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Patented Dec. 1, 1953 2,661,280

UNITED STATES PAT. OFFICE 2,661,280 - PROCESS FORREMOVING . FROMANTIMONY. - - - - YuriiKlein, E.Lebedeff Menlo Park, Metuchen, N.J., assignors-to-American and William C. ...and: Refining Company, New-York, N.Y., a corporation of New Jersey, NoDrawing. Application September 15, 1951, V Serial No. 246,874

6 Claims. (CI. 5-69).--. 1. or This invention-relates to the removal-of-tellu Sad rium from . telluriumliqui separated from the molten antimonial, An important object of the invention is-to-pro Any of, the common reducing agents such as vide a simple, efficient and economical process coal, coke or charcoal may be used in the proc, for removing tellurium from antimony. contain ess put it has been found that the use of a re-, ing tellurium as an impurity without removing. ducing gas. Such as natural gas is particularly ad appreciable quantities of antimony with the tel-. vantageous because the gas may. be used to agi, lurium and further-to-provide a process-for-pre-. paring antimony having a low tellurium content. Although the novel features: which are believed. to be characteristic of this invention will be part lurium, and the reducible, compound, ticularly pointed out in the claims appended. gas, producer gas, hydrogenior any, hydrocarbon hereto, the invention itself as to its objects: and gas that is readily available may be used. In advantages. and the manner in which its may be . case a reducing agent is used it is added carried out may be better- understood by refer 15 to the surface of the molten and mechan ence, to the following description. ical agitation of the:metal, reducing, agent, and It has been found that tellurium-contained in alkalimetal compoundisprovided. antimony can be removed therefrom-by-melting. Sodium hydroxideo the-antimony in a refractory vessel, incorporat preferable as the reducibl ing an -reagent in-the-melt, forming. a slag of the alkali metal reagent, containing.: 20 becausereasonable they cost.and ar have melti tellurium, and separating the slag from the body. of the antimony. The alkali metal reagent can low enough for use in the be most effectively...and economically incorp0. droxides or carbonates of the other alkali rated into the melt by treating the liquid metal. with a molten-reducible. alkali metal-compound in the presence of a reducing agent. The alkali metal. compound reacts rapidly in the presences of-the-reducing agent with the tellurium in the. antimony to form a slag containing telluriums. The slag may be readily removed from the anti the molten metal being treated, the mony by skimming from...the surface, thereby: a salt for adjusting the of there: purifying the antimony with respect to the tel ducible compound may be dispensed with. - lurium. The following are specific examples of the It has also been-found that...the tellurium-ins 36 mode of operating the process. the slag is continuously volatilized therefrom as the process proceeds and that the more-prolonged Eacample I the treatment,-the-greater-the-amount of tellu Fourteen-hundred, rium removed from the slag. The-volatilized tellurium, is probably in the form of tellurium . This feature is advantageous particu larly when treating antimony containing a rela tively high concentration of tellurium. In Sugh cases, a relatively low ratio of slag to. melt may be used without obtaining an undesirably high concentration of tellurium in the slag. As stated earlier, the reaction between the rer duced alkali metal and the tellurium in the an timony is sufficiently, rapid so that the tellurium is removed from-the-antimony into the slag. in a same way with the same amount of reagent re relativelyseparated fromshort-time. the molten For liquidthis reason, preferably the contslag duced the tellurium content to .11% tains a major portion of the tellurium removed. Eacample: II. from the antimony, although a slag may also be Fourteen hundred pounds of antimony metal removed which contains a minor portion of the 55 containing .68% tellurium was melted in a suit 2,661,280 3 4. able container to 1300 F. and 25 lbs. of sodium end of the two hour was found to contain hydroxide containing 10 lbs. of sodium chloride 0.9% tellurium and the remaining antimony Was added to the surface of the molten metal. metal contained 0.2% Te. The alkali metal hydroxide rapidly became fuid It will be noted that sufficient tellurium was Whereupon natural gas was passed into the volatilized from the slag during the longer period molten metal through a tube placed beneath the of the second run to reduce the tellurium con Surface of the metal for approximately thirty Centration in this slag to 0.9%. minutes While the temperature of the molten The small amount of antimony lost in the slag metal was held in the range of 1300 to 1350° F. constitutes a particular advantage of the proc Approximately 20 lbs. of slag which analyzed IO ess. By careful control of the process it has been 6.7%. Te and 12.9% Sb was then skimmed from found that the loss of antimony may be main the Surface of the metal. The remaining anti tained as low as 3 lbs. Of antimony per pound of mony contained only .4% Te. TWO additional tellurium removed from the metal. like treatments with similar amounts of reagent While the process for removal of tellurium from reduced the tellurium content of the antimony antimony has been particularly described with to only .03%. reference to specific reducible alkali metal com Eacample III pounds and certain reducing agents, the process is not limited to the specific reducing agents or Fifteen hundred pounds of antimony metal reducible alkali metal compounds, temperatures containing .61% tellurium was melted in a suit or operating procedures described but may be able container to 1300 F. and 36 lbs. of molten practiced in other ways within the scope of the potassium hydroxide was added to the molten claims hereinafter made. metal. Natural gas was passed into the molten What is claimed is: metal through a Carborundum tube placed be 1. A process for removing tellurium from anti neath the surface of the metal for approximately mony which comprises establishing a pool of thirty minutes while the temperature of the molten antimony metal containing tellurium and molten metal was held in the range of 1300 to having thereon an overlying layer of molten slag, 1350 F. Approximately 14 lbs. of slag was then agitating Said molten antimony metal pool in skimmed off. The slag analyzed 5.8% tellurium. the presence therein of an alkali metal, discon The remaining antimony contained only .46% Te. tinuing Said agitation, and Separating from the Two additional like treatments with similar SU body of the antimony a slag containing tellurium. amounts of reagent reduced the tellurium content 2. A process according to claim 1 in which the of the antimony to .15%. alkali metal is formed in situ in said pool. Eacample IV 3. A process for removing tellurium from anti Fifteen hundred grams of antimony metal con mony Which comprises establishing a pool of taining .61% tellurium was melted in a graphite molten antimony metal containing tellurium and crucible to 300 F. under an atmosphere of having thereon an overlying layer of molten ma-. . Seventy-five grams of molten sodium terial comprising a reducible alkali metal com hydroxide was added to the Surface of the molten pound, introducing a reducing gas beneath the metal as a cover for the bath and as a carrier 40 Surface of Said molten pool thereby agitating for metallic sodium. Fifty grams of metallic said pool and Said overlying layer, thereby also sodium then was added to the molten caustic. reducing Said alkali metal compound and incor The melt under the atmosphere of nitrogen was porating the reduced alkali metal into said pool, agitated by passing nitrogen through a tube continuing the introduction of Said reducing gas placed beneath the Surface of the antimony until the tellurium content of said antimony is reduced by a desired amount, thereafter discon metal; the agitation continuing for thirty min tinuing the introduction of said gas, and sepa utes while the temperature of the molten metal rating from the body of the antimony a slag was held in the range of 1300 to 1350 F. Ap Containing tellurium. proximately 125 grams of slag was then skimmed 4. A process according to claim 3 in which the off. The slag analyzed 5% Te and the remaining 50 reducing gas is natural gas. antimony contained .08% Te. 5. A process according to claim 3 in which said Eacample V Overlying layer comprises a member of the Fourteen hundred and eighty-eight pounds of consisting of alkali metal hydroxides and alkali antimony metal containing 0.64% tellurium was metal carbonates. heated to approximately 1300 F. in a refractory 6. A process according to claim 3 in which the container under a blanket of natural gas after separated slag contains a major portion of the which 75 lbs. of melted sodium hydroxide was tellurium removed from the antimony. added to the surface of the metal pool. The YURII E. LEBEDEFE. mixture was agitated by passing natural gas into 60 the molten metal through a tube placed beneath WILLIAM. C. KLEIN. the Surface thereof for a period of ten minutes while the temperature of the metal was held in References Cited in the file of this patent the range of 1300 to 1350 F. At the end of the PATENTS ten minute period a slag containing 3.17% tellu 65 Number Nanne Date rium was skimmed from the surface of the metal. 1,548,854 Schleicher ------Aug. 11, 1925 The antimony remaining after the removal of the 1,654,527 Burkey ------Jan. 3, 1928 slag was found to contain 0.2% tellurium. 1,654,528 Burkey ------Jan. 3, 1928 The above procedure was repeated starting with 1,662,439 Rose ------Mar. 13, 1928 1471 lbs. of antimony metal containing 0.62% Te 70 and using 75 lbs. of melted Sodium hydroxide. OTHER REFERENCES The agitation with natural gas was continued for "Antimony' by Chung Yu Wong, p. 135, pub two hours, however. The slag removed at the lished 1909.