US EPA

5020408 

Journal Article 

Measurement of Dielectric Constant of Organic Solvents by Indigenously Developed Dielectric Probe 

Keshari, AK; Rao, JP; Rao, CVSB; Ramakrishnan, R; Ramanarayanan, RR 

2018 

Yes 

AIP Conference Proceedings
ISSN: 0094-243X
EISSN: 1551-7616 

AIP Conference Proceedings 

1951 

10.1063/1.5031737 

WOS:000446381600029 

The extraction, separation and purification of actinides (uranium and plutonium) from various matrices are an important step in nuclear fuel cycle. One of the separation process adopted in an industrial scale is the liquid-liquid extraction or solvent extraction. Liquid-liquid extraction uses a specific ligand/extractant in conjunction with suitable diluent. Solvent extraction or liquid-liquid extraction, involves the partitioning of the solute between two immiscible phases. In most cases, one of the phases is aqueous, and the other one is an organic solvent. The solvent used in solvent extraction should be selective for the metal of interest, it should have optimum distribution ratio, and the loaded metal from the organic phase should be easily stripped under suitable experimental conditions. Some of the important physical properties which are important for the solvent are density, viscosity, phase separation time, interfacial surface tension and the polarity of the extractant.



The polarity of the solvent and diluent dictates the choice of the solvent/diluent combination that can be used for the extraction of a metal. The polarity of the solvent also limits the amount of metal than can be loaded in to the organic phase without splitting the organic phase i.e. formation of third phase. Generally, the dielectric constant (epsilon) of a solvent is a measure of its polarity. The higher a means, higher the polarity and greater is the ability of the solvent to stabilize the charge. Hence the measurement of dielectric constant is vital in deciding the usage of the solvent for a given application. The present manuscript deals with the development of a probe and the required instrumentation for the determination of dielectric constant of organic solvents. This probe was used to measure the dielectric constant of indigenously synthesized solvents such as Di-iso-amylhydrogen phosphonate (DiAHP) and Di-iso-butylhydrogen phosphonate (DiBHP).



The basic technique for measurement of dielectric constant is based on measuring the capacitance of dielectric probe in solvent. The change of capacitance of dielectric probe with solvent is proportional to change of dielectric constant of solvent. The development of dielectric probe is a challenging task, as the measurement involves the estimation of capacitance over a wide range with high degree of accuracy. The dielectric probe was designed in such a way that the value of capacitance of dielectric probe with solvent is above pico-farad range and also the requirement of the solvent is also minimal (similar to 30 mL). The capacitance of dielectric probe is measured by using astable multivibrator configuration. The change of capacitance is inversely proportional to change of frequency. The Graphical User Interface (GUI) has been developed to acquire the data through RS-232. The software provides an online graphical display of the dielectric constant of solvent which enables the user to determine the regions of stability. The software also provides on-demand pop-up window to check the overall trend of dielectric constant of solvent to view a larger data by click of a button. The datum is stored in a file for analysis. An indigenous dielectric constant measurement set-up has been developed in our laboratory at IGCAR.



The instrument has been calibrated with standard solvents whose dielectric constants are known accurately from the literature. Some of these solvents were taken to validate the precision of the instrument. The instrument has been used to find out the dielectric constants of in-house synthesized solvents whose dielectric constants are not available in the literature. 

Solvents; polarity; Dielectric constant; Astable multivibrator frequency; Dielectric probe; Capacitance; Graphical user interface (GUI); Actinides