SORPTION BEHAVIOR OF PERRHENATE ION ON REILLEX(TM)-HP ANION-EXCHANGE RESIN FROM NITRIC-ACID AND SODIUM NITRATE HYDROXIDE SOLUTIONS/

The distribution coefficients (K'(d)) are reported for perrhenate on t he nitrate form of Reillex(TM)-HP, a weak base anion exchange resin, a s a function of nitric acid concentration from 0.100 to 10.0 M. Perrhe nate K'(d) values were determined in 1.00 M NaNO3 from pH 2 to 13. The K'(d) values were determined in solutions containing 1.35 M NaNO3 and variable NaOH, 0.155 to 4.66 M, and in solutions containing 0.655 M N aOH and variable NaNO3, 0.46 to 5.35 M. Maximum perrhenate loadings we re <2.7% of theoretical capacity. The K'(d) is defined by the followin g equation: K'(d)=Re-total-[Re](sol)xV(sol)/mass of dry resin/[Re](sol )xV(sol)/V-sol mL/g The total mmol of rhenium initially added is Re-to tal and [Re](sol) is the analytical molarity of rhenium in V-sol mL of solution after a batch contact. At 1.0 M HNO3 the value of K'(d) is 7 3 mL/g. The behavior of the perrhenate system in acid can be described by assuming that perrhenic acid, HReO4, is formed with a derived acid dissociation constant of about 6.5 M. In 1.00 M NaNO3 from pH 2 to 13 the sorption behavior is initially what is expected for a weak base r esin with an acid dissociation constant of 1.24 x 10(-5) M. Thus, the K'(d) value decreases with pH values above the pK(a) value. However, i nstead of the value of K'(d) decreasing to zero at higher pH values, i t becomes constant at 15 mL/g. In a solution containing 1.00 M NaOH an d 1.00 M NaNO3, the value of K'(d) is 25 mL/g. The unusual behavior of the Reillex(TM)-HP anion exchange resin suggests that the resin's unp rotonated pyridine functionality is solvating a {Na+,ReO4-} ion pair. The interaction of the perrhenate ion with Reillex(TM)-HP is more invo lved than a simple ion exchange phenomenon and the presence of NaOH af fects the resin-perrhenate interactions.