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United States Patent Office 2,988,421

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United States Patent Office 2,988,421 United States Patent Office Patented June2,988,421 13, 196 heavailaaaar 1 2 contain more than 200 gms. alkali metal and chloride ions 2,988,421 per litre. The following tables show the loss of thorium PROCESS FOR THE SEPARATION OF THORUM and lanthanons under various conditions in the presence WilliamANDRARE Palmer Kemp, EARTHS Shenfield, FROM and MONAZTE James Johnston, 5 of sodium and potassium chloride. Hainault, England, assignors to Thorium Limited, Lon don, England, a corporation of Great Britain NaCl, ThO Ln2O No Drawing. Filed Aug. 20, 1957, Ser. No. 679,126 Acidity gm.fl. loss, loss, Claim priority, application Great Britain Aug. 24, 1956 gm.fl. gm.fl. 9 Claims. (C. 23-145) -ror-rm-m-m------- 10 : 122 This invention relates to a process for separating thori- 4.5 8: um and lanthanon salts from other materials present in : g monazite. The invention is particularly useful in that it 55 i. provides a process for separating salts of thorium and the : 8. lanthanons from phosphate and impurities present in 1655 400 6.65 ground mineral monazite. The term lanthanon in this specification includes the elements with atomic numbers KC ThO Ln2O from 57-71; this group is also known as the rare earth Acidity fi. is is elements. gm.fl. gm.fl. Monazite sand is a mineral phosphate containing thori- .am-m-m-m-m-m-m-wn um and the lanthanon phosphates to the extent of about 38 o' 95-98% by weight. Another source is ground mineral 300 0.005 1.0 monazite which is far less pure than monazite sand and contains only about 75% of the thorium and lanthanon In a preferred form of the process the filtered extract phosphates. has an acidity greater than 4.5 N. Further, more eco An approximate analysis of a typical sample of ground nomic results are obtainable with a concentration of 200 mineral monazite is as follows: 400 gms, alkali metal and chloride ions per litre with the Percent normal concentration of thorium and lanthanon being ThoaLanthanon -------------------------------------- oxide ------------------------------ 46 50-60It has gms./litre been found of mostsolution satisfactory expressed to asadd oxide. a portion of CaO ---------------------------------------- 5 the filtered extract to the alkali metal chloride to form Feaos --------------------------------------- 5 a slurry and then add to the slurry the remainder of Al2O3, etc. ----------------------------------- 4. the extract. The precipitation of the double sulphates CuO ------------------- wrk or m r milm me a were man wa'w owns w i wo air 85 should preferably take place at about 60° C. as below this PbO ---------------------------------------- 0.3 temperature losses tend to increase; higher temperatures Usos --------------------------------------- 0.1 may be used but are not necessary. The double sulphate EQs ---------------------------------------- 27 is then filtered off and washed carefully with an alkali SiO2 ---------------------------------------- 5 metal chloride solution, care being taken to avoid un In the process for obtaining thorium and the lanthanons 40 necessary Washing, so keeping losses at a minimum. from these materials the monazite in finely divided state In its preferred form this process enables more than is treated with sulphuric acid and extracted with water. 99% of the thorium and lanthanon compounds to be pre Insoluble matter is filtered off and then by means of our cipitated from solution. A certain amount of phosphate invention the thorium and lanthanon compounds are sepa- remains with the thorium and lanthanon double sulphate ratedThis from invention the impurities provides present a process in thefor extract.the separation of As butwith the the amountsalts produced is substantially by earlier less processes. than that associated thorium and lanthanon salts from impurities such as iron, calcium, copper and aluminium, phosphate present in Example I monazite, in which process thorium and lanthanon double 200 lbs., ground mineral monazite (containing about sulphate is precipitated from a filtered acidic extract of 50 75% monazite) were mixed with 400 lbs. 96% sulphuric ground monazite in the presence of alkali metal and chlo- acid and stirred and heated to 200 C. This reaction mix ride ions. ture was allowed to stand overnight and then added to The chloride ions may be most easily introduced in the 130 gallons of water and stirred. The mixture was passed form of hydrochloric acid or as an alkali metal chloride. through a filter-press to remove insoluble material. A The alkali metal chlorides which it is preferred to use 55 portion of the clear liquor, containing 51 gm./I. of in the invention are those of sodium or potassium. For Ln2O-ThC) was added to 350 lbs. sodium chloride to reasons of economy and efficiency it is preferable to use form a thick slurry and then heated to 60° C. The re sodium chloride. maining liquor was then added to the slurry slowly while The separation of thorium from the lanthanons pre- heating sufficiently to keep the temperature at 60° C. cipitated as the double salt is carried out in the normal 60 After settling the clear mother liquor contained only 0.01 way, that is to say, the double salt is converted with ex- gm./1. of Tho, indicating over 99% of the thorium was cess caustic soda to hydroxides from which on careful precipitated. The solid was filtered on a rubber-lined treatment with mineral acid can be obtained a solution spinner and washed on the spinner to remove undesirable containing the lanthanons which may be separated from impurities in the mother liquor. This washing is kept the thorium hydroxide precipitate. 65 down to a minimum to avoid losses. A wash liquor con The acidity of the filtered acidic extract with which the taining 200 gm./l. NaCl and 50 gm./l. Na2SO4 is used. alkali metal and chloride ions are mixed must be care- The double sulphate contains about 35% Ln2O--Tho, fully controlled to obtain maximum precipitation of the and POs:ThO ratio of 0.2. double salt. Likewise, the concentration in the solution What we claim is: of the alkali metal and chloride ions must be carefully 70 1. A process for the separation from monazite of thori chosen to obtain the best results. um and rare earths substantially free from impurities The solution should be acid and preferably should present in monazite, comprising digesting with excess sul 2,988,421 3. 4. phuric acid a finely-divided monazite selected from the divided monazite seleceted from the group consisting of group consisting of monazite sand and ground mineral monazite sand and ground mineral monazite, diluting the monazite, diluting the digest with water, filtering the digest with water, filtering the resulting product to re resulting product to remove insoluble material, treating move insoluble material, treating the filtrate so obtained the filtrate so obtained with material providing alkali with sodium chloride in a concentration of 200-400 metal and chloride ions, and removing the precipitate thus gins./liter of filtrate, the concentration of acid in the obtained containing thorium and rare earths, the concen filtrate being from 4.5 N to 5.5 N, and removing the tration of Sulphuric acid in the filtrate being at least 3 N precipitate thus obtained containing thorium and rare and the concentration of alkali metal and chloride ions earths. taken together being at least 50 gms./liter. O 9. A process according to claim 8, in which the filtrate 2. A process according to claim 1, in which the mate is treated with sodium chloride at a temperature of at rial providing the chloride ions is hydrochloric acid. least about 60 C, 3. A process according to claim 1, in which the mate rial providing alkali metal and chloride ions is an alkali References Cited in the file of this patent metal chloride. UNITED STATES PATENTS 4. A process according to claim 3, in which the alkali metal chloride is one selected from the group consisting 1,100,743 Keetman et al. -------- June 23, 1914 of sodium chloride and potassium chloride. 2,425,573 Soddy ----------------- Aug. 12, 1947 5. A process according to claim 4, in which the con centration of acid in the filtrate is from 4.5 N to 5.5 N. 20 OTHER REFERENCES 6. A process according to claim 4, in which the con Pilkington et al.: Rare Earths and Thorium Compounds centration of the alkali metal chloride in the filtrate is from Monazite J. Soc. Chem. Ind. (London), 66; 387 94, 1947 (Copy in Sci. Lib.). - greater than 200 gms./liter. Mellor: Comprehensive Treatise on Inorganic and 7. A process according to claim 6, in which the con 25 Theoretical Chemistry, vol. 7, pp. 178-181 (1927), Long centration of alkali metal chloride in the filtrate is 200 mans, Green & Co., London. Copy in Div. 59. 400 gms./liter. Audsley et al.: Extraction and Refining of the Rarer 8. A process for the separation from monazite of thori Metals, pp. 351-360, March 22 and 23, 1956, Stephen um and rare earths substantially free from impurities, Austin & Sons, Ltd., Great Britain. Copy in Div. 46. comprising digesting with excess sulphuric acid a finely 30 .
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