Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1953 A process for separating thorium compounds from monazite sands Kernal Glenn Shaw Iowa State College Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Chemical Engineering Commons Recommended Citation Shaw, Kernal Glenn, "A process for separating thorium compounds from monazite sands " (1953). Retrospective Theses and Dissertations. 12740. https://lib.dr.iastate.edu/rtd/12740 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. 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ProQuest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600 NOTE TO USERS This reproduction is the best copy avaiiable. UMI A PROCESS FOR SEPARATING THORIUM COMPOUNDS FROM MONAZITE SANDS BY j Kernal Glenn Shaw A Dissertation Submitted to the Graduate Faculty In Partial Fulfillment of The Requlretnenta for the Degree of DOCTOR OP PHILOSOPHY Major Subject; Chemical Engineering Approved; •••••••• • «... .•• • . •• •••• • • Signature was redacted for privacy. In Charge of MaJoi(yWork '" ./ /•' V ' ;!' ' • VI • • ' ••••••••• • • •••••• Signature was redacted for privacy. kead or Major Depiiftraent Signature was redacted for privacy. Dean of Graduate College Iowa State College 1953 UMl Number: DP12066 ® UMI UMI Microform DP12066 Copyright 2005 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 > .. lla t;, r: (a ]... \ TABLE OP CONTENTS SUMMARY 1 INTRODUCTION 3 REVIEW OP LITERATURE 6 Monazlte Sands ..... .... 6 Digestion of the Sands 8 Recovery and Purification of Thorium 11 Recovery of the Rare Earths 15 Uranium Recovery and Purification ........ l6 Previous Ames Laboratory Studies 17 LABORATORY INVESTIGATIONS 21 Raw Materials 21 Digestion of Monazlte Sands 29 Minimum acid-to-sand ratio ... 3^ Low temperature digestions 38 Recycle of undigested monazlte sand .... 39 Dissolution of digestion mass 42 Fractional Precipitation Studies 44 Experimental methods 45 Experimental results 48 Bench-Scale Processing 6l Discussion Results ... 64 PILOT PLANT INVESTIGATIONS 6? Digestion of Monazlte Sand 68 Equipment and materials 68 'T\^.Q>Oe lib Pilot plant digestion and dissolution procedure 73 Pilot plant digestion runs JS Removal of silica sludge and recovery of undigested sand 83 Fractional Precipitation Studies , 85 Equipment . 86 Preliminary pilot plant znins . 88 Dilution ratio studies ..... 91 Pilot plant studies 9^ Filter characteristics of concentrates . 109 Sedimentation of concentrates II8 Caustic Digestion of Thorium-Rich Concentrate , 121 COST ANALYSIS 126 Equipment Costs 127 Processing Costs 131 Cost Comparison 135 Cost of Caustic Digestion of Thorium-Rich Concentrate ..... 1^0 DISCUSSION 143 CONCLUSIONS LITERATURE CITED 150 ACKNOWLEDGEMENT 155 APPENDIX A ANALYTICAL PROCEDURES 156 APPENDIX B SOLVENT EXTRACTION OF THORIUM PROM MONAZITE SULFATE SOLUTION 159 APPENDIX C LEAD RECOVERY 166 ill LIST OP TABLES Table 1. Chemical Analyses of Monazlte Sands, As- Received Basis 2k Table 2. physical Properties of Monazlte Sands . 25 Table 3. Effect of Recycle of the Residual Sand on the Digestion of Monazlte sand 43 Table 4. Effect of Time on Fractional Precipitation of Thorium and Rare Earths 53 Table 5. Effect of Acld-to-Dlgested Sand Ratio on the Fractional Precipitation of Thorium and the Rare Earths 55 Table 6. Separation of Thorium Phosphate from the Rare Earths by Dilution of Monazlte Sulfate Solution 57 Table 7. Results of Bench-Scale Fractional Precipi­ tation Test 63 Table 8. screen Analysis of Ground Idaho Monazlte Sand 74 Table 9. Summary of Operating Conditions and Results of Pilot Plant Digestions .... 82 Table 10. Pilot Plant Equipment 87 Table 11. Effect of Dilution Ratio and pH on the Fractional Precipitation of Thorium and Rare Earths 92 Table 12. Distribution of Thorium, Rare Earths, and Uranium in Concentrates, Runs PP45A and PP45D 104 Table 13. Material Balance for Filot Plant Runs PP45F, PP45G, PP45H IO8 Table 14. Filter Characteristics of Thorium Phosphate Precipitate 114 Table 15. Filterability of Rare Earths and Uranium- Rich Slurries 117 Iv LIST OP TABLES (Continued) Table 16. Sedimentation of Concentrates 120 Table 17. Removal of Sulfate and Phosphate from Thorium-Rich Filter Cake by a Caustic Digestion 123 Table I8, Installed Process Equipment Costs , , , , 129 Table 19. Capital Investment for Proposed Thorium Plant 133 TaVle 20, Preliminary Process Cost Estimate for Proposed Thorium Plant 13^ Table 21. Revised Preliminary Cost Estimate of Battelle Process 139 Table 22. Processing Costs for the Caustic Digestion of Thorium-Rich Concentrate l4l V LIST OP PiaURES Figure 1. Digestion of Monazite Sands with Sulfuric Acid 19 Figure 2, Correlation of Specific Gravity of Monazite Sands with ThOg Content 30 Figure 3. Effect of Sulfuric Acld-to-Sand Ratio on the Digestion of Monazite Sands and on Solution Stability 37 Figure 4. Low Temperature Digestion of Monazite Sands 40 Figure 5. Effect of Neutralizing Agent on Precipita­ tion of Thorium and Rare Earths ...... 50 Figure 6. Fractional Precipitation of Monazite Sulfate Solution from Idaho and Indian Monazite Sands 60 Figure 7. Pilot Plant Reactor for Digestion of Monazite Sands 70 Figure 8. Pilot Plant Reactor and Temperature Record­ er in Operation ..... 72 Figure 9. Time-Temperature Relationship for Pilot Plant Digestion Number Five 80 Figure 10. Flow Diagram for Precipitation of Thorium, Rare Earth, and Uranium Concentrates ... 95 Figure 11. Pilot Plant Equipment Layout ....... 97 Figure 12. Pilot Plant Filtration of Thorium-Rich Concentrate 102 Figure 13. Effect of Dilution Ratio on Filterablllty of Thorium Phosphate 113 Figure 14. Removal of Sulfate and Phosphate From Thorium-Rich Filter Cake by Caustic Digestion ..... 124 1 SUMMARY The purpose of this investigation was to study the sulfuric acid digestion of raonazite sand, and to prepare a thorium-containing ra^-terial from the resulting solution which .'ould be suitable for further purification by liquid- liquid extraction. It was also desired that the by-product rare earths and uranium be recovered in a form convenient for further processing. Studies were made in the laboratory and in a pilot plant to determine the optlniura conditions for the digestion of monazlte sand and for the separation of thorium, rare earths, and uranium by fractional neutralization of the raonazite sulfate solution. The most effective separation was obtained when the monazlte solution was dilute and when ammonium hydroxide was used as a neutralizing agent. The resulting process consisted of the following; steps; 1. Digestion of ground monazlte sand in 93 per cent sulfuric acid for five hours at 155° -230°C. The acid-to-sand weight ratio was 1,56. 2. Dissolution of the solid reaction products in water and clarification of the solution by allow­ ing the acid-insoluble sludge to settle, 3. Fractional precipitation of thorium phosphate by dilution of the monazlte sulfate solution with six parts of water and neutralization to a pH of 1,05 with ammonium hydroxide. 2 k. Fractional precipitation of the rare earth phos­ phates by neutralization of the filtrate from the thorium separation to a pH of 2.3 with ammonium hydroxide. 5. Fractional precipitation of uranium phosphate and the remainder of the rare earths by neutralization of the filtrate from the rare earth separation to a pH of 6.0 with ammonium hydroxide. The precipitates from each fraction were thickened and filtered. The over-all recovery of thorium was 96-97 per cent, of rare earths 98-99 per cent, and of uranium 53-5^ per cent. The remainder of the thorium and uranium can be recovered by further processing. A cost comparison was made between the Ames Laboratory process and a process developed by the Battelle Memorial Institute for a plant which would produce five tons of tho­ rium per month from Idaho monazlte sand. The estimated processing cost for the Ames Laboratory process was $9.11 per pound of thorium as compared with $11.48 per pound for the Battelle process. Both of these costs Included $4.67 for