Патент USA US3036891код для вставки
United States Patent 0 _‘ aasassi Patented May 29, 1962 1 2 3,036,881 Still another object of the invention is to provide a catalytic method for promoting the oxidation of uranium in a carbonate solution with air, oxygen gas, and hypo CATALYZED OXIDATION OF URANIUM IN CARBONATE SOLUTIONS Warren E. Qliiford, San Francisco, Calif., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Com chlorite oxidizing agents. One other object of the invention is to provide a car bonate leaching process employing hypochlorite oxidiz ing agent for the more economical leaching of lower valent uranium compounds and minerals from solids. A further object of the invention is to provide catalyz 10 ing agents for promoting the oxidation of lower valent The invention relates, in general, to the processing of uranium ionic species and/or uranium compounds in uranium in a carbonate solution and, more particularly, a carbonate solution. to improved methods of catalyzing the . oxidation of A still further object of the invention eiseto provide 8. uranium in a carbonate solution. catalyzed oxidation carbonate leaching process for im Aqueous solutions of alkaline carbonates are used ex 15 proving the recovery of uranium from ores containing tensively for leaching uranium from various solids such uranium in lower valent oxidation states. as ores and residues in a variety of recovery and puri?ca Other objects and advantages of the invention will tion processes. The carbonate solutions are alkaline and become apparent by consideration of the ‘following de contain variable ratios of carbonate and bicarbonate ions scription. dependent on operating pH conditions. In such a solu 20 The starting material in the present process may com tion hexavalent uranium is complexed by the carbonate prise uranium oxides such as U303, U02, lower valent ion to form uranyl tricarbonate ion, UO2(OO3)3-4, as hydroxides such as U(OH)4 or primary~secondary urani the soluble species; however, at least a part of the uranium um minerals such as carnitite-uraninite ores, all of which mission No Drawing. Filed May 23, 1957, Ser. No. 661,264 9 Claims. (Cl. 23-145) in such ores and residues often occurs in a lower valent oxidation state which does not readily produce a species 'which is soluble in such leach solutions. Also, the uranium may be partially reduced by contact with steel processing equipment or other etfective reducing agent during mining or preliminary processing. For example, if a uranium mineral such as pitchblende, uraninite or co?inite is present in the ore the carbonate leach solution does not eifectively dissolve all of the available uranium since the lower valent states, especially the tetravalent, does not dissolve in the solution or react to produce insoluble hydrous oxides or hydroxides on contact with the ore. Under other process conditions in which the leach solution contains an excess of CO3= and the OH“ is buffered out with H003“, a soluble tetra may contain uranium in oxidation states lower than the hexavalent and particularly the uranous and mixed uranous-uranyl states. Residues obtained in other proc esses and having generally similar characteristics may likewise be processed. Solutions or other materials con taining lower valent uranium compounds can likewise be converted to the carbonate form and the oxidative proc ess of the invention applied thereto. The ore materials or other solid, if necessary, ‘are ?rst subjected to grind ing and screening to provide the proper particle size to render the uranium content accessible to the leaching solution. 'Customarily, particle sizes in the vicinity of minus 100 mesh are adequate; however, with certain ores, e.g., limestones, grinding to nominally minus 325 mesh may be required. Solutions are converted to the valent uranium carbonate may ‘be produced; however, carbonate form by adding Na2CO3 or NaHCO3 thereto. this complex is very unstable if the OH— concentration 40 In accordance with the invention, the iinely divided increases during processing and uranium can be lost source material is disposed in equipment adapted for from the solution by precipitation as U(OH)4 at an in-, heating, agitation, and the introduction of reagent solu appropriate time in the procedure. In conventional prac tions and gases if air or 02 is to ‘be employed as the oxidant. The solid is then contacted at elevated tem This tice, procedure uranium ores is not mayalways be oxidized effective,byentails roasting additional 'in peratures with an aqueous alkaline carbonate solution operations and equipment, and cannot be applied to under catalyzed oxidizing conditions to selectively leach solutions. Chemical oxidation may be slow and reagent uranium therefrom. In the event that vanadium is pres cost high. ent some vanadium is also leached; however, most other The present invention is predicated on the discovery 7 materials which are present in ores and residues are not leached to any great extent. 50 valent states of uranium in such a solution with the More particularly, carbonate solutions containing from that certain metallic ions catalyze the oxidation of lower oxygen in air, 02, and also by hypochlorite. Such catal ysis is made more effective by the provision of superior operating conditions and combinations of reagents in oxidizing uranium contained in carbonate solutions in general, and is equally effective in oxidizing uranium pres- a ent in solid materials during leaching operations thereby ‘preventing the formation of insoluble lower valent hy droxides in such solutions and speeding up as well as in about 4 to 10% of sodium carbonate and/or from about 0.25 to 7% of sodium bicarbonate are generally used. Certain very favorable ratios and regent concentration limits of the reagents and concurrent pH conditions will be set forth hereinafter. For the purposes of the invention catalytic quantities of compounds of certain metallic elements are added to the solution to provide ionic oxidation states of the creasing the amount of uranium leached thereby. Sub metals which effectively promote the oxidation of the sequently, the carbonate solution may be processed for 6 uranium in the solution. In theory the ions of any ox the recovery of uranium by various procedures includ idation-reduction couple above OHr-air and UO2-— ing processes as conventionally practiced, e.g., in the do UO2(CO3)3—4 could act as a catalyst; however, it is found mestic mining industry. ‘experimentally that some substances meeting that quali Accordingly, it is an object of the invention to pro ?cation and which will oxidize reduced uranium com ‘vide a catalytic process for promoting the oxidation of Ga 5 pounds when introduced in the oxidized state are not lower valent uranium compounds in an alkaline carbonate effective when introduced in the reduced state. These solution. materials include PbO-PbOg, Fe(CN)(,-4---Fe(CN)6-3 Another object of the invention is to provide a cata and Hg——HgCl2. These materials therefore cannot be lyzed air oxidation method for use in the carbonate have in a catalytic fashion. > leaching of uranium containing solids to improve the Ionic species corresponding to the oxidation states recovery of uranium therefrom. of the following couples produced by the addition of 8,036,881 3 4 solutions by reducing agents such as Na2S2O'4, Zn and ammonia, and Zn and cyanide. Treatment with 0.2% sodium amalgams ?nely dispersed in solutions at about appropriate compounds to carbonate solutions are cata lytically active in oxidation with 02 or air: C+ +--Co+++; V+4—V+5; Tl+-—Tl+3; and Mn+2—Mn+4 or possibly 25° C. also precipitates the uranium as a hydrous oxide. Mn+3--Mn+4 on consideration of the oxidation poten tials. The ions of the couple Cu+--Cu++ are very eifec Necessary conditions and procedures for obtaining bene?cial results in accordance with the teachings of the invention will be apparent from the following descrip tion of systematic experimental studies of various op tive for the indicated purpose. Moreover, the catalytic eifect of the Cu species is greatly enhanced on addition of ammonia to the system and the Cu catalysis is also effective when using hypochlorite (or C12) as the oxidant. Consideration of the various couples indicates that suit able couples require, as a minimum, that the oxidation erating conditions. At the outset, the distinctive behavior of various ad ditive agents with reference to oxidative leaching was ex potential be above the OH--air couple and about equal plored using a standard procedure. wherein various to or greater than the H2O2—HO2'— couple consistent with the view that oxygen reduction which is concurrent taining 0.5M Nazcoa and 0.5M NaHCO3, in contact with with uranium oxidation proceeds stepwise through perox ide. The potentials of the foregoing couples are dis closed, for example, in chapter IV,, under “Oxygen” of amounts of the agent were added to a leach solution con 15 5 g./liter of U308 at a temperature of 90° C., with air blown at a standard rate therethrough and for a standard time period. A number of control runs with no additive were made to serve as standard, giving a range of 20 to “The Oxidation States of the Elements and Their Po 30% of the U303 being dissolved. From the results, tentials in Aqueous Solutions,” by Wendell M. Latimer, published by Prentice-Hall, Inc., 1938. The above-indi 20 tabulated below, the materials can be classed as in~ hibitors, as having no effect, as being oxidants, or as cated catalytic species are produced on the addition. of being catalysts.‘ The di?erentiation between the latter compounds such as KMnO4, MnO‘Z, MnSO4, CuSO4, is made on the basis that catalytic agents improve the Cu2O, CuCl2,TlNO3, and V205 in amounts ranging from leaching when either the oxidized or reduced form of 0.1 mg./liter for the more effective catalysts such as the copper couple to a few grams/ liter of the less e?ective 25 the agent is introduced, while oxidants improve the leach ing onlywhen the oxidized form is added generally in materials as discussed further hereinafter. much larger amounts than is required for catalysis. 'In practice, leaching is conducted at temperatures TABLE I Agent (Inhibitors) Percent Agent (No Effect) Leached 25 g./1_ FeSO4 ______ .; ___________ -. Percent Leeched 1 5 g./l. Na indigodisulionate ____ __ 25 g./l. Pyrogallolm? _. 1 5 gJl. Na diphenylamine p-sul» 25 g,/l. NH1OH~HCL_ -_ 3 .._ 6 5 g./l, SnClz-ZHzO .............. __ 5 5 g./1. Quinhydrone-.. 20 ionate _______________________ __ 20 5 g./l. Na 1-10 phenanthroline monohydrate. _ 20 25 30 30 25 15 20 Agent (oxidants) Percent ' .25M H201 ..................... -_ ___ . . Agent (Catalyst) Percent Leeched . Leeched 100 55 100 . 30 . . 5 g./l. - 75 v 5 g./l. P - 20 5 g. . 5 ELI]. - 100 5 g./l. 011504515120“ _ 100 5 g /l. .. 25 8.5 gJl. OHSOA’SHZO +NH4OH_ 100 5 gJl. _ 50 5 all. C1120 ____ _.'_____________ __ 70, 85 5 g./1. _ 100, 90 5 g./l. CoO1z-6Hq0 _____________ -- 55 5 g./l. _ 100 5 g./l. OOOln-GH; +NH4OH 45 5 g./l. 5 gJl. Hg __________ ._ 8 g./l. NaC10(Purex)_. _ _ _ 100 20 85 5 g./l. TIN 5 g.[l. 45 60 above about 80° C. and preferably at about 90° C. toob I A standard procedure and experimental apparatus was 5 employed for a more complete elucidation of the oper tain maximum rates and degrees of dissolution. The oxidant, if air or 02, is bubbled continuously through the agitated mixture, if hypochlorite, is added incrementally ' ating conditions‘using U308, U02, .ulraninite and other ores. 300 m1., of leach solution. was disposed in a ‘500 C12 gas should be 7 ml. 3-neck'flask and the system‘ purged with the test gas leach solution by a variety of conventional ?ltration or ‘desired level and solid containing uranium equivalent to 1 g./liter of solution was added. Copper and other 675 catalysts were added as solids-or solutions, e.g., CuSO4 or at the beginning of the leaching. equivalent to the hypochlorite and other strong oxidizing 60 (air, 02, or N2) and a bubbling ?ow of about. 10 mL/min. of the gas was continued during the experiment with agents should produce similar results. Following leaching, the uranium is separated from the’ . ,Oontmuous stirring. I Thetemperature was brought to the centrifugation processes. The uranium can’ be'precipi tated from leach solutions containing vanadium as a syn thetic carnotite by acidi?cation to a pH of about solutions. ' Samples were taken hourly and uranium de 6 from which the uranium and vanadium can be obtained a. V termined’ ?uorinietrically. ' as U02 and V205 by standard processes. The uranium can also be recovered and puri?ed from such solutions ‘ l" compositionof U03 (Shattuck) at'1100°' C. yielding a A. stock quantity of UaOs'was prepared by the de by adsorption on a strong base anion exchange,’ resin 7 0' material whose X'-ray diffraction pattern‘ agreed with that given in ASTM 'data card No. 4-0518. The U02 such as Dowex 1 followed by selective elution as .dis closed in the copending application of Richard ‘H. Bailes et -a1., Serial No. 362,122, ?led June 16, 1953, which issued as Patent No. 2,864,667 on December 167,‘ 1958. ' Was also obtainedfrorn S. W.’ Shattuck _Co., lot No. 10054:and, yielded 'X-rayzdifr'raction data typical of pre pared UO2. j ;Uraninite labeled “'Urananite (Pitc'hblende)” Uranium is also precipitated ‘from such carbonate leach" 75 from theGreat Bear» Lake area and analyzing 50% U303 3,036,881 5 6 was obtained from Wards. The ores, all ground to —l00 mesh, tabulated below were also used. It is to be ex substantial amounts of sodium salts were used to leach U308 at 90° C. air bubbling with other conditions and results tabulated below: pectedpthat lots of di?erent origins and different meth~ ods ‘of preparation will vary in behavior; however, re sults with identical lots will be self-consistent and ac TABLE V ‘curately indicate consistent trends in the several varia tions of the process described hereinafter. TABLE II _ 10 Ore Percent Percent Percent Percent V205 Monticello N o. 27__________________ __ ACM Grey Special ________________ __ 0. 16 0.96 0.06 trace Garwood & Gerlock No. 10453 _____ ._ 0. 43 1. 35 Big Buck No. 10521-___'_____'_ ______ __ 0.38 0.03 CaCOa V leached per hour Analyses of Tested Ore 3 8 Fraction U305 Conditions .5M Na2CO3—.5M NaHCO3, 25 mg./1. Cu ___________ ._ 0.14 .5M NazCO3—.5M NaHCO3, 25 mg./1. Cu, AM Na1SO4_ 0.14 .9M Na2CO3-—.1M NaHOO; _________________________ _- 0.035 .9M NtizCOr-JMI NaHCOa, .41“ NaNO; ___________ -_ 0. 040 Fe 6.16 92.8 2. 90 0. 26 9. 96 0. 40 . 1. 68 0.28 As may be seen therefrom, variations in ionic strength have little, if any, eifect on leaching rates. EFFECT OF COPPER CATALYST CONCENTRATION Leach rate variations with various copper catalyst con centrations, added as CuSO4 solution, were determined EFFECT OF SOLID CONTENT IN SOLUTION The effect of variations in the amount of solid source using two different leach solution compositions, with both air and N2 bubbling at 90° C. to leach U308 with the results tabulated below: material present in the solution was determined using 25 mg./liter of Cu added as CuSO4 at 90 C. air bubbled yielding the maximum leaching rates with the leaching solutions as tabulated below: TABLE 25 TABLE VI Fraction UaOs Leeched Per Hour Fraction U309 leached per hour Conditions ' 1 g./1. max. 2 g./1. max. .5M NazCOz-—.5M NaHCOa ____________ __ 0.14 .'5M NazOO3—.5 NaHCO3, .lM NHQOHH 0. 30 0.31 .9M NélzC 03——.1M NaHCOa ____________ _- 0. 23 0. 24 Air Air 0. 15 As anticipated the initial leaching rate, i.e., the max. rate, is directly proportional to solid content within ex perimental error; however, since the relative rate of leaching was essentially independent of the solid content the remainder of the experiments were done using solid It will be seen from the foregoing that the leach rate equivalent to 1 g./l. of U308. That the absolute rate increased with increasing Cu catalyst concentration in of leaching does not fall off as rapidly as might be ex all cases although the power dependence is considerably pected may be due to the fact that surface area (to less than one. The remarkable effectiveness of the cat which the rate should be proportional) does not decrease 45 alysis on air oxidation with even very small amounts of as rapidly as the volume (to which the weight is pro Cu is apparent. Under N2 the dependence on Cu ap portional). The large increase in extraction rate using pears to be approaching the ?rst power at low Cu con— ammonia is apparent therein. centrations. Under air the dependence is much less even correcting for direct air oxidation which might be oc TEMPERATURE EFFECT 50 curring simultaneously. Note that at 25 mg./l. On the 0.5M Na2CO3—0.5M Natl-I003 solutions catalyzed with Cu(lCuSO4) with and without ammonia were used ‘to leach U308 at 70 and 90° C. with air bubbling and with the results tabulated below: TABLE IV Conditions rate under N2 is much lower than under air even ‘when the latter is corrected for air oxidation. This observa tion can only .be explained by the formation of oxidizing species other than cupric in the air ‘blown system. The 55 obvious explanation is the formation of peroxide in the reoxidation of cuprous ion or copper metal if, during the catalytic reaction, the cupric state is reduced to that ex Fraction U508 leached per hour tent. Various mechanisms are possible to explain the results 90° C 70° C O. 019 0.009 25 rug/11. ou ............................ _- 0.14 0.043 25 mgJl. Cu+.1M NHAOH _____________ -. 0.29 0. 074 60 although simple mechanisms alone cannot explain the data, i.e., that the rategunder air (corrected for meat ialyzed direct air oxidation) is .10 65 The results indicate that leaching at temperatures as - .0364‘? times that under N2 instead of twice or four times which may be explained by simple mechanisms. C. is much more preferable so that the remainder of the experiments were done at 90° C. At temperatures above EFFECT OF INCREASED O2 CONCENTRATION 70 80° C. the leaching rate increases at a rapid rate. U 303 was leached under standard conditions described EFFECT OF IONIC STRENGTH V low as 70° C. are uneconomical and that leaching at 90° above at 90° (3.; however, 02 was bubbled through the leach solution of the character and with the results tab ulated below. The results of comparable operations tion pairs in one of the members of which was included 75 with air are included for comparison. Since pH changes in a CO3=-—HCO3- system result in large changes in ionic strength, controlled leach solu 3,036,881‘ 8 mainingconstant, CO3: concentration and pH are inter related. The change in ratio of 0.5M Na2CO3-—0.5M TABLE VII H003‘ to‘ 0.9M Na2CO3-—0.1M'NaHCO3' corresponds Fraction Conditions U303 Leached Per Hour to a pH change from 9.9 to 10.9 or a‘factor of 10 in OH- concentration. The bene?ts'to be derived’ from Air operating with CO3=/-HCO3— ratios givinga'pI-I near 10.9, i.e., a practical range of about pH 10.5 to 1121 being 02 indicated, are obvious. .5M NazCOa-.5M N aHCOa ____________________ __ 0.01 0.04 .5M Na2CO3-5M NaHCOa, 2.5 mgjl. Cu“, ____ __ 0.11 0.12. NH4OH _______________________________________ -_ 0.165 0. 17 .9M NazC03-——.1l\/I NHHCOx, 2.5 mgJl. Cu ...... _- 0.19 0.23 .5M N22C0$——.5M NaHCOg, 2.5 mgJl. Cu+.1M . . . CATALYTIC ENHANCEMENT ‘VITH COMPLEXING 10 ' AGENTS ' Leaching solutions of constant 0.5M NagCO3--0.5M NaHCOa composition with various complexing agents present were used to leach U303 at 90° C. with air bub It will be noted that the use of 02 increased the leach ing rate slightly; however, the increase is no more than which can be accounted for by the expected increase in normal uncatalyzed oxidation. The use of 02 produces no increase in the rate of catalyzed oxidation and leach bling with the results tabulated below: TABLE X Fraction ing. Conditions > U305 Leeched Per Hour EFFECT OF VARYING TOTAL CARBONATE SPECIES CONCENTRATION 25mg./l. Cu __________________________________________ __ 25 rug/l. Cu +.1M NH4OH_____ ____ 25 mg/l. Cu + .lM Pyridine__.. ...1 ‘Pairs of catalyzed leaching solutions having two dif ferent ratios of CO3=/HCO3- at two different total con centrations were used to leach U308 at 90° C. with air 25 mg/l. Cu +.1M NaCN ____________________ __ -.__ 0.017 25 mg./l. Cu as C11(NH2CH2CHzNH2)2(NO3)2 ________ __ 0. 16 bubbling under standard conditions with the results tab ulated below: TABLE VIII It will be observed thatammonia greatly increased the rate while pyridine and ethylenediamine have a slight bene?cial e?ect. Cyanide had a strong adverse eifect Fraction explainable by the fact that CN- complexes the cuprous U303 Leached state so strongly that reoxidation cannot take place and r Conditions Per Hour the catalytic cycle is blocked. The ammonia undoubt .5M NagCOs-JSM NaHCOg, 25 mgJl. Cu ____________ __ 0.14 .25M NazCOa—-.25M NaHCOa, 25 mg/l. Cu_- 0.14 .9M NarCO3—.1M NaHOOS, 25 mg./l. Cu.-. .45M Na2CO3--.05M NaHCOg, 25 mgJl. Cu__ 0.14 0. 29 0.17 _ _ edly converts the copper to a more e?ectiveionic species having different charge characteristics and more favor able oxidation-reduction potentials than those present in 0.23 0.16 the absence of ammonia. ‘ , COPPER-AMMONIUM CATALYSIS VARIABLES -It will be noted that a CO3=/=HCO3— ratio of 1, the (1) Concentration of catalyst: Pairs of indicated change in total carbonate species concentration ‘ produced no change in the leaching rate. At a ratio of 9, the rate fell 0E considerably indicating that the leach 0.5M Na2CO3—-0.5M NaHCOa solutions containing diiferent amounts of Cu(CuSO4) ing rate is critically and increasingly dependent on the HCO3- concentration in the range of 0.05M to 0.1M with and without ammonia added were used to leach UaOa-at 90° C. and with air bubbling, with the results tabulated below: than it is in the range of 0.25M to 0.5M. Also, the rate TABLE. XI at 0.45M OO3=—0.05M HCO3— is higher than at 0.5M CO3=-0.5-M HCO3" even though the total concentra tion of carbonate species as well as HCOg'" is lower. These facts indicate that the variations noted are attrib— utable to pH variations and not to ionic strength or total carbonate concentrations, a deduction which is con?rmed hereinafter. Fraction U305 Leached Per Hour Conditions _________ __ .5M NazOOg .5M NaHCOa .5M NaHCO3—— Ratio EFFECT OF VARYING pH Pairs of solutions with varying amounts of @801 catalyst with ratios of 1:1 and 9:1 of CO3=/HCO3" were used to leach U308 at 90° C. in’ air and N2 with the results tabulated below: . ' a _ a. 55 TABLE IX Fraction U30, Leached Per Hour' j 1 Conditions _________________ __ .5M NazCO1-1 jfiM N211CO3- j;Ratio .5M NaHOOa .lM NaHCOa V As may be noted the rate of leaching increases much more rapidly with increasing Cu(NH3)4++ concentration than'with Cu. (ionic species) alone, though the depend ence is still less than'?rst power. .The enhancement ef fect of ammonia. may be quite speci?c for copper since 60 in similar e'irperimentswith Cot+ and 0.1M NH4OH ' ‘the rate was only 0.021 ‘as’ compared to 0.020 for no . . 0. 074 0.12 . 0.11 0.185 5 mg /l. Ou(air) 0. 14 0.23 0. 036 0. 0s 2. 2 ' 0.10 0.14 1. 4 25 rug/l. ou(N2)___ -- > 125 mg./l. 011(Nz) ___________ -_ » 1. 62 catalyst as above. 1. 68 (2) NH4OH'concentration'e?ects: Solutions contain ing 0.5M Na2CO3'—'0.5M NaHCO3 and equivalent 1. 64 65 , r ' amounts of Cu (25 mg.)?w.ere usedv to leach U308. at 90° C. with air bubbling withthe'results tabulated below: It will be noted that'increasing the ratio of ' ' from 1 to 9 increased the rate. of leaching ‘in all'cases. 70 ' r ' TABLE r ' ' " ' V XII ' 1 ' ' Fraction U308 Conditions When the ratio was changed to 0.11 the’, leachingrate was lower. The leaching rate ratios. under 'air?are re markably constant indicating the complete elfectiveness . of even very small amounts of Cu catalystunder vthe’ ‘ Leached Per . Hour intimation;..;.l._r;_...--_rV 0.29 ,25M NH1OH___ _____ .5 _____ __ 0. 29 indicated conditions. With total carbonate- species re— 75'. 3,038,881 10 It will be observed that increasing the ammonia con Various ores were leached for 6 hours at 90° C. with centration from 0.1M to ‘0.25M had no effect. The air bubbling with the results tabulated below. Control possibility that the catalytic couple is runs using a standard oxidant are included for com parison. TABLE XV Ore Leaching Results Percent U305 Leaehed .5M NazOOa .9M NagCOrJM NaHCOs .5M NaHCOa, .IM NH40H Ore 600 mgJl. N0. Cat. 25 mg./l. Cu KMnOl 25 mgJl. Cu 67 65 77 78 . AOM Grey Special _______________ __ 47 66 47 89 63 90 58 96 Garwood and Gerlock No. 10453.... 74 86 94 94 is therefore doubtful since the ammonia concentration As may be noted the copper-ammonia catalyzed aerat would effect the potential of such couple thereby aifect ed leaching is at least as good if not superior to any ing the leaching rate. This circumstance may indicate other tested. The results with the indicated ores would 25 that the catalytic couple involves a mixed ammonia-car be further improved with ?ner grinding in accordance bonate complex, e.g., Cu(NH3)2+—Cu(NI-I3)2CO3. It with conventional practice. is apparent that ammonia concentrations lower than 0.1M should also be effective, e.g., 0.025 or 0.050 and above. ' HYPOCHLORITE OXIDATION AND LEACHIN G While copper catalyzed aeration oxidation leaching, 30 especially with ammonia, is very economical and at least CATALYTIC LEACHING OF OTHER SOLIDS as good as any other, the required equipment may some times be more complex and engineering costs are some Carbonate solutions were used under control and var~ ious catalyzed conditions to leach U02, uraninite and what greater than using standard chemical oxidants. various ores at 90° C. with either air or 02 bubbling and‘ with the results tabulated below: 35 Permanganate has generally been found most elfective TABLE XIII found that hypochlorite oxidation is quite rapid and ef ?cient and, moreover, is also improved by copper catal ysis. The equivalent reagent cost of hypochlorite is less in conventional practice. U02 Leaching Results Fraction U02 Leaehed Per Hour Conditions .5M NaiCO;—-.5M NaHOO3—air ____________________ __ .5M N a2O03-—.5M N aHCO3+25 n1g./l. Ou-air ______ __ NH4OH-air ___ ____ __ 40 than with permanganate. For example, a 25% excess of hypochlorite over the stoichiometric amounts required to oxidize 0.0037M U02 gave 100% leaching with a car bonate leach solution in 6 hours at 90° C. Variables in hypochlorite leaching were studies as follows: 0. 038 0. 040 .5M N azCO;-.5M NaHOOa+25 mgJl. Ou+.1M However, it has now been 45 HYPO CHLORITE CONCENTRATION 0. 083 .5M N &2CO3—.5M NaHOO3+25 mgJl. Cu+.1M The effect produced by varying the hypochlorite con centration was determined by leaching U03 solid with 0.5M Na2CO3—0.5M NaI-ICO3 solutions at 90° C. N2 The improved results were similar to those obtained 50 atmosphere with aqueous hypochlorite added in the with U308, i.e., Cu catalysis improved leaching and the amounts and with the results tabulated below. The NZ improved leaching is enhanced at higher pH and in the atmosphere is employed to eliminate air oxidation effects presence of ammonia. Moreover, the use of 02 also . which would complicate interpretation of results. In yielded a more pronounced enhancement in the present 55 actual practice air atmosphere could be used thereby ob case than with U308 supra. taining enhanced results and additional economics. Uraninite was leached similarly to the U02 above with the following results: TABLE I i [ NH4OH+O2 _______________________________________ __ 0.165 .9M N azCO3—.1M NaHCO3+25 mgJl. Cu-air ______ ._ , 0. 050 . TABLE XIV _ . 60 Uraninite Leaching Results Conditions Fractions .Uraninite Leached Per Hour - Flrst?w“ ' h. Last 40% 0 GT Fraction U0, on 1 Ions MZ‘E‘ESIPQ‘ 16.7 m1./1.5% N aCl0r___ 6.7 m1./1.5% NaClO_____ 65 0, 83 0. 46 . . . As may be noted the rate of leaching increases with 0 20 0 085 goglgllr/llgffjfl'gfiiij::::::::"I: 0:38 0:087 tween ‘0.5 and 1.0). The lower apparent rate may be 25mgJ1- Cu+-1M N1140H——air ----- -- 0-46 0-105 , due to disproportionation of C10_ into Cl‘ and C1O3-. As may be observed copper and copper-ammonia increased ClO- but with a low power dependence (be 70 TEMPERATURE catalysis gave successively higher leaching rates over the 6.7 ml. of 5% NaClO was added to 0.5M 'control as above with U308 and U02. The catalytic Na2CO3——0.5M NaHCOg "effect appears to'be most pronounced during dissolu tion of the initial 60% of the uranium. 75 solutions and the solutions were employed to leach U02 3,036,881 11 explanation is apparent. below: EFFECT ‘OF pH ON HYPOCHLORI'I‘E LEACHING (U305) TABLE XVII U308 was leached with 1M total carbonate species con centration at different pH values with a carbonate leach solution containing 6.7 ml. of 5% NaClO at 90° C. in N; as with U02 with the results tabulated below: TABLE XPG Fraction U09 Conditions, ° C. 12 sults with the same lotrof U308 and U02 for which no solid at 70 and 90° C. in N2, with the results tabulated Leached Per Hour 0. 46 0.25 10 Fraction UaOs Conditions As in air oxidation lowering the temperature decreases Leaehed Per Hour the leaching rate signi?cantly and it is therefore preferred to operate in the range of 80° C. to above 90° C. 15 CATALYSIS Various possible catalytic agents were added to 0.5M Na2CO3—-0.5M NaI-ICO'3 solutions with 6.7 ml. of NaClO present which solutions were used to leach U012 at 90° C. N2 atmosphere with the results tabulated below: ' TABLE XVIII 0.45 .5M NaHC03—.5M N81200:; _________________________ __ 0. 32 Note that the rate in 1M NaI-ICO3 is substantially greater than with 0.5M Na2CO‘3-—'0.5M NaHOO'a (and similar reasoning is applicable as with U02. 20 OVRE LEACHING WITH HYPO‘CHLORITE Various carbonate solutions with 6.7 ml. NaOlO were used to leach various ores for 6 hours at 90° C. with Fraction U02 Conditions 1M NaHCO3 ___________________ _; ___________________ __ Leeched Per Hour 0. 46 25 mgjl. Cu __________________________________________ _. 0.60 .004M Mn“...004M Fe(ON)-4 0. 46 0.43 25 air blowing (oxidation) with the results tabulated below: TABLE XXII Percent U303 Leeched Ore As above Cu(C‘uSO4) ‘exerts a pronounced catalytic ef 30 feet. The fact that cupric materials should exert about 1M HCOr .5M CO3—.5M H003 .QM CO3" .lM H003 the same absolute effect as in air is reasonable since the Monticello N0. 27 ______________________ _- reoxidation of the reduced copper species is not the slow step in the catalytic cycle, hence the character of the Big Buck No. 10521... 47 58 ACM Grey Special _______ __ 93 ____________ __ 91 ____________ __ oxidant makes little difference. ' 81 ____________ __ Garwood & Gerlock No. 35 EFFECT OF pH VARIATION 10453 ______ _, _________________________ __ Under ‘the observed conditions, the pH dependence Leach solutions of varying carbonate species content noted above ‘apparently does not apply; however, the re and containing 6.7 ml. of 5% NaOlO were used to leach sults are explainable on the basis that air-oxidation leach U02 at 90° C. and with an N2 atmosphere with the ing increases with increasing pH and that this e?ect is 40 results tabulated below: dominant. in any event it can be seen that leaching as above is comparable to that achieved with 0.600 g./l. of TABLE XIX Conditions Fraction U01 Leached Per Hour KMnO4, or copper-ammonia catalyzed air oxidation leach ing. The amount of hypochlorite is cheaper as chlorine 45 than the amount of KMI‘LOL; required to obtain equivalent , recovery. Moreover, a far less objectionable contaminant is introduced into the system. 7 7 1M NaHCO; ________________________________________ __ 1(i.e.:l:.75) .5M NaHCO3-—.5M NazC03 _________________________ __ 0.46 While there have been described in the foregoing what may be considered to be preferred embodiments of the Also the leaching rate was greater in 1.0M NaI-ICOa 50 invention, modi?cations _may be made therein without departing from the teachings of the ‘invention and it is than in the ‘0.5M Na2CO*3-—-0.5M NaHCO3 solutions. intended to cover all such as fall within the scope of These results are contrary to those obtained with air oxida tion but are reasonable in the present case, since the the appended claims. Cl2—-OlO~ potential becomes more favorable for U02 oxidation with decreasing pH and the tendency of C10" 55 to disproportionate into 01- and 0103* is less. What is claimed is: j ’ ' ' ' , 1. In a process for leaching uranium from a solid con taining uranium in hexavalent and lower oxidation states, the steps comprising contacting said solid with a carbonate EFFECT OF HYPOCHLORITE CONCENTRATION (UaOs). leach solution containing catalytic amounts of the ionic The eifect of varying ClO‘" concentration on the leach species of copper in the presence of'aminonia at a tem ing of U from U308 was studied by adding two diiie'rént 60 perature of above aboutj80° C., and simultaneously add "ing anroxidizing agent torsaid solution vto oxidize and amounts of 5% NaClO to 0.5M NagCO3——0.5M NaHCO3 solution in contact with U308, at 90° C. in an N2 atrnosl ' ,dissolve the‘ uranium" from said solid. 7 7 L 2. A process for recovering ‘uranium from a solid con phere under the conditions and with the results tabulated taining uranium in hexavalent and lower valent states below: TABLE XX 65 comprising reducing said solid to Ia particle size of below about v--100 mesh, contacting said solid with a carbonate ,leach solution containing, ammonia together with catalytic Fraction U508 Conditions Leeched Per Hour 6.7 ml./l. 5% NaClO ________________________________ __ 2.2 1nl./l. 5% NaClO _________________________________ __ 7' 0. 32 . 0. 22 ' amounts of ionic’ species ‘of copper at a temperature of above about 80° C., simultaneouslyadding an oxidizing .70 agent to said solutionto oxidize and, leach the uranium fronfsaid ‘solid to, produce a carbonate leach solution con taining hexavalent uranium, and recovering uranium from the leach solution. > i j ' > ' It is interesting to note that the leaching rate with; 3. 'A process for, recovering uranium from a solid _con U308 is less than with U02 with the same NaClO‘con centration. This is the reverse of the ‘air oxidation re .75 taining uranium in hexavalent and lower 'valent states 3,036,881 13 14 comprising reducing said solid to a particle size of below about -—100 mesh, contacting said solid with a carbonate leach solution containing catalytic amounts of ionic about ~10!) mesh, contacting said solid with a carbonate leach solution having a pH in the range of about 10.5 to species of copper in the presence of ammonia at a tem of ionic species of copper at a temperature of above about perature of above about 80° C., simultaneously adding at least one oxidizing agent selected from the group con sisting of air, 02 and hypochlorite to said solution, said 11.1, containing ammonia together with catalytic amounts 80° 0., simultaneously providing an oxidizing agent in said solution to oxidize and leach the uranium from said solid to produce a carbonate leach solution containing carbonate solution having a ratio of CO3=/HCO3"- con hexavalent uranium, and recovering uranium from the centrations yielding a pH in the range 10.5 to 11.1 with leach solution. said air and O2 oxidants and a HCO3" concentration of 10 9. The process as de?ned in claim 8 wherein said about 1M with said hypochlorite oxidant to oxidize and carbonate leach solution is at a temperature of about leach the uranium from said solid to produce a carbonate 90° C. leach solution containing hexavalent uranium, and re covering uranium from the leach solution. 4. The process as described in claim 3 wherein said 15 oxidizing agent comprises air. 5. The process as described in claim 3 wherein said oxidizing agent comprises air and said temperature is about 90° C. 6. The process as de?ned in claim 3 wherein said 20 oxidizing agent comprises 02. 7. The process as de?ned in claim 3 wherein said oxidizing agent comprises hypochlorite. 8. A process for recovering uranium from a solid con References Cited in the ?le of this patent UNITED STATES PATENTS 2,813,003 Thunaes et al _________ __ Nov."12, 1957 OTHER REFERENCES Brown: Preliminary Investigation of Carbonate Leach~ ing ACCO-36, Oct. 15, 1953, declass. Sept. 23, 1955, pages 5-32 relied on. Proceedings of the International Conference on the Peaceful Uses of Atomic Energy, Aug. 8~20, 1955, vol. taining uranium in hexavalent and lower valent states 25 8, pages 8, 9, 18-22, 28 and 32-37. comprising reducing said solid to a particle size of below AEC Document RMO-2621 June, 1956, pages 1-27.