Strontium removal from acid solutions

PAN-KCoFC and PAN-4A composite adsorbents were prepared for the removal of cesium and strontium ions from acidic nuclear waste solutions. High porous spheri( composite adsorbents could be prepared using a dual nozzle technique. The acid and radiation stability tests showed that the both composite adsorbents were stable against acid solutions higher than pH - 2 and radiation dose less than 1.89 MGy, respectively. Adsorption tests showed that the PAN-KCoFC was selective for cesium ion and the PAN-zeolite 4A was for strontium ions, respectively. The ion exchange equilibrium isotherms were obtained and evaluated for the binary systems. 

In the experiments, all the four extractants synthesized were used for strontium removal from aqueous feed solutions containing about 5.5 ppm of nonradioactive Sr-87 at pH 3. Figure 28.8 shows the results for all of these four extractants by the use of 1 M HCl as the stripping solutions (Ho, 2001b, 2003 Ho and Wang, 2002). As shown in this figure, all of these four extractants removed strontium from the aqueous feed solutions and recovered it in the aqueous strip solutions. The strontium concentration in the aqueous strip solutions was about 40 ppm, which was nearly the maximum concentration achievable for a feed-to-strip solution volume ratio of 8. Thus, the stripping with hydrochloric acid... 

Uranium mineral first is digested with hot nitric acid. AH uranium and radium compounds dissolve in the acid. The solution is filtered to separate insoluble residues. The acid extract is then treated with sulfate ions to separate radium sulfate, which is co-precipitated with the sulfates of barium, strontium, calcium, and lead. The precipitate is boiled in an aqueous solution of sodium chloride or sodium hydroxide to form water-soluble salts. The solution is filtered and the residue containing radium is washed with boiling water. This residue also contains sulfates of other alkahne earth metals. The sohd sulfate mixture of radium and other alkahne earth metals is fused with sodium carbonate to convert these metals into carbonates. Treatment with hydrochloric acid converts radium and other carbonates into chlorides, all of which are water-soluble. Radium is separated from this solution as its chloride salt by fractional crystallization. Much of the barium, chemically similar to radium, is removed at this stage. Final separation is carried out by treating radium chloride with hydrobromic acid and isolating the bromide by fractional crystallization. 

As already pointed out, some of the products of periodate oxidation, especially the mixed acetals from the glycosidic derivatives of the sugars, are readily hydrolyzed by acids. Although the known compounds of this type are stable in dilute aqueous solution of iodic acid at room temperature, heating the acid solution would be expected to cause hydrolysis. Before isolation of these oxidation products, the reaction solution customarily is neutralized to a pH of 8-9. Barium hydroxide and strontium hydroxide have proved to be advantageous bases for neutralization of the reaction solution, since iodate and excess periodate are largely removed at the same time as the slightly soluble barium or strontium salts. Silver acetate and hydriodic acid also have been used to remove iodic add.128... 

After Irradiation, the meteorite samples were placed In nickel crucibles containing 2 mg lead carrier and about 10 grama of sodium peroxide was added. The mixture was then fused. The fused mass (after cooling) was broken up with water and removed from the crucible. The mixture was then acidified and a clear solution was obtained. After making the solution 0.5 M In hydrochloric acid, 200 mg of strontium was added and lead and strontium sulfates were precipitated with ammonium sulfate. 

Aqueous hydrofluoric acid can be freed from lead by adding ImL of 10% strontium chloride per KXhnL of acid, lead being co-precipitated as lead fluoride with the strontium fluoride. If the hydrofluoric acid is decanted from the precipitate and the process repeated, the final lead content in the acid is less than 0.003 ppm. Similarly, lead can be precipitated from a nearly saturated sodium carbonate solution by adding 10% strontium chloride dropwise (l-2mL per lOOmL) followed by filtration. (If the sodium carbonate is required as a solid, the solution can be evaporated to dryness in a platinum dish.) Removal of lead from potassium chloride uses precipitation as lead sulfide by bubbling H2S, followed, after filtration, by evaporation and recrystallisation of the potassium chloride. 

Di(2-ethylhexyl) phosphoric acid (HDEHP) is an extractant molecule used for An(III)/Ln(III) separation. Used in TALSPEAK-type processes in a mixture with TBP, or in the DIAMEX-SANEX process in a mixture with a malonamide (154-157), it has also been proposed, in a mixture with TBP, to remove strontium from PUREX acid waste solution in the Hanford B plant (158). Therefore, numerous studies have focussed on the radiolytic degradation of HDEHP and its effects on the extraction of Sr(II), lanthanides(III), and actinides(III) (10, 158-163). 

An aqueous solution of sulfuric acid and a salt of periodic add, trisodium paraperiodate, or one of the potassium periodates, has been used frequently as a substitute for pure periodic add. When the product of the oxidation reaction is to be isolated, the effect of the presence of metal ions on the yield should be considered. If the product is volatile or slightly soluble, or is isolated either as a slightly soluble derivative or by extraction with organic solvents, the presence of metal ions should not reduce the yield. In the Case of certain methylhexosides34 which were oxidized by periodic acid formed from potassium metaperiodate and an equivalent of sulfuric add in aqueous solution, the presence of potassium ions was found to cause a low yield of the crystalline strontium salt prepared by the strontium hypobromite oxidation of the dialdehyde resulting from the periodic add reaction. Oxidation by pure periodic add, a solution of which is prepared either from crystalline paraperiodic add or by the previously mentioned method from potassium metaperiodate, is desirable when the presence of difficultly removed metal ions affects the yield adversely. 

After strontium carrier is added to a small volume (<10 ml) of °Sr solution, sufficient fuming nitric acid is added to attain a nitric acid concentration of 14-16 N. The solution with strontium nitrate precipitate is cooled in an ice bath and then centrifuged. The supernatant solution is thoroughly decanted and the strontium nitrate precipitate is dissolved in water. Barium and yttrium carriers are added. Precipitation of barium chromate at pH 5.5 removes and natural radium from the supernatant strontium solution (for counting, if needed, of these two separated radioelements). Precipitation of yttrium hydroxide in basic solution then removes the daughter that has grown into the °Sr parent. Ammonium oxalate is immediately added to the supernatant solution to precipitate strontium oxalate. The precipitate is washed and dried in the filter holder with alcohol and ether, promptly weighed for yield determination, and counted with a beta-particle detector (Chieco 1997) such as a proportional detector. 

---