Phosphate resources and processinc
- K. D. J acob
- ed. Fertilizer technology and resources
iii The tremendous domestic reserves of phosphate rock together with the large annual production of normal superphosphate from phosphate rock have made the recovery of the small amounts of uranium (0.01 to 0.02 percent) in phosphate rock during the production of superphosphate an important problem. At current superphosphate pnoduct,i-on rates there Ett:iBI:S . a' •:uranium potential of approximately 1000 tons per year. In most phosphate rocks 80 percent or more of the phosphqrus content is unavailable to plant life. Normal superphosphate is produced by the reaction of sulfuric acid and phosphate .rock to convert the phosphorus to a f orm available to plant life. The purpose of this investigation was to make a quantative study-o~ the effect o~ p~phate rock partic~e · size on the recovery of uranium during the production of normal superphosphate. Florida land pebble phosphate rock was used in this work. The uranium content of this rock was 0.0184 percent UJOB· Phosphate rock particle sizes of 62, 77, and 92 percent through 200 mesh were studied. Both a 1.81 and a 2.50 acidulation ratio (pounds of 100 percent sulfuric acid per pound of P205) were studied at each particle size. Industrially, a 1.81 acidulation ratio is used for the production of normal superphosphate; a 2.50 acidulation ratio is used· for phosphoric acid production. The acidulation of the phosphate rock to superphosphate and the extraction of the uranium into the solvent vmre accomplished simultaneously by adding the sulfuric acid to a slurry of the rock and solvent. The solvent used was a 10 percent di-octyl pyrophosphoric acid solution in normal heptane. A solvent to rock ratio of 0.8 milliliters per gram was used throughout; 60 percent sulfuric acid was also used throughout. The most favorable uranium recovery was 73 percent. When the 2. 50 acidulation ratio was used an additional quantity of rock was added to the reaction products, after the solvent had been removed, to reach an overall 1.81 acidulation ratio. Superphosphate was thus produced. This additional rock was not finely ground as it did not contact the ,solvent for uranium extraction. 1 This report is based on an M.S. thesis by William Wayne Davis submit ted December, 1955 at Iowa State College, Ames~ Iowa. This work was performed under contract with the Atomic Energy Comm1ssion. iv ISC-678 It was found that the .uranium recqvery obtained in a 30 minute reactionextraction increased sienificantly with a decreasing particle size. The process based on an initial over-acidulation ratio (2.50) did not appear to have any advantage over the process based on the normal acidulation ratio (1.81).