The document summarizes experiments on extracting nitric acid using tri-n-butyl phosphate (TBP) in batch and minichannel systems. In batch experiments, the percentage extraction of nitric acid increased with higher acid concentration, stirring speed, and volume of solvent. A mathematical model was developed and showed that the mass transfer coefficient increased with stirring speed and initial acid concentration. Minichannel experiments observed slug flow and found that extraction percentage increased with slug length and was higher than in batch experiments due to greater interfacial area.

1. Sandeep V.a, Chandramouli G.a, Anil B. Vir b, S. Pushpavanam b
a Department of Chemical Engineering, SASTRA University, Thanjavur, TN, India 613401.
b Department of Chemical Engineering, Indian Institute of Technology, Madras (IIT, Madras), TN, India 600036.
Email: anil.vir8@gmail.com , spush@iitm.ac.in
Webpage: http://www.che.iitm.ac.in/~spush/index.html
1
Extraction of Nitric Acid using Tri-n-butyl
phosphate (TBP) in Batch and Minichannel
Chemical
Engineering
Department,
IIT Madras
Chennai,
INDIA
CHEMCON-
2014
Dec 27-30
Punjab
University
INDIA
Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

2. OUTLINE
• Objectives
• Experiment in batch
• Results and discussion of batch extraction
• Mathematical approach
• Extraction performance in minichannel
• Concluding remarks
2Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

3. Objectives
• Nitrates being toxic, prove detrimental to aquatic life.
• Extraction of nitrates from nuclear wastes is therefore
essential.
• Since the wastes are radioactive, Nitric acid is
initially experimented with the solvent.
• Furthermore micro-channel experiments need to be
used.
3Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

4. Extraction system chosen
 Extraction of Nitric acid from aqueous to organic phase.
 Aqueous phase: (Nitric acid + Water)
 Organic phase : Tri-n-butyl phosphate (TBP)
Aqueous
phase
Organic
phase
Picture: Batch experimental set-up
Parameters studied:
 Effect of stirring speed.
 Effect of aqueous to organic
volume ratio.
 Effect of initial concentration of
nitric acid.
4Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

5. Effect of stirring speed
5Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

6. Effect of volume ratio (Aqueous: Organic)
6Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

7. Effect of Initial Nitric Acid Concentration
7Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

8. Effect of solvent concentration
Figure: Effect of solvent concentration (a) 30% TBP (b) 50% TBP
(a) 30 % TBP (b) 50 % TBP
8Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

9. Mathematical model for Batch process
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org
orgdaqma
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ckck
dt
dc
ckck
dt
dc

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 Mathematical model developed to analyse performance of batch extraction.
 Overall mass transfer coefficient found using optimization approach.
 lsqnonlin used in MATLAB R2014A for optimization.
9Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

10. Mass transfer coefficient
Figure : Effect of (a) stirring speed and (b) initial concentration on
overall mass transfer coefficient (sec-1)
10Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

11. Minichannel experimental set-up
• The channel has a diameter of 500 µm and length 60 cm.
• T-junction channel is used for the experiment.
Figure : T-junction minichannelFigure : Minichannel Experimental Set-up
11Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

12. Slug flow
Figure : Slug flow in a minichannel for aqueous nitric acid and tri-n-butyl phosphate (TBP)
 Slug flow:
 Aqueous nitric acid-forming continuous phase.
 Organic phase (TBP)- forming slug.
 Slug flow observed at low flow rates.
 Length of slug depends on flow rates.
12Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

13. Extraction performance in minichannel
(a) Slug length variation (b) Extraction performance
Figure: (a) Slug length variation (b) % Extraction of Nitric acid with organic phase flow rate
13Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

14. Concluding Remarks
• In Batch Experiments, the percentage extraction was found to
increase by concentrating the acid , increasing the stirring
speed and also by increasing the volume of the solvent in the
organic phase.
• In Minichannel Experiments, the extraction percentage
increased with the increase in slug length which is dictated by
the TBP flow-rate.
• Efficiency of extraction in minichannel was higher than that in
batch experiments on time basis due to higher interfacial area
for mass transfer.
14Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com

15. 15Anil B. Vir Chem Engg, IIT Madras anil.vir8@gmail.com