This document discusses the extraction of nitric acid using tri-n-butyl phosphate (TBP) in batch and microscale flow systems. Batch experiments were conducted varying the aqueous to organic volume ratio, nitric acid concentration, and stirring speed. The extraction performance increased with higher stirring speeds. Microchannel experiments using a T-junction glass capillary observed slug flow and examined extraction for varying residence times and flow rates. A lumped parameter model was developed and the overall mass transfer coefficient was determined. The batch experiments provide data on the effect of parameters on nitric acid extraction with TBP, while microchannels show potential for liquid-liquid extraction due to characteristics like laminar flow and high surface area to volume ratio.

1. CHEMCON-2014
*Presenting author: Anil B. Vir
1
Sandeep V.1
, Chandramouli G1
., Anil B. Vir2*
, S. Pushpavanam2
1
Department of Chemical Engineering, SASTRA University, Thanjavur, TN, India 613401.
2
Department of Chemical Engineering, Indian Institute of Technology, Madras (IIT, Madras), TN,
India 600036.
* Corresponding author. Email- anil.vir8@gmail.com.
( Research Program: Mass Transfer )
Introduction
Liquid-liquid extraction is an important unit operation in
chemical and fine chemical industries. Numerous
applications of extraction includes purification and
separation of components from waste streams such as
acid recovery [1,2], metal recovery [3] etc. In the
literature several studies have been found for extraction
of nitric acid using 30% tri-n-butyl phosphate (TBP) as a
solvent in batch system in the context of nuclear industry
[4–7].
In this work nitric acid extraction using 100% TBP using
batch and microscale flow is analysed experimentally and
theoretically. Microfluidics offers several advantages
such as laminar flow, high surface volume ratio, shorter
diffusion path which favor liquid-liquid extraction [8].
Here nitric acid extraction from aqueous stream to
organic stream using Tri-butyl phosphate (TBP) as
solvent is analysed. The experiments are carried out in
batch reactor and minichannels. The batch experiments
are done for three different cases by (i) varying the
aqueous to organic volume ratio in the proportion of 1:1 ,
1:2, and 1:3 (ii) Varying the nitric acid concentration 0.5,
1, and 2 N (iii) varying the stirring speed in the range of
200-800 rpm. A lumped parameter model is developed
and the overall mass transfer coefficient is found. The
minichannel experiments are carried out in a T-junction
glass circular capillary of 500 µm diameter. The slug flow
was observed and the extraction performance in a
minichannel was observed for different residence time by
varying the flow rates of aqueous and organic stream. The
slug length is calculated using image processing.
Result and Discussion
The batch experiments are carried out for different
concentration of nitric acid, different stirring speed and at
different aqueous to organic volume ratio. Figure 1
shows effect of stirring speed on nitric acid extraction
with 100% TBP as a solvent in a batch system. It shows
that with higher stirring speed the mass transfer limitation
EXTRACTION OF NITRIC ACID USING TRI-N-BUTYL-PHOSPHATE
(TBP) IN BATCH AND MINICHANNEL

2. CHEMCON-2014
2
can be reduced. At stirring speed 400 and 800 RPM %
extraction of nitric acid is comparable.
Figure 1 Effect of stirring speed on Nitric acid extraction
using 100% TBP in batch
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