Pertechnetate separation from molybdate

Pertechnetate can be separated from molybdate with separation factors as high as 10,000 (Fig. 24 [43])- The two most important salt solutions are OH and MoO . As shown, high concentrations of MoO (as would be needed to produce enough - "Tc activity from low-specific-activity, cyclotron-produced ) are not deleterious but actually enhance the... 

Appreciable separation of pertechnetate from molybdate is achieved by pyridine as extracting agent However, the high boiling point of pyridine complicates the recovery of technetium by steam distillation of pyridine. Therefore, this method is rarely used. 

Technetiiun can also be isolated quantitatively from molybdate using Dowex-1 resin in the chloride form . Molybdate can be eluted with 0.1 M hydrochloride acid pertechnetate, however, is firmly adsorbed under these conditions. It can be readily eluted with 4.0 M nitric acid. The only drawback of this separation is the need to recover technetium from nitric acid solution. If the acid is evaporated with great care, losses may be kept quite low. 

In addition, thin-layer chromatography was employed for the separation of technetium and molybdenum. Neutron-irradiated molybdate was separated from produced 99niTc04 on cellulose MN 300 using butanol saturated with I M HCl [180]. Molybdate was identified in pertechnetate solutions by means of thin layers of silica gel or AI2O3 with mixtures of 1 M HCl/methanol or 1 M HCI/ethanol as solvents. ITic TCO4 spot revealed a higher mobility than the M0O4 spot [181]. 

Pertechnetate and molybdate are reduced in acetic acid media by p-thiocresol and form complex compounds. As mentioned above the technetitun compound can be extracted by chloroform. Since the blue molybdenum complex is insoluble in this solvent separation of technetium from molybdenum can be achieved " . 

The chromatographic separation of technetium from molybdenum is based on the different extent to which molybdate and pertechnetate are adsorbed from alkaline and acid solutions. The distribution coefficient of molybdate between the anion exchanger Dowex 1-X8 and 3 M NaOH is 12, while it is 10 for pertechnetate under the same conditions. Molybdate is also adsorbed to a much lesser extent from hydrochloric acid solutions than pertechnetate. Thus, molybdemun can be eluted by hydroxide or HCl solutions while nitric acid, perchlorate or thiocyanate are used for the elution of technetium . 

Hall and Hohns have found that 10 /ig of technetiiun can be separated quantitatively from as much as 50 g of molybdenum using the Amberlite IRA-400 anion exchange resin in the perchlorate form. The irradiated metal is dissolved in a NaOH/HjOj mixture and the solution passed through the column. Molybdate is removed by elution with 10% NaOH solution pertechnetate is eluted with 0.5 M NH4SCN. 

Some precipitation methods have been applied to the separation of technetium from molybdenum when the former occurs as a radio-active daughter-product of the latter. The separation of technetium is performed by co-precipitation with tetraphenylarsonium perrhenate from an alkaline molybdate solution . In this way, also ruthenium remains in solution. Molybdate may be precipitated away from pertechnetate using 8-hydroxyquinoline " or a-benzoinoxim Pb or Ag" ions can also be used . Kuzina and Spitsyn have developed a method for concentrating technetium from ammoniacal molybdate solutions by co-precipitat-ing pertechnetate with the slightly soluble crystalline MgNH PO. ... 

The separation of TcO, formed by neutron bombardment of molybdenum, from its molybdenum matrix, was accomplished by means of the Ambcrlite anion exchange resin IRA-400. Irradiated molybdenum was dissolved in NH4OH + H2O2 and molybdate was eluted from the anion exchanger with a mixture of potassium oxalate and potassium hydroxide, while the elution of pertechnetate was achieved with 0..5 M NH4SCN. 80 to 93 % of the calculated Tc could be recovered from the irradiated molybdenum [167]. 

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