CA2113650C - N-ethyl hydroxamic acid chelants - Google Patents

Abstract

N-ethyl alkanohydroxamic acids, where said alkyl group is a straight chain alkyl group of 8 to 10 carbon atoms, or a branched alkyl group of 8 to 18 carbon atoms, provided said alkyl group is not cyclic, useful as metal chelants for use an organic solvent extractant solutions such as kerosene to extract metals from aqueous solutions by forming complexes of the extracted me-tal with the N-ethyl hydroxamic acid. Metals can be stripped from complexes of N-ethyl hydroxamic acids at higher concentra-tions into lower strength acid stripping agents. The N-ethyl hydroxamic acid-containing organic solvent extraction solutions exhi-bit rapid phase separation from aqueous solutions, good hydrolytic stability and resistance to forming emulsions.

Description

!~ 93/~2~Id7 ~ ~ ~ ?~ ,~~ r~ ~~ P~T/~JS92J0562~
°-1 ~.
N-ETHYL HYDRUxAI~'IIC ACID C~iELANTS
Disclosed herein are novel N-ethyl hydrox-a~nic acids, methods of making them and using them as metal chelants.
B~1CKGROUT~1D CAF' THE I~IEIdTI~I~
Hydroxamic acids can be represented by the structural formula R1C ~9) N (~H) R~, where R1 is typically hydrogen or a hydroca~°bon radical such as an alkyl radical, a cycloalkyl radical or an aromatic radical and R~ can be a hydrogen atom or a hydrocarbon radical such as an aromatic radical or an alkyl radical. ~,s disclose$ by lucid in U.S. Patent 3,821,351, Coleman et al, in U.S. Patent 4,741,88 and Mon~yk et al. in U.S. Patent 4,75,253, such hydroxamic ac~.ds are use--~.5 ful as chelants for extracting metals, e.g. from an agiaeous solution of a mixture of metals. Hydroxamic acids containing at least about 7 carbon atoms are especially suitable for metal extraction being sub-stantially insoluble in ae~ueosus solutions and highly a~D soluble in industrial organic solvents, e.c~: ker~sez~e.
Many ~aydr~xa~aic acids exhibit distinct ex-tradtion profiles ~ith~.n a narrow band of pH for dif-ferent metal ~peGi:e~ that allb~s f~r selectivity dur-i~ng extraction arid/~r ~trippa.ng ~f aaetals. In a typi-25 cal appla.cation ~ kerosene sol~t3~on of such hydr~x,~mic acid intimately ~~:xed with ~n ~e~us so3.ut~.o~ of ~ .
mi'tture ~f metals ~al~nitransfer fe aeons phase into the ~rganic phase as oo~n~lexe~ bf the hy-d~oxamic ~~i~. Speoific metal species can be ~elec--tively ~tgip~od f~~~ the k~rdse~e phase by mixing the metal~loadod cactra.ctant ~'~.th a ser3:es of ague~us s~lur tion~ having ~ pH matching the distinct e~ctracti~n' prof~:l.e cf each aztetal . species: The commercial util~
ity ~f such hydx~aca~~c $cids also depends to a barge 3 5 cxte~at on thea.r ~yarolytic sta3~il ity, i . a ~ the resin-taa~ce of the hydi°oxamic acid to d~.ssociate in the ague~us solutions into hydroxylamir~e end carboxylate ~~o ~3i~~na~ , ~ l 4~ ~~ r,, ~~ ~~e~~9zms62~...
_.~-tance of the hydroxamic acid to dissociate in the a~aeous solutions into hydroxylamine and carboxylate . species, e.g. at an extreme pFi typically used for stripping complexed metal from the hydroxamic acid.
Hydroxamic acids that are hydrolytically unstable, e.g. useful for only a single, or at most a few, extraction/'stripping cycles, are essentially of no commercial utility, In this regard Coleman et al.
have shown that hydrolytic stability of hydroxamic 1~ acids depends ~f the nature of the R~ radical. For instance, hydroxamic acids having hydrogen or an aro-matic radical such as a phenyl group are substantially hydrolytically unstable, especially when exposed to low pH agiaeous soluti~a~ commonly used to strip metal from hydroxamic acid comple:~es. Coleman et al. also demonstrated superior hydrolytic stability for hydrox-amic acids where the RZ rada.cal is an alkyl group, e:g.
a methyl group~ such hydroxamic acids are referred to in the full~wing descr~.ptio~ra of this invention as ba-aryl , ~ a g a ~ ~~-methyl ~ hyd,~'~xam~.L' a~..,.do.~ .
~N~~~N
Despite their hydrolytic stability it has beers found that c~rta~:n N-~lky3 hy~iroxamic aG3ds form . ~ra.scous emulsions, or even solid pastes; in organic ~5 extractants. a~ h.ig~a metal leactiregs, e.g~ ~~fi seluticr~s in ker~ser~~ ~t roeam t~nnp~rature. ~n my ~rork to find hydr~xa~aic aids capable ~f hge~h metal 1~adin~ in extracta~ats, 1 hare d~.scover~d that noel N-eye alk~nchydrc~aca~na:c kids have surprising and u~exp~c~ced 3~ propert~.es, as compared t~ N-methyl hydroxa~aic acids, e.g~, they allow the production and use ~f extra~t~nt' solutions that exhibit faster phase diseng~gr~~ent f~~a~
ac~.aeous a~ixture~, higher metal loadings without form-ing emulsion, ~n~re efficient strspping of canons 35 that.typicaily ire ~~re tightly bound by other h~~rox-amic acids and h~,gher and longer term hydrolytic sta-bility. Another aspect of this in~rention comprises ,,> .,.
~~ :~.~~'~>~
~~V~ ~3loxo47 ~~a'i~ls9zeo~6z2 ._3-extractant solut~.ons containing N-ethyl alkanohydrox-amic acids. Still another aspect of this invention comprises methods of extracting metals from aqueous solutions using organic extractants containing N-ethyl alkanohydroxamic acids.
DESC~tI~ION ~F PREFERRED EMR~DIIKEIdTS
Unless expressly stated otherwise, in the description and claians of this invention, percentages of components in solutions, e.g. laydroxamic acids in kerosene, are in weight percent of the soluta.on~ kine-matic visGOSities are reported in units of millimete~sZ
per second (mm2fs~, equivalent to cewtis~okes.
the Pd-ethyl al.kanohydrox~a.c scads of this invention are pre9~erably essentially water insoluble, where the a~.kyl group is a straight chain alkyl groexp of 8 to 10 carbon atox~s, o:r a ~sraxtched alkyl gr~up of 8 to 18 carbon at~ms, pr~vided said al%yl group ~.~ not cyclic. Preferres3 ~-ethyl alkanohydroxaangc acids of this invention are sele~~~~~ from tine group consisting 2p df N1~ethyl n-o~thn~hydxoxa,~ic a~zd; i~-~th~l 2~°ethyl-laexanohydr~xam~.c acid, N-~~tk~yl n-nonanohydroxantic acid, N-eth~r3 n~de~,a~ohydr~xa~mic amid, N-ethyl neode-~an~ ~ydroxamic ~diei, N~ethyl n~ot~ide~anohydr~xa~a.~
arid end N-eth~rl isost~aroh~rdr~xa~ic ac~.d. An; espe-~
ci:~lly pr~a~err~d N-ethyl alkan~hyclsokic acid is N~eth~i n-~ds~anohy~r~acic ~ci~.
'~h~ ~-ethyl alk~a~hydroxc acids of thaws ~,nvention ~~chibit the unexZaectedly advant~g:eou,s ~r~p~
arty of 1~~ ki:nema~ic viscc~~it~r when provic~~d ia~ high ~ ~ conc~r~tr~~~.on~ o Fir instance, 5~ weight p~arc~nt solutions ~'f t'he I~=ethyl alk~anohydr~xa~a.c : acid in ;
~,s~osene e~thibit ki.nem~tic v~.scos3;'ty ~f l~~s 'khan 2~
ma:lli~ete~°s~/~ec~nd (mm2/~) at room t~~p~ratureP e.g . ~3 d~: preferably such solutions wild. each~.~~t a k3.ne-35 ~natic viscosity erf less than ~8 m~z,s or lower, e.g.
less than 7.~ Z~s, ~~r inst~r~ce, t~her~ the S0~ so~u~
Lion of N-methyl ra-d~canohydroxamic acid in kerosene W~ 931OZ047~ ~'~-'~' sa~~.~ ~~ P~.°I'/~1592/0Sfi22.
is a solid, the anaio~ou~ solution of the ~f-ethyl n-decanohydroxamic acid has a kinemtic viscosity of about 15 mm2/s. specifically excluded from this inven-tion are the N-ethyl cycloalkanohydroxamic acids such as N-ethyl naphthenohydroxamic acids (the naphtheno radical. is any of a group of cylcic p~wtyl radicals) which, apparently due to the cyclic ring structure, provide~high viscosity solutions, e.g. greater than 20 mm2/s in 50~ kerosene soluti~ns at 23°C.
1p This invention also provides x~ethods of extracting metal from aqueous solutions comprising contacting said aqueous solution with an organic sol-v~:nt so~.ution containing an N-ethyl alkanohydroxamic acid to extxact the ~~~al i.nt~ the organic solvent solution as a hydroxa~n~.c acid co~aple~c. .~ftes the extracted solutions are separated; the separated or-ganic solvent solution is ~.onta~ted with an aqueous stripping ~~lutio~ at a pFi less than 5 or greater thin 9 to strap the co~ap~.exed medal fro~a the hydroxa~aic aced into the ~e~u~~us stri~api~ag' s~luti~n: ~: preferred orgat~~LC su~v~l1't s~Zutio8l Ce~pabl~.' ~f ~'l~:gh Im~tal ~.9~ding c~~nprises ker~sene ahd ~t le$st about 50~ of an N~-ethyl. alkan~3a~droxa~~:c acid of this ~.nventi:on.
These N-ethyl ~lkan~hydroxazaic acids of ~h~a ~5 in~ren~~.~n eon be gar~pa~ed by ~eactirag ~T-ethyl hydr~x-yl~min~ ~ri~h a carboxylic acid chl~d~~.de, a~g. n-oct~-noyl chloride~ 2~ethYlhexan~yl'.h~ide, n~~ec~noyl chlbride, i~o~st~a~°~yl ~hl~ride and th~ Zike. The exaction can be effected, pxeferabl~ a~ log te~pera°
3~ tutee, e.g~ lest than ~~ °C, by adding the carboxylic ~C~d~h~~r~d~s~.~u~tan~o~,~ly~l.tha baa~°9~, es~oa~.eoua~~
sodium h~dr~xi~l~ P to a solution of the ~1-ethyl hydrox-y~a~3.n~r ~no~g~n~Cs~lv~nt, toga t~trahyd~~fu~a~, methyl~n~e chlorideP e~tc. the hydr~xaa~~.c ac3.d pr~e~uct 35 can be Pu~ra~fied by washimg with weak aqueous a~~d soluti~ns, a:g. 7.~ acetic acid, then stripping the organic solvent: TJs~efu~. reaction cc~nditi~ns are dis-closed in U.S. Patents 3,821,351 and 4,741,887 The organic metal extractant solutions of this invention comprise an N-ethyl alkanohydroxamic acid in an organic solvent which is substantially immiscible with water so as to allow phase disengage-ment of extractant solutions from aqueous metal-bear-ing feed streams. Suitable solvents include aliphatic and/or aromatic hydrocarbon solvents such as kerosene, hexane, toluene, naphtha, cyclohexane and proprietary hydrocarbon solvents such as Chevron° Ion Exchange Solvent, Kerr-McGee's Kermac° 470-B kerosene solvent and Xermac 400-500 naphtha solvent, and Exxon's Isopar M, D 80 and Norpar 13 solvents, and Solvesso° 100 kerosene solvent. Refined kerosene-based solvents having high flash point and high levels of aliphatic components are commonly preferred for industrial metal recovery applications. Generally at least 2% of the N-ethyl alkanohydroxamic acid component will be pres-ent in the organic solvent, e.g. about 2% to 60%, generally about 10% to 35%. Depending on the organic radical constituting the precursor carboxylic acid, the amount of hydroxamic acid in the solvent may vary to provide extractant solutions with appropriate vis-cosity and performance characteristics, e.g. high metal loading and rapid phase disengagement without forming emulsions.
The extractant solutions may also contain commonly used additives such as branched or long chain aliphatic alcohols, e.g. isodecanol, or phosphate esters, e.g. tributylphosphate. Such additives serve to prevent formation of third phases when extractants are intimately mixed with aqueous metal-bearing solu-tions, aid in phase disengagement and/or increase extractant solubility in the solvent. Such additives may find utility in a various concentrations depending to a large degree on the components of the aqueous WO 9'~/02i~7 ~ f a~ ~~~ ~~~ ~ E ~ ~'Olf'1US92/~5622...;.
h. .~
metal-bearing solutions, e.g. in amounts ranging from about 1 to 5o volurQe percent, commonly about 5 to 1~
volume percent.
The methods of this invention comprise the .
S use of N-ethyl alkanohydroxa3aic acid-containing extractant solutions to extract metal from aqueous metal-bearing solutions. Such methods comprise con-tacting, e.g. intimately blending, the aqueous solu-tion with an organic solvent solution containing an t0 N-ethyl alkanohydroxamic acid to extract metal species into the organic solvent solution as a complex of the, hydroxaa~ic acid. after such ~cixing the mixed liquids are allowed to disengage into an ~aeta~.-depleted aqueous phase and a metal-enriched organic sol ent 15 phase. The phases of disengaged solutia~ns are readily separated, e.g. by decanting: The separated orgainic solvent s~luti.on can be contacted with a aqueous stripping solution, e.g. again by intimately blending, to strip the ~~tai ~r~~ t~~ h~~roxa~ic ~~i~ c~~pi~~c 20 and transfer the aaetal into the stripping ~d~.ution.
Depending on the unique ee;ui~.ibxiu~ extrac-t~.~~ curves (c~~ni~ c~amd attraction ~~oth~rr~~a which are re~d~.l~ determined for any ca~abination ~f a paicu~.~r hy~~~xa~i~ acid arad m~ta1 species, the p~I
~~ of the str~:~ping s~luti~ra can ba xeadily adjusted ~o sel~ct~.vel.y str~.~ paxtic:ula~ ~~t~,~. ~p~ci~s frog the ~~~~nic solvent solution: irdt~ltiple c~rat~~tinc~ ~trit~
~tripp~n~f ~~lu~ioris ~f d~:f~e~e~t pli can ~3e u~~d to e~~ect.w~ely strip di~aFerent a~~tals ~ro~ mixed petal 30 n~~~~x~~i~ ~~~.~ ~~m~i~x~~. ~n~ ~~~~a~~g ~~~ the ~~-°
t~actin~ arad ~tri~p~.ng rah be effected by a v~ra.~ty of wellmaoran unit ~~~ratio~ns, e.g. batch ~p~rati~ns in d~can'tex ve~a~ls or an ~ontanuou~ operatioa~s witk~
count~e~currer~t flow bets~een era alt~x°na~.ing series of 35 stirred mixers and ~quie~cent phase separators. tJse~ul selective stripping ~dlutio~rs often have a pH lest than ~ or greater than 9 to strip said complexeci metal from the hydroxamic acid into said aqueous stripping solution. Preferred general stripping solutions in-clude 10-20% sulfuric acid, 10% hydrochloric acid or acid blends such as 20% sulfuric/20% phosphoric acid.
Although extraction techniques are well known to practitioners in the art, several especially useful methods of increasing the purity of extracted metals are disclosed by Monzyk in U.S. Patent 5,030,427 Among the advantages of metal extraction operations using the N-ethyl alkanohydroxamic acids of this invention are that the higher metal extraction capacity allows for smaller sized equipment and/or higher throughput, that higher stripping efficiency 15' allows more thorough stripping resulting in higher concentrations of metal in stripping solutions, that speed of disengagement allows for shorter residence time or smaller volume of phase separators, and that higher resistance to hydrolytic degradation provides more longer on-stream time without replenishing the hydroxamic acid chelant. These and other advantages of the N-ethyl alkanohydroxamic acids of this inven-tion will be apparent from the following illustrative examples which are not intended to indicate any par-ticular limitation of the true scope of this inven-tion.

This example illustrates one method of pre-paring an N-ethyl alkanohydroxamic acid and an extrac-taut according to this invention. N-ethyl decanohy-droxamic acid was prepared by reacting n-decanoyl acid chloride with ethyl hydroxylamine. 5.68 moles each of decanoyl chloride (1179 ml) and sodium hydroxide (309 ml of 50% NaOH) were separately and simultaneously slowly added to a solution of 6.27 moles of N-ethyl-hydroxylamine in a mixture of 683 ml of water and 1 liter of tetrahydrofuran cooled to 15 'C. The temper-w ' ~ ~~.~ ~'~'n~'~ ~'wl ''~ViU 93/027 P'~'/~JS92/OS622 ,....
..~ g ~.
i atura of the reactant mixture was maintained at less than ~o °C. i~Then addition was coanpleted, the mixture was stirred. far 1 hour: theta, the reactant Mixture was allowed to separate into phases. The lby product salt was xemoved with the aqueous phase. -The organic phase was washed twice with 1 liter of 1~ aqueous acetic acid. ,About 118o g of N-~ahyl n°decanohydroxamic acid product was recovered by vaporizing residua. solvents und~.r vacuum at ~0 ° C: s ~Il E'_xtractant solutl.on waS
1o prepared by mixing 29.26 g of N-ethyl n-decanohydrox-amic acid with 3.31 c3 of a mixture of 9~ volume percent s kerosene (I(ex~n~c~ 470 kerosene ~ a his~h aliphatic, high fl=ash poi~at kerosene obtained from Kerr-i~cGee) and 5 volume percent isodeca~nol, providing a clear extractant solution having a density of o.8 gAm1 ~) a A prior art e~ttractant solution was prepared by dissolving ~:8 g of N-methyl n~decanohydroxamic acid 2o in a mixture ~f 13~ c~ of 9!5 volume percent kerosene (ICex-~.ac~ 4~~~ ~ex°~sene) and ~ volu~ae percent isodeca-n~1. pr~~idi.rag a clear ext~acta~t soluti~n having ~
de~a~~.ty of ~:8 ~h~ (~ ~) ~ 2 ~5 Tlai~ example il7:ustra~.es the extili.ty ~f ~~
~T:~~,thyl al~an~hyd~~xa~~c acid of his ~nv~nt~.on in extracting it~a~ ~'~~~ ~~ae~aas ~~lutions and the rapa:d phase dis~ra~age~ent ~f the ~a~ract~nt ~r~m aeous ~~hations: ~ ~~ ~1 volume: ~f E ~1~ 1~ was l~i~nded 30 fox° ~~ m~.nutes ~$,th ai 5~ m~. volume caf an acidic ~qaae-ous iron solut~.on ( ~ s 1.5~: ferric na.trate and ~ .1.M
nitric acid) , pig l a When bl~ndirag was ~toppec~, co~n~
pl~t~ separation ~~ the ague~us'and ore~arai~ pha~~~ was a f belted i.~ ~ 8 seconds .

.X. :.i~ ~ir '~O 9310x047 t~G'~'/iJ~92105622 -g_ c0'~dPAI~TTVE EXAMPi~ 2 A f3 ml volume of EXT~~TA~iT ~ (N-ethyl decanohydroxamic acid) was blended for 20 minutes with a 50 ml volume of the acidic, a~sous iron solution according to Exa~npl~e 2. When blending was stopped, complete separation of the ae~-ueous and organic phases rec~a.ired 120 minutes. The short disengagement time for phase separation of the extractant containing an N-ethyl alkanohydroxamic acid provides a significant 1t~ commercial utility compared to the prohibitively long disengagement time for the extractant containing the , N-methyl alkanohydroxamic acid.
EXLaE 3 Th~.s ~xaanple further illustrates the utility of an IJ-ethyl h'ydroxamic ac:8,d of t~i~.s l.~ivention in extracting iron from aqueous solutions and the rapid phase: d~aengagem~nt of er~ctaa~t from ac~e~u~ solo-tion~. The 3.ron extraction procedure of Example 2 was r~~aeated with the f~11~wing modification~ the pFi ~f the aqueous ~:~con soluta.or~ w.as raised to 2 . ~ by addi-ti~n of 1~ 3d sodium h~rdrbxide solut~.on and EXT~C;TAI~TT
Haas blended with the ac,~u~o~as ~r~n solution for 3~
~ai~x~tes a den blend~.ng was Mopped r co~npl~~ce separ~-tion ~f the aqueous; anc~ ~rganic phases w~~ ~ffedted ~:n 2~ less than ~~ seconds. her 99,P~rc~n~ ~f ~a.e i~~an was extracted from the aqt~e~~as s~lu~3.~~.
C~1~I'AE ' P3~ 3 Tfii~ it~n extraction p~coc~lur~ bf Ex~a~pl~ 3 ~~a~ ~~p~at~~ ~a~~ng~~~e ~n ~len~~ng.~ar~7' ~ Mopped, the ~~ueeaus anc~ organic phases were are emul~
sioaa fat fail,~~ to separate. .
EdPZ~ ~
This eacample illustx°at~s the ability of an ~~~f;hyl al~anohydroxam~.c acid ~xtx~ct~nt solutioa~ of 35 this invent~.on'to bye rapidly stripped df metal b~
strong ac~.d stripping soluti~ns co~ta~.ning high can-d~ntrations of strip~aed iron. fix 1~ ml volua~ds of :Y'1 r.
wvo ~3roxoa~ '~,.~~,. ~.~ ~4~ ~'i ~ ~~rrus~xros~xx i iron-loaded EXTR~.CTANT A from Eacampla 2 were sequen-tially stripped of iron by blending with a single l0 ml volume of a ~0~ acid stripping solution containing 20 weight percent sulfuric acid and 20 weight percent phosphoric acid. Each 10 ml volume of iron-loaded EXTItACTP~1T A was blended with the 10 ml volume of stripping acid for 2 minutes, the phases were allowed to separate (phase disengagement was effected within 1-2 minwtes) and were decanted. The concentration of iron in 'the stripping solutions was deter~ained to be 1.3%, 2.8%, 4.3%, 5.~%, '7.~.%, and 8.4% iron, respec-ti~ely, after each contact with an EXT~CT~%T 1~ solu-tion. Iron concentration in the strapping solution increased with each mixing with fresh eattractar~t with Z5 no .indication of maturation of the stripping solution.
In a similar experiment a ~~% acid stripping solution was loaded to 1.4.1% iron from iron-loaded ~EXT~CT~NT A
C~t~iPTIi~E EP4 Seven la ml vblu~~s of ison-loaded ~XTB~C-' T~iT B from Comparative Exar~p~.e 2 were sec~a~ntially stripped df stun by blea~ding ~rith ~a sin~g3.e l0 ml vol-u~~ of a 40~ acid scrapping s~l:uti~n of Example 4.
each 10 ~l vvol~me ~f it~r~-loaded EXT~CT~TT B waa blended wit~i the 1~0 ml ~oiu~e of shipping acid f~r 2 minutes, the phases wire allowed t~ separate (d.~.s~h~°
~a~e3aen~t reared x~S ~a~;nutes) aa°~d! were 'decanted: The ~oncentrat~:~an of i~~n 3.n the strapping solu~ioa~s ~ra~
~~~ i,8%, ~.~%, 3:3$, 4.7%, 5% ahd 5.3%~ respectively, aft~r~a~rh contatst within. ~B..solution.
1~, c~mpar~.s~n ~f the results of Example: ~ aid ~omparat~.v~ Example ~ indicates that enhanced, ability ~f N-ethyl deGanohydroxamic adid ~o release ~complexed iron into 40% stripping acid containing at least up t~
8.5% iron: the'saturati~n level f~~r stripping ~actr~c-tents of N~methyl de~anohyd~oxamic acid appears ~o b~
about 5.a~~.ln ~~~s~rlpp~.ng. ac~.de Thl.s ~nd~~rat~ws that 4 ~~ °~o ~~ F.~ ~ v wt~ ~3iozo4~ ~ . -~. P' ~ : ~ u~ ~c: rri~~gz>os~zz iron can be ce~ncentrated to at least a 55% higher level in the 4~0% acid stripping s~lutions when the extractant contains Id-ethyl n-decans~hydroxamic acid compared to ~1°°methyl n-decanohydroxs.mic acid.
EXA~iP~E 5 This example further illustrates the ability of an N-ethyl al~canohydrs~xamie acid extractant solu-tion of this invention to be rapidly stripped of metal by weakex acid stripping solutions containing stripped iron. Six 10 ml volumes of iron-loaded ExT~~TC .~
from Example 3 were sequentially stripped of'it~r~ by , b~.ending with a single 1t3 aail volagme of a 10% sulphuric acid str:~pping solution. Each 1~~? and ~roi~e of iron~-loaded ECTa.A was blended with tae 10 ~a~. vc~lua~e of stripping acid f~r ~ minaates, the phases were allowed to separate (phase disengagez~ent was effeoted within 3-5 minute, end were: dec~y'lted. The concen-tration of iron a.n the stri~apa.ng solution was 1. 3 ~ , ~.2%, 2.~%, 3.4%, 3.3%~ end 3.~%, respecta.~r~ly; after z0 each contact with 'aaa EX'.'~ s~laata:~n.
c~ra~~~v~; ~r.~ 5 ~ ~;~ and: v~~.um~ - ~f t~r~ a.r~n~~.o~aed ~
E from Comp~~a~ive Exaanapl~ ~ was blended with a 1~ m1 ~rolaxme of. 10% sulfu~~.c acid stripp~:ng solution. l~ftc~r ~~ hour s tdEe, phar7~shG6d n~t a~'. ~p~~at~nd s 1~ ' do~p~ri~~n ~ti.t~ the aresaa~.ts ~~ Examp~~ 5 ill;ust~~t~~ tlae ea»haaaoed a~il~.ty of N~~thyl b~-ehc~no--hyd~ox~m3.~ ~cisl tt~ ~el:ease ~~m~l.~x~d ia:°on ints~ stxip~
ding so3~utions conta3ni~nc~ ~n1y su~.furic acid ~.s coma 3 0 p~re~ to N-methyl h-~d~eoanahydr~ataa~ic ~adid .
~PIaE ~
This examp:~e illustrates the brag , t~hy~
~ro~;ytic ~taba~l~.ty ~~ ~g~~t~xy7 al%anohydroxa»ic ~ci~s~
~f~ ~ of a ~oluti~n of ~.0% ~y w~fght td~ethyl d~cano 35 hydraxamic aoid in KEa~~ 4'~0~ ker~sene°bas~d colorant ~on°ta~.hing 5% day voluaae is~de~canol was blended coratin-u~usly at roc~an t~emperataar~ with 50 g of a 40% acid P'L'~'liJS92/056~2 W9D 93/02047 1 ,; ~~ c, ~ ~; a ~.~2~
t stripping solution (according to ~xax~pla 4). The hydroxa~nic acid was gradually hydrolyzed so that about 85~ of the hydroxaaaic acid r~~nain~d after C~ days and about E0~ re~aain~d after 18~ days. .
CO~'F'~A'T°l~ EI~'IrE . 6 The procedure of Exa~pl.e ~ was repeated t using N-~aethyl n-decanohydroxa~aic acid which was hydrolyzed so much that about 25~ of the hydroxa~nic acid re~aain~el after 5~ days.
0 ~P~E 7 This example illustrates the advantageous , ~ solub~.li~y characterista.cs of concentrated (50~) solaa-tions of Nf-ethyl alkanohydroxamic acids. The hydrox-a~nic acids indicated in Tabie 1 were mixed with equal 15 parts by weight with kerosene at 23 "C. t~eri tie mixture provided a solution, the lcine~atic viscosity was determined ~a~ flowing the solution at ~3 'C
thr01$t~h ~ CF'~YlI10T8-~'~11~~C~ R01,8t~Il~ 'VS.~CO~~t~r, ~1~~ ~.r'J~, obtained frog ~ar~non Instr~aent ~o~pan~r, State 20 ~oilegre, P~r~~sylvan~,a.
~~r~l~ 1 vd b ~~~~sd~ "~yv N-~thy1 ne~decano- 1~..3 ~m2Js (cst) -~y~, n~decara~- 15 a 3 ~~ ~-ethyl i~ostea~~- 14~~
~o~~a~at~~~~~a~~~~~o ~-eyl naphtheno- '22 ~ ~yl, i~o~tear~- l:~ ~ 5 -ethyl. n-.d~c~t~o- solid ~aa~te 30 N-m~thy7: naphth~no- 28 ilk spec3.fic ~~aodi~aerats have beer described Bahrein ~ 3t staauld b~ app~r ent t~ th.o~~
~l~illed in the art that various ~~clif~.cat~.~aras thereof ~~n be ~aad~ wighotat departing fro~a the tree spirit arad 35 scope of the ~:~~renti~n. ~dcvrdin~~.y, ~t i~ intended ' that the following clai~as ce~rer ~1~. such a~odi.fic~tion ~ait'hin tae full ~.n~remtiv~ c~ncept.

Claims (11)

WHAT IS CLAIMED IS:

1. N-ethyl alkanohydroxamic acid wherein said alkyl group is a straight chain alkyl group of 8 to 10 carbon atoms, or a branched alkyl group of 8 to 18 carbon atoms, provided said alkyl group is not cyclic.

2. N-ethyl hydroxamic acid according to claim 1 selected from the group consisting of N-ethyl n-octanohydroxamic acid, N-ethyl, 2-ethylhexanohydrox-amic acid, N-ethyl n-nonanohydroxamic acid, N-ethyl n-decanohydroxamic acid, N-ethyl neodecanohydroxamic acid, N-ethyl neotridecanohydroxamic acid and N-ethyl isostearohydroxamic acid.

3. N-ethyl hydroxamic acid according to claim 2 consisting of N-ethyl n-decanohydroxamic acid.

4. An organic metal extractant solution comprising a kerosene solvent and at least 50 weight percent N-ethyl alkanhydroxamic acid wherein said solution has a kinematic viscosity at 23 °C less than 20 mm2/s, wherein said aryl group is a straight chain alkyl group of 8 to 10 atoms, or a branched alkyl group of 8 to 18 carbon atoms, pro-vided said alkyl group is not cyclic.

5. A solution according to claim 4 wherein said N-ethyl hydroxamic acid is selected from the group consisting of N-ethyl n-octanohydroxamic acid, N-ethyl 2-ethylhexanohydroxamic acid, N-ethyl n-nona-nohydroxamic acid, N-ethyl n-decanohydroxamic acid, N-ethyl neodecanohydroxamic acid, N-ethyl neotride-canohydroxamic acid and N-ethyl isostearohydroxamic acid.

6. A solution according to claim 5 wherein said N-ethyl hydroxamic acid consists of N-ethyl n-decanohydroxamic acid.

7. A method of extracting metal from aqueous solutions comprising contacting said aqueous solution with an organic solvent solution containing an N-ethyl alkanohydroxamic acid to extract said metal into said organic solvent solution as a complex of said hydroxamic acid, wherein said alkyl group is a straight chain alkyl group of 8 to 10 carbon atoms, or a branched alkyl group of 8 to 18 carbon atoms, pro-vided said alkyl group is not cyclic; separating said solutions; contacting said separated organic solvent solution with an aqueous stripping solution at a pH
less than 5 or greater than 9 to strip said complexed metal from the hydroxamic acid into said aqueous stripping solution.

8. A method according to claim 7 wherein said organic solvent solution comprises kerosene and at least about 50 weight percent of hydroxamic acid selected from the group consisting of N-ethyl n-octanohydroxamic acid, N-ethyl 2-ethylhexanohydrox-amic acid, N-ethyl n-nonanohydroxamic acid, N-ethyl n-decanohydroxamic acid, N-ethyl neodecanohydroxamic acid, N-ethyl neotridecanohydroxamic acid and N-ethyl isostearohydroxamic acid.

9. A method according to claim 8 wherein said N-ethyl hydroxamic acid is N-ethyl n-decano-hydroxamic acid.

10. A metal extractant solution comprising an organic solvent and an N-ethyl hydroxamic acid selected from the group consisting of N-ethyl n-octanohydroxamic acid, N-ethyl 2-ethylhexanohydroxamic acid, N-ethyl nonanohydroxamic acid, N-ethyl n-decanohydroxamic acid, N-ethyl neodecanohydroxamic acid, N-ethyl tridecano-hydroxamic acid, N-ethyl 2-hexyldecanohydroxamic acid and N-ethyl isostearohydroxamic acid.

11. N-ethyl N-decanohydroxamic acid.