Washing and caustic leaching of Hanford tank sludge: Results of FY 1997 studies

Abstract

DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. AbstractSludge washing and parametric caustic leaching tests were performed on sludge samples fiom five Hadord tanks: B-101, . These studies examined the effects of both dilute hydroxide washing and caustic leaching on the composition of the residual sludge solids.the P, and 63 to 99% of the Na from the H d o r d tank sludge samples examined. The partial removal of these elements was likely due to the presence of water-soluble sodium salts of aluminate, chromate, hydroxide, nitrate, nitrite, and phosphate, either in the interstitial liquid or as dried salts.The response of Al to caustic leaching was v~a b l e .When leached with 3 M NaOH for one week at 95 to 100°C, the cumulative Al removals were 62,99,61,95, and 89% for the B-101, BX-110, BX-112, (2-102, and S-101 samples, respectively. For the B-101 and the BX-110 samples, Al dissolution was rapid, with the AI concentrations reaching >SO% of their final values within the first 5 h of leaching.Interestingly, for the BX-112 sample, A I removal decreased with increasing leaching time and temperature-a trend contrary to what was expected. We hypothesize that this is due to the formation of aluminosilicate minerals. For the C-102 sludge, there was clearly a benefit in increasing the NaOH concentration from 1 M to 3 M. Leaching with 1 M NaOH removed -20 to 30% of the Al from the dilute hydroxide-washed solids while 3 M NaOH removed -95% of the Al. Aluminum dissolved slowly from the S-101 sample, which is consistent with boehmite being the predominant Al-containing phase.all the sludge samples examined, Cr removal during caustic leaching was highly time-dependent, but the Cr dissolution did not fit simple zero-, first-, or second-order kinetic models. Consistent trends in the effects of temperature and hydroxide concentration on Cr removal were difficult to discern. P from the sludge samples examined. Except for the Tank C-102 sample, cumulative P removals,were 285%. For C-102, the cumulative P removals were only -60%. Increasing temperature or hydroxide concentration generally did not result in large improvements in P removal; that is, relatively mild conditions tended to be adequate to remove P. 'The projected 137Cs content for the low-level waste (LLW) resulting fiom immobilizing the sludge washinglleaching solutions would range fiom -50 to -540 CVm3 for the samples examined. Although these concentrations are below the U.S. Nuclear Regulatory Commission Class C LLW limit of 4,600 Cum3, they are well above the proposed guideline of 3 Cum3 for the immobilized LLW product fiom the proposed private-processing facilities. Thu, it is likely that I3'Cs will need to be removed fiom the washing and leaching solutions. On the other hand, transuranic and Sr removal would likely not be required for the washing and leaching solutions fiom processing the sludges examined here. An estimate of high-level waste (HLW) glass produced in im...

Selective Leaching of Chromium from Hanford Tank Sludge 241-U-108

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Process Development for Permanganate Addition during Oxidative Leaching of Hanford Tank Sludge Simulants

“…TGA studies provided the hydration number for the above empirical formula. However, previous microscopic studies report a O:Cr ratio of two, which results in a tentative identification as Cr(O)(OH) (Lumetta et al 1997), or for these materials, Cr(O)(OH)-xH 2 O.…”

Colloidal Agglomerates in Tank Sludge: Impact on Waste Processing

“…Table 1. Properties were measured during sludge caustic leaching (2 M NaOH at 100°C) and washing (0.01 M NaOH/0.01 M NaNO3 at 50°C) from over fifteen different Hanford tanks 16,17,18,19 . For actual wastes, the standard initial solids loading of …”