Anand V. Patwardhan

Mathematical Model for the Extraction of Neodymium from Nitrate Media using Hollow Fiber Supported Liquid Membrane Operated in a Recycling Mode

A mathematical model for facilitated extraction of Neodymium (Nd3+) ions from nitrate media using microporous hollow fiber supported liquid membrane (HFSLM) operated in a recycling mode is presented. Extractant N,N,N′, N′-tetraoctyl diglycolamide (TODGA) diluted with n-dodecane was used as the membrane phase. Di-n-hexyl octanamide (DHOA) has been used as a phase modifier for the extractant. The model developed is not specific to the case considered and has a more general and wide applicability. The model has been developed using equilibrium-based approach. The complexation and de-complexation reactions were assumed to be fast and at equilibrium. Mass balance equations for both acid (HNO3) and TODGA were also incorporated in the model. It was observed that the model results are in good agreement with the experimental data when diffusivity of metal-complex (D m ) and acid-complex (D hm ) through the membrane phase in the pore is 6 × 10−12 m2/s and 1.2 × 10−10 m2/s. Once the values of D m and D hm are estimated by simulation for one set of data, there are no further fitting parameters in the model. The model can then be used in a truly predictive mode for all the remaining data sets.

Mathematical Model for the Extraction of Metal Ions using Hollow Fiber Supported Liquid Membrane Operated in a Recycling Mode

The role of cations H+ and Na+ on the transport of Nd3+ ions was investigated using microporous Hollow Fiber Supported Liquid Membrane (HFSLM) contactor. Extractant N,N,N′,N′-tetraoctyl diglycolamide (TODGA) diluted with n-dodecane was used as the membrane phase. Di-n-hexyl octanamide (DHOA) was used as a phase modifier for the extractant. Transport of Nd3+ ions and HNO3 was studied at varying concentrations of NaNO3 and HNO3 while keeping total nitrate ( ) concentration nearly constant at 3 M. The extraction equilibrium constant (K ex ) for the complexation reaction was experimentally measured for various conditions. The maximum rate of extraction of Nd3+ ions was observed at an equimolar concentration (1.5 M each) of HNO3 and NaNO3 in feed solution under otherwise identical conditions. A mathematical model has also been developed to simulate this system. Mass balance equations for both acid (HNO3) and TODGA were also incorporated in the model. It was observed that the model results are in good agreement with the experimental data when diffusivity of metal-complex (D m ) and acid-complex (D hm ) through the membrane phase in the pore is 6 × 10−12 m2/s and 1.2 × 10−10 m2/s. Once the values of D m and D hm are estimated by simulation for one set of data, there are no further fitting parameters in the model. The model can then be used in a truly predictive mode for all the remaining data sets.

Simultaneous Extraction of Neodymium and Uranium using Hollow Fiber Supported Liquid Membrane

Simultaneous extraction of neodymium and uranium ions from aqueous nitrate media was investigated using hollow fiber supported liquid membrane (HFSLM). The organic phase supported in the membrane pores consisted of extractant N,N,N’,N’-tetraoctyl diglycolamide (TODGA), phase modifier isodecanol, and diluent n-dodecane. Experimental results suggest that there is competition between neodymium and uranium ions for complexation with TODGA. The initial rate of extraction of Nd3+ ions was found to be approximately six times to that of UO22+ ions. Experimental data was explained by a mathematical model for simultaneous transport of two metal ions. The model results were found to be in good agreement with the experimental data when the diffusivities of neodymium-TODGA complex (Dnm) and uranium-TODGA complex (Dum) in the membrane pore are 1.1 x 10−11 and 4 x 10−12 m2/s, respectively.

Development of Synthetic Ketonic Resin

In the present work, the self-polymerization reaction of cyclohexanone was studied to develop a synthetic resin. Synthetic resins are extensively used in paint industry to improve the adhesiveness of paints. Polymerization reactions were carried out in a high-pressure reactor. The results suggest that the self-polymerization of cyclohexanone mainly depends on alkali concentration, reaction temperature, and reaction time. As the ketone-to-alkali ratio decreases, the degree of polymerization increases, which leads to an increase in the hydroxyl value and softening point and a remarkable decrease in solubility. A good-quality solid resin could be obtained with a ketone-to-alkali ratio less than 5 in the temperature range between 130°C and 160°C and within the time duration of 12–22 h. These data may be useful to develop the desired quality of resin in the field of paint application.

Non-Dispersive Solvent Extraction of Neodymium using N,N,N’,N’-Tetraoctyl Diglycolamide (TODGA)

Hollow fiber contactor was used to study non-dispersive extraction (NDSX) of Nd3+ ions from aqueous solutions. N,N,N′,N′-tetraoctyl diglycolamide (TODGA) diluted with n-dodecane was used as the organic phase with di-n-hexyl octanamide (DHOA) as the phase modifier. The role of cations (H+/Na+) on the transport of Nd3+ ions has been investigated for this system. It was observed that H+ ion has a significant role to play in the Nd3+/TODGA complexation reaction. A mathematical model has also been developed to simulate the NDSX process in a hollow fiber contactor. A comparison has also been made between extraction profiles from the NDSX process and the hollow fiber supported liquid membrane (HFSLM) process. It was observed that NDSX gave comparatively faster rates of extraction in the presence of H+ ions but slower in the absence of H+ ions.