanadium stripped organic phase then proceeds into a two stage phosphoric acid scrubber. The scrubbing is utilized to limit the advancement of vanadiu~ containing solution into the do~n-stream uranium stripping section. Iron is dissolved in the resultant vanadium scrub aqueous phase to provide the aqueous stripping solution employed in the first stage vanadium stripping sec-tion. In this manner, any vanadium A
lO9S689 scrubbed from the organic phase is returned to the vanadium stripping section to facilitate recovery.
The vanadium stripped and scrubbed organic phase then proceeds into the uranium stripping section comprising the fourth stage in the stripping module. In the fourth stage, the vanadium stripped and scrubbed organic phase contacts a controlled volume of phosphoric acid which contains a reducing ~gent in sufficient quantity to reduce any residual vanadium (V) and the uranium ~VI) content to the lower vanadium (irV) and uranium (IV) states. It has been shown in the practice of this invention that the presence of the reducing agent in quantities in excess of the stoichiometric requirement is beneficial to uranium stripping. The uranium and vanadium stripped organic phase then enters a two stage phosphoric acid scrubber. Th scrubbing is utilized to prevent the advancement of high grade uranium strip solution to the organic phase recycle storage tank. The scrubber aqueous phase was separated and split into two portions.
Iron was dissolved in one portion of the resultant aqueous phase to provide the aqueous stripping solution employed in the fourth stage uranium stripping section. The remaining portion of the scrubber aqueous was recycled as aqueous feed to the two-stage vanadium scrubbers. In this manner, any vanadium or uranium that was scrubbed from the organic phase was caused to finally separate with the vanadium or uranium stripping products.
~ he preferential vanadium and uranium stripping of the loaded oxganic phase described hereinabove, produced a .
~LOS~S~89 vanadium strip product solution containing in excess of 97 percent of the recoverable vanadium and a uranium strip product solution containing more than 93 percent o~ the recoverable uranium.
In the particular test described above, a 70 percent phosphoric acid solution was employed in all of the stages in the stripping module. Satisfactory phosphoric acid concentrations for this process are from about 20 percent to about 95 percent H3PO4. However, the phase ratios an~
number of stages required to effect stripping may change with varying concentrations. In addition, differen-t acid concentrations may be used in different stages of the stripping module.
While this particular test employs iron as the reducing agent in the aqueous acidic solution, any reducing agent which is compatible with phosphoric acid and that is capable of reducing vanadium (V) and uranium (VI) to lower valence jl~ states can be used in this process.
While the present invention has been described with respect to pre~erred embodiments thereof, it will be under-stood, of course, that certain changes may be made therein without departing from its true scope as defined in the appended claims.
_ .
~ ~ - 38 _ . .
'
~roadly, the present invention provides a process for the simultaneous coextraction of uranium and vanadium from acidic solutions. In practicing the process, the aqueous acidic solution containing uranium and vanadium values first is treated with an oxidant to oxidize the uranium to the hexavalent oxidation state(VI) and the vanadium to the pentavalent oxidation state(V).
The oxidized aqueous acidic solution then is contacted with an organic solvent comprising a mixture of (a) an alkyl substituted diaryl phosphoric acid, (b) a trialkylphosphine oxide compound and (c) an organic diluent. The molar ratio of alkyl substituted diaryl phosphoric acid to trialkyl-phosphine oxide compound is within the range of from about 1:10 to about 1.5:1, with a preferred range of from about 1:8 to about 1:1 and an especially preferred range of from about 1:3 to about 4:5. It has been found that by utilizing such ratios, substantial quantities of uranium and vanadium are coextracted into the organic phase.
X
. . .
The loaded organic phase is separated from the aqueous phase. Thereafter, the uranium and vanadium are stripped from the l~aded organic phase with, for example, solutions of an aqueous base or reducing agents.
According to a preferred embodiment, the vanadium is preferentially stripped from the loaded organic phase utilizing a base such as, for example, sodium hydroxide, and controlling the addition of the stripping solution so that the equilibrium pH is about 5.5 Subsequently, the uranium can be stripped from the organic phase by an aqueous basic sol~ut1on such as sodium carbonate, for example.
Speciflcally the present invention provides a process for the ~imultaneous recovery of uranium(VI) and va~adium(V~ from an aqueous acidic solution containing the same which comprises:
contacting said sblution in the presence of at least about 0.25 mole fluoride per mole vanadium with an organic extractant phase comprising (a) a substantially water-immiscible organic diluent:
(b) an ~ substituted diaryl phosphoric acid having the formula ON
Rl--O--P=O
where R] and R2 represent aryl radicals at least one of which is substituted with an alkyl group and the total number of carbon atoms in the alkyl substituted diaryl phosphoric acid is at least 13 and !C) a trialkylphosphine oxide having the formula R
R ~ P=O
R"
where R, R' and R" are àlkyl radicals, whereby the uranium and vanadium are preferentially coextracted into the organic phase and, recovering the uranium and vanadium containing organic phase- the alkyl substituted diaryl phosphoric acid and trialkylphosphine oxide~being present in the organic extractant p~ase in an amount sufficient to provide a molar ratio of alkyl substituted diar~l phos-phoric acid- to trialkylphosphine oxide ~f from 1:8 to 1:1.
R, R' and R" each are organic saturated hydrocarbon radicals containing from 4 to 14 carbons. Mixtures of compounds having the general formula as defined above also may be used.
Exemplary alkyl radicals of the above formula are .
the butyl, amyl, hexyl and octyl radicals.
In addition to the tertiary phosphine oxides, it is to be understood that within the scope of the claime~
invention the corresponding oxonium salts are also contem-plat-d- As examFles of such o~onium salts ~y bé~
.
l~9S68~
mentioned tri-n-octylphosphinoxonium bisulfate, tri-n-octylphosphinoxonium phosphate and tri-n-butylphosphinoxo-nium nitrate. These salts are typically prepared by con-tacting an organic solution of a phosphine oxide with an aqueous solution of the appropriate acid.
According to a preferred embodiment of the present invention,the trialkylphosphine oxide compounds are those wherein R, R' and R" are a~l radicals of from 6 to 12 carbon atoms.
An especially preferred trialkylphosphine oxide compuond according to the present invention is tri-n-octylphosphine oxide.
Examples of applicable alkylaryl groups include 2-ethylhexylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, -~
n-octylphenyl, nonylphenyl, dodecylphenyl and the like.
A preferred group ~f alkyl substituted diaryl phosphoric acids are those containing from about 16 to 36 carbon atoms. EKamples of such acids include butylphenyl-phenyl phosphoric acid, butylphenyl-octylphenyl phosphoric acid, didodecylphenyl phosphoric acid and dioctylphenyl phosphoric acid. An especially preferred acid is dioctylphenyl phosphoric acid.
In accordance with the present process, the trialkyl-phosphine oxide compound and the alkyl substituted diaryl phosphoric acid are dissolved in a water-immiscible organ-ic diluent prior to contacting the same with the aqueous acidic solution containing the uranium and vanadium.
., . ~ , .
The term Iwater-immiscible organic diluent" as used here-in refers to an organic material normally liquid at am-bient temperatures which may be substantially, but not necessarily entirely, insoluble in water. The preferred organic diluents for the process of the present invention are hydrocarbons. Examples of suitable hydrocarbon sol-vents include isooctane, kerosene, and the li~e. Solvents which contain functional groups can also be employed pro-viding that the functional groups do not adversely affect the extraction. Particularly good results are obtainable when the organic diluent is a substantially nonreducing diluent with respect to oxidation by the vanadium(V) present.
The amount of organic extractant phase to be used for most efficient extraction is from about O.I5~to ~'bout ~O;~imes the volume of acid solution to be treated. Parti-cularly good results have been obtained with an organic to aqueous ratio of from about 0.5:1.to about 1.5:1. The ratio of organic phase to aqueous acid phase to be used is dependent upon the concentration of extractants in the organic phase, the temperature at which the extraction is performed, the contact time~ between the two phases and the amount o~ vanadium(~) in the acid solution. The concentra-tion of trial~ylphosphine oxide in the organic phase may range from about 0.05 molar to about 0.5 molar. An espec-ially preferred range is from about 0.1 to about 0.3 molar.
The amount of alkyl substituted diaryl phosphoric acid lo9S689 present in the organic phase may be determined based on the desired ~atio of trialkylphosphine oxide compound to alkyl substituted diaryl phosphor~c acid. The molar ratio of alkyl substituted diaryl phosphoric acid to trialkylphosphine oxide may vary from about 1:10 to about 1.5:1. the especially preferred range being from about 1;3 to about 4:5.
The proces.s of the present ~nvention is applicable to any aqueous acidic solution containing uranium and vanadium. The instant process is particularly applica- -ble to wet process -9=
:
,,~, 1~)95689 phosphoric acid obtained from the western phosphate deposits which contain significant quantities of both uranium and vanadium.
It has been found in the practice of this invention that fluoride must be present in the aqueous acidic solution in order for the complexing agents of the present invention to properly complex the vanadium(V3. Although the exact theory of the complex is not known, it is believed that the fluoride is complexed with vanadium(V) and the complexing agent. The amount of fluoride present in the mixture preferably is at least about 0.25 moles per mole of vanadium present, although a large excess of fluoride does not harm the extraction. ~luoride is a natural component of wet process phosphoric acid and thexefore wet process phosphoric acid is particularly suited to the extraction process of the present invention.
- Prior to contacting the aqueous acidic solution with the organic extractant mixture, the aqueous solution is treated, if necessary, with an oxidizing agent to make certain that the vanadium contained therein is in the pentavalent oxidation state(V) and the uranium is in the hexavalent oxidation state~VI). When the vanadium and uranium are not present as vanadium(V) and uranium~VI), the extraction process with the solvent extractants of the ` present invention is not satisfactory as vanadium and uranium in the lower oxidation states do not form a complex with the extractants contemplated in the scope of the invention.
~)95t~89 The aqueous acidic solution may be oxidized by any known method such as, for example, with sodium chlorate, manganese dio~ide, ozone, and the like. The oxidizer should be added in an amount sufficient to provide at least the stoichiometric requirements for oxidation o, all the vanadium to vanadium~V) and uranium to uranium(VI). ~en there are other oxidizable species present in the aqueous acidic solution, such as are found in wet process acid, for example, it is desirable to provide an excess of the stoichiometric requirements of the oxidizer. This being necessary, of course, to insure that substantially all the uranium and vanadium values present are oxidized.
The process of the present invention may be practiced within a temperature range of from about 20C to about 80~C
with a temperature of about 35C to about 55C being preferred.
^ It has been found that the contact time between the organic phase and the acid phase is an important variable to consider when extracting vanadium from acidic solutions.
~onger contact times result in increased vanadium extraction.
In practice, contact times of from about 1 minute to about 60 minutes are satisfactory with about 5 minutes to about 30 minutes per contact being especially preferred at temperatures of from about 40C to about 50C. The extraction may be performed on a batch basis or a continuous basis, such as in a continuous countexcurrent multi-stage extraction system.
In the process of the present invention, the organic phase is contacted with an aqueous acidic solution containing .109S6~9 ranium and vanadium, at least a major portion of the vanadium and ura~ lues being in the pentavalent and hexavalent oxidation states respectively, whereby the uranium and vanadium are simultaneously coextracted in the organic phase. The loaded organic phase may be stripped by conven-tional methods; for example, the loaded organic phase may be contacted with an aqueous solution of sodium carbonate, ammonium carbonate or similar base at a pH above about 8.~ -to simultaneously strip both the vanadium and uranium values contained therein.
According to a preferred embodiment of the invention, the vanadium can be stripped from the organic extract phase, free from the uranium. In this embodiment the loaded organic phase is contacted with an aqueous sodium hydroxide, sodium carbonate or other suitable basic stripping solution under-carefully controlled conditions so that the equilibrium pH
of the resulting mixture does not exceed about 6. However, the equilibrium pH may rise to about 8.4 without causing an adverse effect. It has been discovered that by such control of the equilibrium pH that vanadium is pre~erentially stripped from the loaded organic phase. Particularly good results have been obtained when the addition of a stripping solution is controiled such that the equilibrium pH is from about 5.5 to about 6Ø Under such conditions, substantially all the vana~ium is stripped from the loaded organic phase with less than about 1 part per million of U308 being removed.
Thus, stripping with an aqueou~ sodium hydroxide or similar , ' - ~a -.... ,_ . . . . . . . .
1~95689 solution at a controlled pH results in the preferential removal of only the ~anadium values. The remaining uranium loaded organic can be processed by ~nown me~hods for the subsequent removal of the uranium values. For example, the uranium loaded organic phase can be stripp~d with an aqueous solution of sodium carbonate, ammonium carbonate or similar base at a pH above about 8.4.
Suitable aqueous base strip solutions may contain any one of a number of alkali metal hydroxides, carbonates or mixtures thereof. Ammonium hydroxide can be used but is not as desirable for stripping vanadium as the alkali metal hydroxides or carbonates as it will also cause the formation of solid precipitates during the stripping process.
Stripping may be accomplished in a batch or continuous operation. A preferred method utilizes a multi-stage countercurrent stripping process.
The foregoing description and the following specific examples are for the purpose of illustration and are not to be considered as limiting the scope of the invention, reference being had to the appended claims for this purpose~
EXAMPLE I
This example demonstrates, in a one stage extraction, the effect of varying the molarity of the trialkylphosphine oxide compound and alkyl substituted diaryl phosphoric acid in the organic phase as well as the effect of ~arying the~
ratio of trialkylphosphine oxide compound to alkyl substituted diaryl phosphoric acid.
~395ti~3g In a single stage extraction, a separatory funnel mounted in a wrist shaker is utilized. The aqueous acidic solution is an oxidized wet process phorphoric acid (WPA) obtained from a western phosphate deposit and containing 1.53 ~rams per liter vanadium as V2O5 and 0.148 grams per liter uranium as U3O8. The organic extractant phase is a kerosene diluent containing various quantities of tri-n-octylphosphine oxide (TOPO) and dioctylphenyl phosphoric acid (DOPPA) as set forth in Table I below. The separatory funnel contains a portion of the organic extractant solution and is contacted with the oxidized wet process phosphoric acid~ The organic to aqueous ratio is maintained at 1 and the extractions are conducted at 50C with a 20 minute mix time. After the extraction, the aqueous phase is analyzed to determine the percent vanadium and uranium remaining therein. The results are set forth in Table I below.
Further, Table I also shows the percent of V2O5 and V3O8 extracted.
.
TABLE I
SIMULTANEOUS EXTRACTION OF VANADIUl AND
URANIUM FROM OXIDIZED WPA BY VARIOUS
MOLE RA~IOS OF DOPPA AND TOPOi ~
Solvent CompositionAnalysis, g/l ~ Per Cent Molarity A~ueous PhaseExtracted : TOPO DOPPA ,V205U30aV205 U30a 0.2 0.1 0.71 0.05846.~60.8 0.2 0.15 1.07 0.04830.167.6 0.2 0.2 1.42 0.0457.269.6 0.2 0.3 1.42 0.0367.275.7 0.3 0.15 0.59 0.03961.473.6 0.25 0.125 0.620.05259.5 64.g 0.20 0.0 0.31 -0.1~279.74.1 0.0 - 0.2 1.~4 0.1365.9 8.1 ~ -.
`~ ~
.
' :,` ~ `
-- ~ _ 56~39 From the results set forth in Table I, it will ~e seen that the optimum simultaneous coextraction of uranium and vanadium occurs when the molar ratio of alkyl substituted diaryl phosphoric acid to trialkylphosphin~ oxide is about 0.5. The exact concentration utilized depends on the con-centration of vanadium in the solution to be processed and on the relative economic value of~ the two metals compared with the total costs of the recovery process.
EXAMPLE II
This example more fully demonstrates the simultaneous coextraction capability of this invention.
In a four-stage extraction process, four separatory funnels mounted in wrist shakers are utilized. The aqueous acidic solution is WPA obtained from a western phosphate i deposit containing 1.53 grams per liter vanadium as V2O5 and 0.148 grams per liter uranium as U3O8. The organic extractant phase is a kerosene diluent containing 0.25M tri-n-octyl-phosphine oxide (ToPOj and 0.125M dioctylphenyl phosphoric acid (DOPPA). Each of the four separatory funnels contains a portion of the organic extractant solution and is contacted serially with the WPA. The organic to aqueous ratio is maintained at 1 and the extractions are conducted at 50C
with a 20 minute mix time per stage. Af ter each extraction stage, the aqueous phase is analyzed to determine the percent vanadium and uranium remaining therein. The results are set forth in Table II below.
.
~ 5689 TABLE II
.
SERIAL SIMULTANEOUS EXTRACTIONS OF
VANADIUM AND URANIUM FROM OXIDIZED ~PA BY
'''' O.125M DOPPA AND 0.25M TOPO SO~VENT - .
- .
Extraction Stage' Analysis, g/l Cumulative Percent '' ' # ''' ~ ~ ~queou's Phase ' EXtract'ed ' V20~' UaOa V20~i U30~
' 1 ' 0'.57 '0.050 , 62.7 66.2 .
2 , 0.38 0.01575.2 '89.9 . 3 . 0.28 0.00581.7 96.6 " ' 4 0.26 0.00183.0 99.3 ': , .: , .
.
, , ' ~ , 1'7 , . . , .
" 1~;)~35689 EXAMPLE III
This example illustrates the preferential separation of vanadium from a vanadium-uranium loaded extractant organic phase.
A sample of organic extract phase loaded with vanadium and uranium is prepared containing 0.25M tri-n-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid ~DOPPA) in kerosene loaded with 2.61 grams per liter V2O5 and 0.175 grams per liter U3O8.
The sample is scrubbed with water in a two-stage process. It has been found that an initial water scrub removes some of the impurities tha~ are coextracted from WPA, such as phosphoric acid and hydrofluoric acid. The removal of such impurities reduces the amount of sodium carbonate or other base required to strip the uranium and vanadiwm from the loaded extractant. The sample of loaded organic is serially contacted with an equal amount of water placed in separatory funnels mounted on a wrist action ~; shaker and agitated for 5 minutes at a temperature of 50C.
: . .
;~ Following the water scrub, a sample of the aqueous phase of each stage i8 obtained and analyzed. The analyses are set forth in Table III below.
: : : . . . .
.
, ~ , ' , -; ~ ~ ' s ' , ' ' --~ ~og5689 TABLE III
WATER SCRUBBING OF VANADIUM
AND URANIUM LOADED
0.125M DOPPA and 0.25 TOPO SOLVENT
Scrub Stage Analysis of Scrub Analysis o~ Scrubbed Water, g/l__ _ Or~anic Phase, g/l VzOs U~O~ ~'. V20, U30~
1 ' 0.17 . ~0.001 2 0.07 ~.001 2.32 0.175 , .
, ~ ' . ' - .
.
~ ~ , ' ~ - ' . ' Iq ' ~.
lOg5689 The results set for~h in Table III clearly show that ~;ubstantially no uranium and little vanadium is removed by water scrubbing.
The water scrubbed organic extract phase preferen-tially is stripped of its vanadium content u~ilizing the following procedure. In the first stage, the water scrubbed loaded oxganic extract phase is placed in a beaker equipped with a stirrer. A sufficient volume of an aqueous sodium carbonate strip solution is slowly added to the beaker to provide an equilibrium pH of about 6Ø The contents of the bea~er then are stirred for 5 minutes at 50C, following which the aqueous strip solution containing the vanadium is removed from the beaker. That solution and the remaining organic extract phase both are analyzed. The results are set forth in Table IV below. In the second stage of strip-ping, the remaining organic extract phase is contacted with a further solution of sodium carbonàte in an amount sufficient to proYide an equilibrium pH of 8.4. The mixture is stirred for 5 minutes at 50C, following which the aqueous strip solution containing residual vanadium is recovered. That -solution and the then remaining organic phase are analyzed.
The resu1ts are set forth iA ~ahle IV below.
'' `' - . ' .
.
, ' , - ~
, ' TABL~ IV
SELECTIVE STRIPPING OF VANADIUM
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA AND 0`.25M TOPO SOL~'ENT
, Analysis of Va~adium- I
. Containing StripAnalysis of Stripped Stage No. -Solution, ~/l Organic Phase, g/l ~ ~ .
.
' ~ Og ' U308 ~_ ' ~20!1 U308 0 -- -- -- 2.32 0.17~
1 2.14 <0.001 6.0 0.17 0.182 2 0.06 <0.001 8.4 ~0.05 0.18 .
.
: ~ : , ` ' : :: "
'~ ; ~ ' . , , ': . ' ' ' ' ' '~ J
_, ~ _ ... , _., .. . , - , . , .... , E~.~3 i~)95689 The results as set forth in Table IV clearly demon-strate that the vanadium is recovered substantially free of uranium. Less than 0.001 grams per liter lranium are found with the vanadium. The uranium subsequently is recovered from the vanadium strippea extractant by contacting it with a sufficient amount of an aqueous base solution to ma;ntain the equilibrium pH above about 8.4.
Alternatively, both the uranium and vanadium may be stripped by a reducing agent in acid solution, or the uranium alone may be stripped by a reducing agent in acid solution or by high concentration of phosphoric or hydrofluoric acid.
For example, the vanadium stripped organic extract phase is stripped of its uranium utilizing the following procedure.
The uranium loaded organic is contacted with an equal amount of alternate stripping agent aqueous solution placed in separatory funnels mounted on a wrist-action shaker and agitated for S minutes at a temperature of 50C. The organic and aqueous phases are separated and the organic phase is analyzed. The results of these tests are set forth in Table V below.
~ '. ' ' .
, ~ , ' : . . ' , , r~
TABLE V
SINGLE S~AOE S~RIPPING OF URANIUM FROM
VANADIUM STRIPPED-URANIUM LOADED
0.125M DOPPA AND 0.25M TOPO SOLVEN'r -Stripping Agent Analysis of Stripped (In H20) Organic Phase, ~5/1 : ' _ NONE 0.184 85% H P04 0 . 009 *12M H3Po4 0.028 20% H~ 0 . ollo *Containing 2 g/l iron(II) ~ .
~:
~ 23 -: : , , , -1~)95ti89 ~
SUPPLE~ENTARY DISCLOSURE
It is stated in the principal disclosure that stripping with an aqueous sodium hydroxide or similar solution at a control-led pH results in the preferential removal of only the vanadium values and that the remaining uranium loaded organic phase can be processed for the subsequent removal of the uranium values.
Alternatively, the uranium loaded organic phase can be stripped with an aqueous acidic solution of phosphoric acid or hydrofluoric acid. A preferred form of aqueous acidic stripping is obtained through addition of a reducing agent to the acidic solution which is capable of reducing uranium to the tetravalent state.
In alternate embodiments, both the vanadium and uran- ~;
ium can be stripped from the organic extract phase by means of a reducing agent. Selection of an appropriate reducing agent and process conditions provide a means by which the vanadium and uraniu= can be simultaneously stripped from the loaded organic phase into the same aqueous medium or sequentially into the same or different aqueous media.
In one alternate embodiment, vanadium and uranium are simultaneously stripped from the loaded organic phase with a phos-phoric acid solution containing a reducing agent, such a8 ferrous iron, in such an amount so as to reduce the vanadium to a mixture ~; of trivalent and tetravalent states while reducing the uranium to the tetravalent state.
In another alternate embodiment, the amount of reducing agent is controlled such that only vanadium is reduced and strip-ped from the loaded organic phase and the uranium remains primar-ily in the hexavalent state. To produce high concentrations of vanadium in the stripping solution by this technique, it is de-sirable to wash the stripped organic phase in a counter-current fashion with the stripping medium makeup solution prior to ad-,^,, 1 \ ~ss~s~
dition of the reducing agent to the solution.
In yet another alternate embodiment, vanadium can be selectively stripped from the loaded organic phase through use of a reducing agent in an aqueous stripping solution which is not capable of complexing tetravalent uranium. Such non-complexing aqueous stripping solutions include sulfuric acid.
When using ferrous iron as the reducing agent in the sulfuric acid stripping solution, the reduction and stripping of van-adium is essentially complete while virtually no uranium is stripped from the loaded organic phase. The uranium then can be stripped by any of the previously described methods.
An additional means of selectively stripping van-adium from the loaded organic phase is with strong nitric acid solutions, which may also contain additional nitrate salts. While it is not fully understood, it is believed the selective stripping results from the high affinity of the alkylphosphine oxide component of the organic phase for nitric acid.
Stripping by the above procedures may be accomplished in a batch or continuous operation. A preferred method util-izes a multi-stage countercurrent stripping process.
In addition, the process of the present invention has been found to remove certain other impurities from wet process phosphoric acid. These include yttrium, iron, zinc, bromine and possibly trace amounts of other metallic compon-ents. This purification is seen as a valuable side effect of the present process and provides the additional benefit of allowing the recovery of other by-products of economic worth such as yttrium, The following additional Examples are for the pur-pose of illustrating the inventlon.
- 25 _ ~95689 EXAMPLE IV
This example illustrates the preferential separation of vanadium from a vanadium-uranium loaded extractant organic phase using an aqueous acidic stripping solution containing a reducing agent.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illustrated in Example III. The water scrubbed organic extract phase contains 0.25M tri~n-octylphosphine oxide (TOPO) and 0.125M
dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 1.0 grams per liter V2O~ and 0.081 grams per liter The water scrubbed organic extract phase preferentially is stripped of its vanadium content utilizing the follo~ing procedure. The sample is contacted with an equal volume of a sulfuric acid solution containing ferrous iron placed in a separatory funnel mounted on a wrist-action shaker ~ and a~itated for 5 minutes at a temperature of 50C. Follow-: ing the agi.tation, the organic and aqueous phases are : separated and the aqueous phase is analysed. The results ~ of this test are set forth in Table VI belQw~
~ ~ .
A -;26 _ ~ogs~9 TABLE VI
SELECTIVE STRIPPING OF VANADIUM FROM
VANADIUM AND URlhNIUM LOADED
0 125M DOPPA - 0.25M TOPO SOLVENT
Analysis of Vanadium Analysis o .and Uranium Loaded Resultant Strip Stripping_Agent Organic Phase, g/l Solution, g/l ~725 U308 V205 U30B
5 vol. % H2SO4* 1.0 0.081 0.76 0.0019 ; *containing 9 g/l iron II
; ~ , .
' : ~ .
, ~ ~ .
~: ' :: .
~ .
~ ' ` - 27 ~
.
~0~5689 The results as set forth in Table VII clearly demon-strate that the vanadium is recovered substantially free o~ uranium. Less than 0.002 grams per liter uranium are found with the vanadium.
EXAMPLE V
This example illustrates the preferential separation of vanadium from a vanadium uranium loaded extractant organic phase using aqueous nitric acid solutions.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illu-strated in Example III. The water scru~bed organic extract phase contains 0.25M tri-n-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 1.0 grams per liter V205 and 0.~81 grams per liter U308.
The water scrubbed organic extract phase preferentially is stripped o~ its vanadium content utilizing the following procedure. Samples are contacted with an equal volume of a nitric acid solution placed in separatory ~unnels mounted on a wrist-action shaker and agitated ~or 5 minutes at a temperature of 50C. Following the agitation, the organic and aqueous phases are separated and the aqueous phase is anal~zed. The re9ults of these tests are set forth in able VII below.
.
, ~ ~ - 28 _ lOgS689 TABLE VI I
SELECTIVE STRIPPING OF VANADIUM FROM
VANADIUM AND URANIUM LOADED
0 .12 5M DOPPA_-- 0 . 2 5M TOPO _SOLVENT
Analysis of Vanadium Analysis of and Uranium Loaded Resultant Strip Stripping Agent Org~anic Phase, g/l Solution, g/l_ V2O, U3O8 V205 U30tl 0.5M HNO3 1.0 0.081 0.24 <0.0005 0 . 5~1 HNO 3 +
3M NH4NO3 1.0 0.081 0.37 <0.0005 1. OM FINO3 1. 0 0 . 081 0 . 40 <0 . 0005 I :
,: :
- ~ , ' :
-_ 29 _ c ., ~
1~95689 The results set forth in Table VII clearly demonstratethat the vanadium is recovered substantially free of uranium.
Further, the data show that nitric acid solutions supple-mented with additional nitrate salts and stronger nitric acid solutions improve vanadium stripping.
EX~PLE VI
This example illustrates simultaneous aqueous acidic solution stripping of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
A sample of organic extract phase loaded with vanadium and uranium is prepared and scrubbed with water as illu-strated in Example III. The water scrubbed organic extract phase contains 0.25M tr~-n-octylphosphine oxide (TOPO) and 0.25M dioctylphenyl phosphoric acid (DOPPA) in ~erosene loaded with 1.0 grams per liter V2Og and ~.081 grams per liter U30~.
The water scrubbed organic extract phase simultaneously is stripped of its vanadium and uranium by utilizing the following procedure. Samples are contacted with equal volumes o~ aqueous acidic solutions placed in separatory funnels mounted on a wrist-action sha~er and agitated for 5 minutes at a temperature of 50C. Following the agitation, the organic and a~ueous phases are separatea and the aqueous phase is analyzed. The results of these tests are set forth in Table VTI below.
~ . .
' - 30 -A
~95689 TABLE VIII
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA - 0.25~1 TOPO SOLVENT
Analysis of Vanadium Analysis of ` and Ura~iurn Loaded Resultant Strip Stripping Agent Organic Phase, ~ Solution, g/l V205 U308 ~25 U30EI
~50~ H3PO4 1.0 0.081 0.49 0.091*
~ ~ 70% H3PO4 1.0 0.081 0.49 0.078 - ~ ~ 85~ H3PO4 1.0 0.081 0.49 0.062 24% HF 1.0 0.081 0.94 0.087*
: : *value is within the experimental accuracy of the fluorometric analysis empioyed : :~ : :
.
' - 31,-A
1095~9 The results as set forth in Ta~le VIII clearly demon-strate the ability to simultaneously recover substantial amounts of vanadium and uranium from a loaaed organic extract phase.
EX~ ~LE VII
This example illustrates simultaneous aqueous acidic solution stripping of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
~ sample of organic extract phase loaded with vanadium and uranium is prepared containing 0.25M tri-_-octylphosphine oxide (TOPO) and 0.125M dioctylphenyl phosphoric acid ~DOPPA) in kerosene loaded with 3.60 grams per liter V205 and 0.0~3 grams per liter U 30 8 ~
The loaded organic phase is stripped by contacting with an equal volume of an aqueous acidic solution placed in a separatory funnel mounted on a wrist-action shaker and agitated for 5 minutes at a temperature of 50C. Following the agitation, the organic and aqueous phases are separated and the aqueous phase is analyzed. The results of these tests are set f o eh in ~able IX below.
.
.
~' , 1C~95689 TABLE IX
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FRO~I VANADIUM AND URANIUM LOADED
0.125~1 DOPPA - 0.25M TOPO SOLVENT _ ; Analysis of Vanadium Analysis o and Uranium Loaded Resultant Strip Stripping Agent Organlc Phase, g/l Solution, g/l V2O j U3OB V20~ U3OB
8~% H3PO4; 3 . 60 0 . 073 0 . 82 0 . 076*
24% HF 3.60 0.073 3.51 0.066 *value is withi..n the experimental accuracy o~ the fluorometric analysis e~ployed .
~ .
,. j :
- 33. -:
Al . :
109568~
The results set forth in Table IX demonstrate an abilityto simultaneously strip vanadium and uranium from the loaded organic phase.
EXAMP~E VIII
This example illustrates the simultaneous aqueous acidic solution stripping of vanadium and uranium ~rom a vanadium-uranium loaded extractant organic phase.
A sample of organic extractant phase loaded with vanadium and uranium is prepared and scrubbed with water as illustrated in Example III. The water scrubbed organic extract phase contains 0.25M tri-n-octylphosphine oxide (TOPO~ and 0.125M
dioctylphenyl phosphoric acid (DOPPA) in kerosene loaded with 0.49 grams per liter V2O5 and 0.090 grams pe~ liter U30a-The water scrubbed organic extract phase simultaneously is stripped of its vanadium and uranium by utilizing the following procedure. Samples are contacted with equal volumes of aqueous acidic solutions containing a reducing agent placed in separatory funnels moun~ed on a wrist-action shaker and agitated for 5 minu-tes at a temperature of 50C.
Following the agitation, the organic and aqueous phases are separated and the aqueous phase is analyzed. The results of these tests are set rorth in Table X, below-.
.
. - 34 -~' lOgS689 TABLE X
SIMULTANEOUS VANADIUM AND URANIUM STRIPPING
FROM VANADIUM AND URANIUM LOADED
0.125M DOPPA ~ 0.25M TOPO SOLVENT
.
Analysis of Vanadium Analysis of and Uranium Containing Resultant Strip Stripping Agent* Organic Phase, g/l Solution, g~l V2Og U3Oa V2O5 U3O8 50~ H3PO4 0.49 0.090 0.49 0.064 70% H3PO4 0.49 0.090 0.54** 0.093**
85% H3PO4 0.49 0 090 0 54** 0 094**
*containing 2 g/l iron II
**value is within the experimental accuracy of the fluorometric analysis employed . ~
~ ' .
:: :
.
;
' .
_ 35 -~ .l5'J
The results set forth in .able X demonstrate the ability to simultaneously strip substantial amounts of vanadium and uranium from the loaded organic phase.
EXAMPLE IX
This example illustrates individual preferential stripping and separation of vanadium and uranium from a vanadium-uranium loaded extractant organic phase.
~ n organic phase containing 0.~M tri-n-octylphosphine oxide (TOPO) and 0.2M dioctylphenyl phosphoric acid (DOPPA) in kerosene continuously is loaded with vanadium and uranium in a small multistaged extraction module. The loaded organic extract phase then enters a multistage stripping module.
Vanadium stripping and separation is accomplished in the first stage of the stripping module using a controlled volume of phosphoric acid solution that contains sufficient reducing agent to provide the stoichiometric quantity required to reduce the vanadium (V) content of the organic phase to the quadravalent state. This permits the preferential separation of vanadium and allows only a small quantity of the uranium to be stripped. The aqueous phase resulting from the stripping is quite rich in vanadium~ The vanadium stripped organic phase then proceeds into a two stage phosphoric acid scrubber. The scrubbing is utilized to limit the advancement of vanadiu~ containing solution into the do~n-stream uranium stripping section. Iron is dissolved in the resultant vanadium scrub aqueous phase to provide the aqueous stripping solution employed in the first stage vanadium stripping sec-tion. In this manner, any vanadium A
lO9S689 scrubbed from the organic phase is returned to the vanadium stripping section to facilitate recovery.
The vanadium stripped and scrubbed organic phase then proceeds into the uranium stripping section comprising the fourth stage in the stripping module. In the fourth stage, the vanadium stripped and scrubbed organic phase contacts a controlled volume of phosphoric acid which contains a reducing ~gent in sufficient quantity to reduce any residual vanadium (V) and the uranium ~VI) content to the lower vanadium (irV) and uranium (IV) states. It has been shown in the practice of this invention that the presence of the reducing agent in quantities in excess of the stoichiometric requirement is beneficial to uranium stripping. The uranium and vanadium stripped organic phase then enters a two stage phosphoric acid scrubber. Th scrubbing is utilized to prevent the advancement of high grade uranium strip solution to the organic phase recycle storage tank. The scrubber aqueous phase was separated and split into two portions.
Iron was dissolved in one portion of the resultant aqueous phase to provide the aqueous stripping solution employed in the fourth stage uranium stripping section. The remaining portion of the scrubber aqueous was recycled as aqueous feed to the two-stage vanadium scrubbers. In this manner, any vanadium or uranium that was scrubbed from the organic phase was caused to finally separate with the vanadium or uranium stripping products.
~ he preferential vanadium and uranium stripping of the loaded oxganic phase described hereinabove, produced a .
~LOS~S~89 vanadium strip product solution containing in excess of 97 percent of the recoverable vanadium and a uranium strip product solution containing more than 93 percent o~ the recoverable uranium.
In the particular test described above, a 70 percent phosphoric acid solution was employed in all of the stages in the stripping module. Satisfactory phosphoric acid concentrations for this process are from about 20 percent to about 95 percent H3PO4. However, the phase ratios an~
number of stages required to effect stripping may change with varying concentrations. In addition, differen-t acid concentrations may be used in different stages of the stripping module.
While this particular test employs iron as the reducing agent in the aqueous acidic solution, any reducing agent which is compatible with phosphoric acid and that is capable of reducing vanadium (V) and uranium (VI) to lower valence jl~ states can be used in this process.
While the present invention has been described with respect to pre~erred embodiments thereof, it will be under-stood, of course, that certain changes may be made therein without departing from its true scope as defined in the appended claims.
_ .
~ ~ - 38 _ . .
'
Claims (32)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the simultaneous recovery of uranium(VI and vanadium(V) from an aqueous acidic solution containing the same which com-prises:
contacting said solution in the presence of at least about 0.25 mole fluoride per mole vanadium with an orgnaic extractant phase comprising (a) a substantially water-immiscible organic diluent;
(b) an alkyl substituted diaryl phosphoric acid having the formula where R1 and R2 represent aryl radicals at least one of which is substituted with an alkyl group and the total number of carbon atoms in the alkyl sub-stituted diaryl phosphoric acid is at least 13 and (c) a trialkylphosphine oxide having the formula where R, R' and R" are alkyl radicals each containing from 4 to 14 carbon atoms, whereby the uranium and vanadium are preferentially coextracted into the organic phase and, recovering the uranium and vanadium containing or-ganic phase, the alkyl substituted diaryl phosphoric acid and trialkylphosphine oxide being present in the organic extractant phase in an amount sufficient to provide a molar ratio of alkyl substituted diaryl phosphoric acid to trialkyphosphine oxide of from 1:8 to 1:1.
contacting said solution in the presence of at least about 0.25 mole fluoride per mole vanadium with an orgnaic extractant phase comprising (a) a substantially water-immiscible organic diluent;
(b) an alkyl substituted diaryl phosphoric acid having the formula where R1 and R2 represent aryl radicals at least one of which is substituted with an alkyl group and the total number of carbon atoms in the alkyl sub-stituted diaryl phosphoric acid is at least 13 and (c) a trialkylphosphine oxide having the formula where R, R' and R" are alkyl radicals each containing from 4 to 14 carbon atoms, whereby the uranium and vanadium are preferentially coextracted into the organic phase and, recovering the uranium and vanadium containing or-ganic phase, the alkyl substituted diaryl phosphoric acid and trialkylphosphine oxide being present in the organic extractant phase in an amount sufficient to provide a molar ratio of alkyl substituted diaryl phosphoric acid to trialkyphosphine oxide of from 1:8 to 1:1.
2. The process of claim 1 wherein the ratio of alkyl substituted diaryl phosphoric acid to trialkyphosphine oxide is in the range of from 1:3 to 4:5.
3. The process of claim 1 wherein the concentration of trialkylphosphine oxide in the organic phase is in the range of from 0.05 molar to 0.5 molar.
4. The process of claim 1 wherein the trialkylphosphine oxide is tri-n-octylphosphine oxide.
5. The process of claim 1 wherein the alkyl substituted diaryl phosphoric acid is dioctylphenyl phosphoric acid.
6. The process of claim 1 wherein the ratio of alkyl substituted diaryl phosphoric acid to trialkylphosphine oxide is about 0.5.
7. The process of claim 1 wherein the alkyl substituted diaryl phosphoric acid is dioctylphenyl phosphoric acid and the trialkylphosphine oxide is tri-n-octylphosphine oxide.
8. The process of claim 1 wherein the aqueous acidic solution is a wet process phosphoric acid.
9. The process of claim 1 wherein the uranium and vanadium are stripped from the recovered organic phase with an aqueous base solution.
10. The process of claim 1 wherein the recovered organic phase is contacted with the aqueous basic solution in an amount sufficient to maintain the equilibrium pH at from about 5.5 to 8.4, whereby the vanadium preferentially is stripped from the organic phase to leave a vanadium-barren uranium containing organic phase.
11. The process of claim 10 wherein the uranium-containing organic phase is contacted with an aqueous basic carbonate solution in an amount sufficient to maintain the equilibrium pH above about 8.4 whereby the uranium is stripped from the organic phase and recovering the uranium substantially free of vanadium.
12. The process of claim 10 wherein the uranium-containing organic phase is contacted with at least one acid selected from the group consisting of phosphoric acid and hydrofluoric acid in a concentration sufficient to remove substantially all of the uranium from the organic phase.
13. The process of claim 10 wherein the uranium-containing organic phase is contacted with a solution containing (i) a reducing agent and (ii) at least one acid selected from the group consisting of phosphoric acid and hydrofluoric acid to remove substantially all of the uranium from the organic phase.
14. The process of claim 1 wherein the trialkyl-phosphine oxide is tri-n-octylphosphine oxide present in an amount sufficient to provide a concentration in the organic phase of from about 0.1 to about 0.3 molar and the alkyl substituted diaryl phosphoric acid is dioctyl-phenyl phosphoric acid.
15. The process of claim 1 wherein the trialkylphosphine oxide is tri-n-octylphosphine oxide present in an amount sufficient to provide a concentration of about 0.25 molar and the alkyl substituted diaryl phosphoric acid is dioctyl-phenyl phosphoric acid present in an amount sufficient to provide a concentration of about 0.125 molar.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
16 . The process of claim 1 wherein the trialkyl-phosphine oxide is tri-n-octylphosphine oxide present in an amount sufficient to provide a concentration in the organic phase of from about 0.1 to about 0.5 molar and the alkyl substituted diaryl phosphoric acid is dioctyl-phenyl phosphoric acid.
17. The process of claim 1 wherein the trialkylphosphine oxide is tri-n-octylphosphine oxide present in an amount sufficient to provide a concentration of from about 0.25 molar to about 0.45 molar and the alkyl substituted diaryl phosphoric acid is dioctylphenyl phosphoric acid present in an amount sufficient to provide a concentration of from about 0.125 molar to about 0.23 molar.
18. The process of claim 1 wherein the vanadium con-taining organic phase is contacted with at least one solution selected from the group consisting of nitric acid and nitric acid containing additional nitrate salts to remove a substantial quantity of the vanadium from the organic phase.
19. The process of claim 1 wherein the vanadium con-taining organic phase is contacted with an aqueous solution containing (i) a reducing agent and (ii) sulfuric acid.
20 . The process of claim 19 wherein the solution contains sulfuric acid in a range of from about 5 percent to about 35 percent by weight.
21. The process of claim 19 wherein the reducing agent is ferrous iron.
22 . The process of claim 1 wherein the vanadium containing organic phase is contacted with an aqueous acidic solution containing a reducing agent.
23. The process of claim 22 wherein the reducing agent is ferrous iron.
24. The process of claim 1 wherein vanadium and uranium are simultaneously stripped from the recovered organic phase by contacting with at least one acid selected from the group consisting of phosphoric acid and hydrofluoric acid in a concentration sufficient to remove substantially all of the vanadium and uranium from the organic phase.
25. The process of claim 1 wherein the recovered organic phase is contacted with a solution containing (i) a reducing agent and (ii) at least one acid selected from the group con-sisting of phosphoric acid and hydrofluoric acid to remove sub-stantially all of the vanadium from the organic phase.
26. The process of claim 25 wherein the reducing agent is ferrous iron.
27. The process of claim 25 wherein the reducing agent is trivalent vanadium.
28. The process of claim 25 wherein the organic phase is contacted with the solution in at least two stages to preferen-tially remove vanadium from the organic phase and then remove the uranium by contacting the organic phase with additional quantities of the solution.
29. The process of claim 1 wherein the aqueous acidic sol-ution is wet process phosphoric acid containing at least one member selected from the group consisting of yttrium, iron, zinc and bromine.
30. The process of claim 29 wherein the organic phase also extracts the member selected from the groups consisting of yttrium, iron, zinc and bromine.
31. The process of claim 30 wherein the member selected from the group consisting of yttrium, iron, zinc and bromine is stripped from the recovered organic phase with an aqueous acidic solution.
32. The process of claim 1 wherein the recovered organic phase is contacted with a solution containing (i) a reducing agent and (ii) at least one acid selected from the group con-sisting of phosphoric acid and hydrofluoric acid to remove sub-stantially all of the uranium from the organic phase.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US72099576A | 1976-09-07 | 1976-09-07 | |
| US720,995 | 1976-09-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095689A true CA1095689A (en) | 1981-02-17 |
Family
ID=24896082
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA281,522A Expired CA1095689A (en) | 1976-09-07 | 1977-06-28 | Simultaneous extraction and recovery of uranium and vanadium from wet process acids |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1095689A (en) |
-
1977
- 1977-06-28 CA CA281,522A patent/CA1095689A/en not_active Expired
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