Papu Naik | IIT Guwahati (original) (raw)

Papers by Papu Naik

Journal of Molecular Liquids, Nov 1, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Chemical thermodynamics and thermal analysis, Sep 1, 2021

Abstract In the current work, two menthol-based hydrophobic deep eutectic solvents (DESs) have be... more Abstract In the current work, two menthol-based hydrophobic deep eutectic solvents (DESs) have been synthesized to extract dodecane from water-dodecane emulsion at 298 K and atmospheric pressure. The equilibrium mixture produces two biphasic liquid-liquid equilibrium systems and one triphasic liquid-liquid-liquid equilibrium system. 1H NMR has been used to calculate the molar composition of each phase. For both the lauric and decanoic acid-based DES, the extract phase of biphasic region-1 is rich in DES; whereas the raffinate phase is predominantly water. However, for the biphasic region-2, the extract phase is the dodecane rich phase and raffinate phase is the mixture of DES and dodecane having a dominant composition of DES. In case of triphasic region, i.e. top phase consists of dodecane and the bottom phase is only water. The middle phase becomes an emulsion where DES is the dominant component. The selectivity analysis in the triphasic region proves that both the DESs have high selectivity to extract dodecane from the water-dodecane microemulsion. The experimental mole fractions are correlated with genetic algorithm (GA) promoted NRTL and UNIQUAC models to predict the phase behavior. An average overall root means square deviation (RMSD, %) of 0.174% is observed for the biphasic region and 0.048% for the triphasic employing GA-NRTL model. GA-UNIQUAC predicts an average overall RMSD of 0.340% for biphasic regions and 0.129% for the triphasic region.

Carbohydrate Polymers, Mar 1, 2021

Xylan and gelatin-based hydrogels are prepared in different molar ratios using ethylene glycol di... more Xylan and gelatin-based hydrogels are prepared in different molar ratios using ethylene glycol diglycidyl ether cross-linker. The hydrogels are characterized by Fourier transform infrared spectroscopy, morphology, thermal analysis, and swelling ratio. The rheological experiment shows the gels are cross-linked successfully by revealing the viscoelastic nature. The xylan-gelatin gel synthesized in a 5:1 molar ratio (hence XG5) has higher storage modulus, gelation temperature, and time among the synthesized gels. The adsorption behaviour of the synthesized gels is studied for the removal of methylene blue, by varying adsorbate concentration, pH, and temperature. Among the synthesized hydrogels, XG5 shows the highest adsorption capacity of 26.04 mg g-1 at pH = 5.84 and 25 °C. The kinetics of the adsorption process follows the pseudo-second-order model, and monolayer adsorption is adequately represented by the Langmuir isotherm model. The adsorption process is established as spontaneous, exothermic, and physisorption from the thermodynamic parameters.

Fluid Phase Equilibria, Sep 1, 2017

The present work attempts to measure the solid-liquid equilibrium (SLE) of glucose in three novel... more The present work attempts to measure the solid-liquid equilibrium (SLE) of glucose in three novel low cost deep eutectic solvents (DES) namely tetrabutylammonium bromide [TBAB]-Imidazole, [TBAB]-ethylene glycol, and [TBAB]-glycerol over the temperature range 299.15 to 353.15 K. The [TBAB]-Imidazole DES gave the highest solubility among all the DES. The experimental solubility data was correlated with the Apelblat empirical equation along with regression using local composition models namely NRTL and UNIQUAC models. The thermodynamic functions of dissolution such as enthalpy o dissol ∆ H , Gibbs energy o dissol ∆ G and entropy of dissolution o dissol ∆ S were also calculated from the modified van't Hoff equation. The dissolution functions gave positive values for all the studied systems indicating that the process is endothermic in nature while being nonspontaneous and entropically favourable. In addition, classical Molecular Dynamic (MD) simulations were performed to disclose the glucose-DES interactions. From MD simulations, the anion and hydrogen bond donor (HBD) molecules is seen to overall dominate the dissolution of glucose. From the MD simulations, the anion of hydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD) molecules are primarily responsible for the dissolution of glucose. The isomerization of glucose to fructose in [TBAB]-Imidazolium DES was observed for temperatures above 313.15 K, which resulted in a lower concentration of glucose at higher temperatures.

ChemistrySelect, Nov 27, 2019

Catalytic hydrogenation is a convenient approach for converting Poly Aromatic Hydrocarbons (PAH) ... more Catalytic hydrogenation is a convenient approach for converting Poly Aromatic Hydrocarbons (PAH) to several small fragments or useful chemicals. In the current study, quinoline is taken as model PAH compound where reactive force field (ReaxFF) simulation is adopted to study its degradation and pyrolytic behavior. To confirm the intermediate and final products, ReaxFF molecular dynamics (MD) simulations at five different temperatures ranging from 2500-4500 K for a total duration of 700 ps were implemented which allows the chemical reactions to be observed at a computationally affordable time scale. Other than 2500 K, all the temperatures provided a pyrolysis scan on the entire quinolone molecule. We have found a qualitative agreement between the previously reported experimental results and our simulation results concerning initiation step of the quinoline hydrogenation along with the formation of major intermediate products such as tetrahydroquinoline (THQ), propylaniline (PA) and decahydroquinoline (DHQ). Further degradation of quinoline with time gives smaller stable products, which include ammonia, ethylene, methane, ethane and acetylene with many intermediates. Most of the intermediate reactions are found to be intramolecular while intermolecular reactions dominate at higher temperatures. Finally, a kinetic analysis was made to obtain the rate constants and activation energies for quinoline hydrogenation.

Journal of energy storage, Mar 1, 2023

Journal of Molecular Liquids, Oct 1, 2017

A low cost Deep Eutectic Solvent (DES) is used in this work to evaluate the selective extraction ... more A low cost Deep Eutectic Solvent (DES) is used in this work to evaluate the selective extraction of Poly Aromatic Hydrocarbons (PAH) from heptane. The DES synthesized is a combination of methyltriphenylphosphonium bromide salt and ethylene glycol as HBD at a molar ratio of 1:4. Quinoline and indoline as model PAH were then extracted from the tolueneheptane mixture at T=35°C. The Liquid-Liquid Equilibrium (LLE) data for the ternary system namely: DES (1) + indoline (2) + heptane (3) and quaternary systems; namely DES (1) + quinoline (2) + indoline (3) + heptane (4), DES (1) + quinoline (2) + toluene (3) + heptane (4) and DES (1) + indoline (2) + toluene (3) + heptane (4) were then measured at atmospheric pressure. The PAH concentrations in the system were varied from 5 to 70 wt% to understand the extraction efficiency of DES. The composition of the respective components in both extract and raffinate phases were measured by 1 H NMR technique. It was observed that all the systems followed a type-II phase behavior where a positive slope was seen towards the PAH peak. The distribution coefficient and selectively values for PAH in extract phase were two times higher than toluene. The reliability of the measured tie line data was then correlated with the local thermodynamic models namely NRTL and UNIQUAC models which gave a root mean square deviation (RMSD) of less than 1%. Further, Quantum chemical based COnductor like Screening MOdel for Real Solvents (COSMO-RS) model was also employed to predict the phase behaviour of investigated systems.

ACS Sustainable Chemistry & Engineering

Journal of Energy Storage

CRC Press eBooks, Sep 8, 2022

Current Developments in Biotechnology and Bioengineering

Deep Eutectic Solvents in Liquid–Liquid Extraction

The Journal of Physical Chemistry B

Journal of Molecular Liquids