Kenneth R. Ashley

Kinetic and equilibrium study of the reaction of [meso-tetrakis(p-sulfonatophenyl)porphinato]diaquachromate(III) with pyridine in aqueous solution

Abstract The reaction of pyridine (py) in aqueous solution with [meso-tetrakis(p-sulfonatophenyl)porphinato]diaquachromate(III) (CrTPPS(H2O)23−) has been studied at 15, 25 and 35 °C in μ = 1.00 M (NaClO4) from pH = 5.00 to 1.00 M NaOH. The free py concentration, [py], was varied from 1 × 10−4 to 1.00 M. The species CrTPPS(H2O)23−, CrTPPS(OH)(H2O)4−, CrTPPS(OH)25−, CrTPPS(py)(H2O)3−, CrTPPS(OH)py4− and CrTPPS(py)23− were all observed. However, the ligation reactions of CrTPPS(H2O)23−, CrTPPS(OH)(H2O)4− and CrTPPS(py)(H2O)3− were the only kinetically important ones observed. The values of the various stability constants, rate constants and activation parameters are reported. The porphyrin ligands labilize the Cr(III) to axial substitution and the OH− ligand labilizes it even more. But, there are no apparent trends reflected in the values of the activation parameters of the various paths. A comparison to reactions with NCS− and imidazole imply that the reactions are dissociatively activated.

SORPTION BEHAVIOR OF PERTECHNETATE ION ON REILLEXTM-HPQ ANION EXCHANGE RESIN FROM HANFORD AND MELTON VALLEY TANK WASTE SIMULANTS AND SODIUM HYDROXIDE/SODIUM NITRATE SOLUTIONS

ABSTRACT The batch distribution coefficients (Kd, mL solution /g dry resin) for pertechnetate (TcO4) between ReillexTMHPQ anion exchange resin and various caustic solutions have been determined. The average Kd value in 1.5 M NaNO3/l.0 M NaOH solution is (262.2 ± 12.6) mL7sol;g for TcO4 − ranging from 1.0 × 10TM M to 5.0 × 10−4 M. Pertechnetate Kd values were measured in a series of NaOH7sol;NaNO3 solutions. The series are: 1.00 M NaOH with 0.010 to 5.00 M NaNO3; 0.100 M NaOH with 0,010 to 5.00 M NaNO3; 0.100 MNaNO3 with 0.10 to 5.00M NaOH; 1.00MNaNO3 with 0.10 to 5.00 M NaOH; 1.50 M NaNO3 with 0.10 to 5.00 M NaOH; 3.50 M NaNO3 With 0.10 to 5.00 M NaOH. The Kd values are described by the following equation. This equation was used to predict the Kd values for a series of tank waste simulants. The predicted Kd values are different from the measured values with an average absolute difference of (29 ± 10)%. Pertechnetate kdvalues for 101-SY, 103-SY, DSS, DSSF-2.33, DSSF-5, DSSF7, 101-AW, and Melton Valley simu...

Feed Adjustment Chemistry for Hanford 101-SY and 103-SY Tank Waste: Attempts to Oxidize the Non-Pertechnetate Species

More than 50% of the technetium in Hanford 101-SY and 103-SY tank waste is not pertechnetate (TcO4−). These non-pertechnetate species (TcN) are stable, soluble, reduced complexes of technetium. In order to remediate these waste, it will be necessary to oxidize these species to TcO4−. For radioanalytical purposes, oxidation requires digestion in Ce(IV)/16M HNO3. Many oxidants are ineffective. Sodium peroxydisulfate, sodium peroxydisulfate/silver(I), and ozone oxidize all of the technetium species to pertechnetate.

Breakthrough volumes of TcO 4 − on Reillex™-HPQ anion exchange resin in a Hanford Double Shell Tank simulant

The breakthrough volumes on Reillex™-HPQ anion exchange resin columns for TcO4− solutions have been determined. The feed solutions were a Handford Double Shell Tank Slurry (DSS) simulant of ionic strength (μ) of 6.22 M and a TcO4− of 5.00×10−5 M and a 1∶3 dilution of the DSS simulant, μ =2.07 M, with a TcO4− of 1.67×10−5 M. The DSS flow rates {mL simulant/(cross section area of column.min)} through the column varied from 0.19 to 20.5 cm/min. The 1% breakthrough volumes varied from 50.0 to 1.3 bed volumes (BV), respectively. The 1∶3 DSS flow rate varied from 0.95 to 11.0 cm/min and had 1% breakthrough volumes ranging from 94 to 20 BV, respectively. At a flow rate of 1.0 cm/min, the breakthrough bed volumes are 10.2 and 95.8 BV for the DSS and 1∶3 DSS solutions, respectively. Obviously, there is an advantage in processing the 1∶3 dilution of the feed stream.

REILLEX™-HPQ ANION EXCHANGE COLUMN CHROMATOGRAPHY: REMOVAL OF PERTECHNETATE FROM DSSF-5 SIMULANT AT VARIOUS FLOW RATES

The 1% breakthrough volumes (BTV) for TcO{sub 4}{sup {minus}} on Reillex-HPQ anion exchange resin columns have been measured as a function of flow rate. The 1% BTV is defined as that point in the column loading when an aliquot of eluent contains 1% of the activity of an equivalent aliquot of column feed solution. The 2.54 x 50 cm resin columns were loaded with a DSSF-5 [Hanford Waste] simulant containing 5.0 x 10{sup {minus}5} M {sup 99}TcO{sub 4}{sup {minus}} and {sup 95m}TcO{sub 4}{sup {minus}} tracer. Seven flow rate experiments were performed with flow rates varying from 15 to 65 mL/min. The columns were up-flow eluted with a 1.0 M NaOH/1.0 M ethylenediamine/0.0050 M SnCl{sub 2} solution. For six flow experiments, the average technetium eluted was (97.1 {+-} 6.0) percent and the average technetium accountability for loading and eluting was (97.8 {+-} 5.9) percent. Loading experiments to 90% breakthrough were performed at a flow rate of 60 mL/min for Reillex-HPQ and AG{reg_sign}MP-1 columns. The Reillex-HPQ displayed better column loading performance as indicated by smaller percent breakthrough volumes. However, in this experiment, the AG MP-1 gave 100% elution, whereas the Reillex-HPQ gave only 70% elution.

Identification of Non-Pertechnetate Species In Hanford Tank Waste, Their Synthesis, Characterization, And Fundamental Chemistry

Technetium, as pertechnetate (TcO4 -), is a mobile species in the environment. This characteristic, along with its long half-life, (99Tc, t1/2 = 213,000 a) makes technetium a major contributor to the long-term hazard associated with low level waste (LLW) disposal. Technetium partitioning from the nuclear waste at DOE sites may be required so that the LLW forms meet DOE performance assessment criteria. Technetium separations assume that technetium exists as TcO4 - in the waste. However, years of thermal, chemical, and radiolytic digestion in the presence of organic material, has transformed much of the TcO4 - into unidentified, stable, reduced, technetium complexes. To successfully partition technetium from tank wastes, it will be necessary to either remove these technetium species with a new process, or reoxidize them to TcO4 - so that conventional pertechnetate separation schemes will be successful.

Fundamental chemistry, Characterization, and Separation of Technetium Complexes in Hanford Waste

The ultimate goal of this project is to separate technetium from Hanford tank waste. Our prior work with Hanford Site tank waste indicates that the presence of complexants has produced unidentified, reduced technetium species not amenable to current separation technologies, or readily oxidized to pertechnetate. Consequently, we are synthesizing and characterizing some of the major classes of technetium complexes that may be formed under tank waste conditions. These complexes will be used as standards to characterize the nonpertechnetate species in actual wastes and to develop efficient oxidation or separation methods.

Technetium Oxidation State Adjustment for Hanford Waste Processing

Technetium, as the pertechnetate anion (TcO4 −), is a very mobile species in the environment.1 This characteristic, along with its long half-life, (99Tc, t1/2 = 213,000 a) makes technetium a major contributor to the long-term hazard associated with the storage of low level waste (LLW) forms.2 Thus, technetium partitioning from nuclear waste stored at DOE sites (Hanford, Savannah River, Melton Valley, etc.) may be required so that the LLW forms meet the DOE performance assessment criteria for storage.

Kinetic study of anation reaction of meso-tetrakis-(p-sulfonatophenyl)porphinatodiaquaruthenate(III) with thiocyanate ion in aqueous solution

Abstract The reaction of NCS − (0.010−1.0 M) with Ru(TPPS)(H 2 O) 2 3− to form Ru(TPPS)(NCS) 2 5− has been studied at 35, 40, 45, 50 and 55 °C in μ = 1.00 M (NaClO 4 ) and 0.010 M HClO 4 . The addition of the second NCS − is rapid compared to the first step. The reaction is interpreted to occur via a D mechanism with a pseudo-first-order rate constant that can best be described by the relationship k obs = a [NCS − ]/( b + [NCS − ]), where a is interpreted to be the rate constant for formation of an intermediate of reduced coordination number and b is a competition ratio {H 2 O/NCS − } for this intermediate. The values of a ( k 1 ) were (1.77 ± 0.45) × 10 −4 , (3.01 ± 0.83) × 10 −4 ), (5.82 ± 0.12) × 10 −4 , (9.90 ± 0.24) × 10 −4 and (1.73 ± 0.73) × 10 −3 s −1 at 35, 40, 45, 50 and 55 °C, respectively. At 35, 40, 45, 50 and 55 °C, the values of b ( k 2 k 3 ) were (2.40 ± 0.81), (1.78 ± 0.69), (1.92 ± 0.55), (1.44 ± 0.52) and (1.09 ± 0.64) M, respectively. The value of ΔH ≠ was (93.7 ± 1.88) kJ mol −1 and that of ΔS ≠ was (−13.3 ± 5.95) J mol −1 K −1 .

Sorption Behavior of Uranium onto Reillex™-HPQ Anion Exchange Resin from Nitric and Hydrochloric Acid Solutions

Experimental distribution coefficients (K′d) are reported for \({\text{UO}}_2^{2 + }\) with the nitrate form of Reillex™-HPQ anion exchange resin as a function of nitric acid concentration. The values of K′d for \({\text{UO}}_2^{2 + }\) at 1.00, 5.00, and 10.0 M HNO3 are approximately 0.5, 10, and 9.0 mL/g dry resin, respectively; the maximum value is 13 mL/g at 7 M HNO3. The plots are bell-shape curves; the interpretation is that K′d increases as UO2(NO3)− 3 — the predominant sorbing species — is formed and sorbed onto the resin, decreasing as it is displaced by NO− 3 ion under high nitric acid concentrations. Comparison data for Dowex™-1×8 and technetium are also presented. Experiments have shown that nitrate ion with sodium and aluminum as counter ions dramatically affects the sorption behavior of uranium. Sodium nitrate shifts the maximum sorption value from 7 to ~4 M NO− 3. Aluminum nitrate increases the distribution coefficient exponentially through 8 M. Plots of elution volume (defined as the number of bed volumes needed to move the maximum concentration of the eluting uranyl-nitrate solution to the end of the column) as a function of nitric acid concentration between 1.00 and 10.0 M display a similar bell-shape curve for the K′d-[HNO3] data. Breakthrough volumes were determined for 0.0100 M \({\text{UO}}_2^{2 + }\) in 2.0 to 10.0 M HNO3. The 2.00 and 4.00 M HNO3 solutions show nearly complete breakthrough at 1.5 and 2.5 bed volumes, respectively. The 6.00, 8.00 and 10.0 M solutions display similar behavior; 10% breakthrough occurs at approximately three bed volumes and 90% breakthrough at six bed volumes. Ordering of breakthrough volumes at 50% breakthrough is 8 M >10M ≈ 6 M ≫ 4M > 2 M. The elution and breakthrough behavior can be explained by the same concepts as those governing K′d trends. Sorption behavior of U(IV) and \({\text{UO}}_2^{2 + }\)> chloride complexes were determined in hydrochloric acid media. The K′d values increase from ~1 mL/g at 1.00 M HCl to ~1100 g/mL at 7 M HCl and then remain constant to 9.5 M HCl.