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Title: REMOVAL OF SILICA FROM DAREX DISSOLVER SOLUTIONS

Abstract

The nature and behavior of silica in Darex dissolver solutions were found to be dependent on solution temperature, the length of time the solution was maintained at temperature, and the concentration of fluoride in the solution. A fluoride-gelatin treatment essentially completely precipitated sllica from the dissolver solution, but the precipitate packed on the filter surface and greatly decreased the solution filtration rate. (auth)

Authors:
;
Publication Date:
Research Org.:
Oak Ridge National Lab., Tenn.
OSTI Identifier:
4077560
Report Number(s):
ORNL-3000
NSA Number:
NSA-15-006050
DOE Contract Number:
W-7405-ENG-26
Resource Type:
Technical Report
Resource Relation:
Other Information: Orig. Receipt Date: 31-DEC-61
Country of Publication:
United States
Language:
English
Subject:
CHEMISTRY; BEHAVIOR; DAREX PROCESS; FILTERS; FLUORIDES; PRECIPITATION; SILICA; SILICON OXIDES; SOLUTIONS; SOLVENT EXTRACTION; SURFACES; TEMPERATURE

Citation Formats

Messing, A.F., and Dean, O.C. REMOVAL OF SILICA FROM DAREX DISSOLVER SOLUTIONS. United States: N. p., 1961. Web. doi:10.2172/4077560.
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Messing, A.F., & Dean, O.C. REMOVAL OF SILICA FROM DAREX DISSOLVER SOLUTIONS. United States. doi:10.2172/4077560.
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Messing, A.F., and Dean, O.C. Wed . "REMOVAL OF SILICA FROM DAREX DISSOLVER SOLUTIONS". United States. doi:10.2172/4077560. https://www.osti.gov/servlets/purl/4077560.
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@article{osti_4077560,
title = {REMOVAL OF SILICA FROM DAREX DISSOLVER SOLUTIONS},
author = {Messing, A.F. and Dean, O.C.},
abstractNote = {The nature and behavior of silica in Darex dissolver solutions were found to be dependent on solution temperature, the length of time the solution was maintained at temperature, and the concentration of fluoride in the solution. A fluoride-gelatin treatment essentially completely precipitated sllica from the dissolver solution, but the precipitate packed on the filter surface and greatly decreased the solution filtration rate. (auth)},
doi = {10.2172/4077560},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 11 00:00:00 EST 1961},
month = {Wed Jan 11 00:00:00 EST 1961}
}
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Technical Report:
View Technical Report (0.46 MB)
DOI:  10.2172/4077560
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  • ;
    The rate of chloride removal varied directly with HNO/sub 3/ concentration fn an APPR-type Darex dissolver product containing 100 g/liter metal loading, 0.58 M initial chloride, and initial HNO/sub 3/ concentrations of 8, 9, 10, 12, and 14 M. The removal rate with 8 and 9 M HNO/sub 3/ was very low. After 6 hr refluxing, the chloride content decreased to 0.50 and 0.36 M, respectively. After refluxing for the same time with 10 to 14 M HNO/sub 3/, the product contained 0.064to 0.0007 M (2270 to 25 ppm) chloride. The effect of air sparging was approximately equivalent to refluxingmore » without sparging at a HNO/sub 3/ concentration 2 M higher. After 6 hr sparging and refluxing the chloride content varied from 0.034 to < 0.00014 M (1200 to < 5 ppm) for initial HNO/sub 3/ concentrations from 8 to 14 M. (auth)« less

  • ;
    The chloride ion concentration of Darex Process dissolver solutions can be reduced readily to 0.1 g/l or less by simple bitch boildown with addition of nitric acid. Efficiency of chloride removal is improved by preliminary concentration of the Darex solution: twofold concentration appears optimum. Utilization of nitric acid during boildown is improved at low boiloff rates but longer time cycles are required for adequate chloride removal. Boildown efficiency was not significantly improved by air sparging. Solvent extraction of Barex dissolver solutions with TBP-diluent solutions is a chemically feasible alternative to the batch boildown procedure for chloride separation and removal. Withmore » 30 per cent TBP-hydrocarbon diluent as extractant, chloride distribution ratios were in the range 0.05 to 0.1. Dual scrubbing--six scrubs with 3 M HNO/ sub 3/, 0.07 M UNH and three scrubs with water at an organic/acqueous volume ratio of 5/1--reduced the chloride concentration of organic phases derived from Darex solutions 0.19 to 1.9 M in HCl to 0.005 g/l. (auth)« less

  • A 2 M NaOH solution is a satisfactory scrubber for the Darex off-gas if sufficient nitrite is present to reduce all hypochlorite to chloride. If there is not enough nitrite produced in the scrubber solution by the reaction of nitrogen dioxide and nitrogen sesquioxide with sodium hydroxide, more reducing agent must be added. Both nitrite and sulfite rapidly reduce hypochlorite in basic solution. The scnubber solution can be used as long as it remains basic. (auth)

  • By the addition of gelatin, small amounts of silica present in nitric acid solutions of metals can be flocculated for ready removal by filtration or centrifugation. In the processing of nuclear reactor fuels by solvent extraction, the prior removal of silica by gelatin reduces emulsification and solids accumulation without complicating product recovery, fission product removal, or waste disposal. (auth)