Organic degradation in uranium and cobalt solvent extraction:
Download
1 / 20

organic degradation in uranium and cobalt solvent extraction: the case for aliphatic diluents and anti-oxidants - PowerPoint PPT Presentation


  • 206 Views
  • Uploaded on

Organic degradation in uranium and cobalt solvent extraction: The case for aliphatic diluents and anti-oxidants. Deon van Rensburg ChemQuest Africa. Introduction to the Problem. Rössing Uranium experienced organic degradation a number of times.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'organic degradation in uranium and cobalt solvent extraction: the case for aliphatic diluents and anti-oxidants ' - sandra_john


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Organic degradation in uranium and cobalt solvent extraction:The case for aliphatic diluents and anti-oxidants

Deon van Rensburg

ChemQuest Africa


Introduction to the problem l.jpg
Introduction to the Problem extraction:

  • Rössing Uranium experienced organic degradation a number of times.

  • They instituted a program of investigation and remedy.

  • A number of cobalt/nickel SX plants also experienced organic degradation.

  • ChemQuest conducted some laboratory testing.


R ssing uranium l.jpg
RÖSSING URANIUM extraction:

  • Organic phase breakdown products detected, related to the presence of nitrosamines.

  • Extensive crud formation, poor stripping efficiency and excessive organic entrainment was noted.

  • Very expensive to replace degraded organic phase. (1986, 2002, 2005 – latter two included entire inventory)


R ssing uranium4 l.jpg
RÖSSING URANIUM extraction:

The presence of high levels of nitrosamines directly correlated with the upset conditions on the SX plant.


Possible reasons l.jpg
Possible Reasons extraction:

  • Ingress of nitrates with process water – from the explosives used in the pit.

    • Nitrates are co-extracted by the amine reagent

    • [R3NH]2SO4 + mNOx [R3NH]2 [NOx]m + SO42—

  • High redox potential from the leach process possibly carried over into the SX

    • Tests show that high Eh causes organic degradation.

    • Undissolvedpyrolusite carryover?


Nitrate monitoring l.jpg
Nitrate Monitoring extraction:


Nitrate monitoring7 l.jpg
Nitrate Monitoring extraction:




Redox monitoring l.jpg
Redox Monitoring extraction:



Oxidation test methods l.jpg
Oxidation Test Methods extraction:

  • Standard test solution used by Rössing, with addition of 5 mg/l KMnO4

  • O:A ratio of 1

  • 45°C, constant air injection, 220 rpm, 180 minutes

  • Used aliphatic and aromatic diluent

  • With and without 0.2% m/v butyl hydroxy toluene


Oxidation test results uranium l.jpg
Oxidation Test Results: extraction:Uranium


Conclusion uranium l.jpg
Conclusion: extraction:Uranium

  • It remains better to tackle the source of the problem, rather than treat the symptoms and effects





Degradation in cobalt circuits18 l.jpg
Degradation in Cobalt Circuits extraction:

  • Increased viscosity and poorer phase disengagement in both circuits

  • Actual cobalt and nickel removal in the D2EHPA circuit

  • High organic entrainment

  • Poorer extraction kinetics of cobalt in 272 circuit

  • Linked to high redox potential in incoming PLS



Conclusion cobalt l.jpg
Conclusion: extraction:Cobalt

  • If organic degradation is found or suspected in SX circuits using solvation-type extractants such as Cyanex 272, Ionquest 290, D2EHPA or Versatic 10, then the use of an anti-oxidant is probably indicated.


ad