US1526943A - Art of extracting rare metals from their ores - Google Patents

Description

Patented Feb. 17, 1925.

UNETED STATES PATENT Fries.

KARL B. THEWS, OF DENVER, COLORADO, ASSIGNOR TO WILLIAM A. J. BELL, OF

' DENVER, COLORADO.

ART OF EXTRACTING RARE METALS FROM THEIR ORES.

No Drawing.

To all whom it may concern:

Be it known that I, KARL B. THEWS, German citizen, and resident of Denver, in the county of Denver and State of Colorado, have inv nted certain new and useful Improvements in the Art of Extracting Rare Metals from Their Ores, of which the following is a specification.

Thisinvention relates to the art of extracting rare metal values such as radium, vanadium and uranium from their containing ores particularly such ores as carnotite and is intended to efi'ect a substantial reduction in high costs and difficulties which have heretofore been encountered in the working of such ores and consequently to render available for commercial working ores or tailings of such low grade that they could not be worked profitably under methods previously used.

' Oarnotite ore, which is the principal radium bearing ore now available, is of rare occurrence and is located remote from lines of cheap transportation. Those deposits now known and worked are found in southwestern Colorado and eastern Utah and con ore, and then unless expensive processes of concentration be used, to sort out or select by hand the richer portions so that about 4 tons of the ore are minedin order to secure 1 ton of commercially extractible ore. Moreover, large amounts of metalliferous tailings are thrown away because of their being of too low grade to rework for their contained values.

The term ore is used herein to broadly designate metalliferous mineral containing commercially extractible values whether that material be in its original or raw state as it occurs when taken from the mine or whether it has been subjected to intermediate processing or treatment which still leaves it with a suflicient metallic content Application filed May 10, 1921. Serial No. 468,359.

worth subjecting it to further extraction processes. It therefore includes both raw ore and ore that has been subjected to proc essing either of a mechanical or chemical nature resulting in the production of ore concentrates, tailings, slimes or the like.

Owing to the great amount of material to be treated and to the transportation difliculties involved, attempts to satisfactorily solve the' problem of cheap extraction of values from these ores have logically tended toward the use of highly concentrated or strong acids for extraction purposes but without achieving satisfactory results.

The essence of my present invention is based on the discovery that a species of extracting agents, previously unrecognized as available for extraction purposes of which oxalic acid is typical and preferable can be used advantageously and economically. Furthermore it will act to eifect such a complete solution of the desired values that each and all of said values present may be put into solution at a single step and then by further treatment, may be separated mechanically.

Heretofore the whole field of organic acids has been disregarded by experts in this field of metallurgy because of their known' acids such as hydrochloric acid, nitric acid,

sulfuric acid and the like.

Moreover no one was likely to suspect. that such a relatively weak acid as oxalic acid or others of the organic type possessingv reducing properties, would exercise any distinctive or selective action in effecting solution of the radium compounds present in carnotite ores or concentrates.

Of the various organic acids that are economically available in a commercial sense for effecting such extraction I have found that oxalic acid is among the most'satisfactory reagents for use under present conditions since it seems to effect a more complete solution of the values sought than some of the other organic acids of a reducing nature that might be used, since with oxalic acid used as hereinafter explained a substantiallywhile from S0 to 90% of thevanmlium value present is carried out in this same solution Y which is a high percentage even in the treatment of vanadium ores for vanadium alone. That is to say, in a practical commercial sense the extraction by direct solution in a single stage is substantially complete since the vanadlum solution is equal to the best vanadium recovery processes in commercial use and the radium uranium extraction is very high.

Because of the relatively small quantities of reagents required in my process it is possible to treat ores of lower grade than has been the case heretofore by other more expensive methods of treatment. The additional advantage resides in the fact that oxalic acid and other reducing acids of organic character lend themselves readily to processes of. recover from the waste liquors by evaporation an crystallization or distillation.

I believe that I am the first to use an organic acid having a reducing property, such as'oxalic acid as a solvent reagent 1n the field of radium'extraction, but whether the advantage derivedfrom the use of such a solvent reagent is due to the reducing action per se or to the inducing of a colloidal condition which prevents or impedes precipitation, or to a direct solvent action I am unable to state and is not necessary to be determined.

For the purpose of illustration I will now give a concrete example of the method of treating a carnotite'ore body of a de that is regarded as commercially wor able under present conditions, it being understood t at the precise proportions and the specific in edients are only illustrative but not prescriptive.

Treating, let us say, 1 ton of carnotite ore with 1.78% uranium oxide (U O content and about 4% vanadium pentoxide (V 0 I first crush or pulverize the ore to a fineness of about 30 mesh in order to prepare it for the acid bath.

, I then mix a quantity of oxalic acid and hydrochloric acid and water so as to provide a li uid bath in the .ratio of'about 2 tons of t e liquid or acid bath for each ton of-comminuted ore to be treated. This acid mixture is then heated or brought to a boiling condition by passing steam through the li uid and the comminuted ore is then added y stirring, and the heating or boiling is continued until substantially the entire recoverable values are put into solution.

With an ore of the grade above mentioned the total quantity of oxalic and hydrochloric acidiused would be about 10% of the weight of the ore. In preparing this bath the whole acid constituents ma be oxalic acid or other reducing acids, ut it will probably be found advantageousto use ydrochloric acid in .a proportion not ex- .smaller, less acid is -Of course, the addition of an undue excess ceeding the amount of oxalic acid, that is, 50% or less of the acid ingredient may be hydrochloric acid instead of the reducing acid with satisfactory results. Itwill be understood that in treating other grades of ore than that above mentioned in which the metallic content difiers from that above described, there should be a corresponding variation in the amount of acid ingredient used in the acid solution. Instead of mixing the oxalic acid and the hydrochloric acid in the bath before pouring in the comminuted ore, the oxalic acid may be put in first, then the ore may be added and the vhydrochloric acid be added shortly thereafter. a

The use of the hydrochloric acid as part of the acid solvent is preferred because of its greater cheapness, and with the aid of the oxalic or organic reducing acid it serves the purpose of putting substantially all of the commercially recoverable values into solution. v

The solution containing substantiall all the values that is, radium, vana ium,

uranium and also barium is then mechanically separated from the mass of gangue and slime by filtration or equivalent means and forms the only material requiring further treatment for the separation and recovery of the different values, and the sand and slime forming tailings or refuse may be discarded since they contain negligible amounts of the values.

This common solution containing all the values is then treated with any suitable precipitating agent, such as sulfuric acid, to precipitate the radium and barium values whlch, in case of sulfuric acid is used, will be found in the form of sulfates.

The liquor, from which the radium and barium have been so recipitated, still contains the uranium and vanadium values and is then treated with a suitable recipitatin a cut such as lime, in accor anoe with we I. own practice, to form a calciumuranal-vandate which may be separated from the liquor by filtration, the liquor being discarded. Any other methods of separating or. preci itating the various values ma be empgiy at discretion.

t is to noted also that the quantity of acid used for the purpose of forming the solution of the values may be decreased with the lower grade ores or tailin since as the values to be put into solution are required for that work.

of acid is to be deprecated as being wasteful and needless.-

While in the specific description of the practice of my process I have referred to the addition of or nic acid solvent .directly to the dilut ore or material to be treated, it will be understood that the process does not exclude the more indirect method of adding salts of the organic acids which are capable of being acted upon by an acid used to produce organic acid in the mixture.

The time periods required for the forming of the complete solution'of the values are affected not only by the temperature conditions and by the proportion of acid solvent used, but are also materially shortened by mechanical stirring or agitation of the fluid mass of ore as will be readily appreciated by those skilled in this art.

What I claim as my invention is:

1. The improvement in the art of extracting rare metals from carnotite ore which consists in treating a comminuted and di- KARL B. THEWS.