UNITED STATES PATENT of FICE METHOD of EXTRACTING LITHIUM WALUES from SPODUMENE Ores Reuben B
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Patented July 25, 1950 2,516,109 UNITED STATES PATENT of FICE METHOD OF EXTRACTING LITHIUM WALUES FROM SPODUMENE oREs Reuben B. Ellestad and Karl-Milne Leute, Minne apolis, Minn., assignors to Metalloy Corpora tion, Minneapolis, Minn., a corporation of Min nesota No Drawing. Application September 16, 1948, Serial No. 49,64 " 4 Claims. (C. 23-12) . 2 Our invention relates to the extraction of lith other reasons which those skilled in the art un ium from spodumene. It relates more in partic derstand. ular to a process in which lithium is extracted We have discovered an entirely new method of from the spodumene mineral without decompo recovering lithium from spodumene ore, which Sition or dissolution of the same, and can be emi method functions to leave the structure of the ployed advantageously to extract lithium from Spodumene mineral intact without breaking it up, relatively low grade spodumene ores. The pres decomposing it, or dissolving it in any way, by ent application is a continuation in part of our directly Substituting for the lithium ion in the prior co-pending application, Serial No. 514,972, mineral a hydrogen ion made available under filed December 20, 1943, now abandoned. 10 Critical conditions of time, temperature, and the While there are in excess of 100 different varie like, as will be described hereinbelow. By this ties and sub-varieties of lithium minerals, and process we have found it possible to treat even ores, the best known are lepidolite, amblygonite, relatively very low grade spodumene Ores to re and spodumene; and most of the laboratory and cover at least of the order of 85 to 90 per cent of commercial extractions have used one or the other 15 the available lithium without extracting from the of these substances. All of these minerals are mineral the aluminum which is present therein different in their physical and chemical make-up and forms a part of the mineral structure. Small and behavior, and processes which may be used amounts of sodium and potassium which appa On One type of mineral are sometimes entirely rently replace some of the lithium in the spodu ineffective on another type of mineral. 20 mene structure are also extracted as sulfates. One of the processes used in early work for the Leaving the aluminum of the mineral undissolved recovery of lithium values comprised decomposi is a function of the process itself, and does not tion of the ore and dissolving all of the metallic result, from the use of a separate insolubilizing constituents thereof in an acid like sulfuric acid, procedure as is the case with some other proc Such a process has been carried out successfully 25 eSSes. on lepidolite and amblygonite ores, relatively rich In carrying out our process, the spodumene is in lithium; but, even in the case of these ores, the preliminarily crushed and heated under suitable required extensive purification makes the decom conditions, as will be described hereinbelow, to position process costly and prohibitive. It has convert the natural occurring alpha-spodumene never been possible to employ the decomposition . into beta-spodumene. The beta-spodumene is proceSS On Spodimene and We have found no con then thoroughly mixed with strong sulfuric acid ditions of acid concentration, time, or tempera in a proportion somewhat in excess of that re ture, which could be employed successfully to ex quired to satisfy the lithium ions in the mineral tract lithium from the spodumene mineral by and within critical temperature limits which will acid decomposition extraction procedures. be pointed out, with the result that the hydrogen Large scale production of lithium, in the form ions of the sulfuric acid replace the lithium ions of the metal or in the form of its compounds, re of the spodumene and the lithium ions combine quires the use, as a Source of lithium, of spodiu with the sulfate ion to form lithium sulfate. The mene ores which are much more abundant, par acid-roasted ore is leached with aqueous liquid to ticularly in the northern part of the United extract the lithium sulfate, leaving behind the States, than are other lithium-bearing : ores. spodumene mineral in its original form, except While the pure spodumene mineral Will contain for the substitution of hydrogen for lithium, and between 6 and 8 per cent of lithium oxide (Li2O), without decomposing the mineral or dissolving the ore, as mined will not run more than about 1. the aluminum content thereof. The leach Solu to 2 per cent lithium oxide. As a consequence, 45 tion of lithium sulfate is then treated in any suit even if the known decomposition procedures able manner. to produce a product comprising could be employed on spodumene, it would be eco dry lithium sulfate, or to convert the lithium sul nomically impracticable to handle the larger vol fate to other chemical forms in which it may be ume of ore and chemicals, which the use of such used commercially. a process would entail... Even some of the base 50 In the first step of the process, the ore which exchange reactions which have been used on is mined as alpha-spodumene and which may other lithium ores and which, with some modifi contain as low as 1 per cent and up to 6 or 8 per cations, might be employed on spodumene, are cent Li2O, depending upon the source of the ore not economically feasible because of the relatively and whether or not it has been concentrated in large proportion of reagents required and for 55 any way, is heated between about 1000 C. and 2,516,109 3 4. 1350° C. to convert the alpha-spodumene into sample held at 1120° C. for three hours was also beta-spodumene. Roasting is carried out in any 100 per cent converted and extraction was 100 per suitable equipment, such as a muffle furnace, ro Cent. tary furnace, direct-fired furnace, or the like, These and other data, indicate that spodunnene and by either a batch or continuous procedure, is relatively quickly and completely converted so long as substantially uniform and adequate from the alpha, to the beta form if an adequately temperature control are possible. The ore should high temperature is reached, but that continued not be too fine or stack losses will be prohibitive, heating at such temperature will not inhibit and the pieces should not be too large or heat, lithium extraction. penetration will be retarded. In general, we have 10. In the acid roasting procedure which follows found that a preliminary crushing with a jaw the conversion of alpha-spodumene to beta crusher, in which pieces will run an average of spodumene and cooling of the resulting beta, 4 to 1 inch, is very suitable, although flotation Spodumene product, it is essential that the acid concentrates may and have been Successfully be brought into contact with the beta-spodumene, used on a commercial basis. and to this end, mixing and control of the pro The temperature and time of heating should portion of acid (some excess preferably is used) be so controlled that substantially all of the are important. Assuming proper mixing of the alpha-spodumene is converted to beta-spodul acid and beta-spodumene, the roasting tempera mene, but not at high enough temperature to ture may then be properly controlled to obtain fuse the ore mass. Pure spodumene fuses at 20 substantially complete recovery of lithium as the about 1418° C., but impurities present in the ore sulfate. We have found that the preferred roast usually may reduce the fusion point markedly. ing temperature is about 250° C. but, practically, In ordinary decrepitation procedures, in which the temperature may be as low as 200° C., but ores are heated at a relatively high temperature should not be above about 300° C. When the to break them up and facilitate grinding, carry roasting temperature is raised substantially above ing the temperature to the fusing point of Some 300 C., there is a marked reduction in the pro of the constituents is frequently not deleterious; portion of lithium sulfate which may later be but is, in fact, an advantage, because the glass leached from the Ore. like material can be more readily ground. We We have made very careful measurements to have found in our process, however, that carry 30 determine the temperature at which the replace ing the ore to a temperature of 1050° C. to 1100° 1nent of lithium ions with hydrogen ions begins C. is ample, because we are concerned with the to take place. Since the action is exothermic, it production of beta-spodumene, and not, prima is not difficult to determine the minimum tem rily, in ease of grinding. perature at which exchange of ions begins; and Experiment and analysis will determine in a 35 we have found that, this temperature is about given instance and with given equipment, the 15° C. The use of a somewhat higher tempera conditions, of time and temperature required to ture is preferred, however, because it affords a convert all of the mineral to beta-spodumene. margin of safety as to temperature. In a series of tests on a sample of kunzite (a very In One series of eXperiments, we treated some pure grade of spodumene) containing 7.6 per cent 40 ore by our process through the stages of conver Li2O, in which tests different conversion tem sion to beta-spodumene, cooling, mixing with peratures and times were employed, and conver acid, and acid roasting, according to a preferred sion determined by subsequent extraction of procedure. The acid-roasted ore was then sepa lithium as the sulfate, employing the process of rated into two parts and one part leached with Qur, invention, the following values were obtained: 45 Water to remove lithium sulfate.