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1. Experiments on liquid film thickness around Taylor finger.

Author

Kumar, Amit, Thakur, Amit K., Gaurav, Gajendra Kumar, and Ravuru, Narasimha Reddy

Subjects
*LIQUID films, *MASS transfer, *NEWTONIAN fluids, *FLUID mechanics, *TWO-phase flow, *REYNOLDS number
Abstract

Most of the studies have expressed film thickness ( I i ) as a function of Weber number HT ( DV ) ht , capillary number HT ( V ) ht , E tv s number HT ( gD2 ) ht , and inverse viscosity number HT Nf{(Eo3Mo)14= }gD3 ht where, Mo = Morton number HT (g 4 3) ht . These are related as follows: HT *= D=12(1-4dQLdt D2U) ht Graph (1)where I i SP * sp is the non-dimensional film thickness, I i is the film thickness, I D i is the diameter of the conduit. [Extracted from the article]

Published
2022
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2. Slurry-phase ethylene polymerization processes: a review on multiscale modeling and simulations.

Author

Thakur, Amit K., Gupta, Santosh K., and Chaudhari, Pranava

Subjects
*MASS transfer coefficients, *MULTISCALE modeling, *BUBBLE column reactors, *POLYMERIZATION, *POLYMERS, *CHROMIUM catalysts, *ETHYLENE, *MOLECULAR weights
Abstract

The exit age distribution, I E i ( I i ), for I N i ideal CSTRs in series using the TIS model is given by HT E( )=NN(N-1)! 2+...+(N-1)N-1(N-1)! N-1] ht Graph (12) Here, I i is the dimensionless time, defined as HT =t/ ht , and I i is the mean residence time of the reactor. The internal age distribution, I I i ( I i ), for I N i - ideal CSTRs in series using the TIS model is given by HT I( )=e-N [1+N +N22!. [Extracted from the article]

Published
2022
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3. Multi-objective optimization of an industrial slurry phase ethylene polymerization reactor.

Author

Thakur, Amit K., Gupta, Santosh K., Kumar, Rahul, Banerjee, Nilanjana, and Chaudhari, Pranava

Subjects
*POLYMERIZATION reactors, *SLURRY, *ETHYLENE, *PARETO optimum, *OPERATING costs, *POLYMERIZATION
Abstract

Slurry polymerization processes using Zeigler–Natta catalysts are most widely used for the production of polyethylene due to their several advantages over other processes. Optimal operating conditions are required to obtain the maximum productivity of the polymer at minimal cost while ensuring operational safety in the slurry phase ethylene polymerization reactors. The main focus of this multi-objective optimization study is to obtain the optimal operating conditions corresponding to the maximization of productivity and yield at a minimal operating cost. The tuned reactor model has been optimized. The single objective optimization (SOO) and multi-objective optimization (MOO) problems are solved using non-dominating sorting genetic algorithm-II (NSGA-II). A complete range of Pareto optimal solutions are obtained to obtain the maximum productivity and polymer yield at different input costs. [ABSTRACT FROM AUTHOR]

Published
2022
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4. Preface: special issue dedicated to the "International Conference on Energy Sustainability and Advanced Materials – 2022 (ICESAM-2022)" part of the Energy Summit-2022 UPES, Dehradun, India.

Author

Thakur, Amit K., Gupta, Santosh K., and Ray, Ajay K.

Subjects
*CONFERENCES & conventions, *CHEMICAL reactors, *CHEMICAL engineers, *CHEMICAL engineering, *ENERGY security
Abstract

This document is a preface to a special issue of the International Journal of Chemical Reactor Engineering (IJCRE) dedicated to the "International Conference on Energy Sustainability and Advanced Materials - 2022 (ICESAM-2022)" held at UPES, Dehradun, India. The conference brought together renowned academicians and industrialists from around the world to discuss topics related to energy security, sustainability, and advanced materials for energy applications. The special issue includes peer-reviewed manuscripts derived from oral presentations at the conference, covering a wide range of topics in energy and chemical engineering. The document expresses appreciation for the contributions of the speakers, reviewers, and authors, and looks forward to future collaborations with IJCRE. [Extracted from the article]

Published
2023
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5. Nanoparticle preparation of pharmaceutical compounds via wet milling: Current status and future prospects.

Author

Kumar, Rahul, Thakur, Amit K., Chaudhari, Pranava, Arya, Raj Kumar, Gupta, Kaushal Naresh, Thapliyal, Devyani, Bedar, Amita, Krishna, R. Shruti, and Pitchaiah, Kancharlapalli Chinaraga

Subjects
*NANOPARTICLES, *SPRAY drying, *DRUGS, *DRUG delivery systems, *CRYOGENIC grinding
Abstract

This review discusses the preparation of nanoparticles/nanosuspensions using wet milling processes. It explores wet milling techniques, such as oscillatory bead milling, planetary bead milling, and cryogenic wet milling. The utilization of polymers and surfactants for the preparation of stable nanosuspensions is critically highlighted. One promising approach to enhance the stability of nanoparticle systems includes solidifying nanosuspensions. This review discusses two methods for producing dry nanoparticles: spray drying and spray freeze drying. The influence of these process parameters on particle size is emphasized in this work. Additionally, the review covers the utilization of nanoparticles generated through milling in the study of various drug delivery systems. There are still certain areas within this field that require further investigation of nanoparticle preparation and their application in particle engineering. These unexplored areas are discussed in this review, offering prospective researchers opportunities to gain deeper insights. [Display omitted] [ABSTRACT FROM AUTHOR]

Published
2024
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6. Investigation on crystallization phenomena with supercritical carbon dioxide (CO2) as the antisolvent.

Author

Kumar, Rahul, Thakur, Amit K., Banerjee, Nilanjana, and Chaudhari, Pranava

Subjects
*SUPERCRITICAL carbon dioxide, *SUPERSATURATION, *CRYSTALLIZATION, *DISCONTINUOUS precipitation
Abstract

The supercritical antisolvent (SAS) recrystallization process is one of the most promising recrystallization techniques for the particle formation of pharmaceutical compounds. In this process, a solution of active pharmaceutical ingredient (API) is sprayed into the supercritical carbon dioxide (SC CO2) environment. The mass transport of both the solvent and the antisolvent results in supersaturation followed by the crystallization of the API. In this work, a model is developed to estimate the supersaturation profile of solute in a droplet falling in the SC CO2 environment. The droplet consists of paracetamol as a solute and ethanol as a solvent. It moves down in the antisolvent (supercritical CO2) environment. Interestingly, the present model predicts a rise in supersaturation followed by a fall for a while and then a sharp increase. The competing phenomena of nucleation and growth mechanisms are used to justify this variation in the supersaturation. [ABSTRACT FROM AUTHOR]

Published
2021
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7. On the extremum dissipation for steady state incompressible flow past a sphere at low Reynolds number.

Author

Arya, Raj Kumar, Thapliyal, Devyani, Thakur, Amit K., Kumar, Rahul, and Verros, George D.

Subjects
*REYNOLDS number, *STOKES flow, *STEADY-state flow, *NONEQUILIBRIUM thermodynamics
Abstract

A methodology based on sound non-equilibrium thermodynamics principles is developed to estimate the extremum dissipation point for steady-state incompressible flow past a sphere at low Reynolds numbers. It is shown, that the extremum dissipation point appears at the point when both the shear stress and the pressure at the surface of the sphere are equal to zero. The Reynolds number and the position of the extremum dissipation flow past a sphere were further estimated with the aid of a mathematical model for pressure distribution on the sphere surface, accounting for both creeping and ideal flow. The parameters of the model were determined by comparison of the calculated pressure distribution at the surface with the available literature data. The conditions at which the separation angle and the extremum dissipation angle coincide were also investigated. It is believed that this work could be used to further elucidate the flow past a sphere. [ABSTRACT FROM AUTHOR]

Published
2023
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9. A critical review on thermodynamic and hydrodynamic modeling and simulation of liquid antisolvent crystallization of pharmaceutical compounds.

Author

Thakur, Amit K., Kumar, Rahul, Vipin Kumar, V.K., Kumar, Amit, Kumar Gaurav, Gajendra, and Naresh Gupta, Kaushal

Subjects
*SALTING out (Chemistry), *BINARY mixtures, *SUPERSATURATION, *MASS transfer kinetics, *CRYSTALLIZATION kinetics, *PARTICULATE matter, *DISCONTINUOUS precipitation
Abstract

[Display omitted] • System thermodynamics of the antisolvent crystallization is discussed. • Supersaturation, MSZW, induction time, crystallization kinetics are critically analysed. • Hydrodynamic modeling and CFD-based approach for LASC are critically reviewed. • A complete outlook of LASC is presented. • Modeling based LASC scale-up guidelines and challenges are discussed. Fine particles are in great demand in the pharmaceutical industry due to their versatile applications. Liquid antisolvent crystallization (LASC) is one of the promising approaches to prepare fine particles without requiring high energy. The interdependence of system thermodynamics, mass transfer kinetics, and the multi-phase hydrodynamics in the liquid antisolvent crystallization process is not well understood. In this review, the different modeling aspects of LASC are described from a fundamental perspective. The system thermodynamics of LASC is discussed and several models used in literature to predict the solubility in pure solvents and binary solvent mixtures are summarized. A detailed description of supersaturation, metastable zone width and induction time in antisolvent crystallization are presented and critically analyzed. The nucleation and growth kinetics are discussed and interpreted in terms of process variables. The hydrodynamic aspect of LASC which involves the mixing at different length scales is discussed and analyzed in detail. The CFD simulation-based approach to describe the interaction among different phenomena is critically reviewed. The crystallization scale-up, which is a major challenge in the LASC process, is discussed. A guideline for crystallization scale-up using the CFD-based modeling approach is presented which will be helpful to prospective researchers. [ABSTRACT FROM AUTHOR]

Published
2022
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10. Phosphorylated cellulose triacetate–silica composite adsorbent for recovery of heavy metal ion.

Author

Srivastava, Niharika, Thakur, Amit K., and Shahi, Vinod K.

Subjects
*CELLULOSE acetate, *PHOSPHORYLATION, *SORBENTS, *METAL ions, *SOL-gel processes, *METAL recycling, *HEAVY metals
Abstract

Phosphorylated cellulose triacetate (CTA)/silica composite adsorbent was prepared by acid catalyzed sol–gel method using an inorganic precursor (3-aminopropyl triethoxysilane (APTEOS)). Reported composite adsorbent showed comparatively high adsorption capacity for Ni(II) in compare with different heavy metal ions (Cu 2+ , Ni 2+ , Cd 2+ and Pb 2+ ). For Ni(II) adsorption, effect of time, temperature, pH, adsorbent dose and adsorbate concentration were investigated; different kinetic models were also evaluated. Thermodynamic parameters such as ΔG °, ΔH ° and ΔS ° were also estimated and equilibrium adsorption obeyed Langmuir and Freundlich isotherms. Developed adsorbent exhibited about 78.8% Ni(II) adsorption at pH: 6 and a suitable candidate for the removal of Ni(II) ions from wastewater. Further, about 65.5% recovery of adsorbed Ni(II) using EDTA solution was demonstrated, which suggested effective recycling of the functionalized beads would enable it to be used in the treatment of contaminated water in industry. [ABSTRACT FROM AUTHOR]

Published
2016
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11. Efficient and stable anion exchange membrane: Tuned membrane permeability and charge density for molecular/ionic separation.

Author

Manohar, Murli, Thakur, Amit K., Pandey, Ravi P., and Shahi, Vinod K.

Subjects
*ION exchange (Chemistry), *ARTIFICIAL membranes, *MEMBRANE permeability (Technology), *CHARGE density waves, *SEPARATION (Technology)
Abstract

Herein, we are reporting improved process for chloromethylation of polysulfone (PS) by in situ Friedel–Craft reaction without the use of chloromethyl methyl ether (CME). Further, in situ amination (Menshutkin reaction) was carried out to prepare quaternized ammonium polysulfone (QAPS). QAPS of varied degree of chloromethylation (DCM) (44.01–65.67%) was used for preparing anion-exchange membranes (AEMs) and it was observed that their pore morphology was highly dependent on membrane drying conditions (temperature and RH). As representative case, QAPS membrane (DCM: 44.01% and named as AEM-1(NF) x : x indicates drying temperature) dried at low temperature (30 °C (RH: 75%); 45 °C (RH: 54%) and 60 °C (RH: 12%)) showed nano-porous nature with 5.28–1.89 L m −2 h −1 bar −1 permeability corresponding to 59.31–80.23% salt rejection. Further, permeability of AEM–1(NF) x followed the trend: AEM–1(NF) 30 >AEM-1(NF) 45 >AEM-1(NF) 60 . Formation of porous structure of these membranes was attributed to the phase inversion of the QAPS polymer due to presence of atmospheric water at low temperature (high RH). In addition, QAPS membranes (different DCM values) dried at 80 °C (RH:<5%), exhibited completely dense nature with negligible permeability and named as AEM-1, AEM-2 and AEM-3 (DCM; 44.01; 53.87 and 65.67, respectively). Especially, AEM-3 (DCM: 65.67%) was designed to possess all the required properties such as high water uptake (22.20%), ion-exchange capacity (1.597 mequiv g −1 ), and counter-ion transport number (0.96), along with reasonable conductivity (8.45 mS cm −1 ) due to quaternary ammonium group functionality. Chronopotentiometric and i – v studies of AEMs revealed excellent electro-transport property for AEM-3, while its electrodialysis (ED) performance confirmed the suitability for electro-membrane applications. Reported method is novel for preparing stable alkaline membrane with tuneable permeability and charged nature for separations of molecules/ions by pressure and/or electro-driven technologies. [ABSTRACT FROM AUTHOR]

Published
2015
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12. Bi-functionalized copolymer-sulphonated SiO2 embedded with aprotic ionic liquid based anhydrous proton conducting membrane for high temperature application.

Author

Thakur, Amit K., Manohar, Murli, and Shahi, Vinod K.

Subjects
*COPOLYMERS, *SULFONATION, *MESOPOROUS silica, *IONIC liquids, *PROTON conductivity, *ARTIFICIAL membranes
Abstract

We prepared highly charged bi-functionalized copolymer (BFC) and sulphonated mesoporous silica embedded with aprotic ionic liquid (IL) (1-ethyl-3-methylimidazolium ethyl sulfate) based anhydrous conducting cross-linked polymer electrolyte membrane (PEM) by sol–gel. Composite PEMs with 0–10 wt% sulphonated silica and 20 wt% IL content (BFC/Si- x /IL) were characterized by their morphology, stability, IEC, water retention ability and temperature dependent anhydrous conductivity. Conductivity of pristine BFC membrane (1.57 mS cm −1 ) was increased with incorporation of sulphonated-SiO 2 (10 wt%) in the membrane matrix (BFC/Si-10) (3.56 mS cm −1 ), may be due to formation of interconnected network or channels in the membrane matrix. After embedding of aprotic IL (20 wt%; ~80 µS/cm conductivity) in highly acidic polymer (BFC/Si-10), conductivity of BFC/Si-10/IL composite PEM was about 8.79 mS cm −1 at 30 °C. High anhydrous conductivity for BFC/Si-10/IL PEM was attributed to the exchanged protons from highly acidic membrane matrix by IL cation, and accordingly a mechanism was proposed. Further, enhanced bound water content and thus slow dehydration of BFC/Si- x /IL composite PEMs, make them a promising candidate for fuel cell application under low humidification. [ABSTRACT FROM AUTHOR]

Published
2015
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13. Hydrodynamic modeling of liquid-solid flow in polyolefin slurry reactors using CFD techniques – A critical analysis.

Author

Thakur, Amit K., Kumar, Rahul, Banerjee, Nilanjana, Chaudhari, Pranava, and Gaurav, Gajendra Kumar

Subjects
*SLURRY, *CRITICAL analysis, *FLUIDIZATION, *SENSITIVITY analysis, *HYDRODYNAMICS
Abstract

This first-of-its-kind review discusses the hydrodynamics for polyolefin productions in slurry reactors using CFD. Past reviews in this field are specifically focused on the CFD simulations of gas-phase reactors. This paper critically discusses the multi-scale behavior of liquid-solid hydrodynamics in polyolefin slurry reactors. The multifarious aspects of liquid-solid and solid-solid interactions and their impact on reactor performance are discussed. The review also discusses the possible methods to avoid the reactor operational difficulty due to various interactions such as slug formation, particle swelling, and aggregation. The in-depth analysis presented in this work can serve as a prerequisite for the design, scale-up, and optimization of any liquid-solid fluidization system. The CFD tools with their framework, simulation parameters, and the importance of parameter sensitivity analysis have been critically analysed. The article stems to provide a roadmap for future research work and proposes the challenges of future research that will help the prospective researchers. [Display omitted] • Hydrodynamic modeling approaches for the slurry polyolefin reactors are discussed. • The multifarious interactions and their impact on reactor performance are analyzed. • Particle swelling, agglomeration and slug formation impact reactor operation. • CFD framework and parameter sensitivity analysis are critically reviewed. • A roadmap for future research opportunities and challenges are discussed. [ABSTRACT FROM AUTHOR]

Published
2022
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14. Preparation, characterization and thermal degradation studies of bi-functional cation-exchange membranes.

Author

Thakur, Amit K., Pandey, Ravi.P., and Shahi, Vinod K.

Subjects
*CHEMICAL sample preparation, *BIODEGRADATION of sewage sludge, *ION-permeable membranes, *CROSSLINKED polymers, *FREE radicals
Abstract

Cross-linked divinylbenzene (DVB) based bi-functional copolymer (BFC) was synthesized using acrylic acid and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) by free radical copolymerisation reaction. Simple solution casting technique was used to fabricate the bi-functional cation-exchange membranes using polyvinyl alcohol (PVA) as plasticizer. To deliberate the structural and morphological analyses and asses the density of functional groups, state of water, and conductivity of developed membranes, physicochemical characterizations were carried out. Well optimized PVA/BFC-70 membrane showed high bound water content (3.60%) with high membrane conductivity (3.67 × 10 − 2 S cm − 1 ) and ion-exchange capacity (1.30 mequiv g − 1 ). The reported CEM, especially PVA/BFC-70, was assessed for the electrochemical applications. [ABSTRACT FROM AUTHOR]

Published
2015
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15. Stable and efficient composite anion-exchange membranes based on silica modified poly(ethyleneimine)–poly(vinyl alcohol) for electrodialysis.

Author

Pandey, Ravi P., Thakur, Amit K., and Shahi, Vinod K.

Subjects
*COMPOSITE materials, *CHEMICAL stability, *ION exchange (Chemistry), *ARTIFICIAL membranes, *POLYETHYLENEIMINE, *SILICA
Abstract

Anion exchange membranes (AEMs) have found numerous electrochemical applications because of their good conductivity and permselectivity. Herein, we are reporting a method to prepare silica modified poly(ethyleneimine) (SMPEI) with 3-Glycidoxypropyl-trimethoxysilan (GPTMS) by epoxide ring opening reaction. Stable AEMs of different compositions were prepared with SMPEI and a plasticizer poly(vinyl alcohol) (PVA) by acid catalyzed sol–gel followed by formal cross-linking. The reported method is simple and a green alternative for the preparation of AEM without the use of hazardous chemicals. Suitability of prepared AEMs for electrodialytic application was assessed by analyzing their physicochemical properties, stabilities under operating conditions, conductivity, electro-osmotic and chronopotentiometry studies. A highly suitable membrane, SMPEI/PVA-40, exhibited 55.32 mS cm −1 conductivity (in equilibration with 0.04 N NaCl solution at 30 °C), ion-exchange capacity (1.31 meq g −1 ) and permselectivity (0.79) with good electrodialytic performance. Preparation protocols and properties of the reported composite AEM represent a promising starting point for architecting highly conducting and stable AEMs, but we have to study the trade-off between properties, stabilities and electro-osmotic mass drag before its commercial exploitation. [ABSTRACT FROM AUTHOR]

Published
2014
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16. An improved protocol for electrodialytic desalination yielding mineral-balanced potable water.

Author

Thakur, Amit K., Srivastava, Niharika, Chakrabarty, Tina, Rebary, Babulal, Patidar, Rajesh, Sanghavi, Rahul J., Shahi, Vinod K., and Ghosh, Pushpito K.

Subjects
*ELECTRODIALYSIS, *SALINE water conversion, *BRACKISH waters, *DISTILLATION, *DRINKING water, *MINERAL waters, *ION-permeable membranes
Abstract

Abstract: Brackish water desalination through distillation produces essentially distilled water devoid of all minerals. In reverse osmosis (RO) all dissolved minerals get depleted but depletion of useful minerals (Mg2+, Ca2+, SO4 2− and CO3 2−/HCO3 −) is even greater than of Na+ and Cl–. Conventional electrodialysis (EDconv) too fails to meet the desired objective, all constituents being depleted in similar proportions with respect to feed. Consequently, re-mineralisation is necessary but in many cases not implemented. We report selective electrodialysis (EDsel), for production of desalinated water containing relatively higher proportions of desirable minerals. Commercial cation- and anion exchange membranes (CEMCNS and AEMCNS) were coated with polyaniline (PANI), and the resultant membranes (PANI-CEMCNS, PANI-AEMCNS) were characterised by physico-chemical and electrochemical techniques. Due to sieving and hydrophobic effects, the PANI coating was demonstrated to improve the retention of Mg2+, Ca2+ and SO4 2− during desalination. Retention of mineral constituents was further enhanced with PANI modified styrene-co-divinylbenzene-polyethylene-based interpolymer cation- and anion-exchange membranes (CEMIP and AEMIP). The total alkalinity of the treated stream increased during EDsel, presumably due to concentration polarisation accompanied by preferential transport of H+ over OH−. The process efficiency was only marginally lower (5%) for EDsel, suggesting that this approach to desalination may be of practical importance. [Copyright &y& Elsevier]

Published
2014
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17. Functionalized chitosan based nano-filter membranes for pH-controlled separation of amino acids

Author

Chakrabarty, Tina, Thakur, Amit K., and Shahi, Vinod K.

Subjects
*MEMBRANE separation, *CHITOSAN, *HYDROGEN-ion concentration, *AMINO acids, *FILTERS & filtration, *ELECTRODIALYSIS
Abstract

Abstract: pH-controlled separation of AAs was achieved by electro-membrane cell (EMC) with three compartments (central, comp. 1 and comp. 2). EMC is based on the principles of electrodialysis (ED) using indigenous cation-exchange and anion-exchange nanofilter (C-NF and A-NF, respectively). Water permeabilities (1.1–1.5mh−1 bar−1) and molecular cut-off (MWCO) values (400–500Da) for C-NF and A-NF, were suggested their nanofilter (NF) nature. Electrochemical properties of these membranes confirmed their suitability for EMC. Chronopotentiometric studies revealed the electro-transport of positively charged lysine (LYS+) and negatively charged glutamic acid (GLU−) across C-NF and A-NF, respectively, at pH: 6.1 under applied voltage. While glycine at its pI (pH: 6.1) remained immobile. Thus, separation of AAs (ternary mixture) by iso-electric point (pI) focusing of one component was proposed. Under optimized experimental conditions (i.e. at 4.0V constant applied voltage, pH: 6.1 for 0.05M equi-molar LYS–GLU–GLY mixture), about 4.0kWhkg−1 of AA separated energy consumption, 82% current efficiency and 90% product recovery showed the economic and technical feasibility of EMC for industrial exploitation. [Copyright &y& Elsevier]

Published
2013
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18. Self-assembled nanofiltration membrane containing antimicrobial organosilica prepared by sol–gel process

Author

Singh, Ajay K., Thakur, Amit K., and Shahi, Vinod K.

Subjects
*MOLECULAR self-assembly, *NANOFILTRATION, *MEMBRANE filters, *ANTI-infective agents, *SILICA, *SOL-gel processes, *SURFACE roughness, *FOULING
Abstract

Abstract: A new silica monomer precursor, bis(4′-aminopropyldiethoxysilylphenyl) 1,3,4-oxadiazole (APDSPO), was synthesized by Barbiar–Grignard reaction. Nanofiltration membranes containing APDSPO (biocide active) and polyvinyl alcohol (PVA), were prepared by acid catalyzed sol–gel followed by formal cross-linking. These membranes were designed with good stabilities (hydraulic, mechanical and chemical), separation performance, and low surface roughness. These membranes showed microbial growth inhibiting properties and thus anti-biofilm/fouling nature. About 35.2Lm−2 h−1 flux and 54.5% salt rejection for feed NaCl solution (1g/L) at 0.62MPa applied pressure, indicate the suitability of membrane (PO-6) for water purification. Membrane performance data also ruled out anti-biofouling nature of PO-6 membrane. [Copyright &y& Elsevier]

Published
2013
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19. A critical review on the particle generation and other applications of rapid expansion of supercritical solution.

Author

Kumar, Rahul, Thakur, Amit K., Banerjee, Nilanjana, and Chaudhari, Pranava

Subjects
*SUPERCRITICAL carbon dioxide, *SUPERSATURATION, *NANOCARRIERS, *PARTICLE size distribution, *PARTICULATE matter, *CARBON dioxide, *SOLUBILITY, *SIZE reduction of materials
Abstract

[Display omitted] The novel particle generation processes of Active Pharmaceutical Ingredient (API)/drug have been extensively explored in recent decades due to their wide-range applications in the pharmaceutical industry. The Rapid Expansion of Supercritical Solutions (RESS) is one of the promising techniques to obtain the fine particles (micro to nano-size) of APIs with narrow particle size distribution (PSD). In RESS, supercritical carbon dioxide (SC CO 2) and API are used as solvent and solute respectively. In this literature survey, the application of RESS in the formation of fine particles is critically reviewed. Solubility of API in SC CO 2 and supersaturation are the key factors in tuning the particle size. The different approaches to model and predict the solubility of API in SC CO 2 are discussed. Then, the effect of process parameters on mean particle size and the particle size distribution are interpreted in the context of solubility and supersaturation. Furthermore, the less-explored applications of RESS in preparation of solid-lipid nanoparticles, liposome, polymorphic conversion, cocrystallization and inclusion complexation are compared with traditional processes. The solubility enhancement of API in SC CO 2 using co-solvent and its applications in particle generation are explored in published literature. The development and modifications in the conventional RESS process to overcome the limitations of RESS are presented. Finally, the perspective on RESS with special attention to its commercial operation is highlighted. [ABSTRACT FROM AUTHOR]

Published
2021
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20. Comparative analysis of various pretreatments to mitigate fouling and scaling in membrane distillation.

Author

Hsieh, I-Min, Thakur, Amit K., and Malmali, Mahdi

Subjects
*MEMBRANE distillation, *FOULING, *OIL field brines, *SURFACE preparation, *FERRIC oxide, *ULTRAFILTRATION, *PERVAPORATION
Abstract

Membrane distillation (MD) has shown strong promise for treating hypersaline produced water (PW) streams. Scaling and fouling on the membrane surface, however, have been identified as major challenges for commercialization and widespread application. The focus of this study was to first identify the nature of foulants and scalants on the membrane surface and then investigate the pretreatment strategies that mitigate the extent of fouling and scaling on the membrane surface. Vacuum MD (VMD) was selected for this study because of its higher flux at more moderate feed temperatures that eventually leads better assessment of fouling and scaling on the membrane surface. VMD flux tests were carried out with three different real PW samples at total dissolved solids concentrations in the range of 120–160 g/L. It was found that an efficient pretreatment prior to MD is required to mitigate the fouling potential of the organic matter, mostly suspended constituents, in PW samples. Suspended organics fouled and quickly wetted the MD membrane. Major conventional treatments, including filtration, oxidation, coagulation, air floatation, and aeration were investigated to pretreat the PW before VMD tests. A comprehensive comparative analysis is presented showing that the ultrafiltration and coagulation pretreatments displayed the best performance in mitigating the fouling and scaling, while oxidative pretreatment was found to be effective in reducing the iron concentration to less than 5 ppm. The surface of scaled membranes was carefully characterized to further evaluate the performance of each pretreatment. The components that had the highest tendency to precipitate on the membrane surface were identified as strontium sulfate, calcium carbonate, sodium chloride, iron oxide, and silica. These findings are supported by thermodynamic estimation of the saturation index. • Membrane distillation proposed for desalinating hypersaline produced water • Suspended organic matter fouls the membrane, leading to immediate membrane wetting. • Pretreatment of produced water required for long-term performance • Fouling and scaling characterized; sulfate and carbonates found as major scalants • Produced water concentrated to 290 g/L and +50% water recovery achieved [ABSTRACT FROM AUTHOR]

Published
2021
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21. Performance of sweeping gas membrane distillation for treating produced water: Modeling and experiments.

Author

Thakur, Amit K., Hsieh, I-Min, Islam, Md R., Lin, Boson, Chen, Chau-Chyun, and Malmali, Mahdi

Subjects
*MEMBRANE distillation, *OIL field brines, *SALINE water conversion, *MASS transfer, *HEAT transfer
Abstract

Membrane distillation (MD) has shown promise for desalination of produced water (PW), but there are very few studies reported on the performance of MD with real PW and the characteristics of the fouling and scaling in MD. Among different MD configurations, sweeping gas MD (SGMD) is the least studied configuration. Here we report the application of SGMD for treating high-salinity PW (123 g L−1). The SGMD operating conditions were first carefully optimized through pure water MD experiments by varying operating conditions. The flux evaluation was accompanied by a detailed Aspen Custom Modeler simulation based on the electrolyte-NRTL thermodynamic model to better understand the heat and mass transfer in the feed and permeate channel. Supported by experiments, modeling results confirmed the partial condensation of the vapor in the permeate channel. Additionally, it was concluded that the saturation of the sweeping gas is controlling the overall mass transfer through the membrane. Selected membranes and optimized conditions were then used to conduct short-term and long-term performance tests with PW. In long-term MD test, the concentration of the PW increased by a factor of two (50% water recovery), while the membrane exhibited small flux decline. Elemental analysis showed that strontium and sodium were the major scalant compounds. • Aspen Custom Modeler (ACM) with e-NRTL thermodynamic model was used to predict the SGMD flux. • Modeling and experiments suggest that the sweep gas in the permeate side controls and limits the SGMD flux. • Produced water was concentrated to 250,000 mg L-1, and no membrane wetting was observed in long-term SGMD tests. • Characterization of the fouled and scaled membranes showed that organic matter can increase the possibility of membrane wetting. • Although at low concentration, strontium and iron were found to be the major scalants on the scaled membranes. [ABSTRACT FROM AUTHOR]

Published
2020
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22. Graphene oxide on laser-induced graphene filters for antifouling, electrically conductive ultrafiltration membranes.

Author

Thakur, Amit K., Singh, Swatantra P., Thamaraiselvan, Chidambaram, Kleinberg, Maurício Nunes, and Arnusch, Christopher J.

Subjects
*GRAPHENE oxide, *ULTRAFILTRATION, *POROUS materials, *MEMBRANE separation, *MOLECULAR weights, *POLYMERIC membranes, *POLYETHERSULFONE
Abstract

Laser-induced graphene (LIG) is a three-dimensional porous carbon material prepared by direct laser writing with a CO 2 laser on various polymers in an ambient atmosphere, leading to electrically conductive, low fouling coatings. Recently, LIG has been synthesized on porous supports, which led to highly permeable and porous separation filters and LIG composites have greatly improved the stability. On the other hand, graphene oxide (GO) has emerged as a promising 2D nanomaterial to coat porous or non-porous polymer membrane supports resulting in separation membranes with enhanced separation and surface properties. Here, we report a robust, hybrid LIG-GO membrane fabricated by filtration and crosslinking of GO onto the LIG membrane support, generating ultrafiltration membranes with tailored performance. Increasing the amount of crosslinked GO on the LIG surface resulted in increased rejection of bovine serum albumin (BSA) up to 69%, and bacterial rejection was increased from 20 to 99.9%, which agreed with the measured molecular weight cut-off determination that approached ~ 90 kDa as the GO content increased. Higher flux recovery ratios and lower BSA adsorption were seen with LIG-GO membranes, and the hybrid membranes showed comparatively good antifouling. These composite membranes showed 83% less biofilm growth compared to a typical polymer ultrafiltration membrane under non-filtration condition. Noteworthy is that the LIG supporting layer maintained its electrical conductivity and the LIG-GO membrane used as electrodes showed complete elimination of bacterial viability with potent antimicrobial killing effects when treated with mixed bacterial culture. In cross-flow filtration, LIG-GO membranes with 3V anodic electric field showed 11% improvement of flux as compared to typical polymer ultrafiltration membrane. The LIG-GO membranes expand possibilities for the use of LIG in membrane separation applications, especially ultrafiltration. Carbon-based antifouling, electrically conductive ultrafiltration membranes were fabricated using laser-induced graphene membrane supports and crosslinked graphene oxide. Image 1 • laser-induced graphene (LIG) integrated into composite membranes. • LIG composites with crosslinked graphene oxide(GO) show ultrafiltration properties. • LIG-GO composite membranes stable under extended sonication at low and high pH. • Membranes electrically active, showing low fouling and bacterial killing effects. • LIG-GO more biofouling resistant than commercial UF membrane in cross-flow testing. [ABSTRACT FROM AUTHOR]

Published
2019
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23. Solar assisted CaCl2 desiccant wheel rotor system for simultaneous cooling and dehumidification operation: experimental and modelling approach.

Author

Prasad, Amarjeet Kumar, Singh, Dhirendra Kumar, Shankar, Ravi, Thakur, Amit K., and Singh, Dheerandra

Subjects
*DRYING agents, *HUMIDITY control, *COOLING systems, *COOLING, *AIR flow, *CALCIUM chloride, *HUMIDITY
Abstract

High temperature and humidity of many reason of India in the summer season is the major challenge for human comfort also in the drying. In the present work, experiments have been performed to examine the cooling and dehumidification process in the summer season for human comfort and industrial application with the help of calcium chloride (CaCl2) based desiccant material solid desiccant wheel integrated with solar heating arrangements. In this study experimental findings are also evaluated by the mathematical model. During the dehumidification of air in the process unit humidity changes from 17.75 to 29.03 g H2O/kg dry air to 2.8–3.9, 6.8–8.15, 8.92–10.9 & 9.79–11.87 g H2O/kg dry air for flow rate at 1, 2, 3 & 4 m/s, respectively. The process air outlet temperature is increased in the range of 2.58–3.53 K for all air flow rates. After humidification of process outlet air, human comfort condition (HCC) is produced with temperature and humidity in the range of 30–33 °C and 7.77–12.47 g H2O/kg dry air for different air flow rates. Overall airflow for velocity 2–4 m/s can be recommended for the HCC condition. The proposed modelled expression indicates less than 10 % error between the actual and modelled value for different sections. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Numerical simulation of fluid flow in microchannels with induced irregularities.

Author

Chaudhari, Pranava, Kapoor, Ashish, Awasthi, Yashraj, Thakur, Amit K., and Kumar, Rahul

Subjects
*FLUID flow, *FLOW simulations, *COMPUTATIONAL fluid dynamics, *PRESSURE drop (Fluid dynamics), *REYNOLDS number, *MICROCHANNEL flow
Abstract

Microchannels are small-scale channels with unique properties that make them useful in various fields, such as electronics, biomedical engineering, and chemical engineering. This research paper investigates the effect of microchannel geometry on fluid flow behavior at different values of the Reynolds number. A rectangular microchannel with a pattern of obstructions and water as the working fluid was used in this study. Computational fluid dynamics (CFD) simulations were used to investigate the impact of different channel geometrical configurations and different values of the Reynolds number on fluid flow behavior. The results showed that the channel geometrical configuration and the Reynolds number significantly affect fluid flow behavior. A geometry with increasing obstruction heights led to higher values of pressure drop than the geometry with decreasing obstruction heights. This study provides valuable insights into microchannel flow behavior and can be used for the development of optimized microchannel designs for diverse applications. [ABSTRACT FROM AUTHOR]

Published
2023
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25. BaCO3 nanoparticles embedded retentive and cation selective membrane for separation/recovery of Mg2 + from natural water sources.

Author

Srivastava, Niharika, Joshi, Kuldeep V., Thakur, Amit K., Menon, Shobhana K., and Shahi, Vinod K.

Subjects
*BARIUM carbonate, *CATIONS, *ARTIFICIAL membranes, *MEMBRANE separation, *MAGNESIUM compounds, *WATER chemistry, *ELECTRODIALYSIS
Abstract

BaCO 3 nanoparticles (NPs) (20 and 100 nm) were prepared using poly(vinyl pyrrolidone) (PVP) as stabilizer. The prepared NPs showed high adsorption capacity for Mg 2 + in presence of other cations (Na + , Ca 2 + etc.). BaCO 3 nanoparticles embedded sulphonated poly(ether sulfone) (SPS) membranes were prepared, which showed Mg 2 + retentive and cation selective properties. These membranes exhibited good thermal, mechanical, and chemical stabilities along with conductivity and ion-exchange capacity due to SPS matrix. Mg 2 + retentive nature of these membranes was attributed to the embedded BaCO 3 NPs. Further, SPS-NPE membrane was assessed suitable for electro-separation process. Electrodialytic studies confirmed very high retention values for Mg 2 + in comparison with Na + and Ca 2 + . The energy consumption of proposed process suggested suitability of these membranes for separation/recovery of Mg 2 + from natural water resources. [ABSTRACT FROM AUTHOR]

Published
2014
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26. Gas-liquid downward flow through narrow vertical conduits: effect of angle of entry and tube-diameter on flow patterns.

Author

Kumar, Amit, Das, Gargi, Ray, Subhabrata, Jha, Jay Mant, Thakur, Amit K., and Panda, Swapna Rekha

Subjects
*STRATIFIED flow, *TRANSITION flow, *TWO-phase flow, *GLASS tubes
Abstract

The present study investigates the flow pattern characteristics of air-water co-current down-flow in millichannels. The experiments have been performed in glass tube of diameter 0.0042 and 0.008 m. The fluids are injected through Y entry the included angle between the Y arms being 45°, 90°, 135°, and 180° (T Entry). The investigation reveals that the flow patterns are function of tube-diameter, and angle of fluid entry. Interestingly, stratified flow has been observed for steeper Y entry section at low liquid flow rates. [ABSTRACT FROM AUTHOR]

Published
2021
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27. Liquid antisolvent recrystallization and solid dispersion of flufenamic acid with polyvinylpyrrolidone K-30.

Author

Kumar, Rahul, Kumar, Sanjay, Chaudhari, Pranava, and Thakur, Amit K.

Subjects
*SIZE reduction of materials, *POVIDONE, *DISPERSION (Chemistry), *DRUG bioavailability, *PARTICULATE matter, *RECRYSTALLIZATION (Chemistry)
Abstract

Flufenamic acid (FFA) is a Biopharmaceutical Classification System- II (BCS-II) class drug with poor bioavailability and a lower dissolution rate. Particle size reduction is one of the conventional approaches to increase the dissolution rate and subsequently the bioavailability. The use of the liquid antisolvent method for particle size reduction of FFA was studied in this work. Ethanol and water were used as solvent and antisolvent, respectively. Experimental parameters such as solution concentration (10–40 mg/ml), flow rate (120–480 ml/h), temperature (298–328 K) and stirring speed (200–800 rpm) were investigated. Furthermore, the solid dispersion of FFA was prepared with polyvinylpyrrolidone K-30 (PVP K-30) with different weight ratios (1:1, 1:2, 1:3 and 1:4) and samples were characterized using SEM, FTIR and XRD techniques. The experimental investigation revealed that higher values of concentration, injection rate, stirring speed, along with lower temperature favored the formation of fine particles. SEM analysis revealed that the morphology of raw FFA changed from rock-like to rectangular-like after liquid antisolvent recrystallization. FTIR analysis validated the presence of hydrogen bonding between FFA and PVP in solid dispersion. XRD analysis showed no significant change in the crystallinity of the processed FFA. [ABSTRACT FROM AUTHOR]

Published
2021
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28. Silver-doped laser-induced graphene for potent surface antibacterial activity and anti-biofilm action.

Author

Gupta, Abhishek, Holoidovsky, Lara, Thamaraiselvan, Chidambaram, Thakur, Amit K., Singh, Swatantra P., Meijler, Michael M., and Arnusch, Christopher J.

Subjects
*SILVER nanoparticles, *GRAPHENE, *WATER pollution, *SILVER sulfide, *POLYETHERSULFONE, *RURAL geography
Abstract

Previously, laser-induced graphene (LIG) coated surfaces were shown to resist biofilm growth, although the material was not strongly antibacterial. Here, we show LIG surfaces doped with silver nanoparticles (Ag0 or AgNPs) as highly antibacterial surfaces. Starting from AgNO3 polyethersulfone (PES) polymer substrates, silver nanoparticles between 5–10 nm were generated in situ during the lasing process and stably embedded in the fibrous and porous structure of LIG in a single step. These silver doped LIG (Ag@LIG) surfaces were highly toxic to bacteria via a mechanism of both Ag+ ion release and possible surface toxicity of the AgNPs. The added antibacterial function of Ag-nanoparticles expands the functionality of LIG coated surfaces and might lead to highly effective point of use/entry devices in rural areas or in disaster situations with contaminated water sources. [ABSTRACT FROM AUTHOR]

Published
2019
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29. Molecular thermodynamics for scaling prediction: Case of membrane distillation.

Author

Islam, Md Rashedul, Hsieh, I-Min, Lin, Bosong, Thakur, Amit K., Chen, Chau-Chyun, and Malmali, Mahdi

Subjects
*MEMBRANE distillation, *THERMODYNAMICS, *PHASE equilibrium, *SOLUTION (Chemistry), *PRECIPITATION forecasting
Abstract

[Display omitted] • A parametrized thermodynamic model proposed to predict phase equilibria. • Performance of the MD simulated in a subroutine custom model. • Scaling of salts are predicted during MD operation. • Scaling prediction is validated via experimental results. • Complex interaction among molecular and ionic species are highlighted. Membrane distillation (MD) for water treatment is significantly impaired by the scaling of dissolved minerals. The type and content of minerals generally measured as total dissolved solids (TDS) in hypersaline brines not only reduce the MD flux but also control the scaling behavior on the membrane surface. The scaling-induced pore blockage further reduces water flux and eventually leads to membrane wetting. The scaling problem is even more pronounced in the treatment of produced water (PW) as it contains 3–7 times higher TDS concentrations, compared to seawater. Theoretically, the necessary conditions for a salt to precipitate can be traced from its solubility product constant and activity of the constituents within the solution. Therefore, a comprehensive thermodynamic model is necessary to represent the electrolyte behavior and to predict the precipitation of different salts in a complex solution like PW. We pursued electrolyte Nonrandom Two Liquid Theory (eNRTL), a state-of-the-art electrolyte model, to address the PW fluid phase equilibria. With a fully parameterized eNRTL model, we predicted salt precipitations in two different PW samples and compared the results against the experimental findings. Furthermore, we forecast the precipitation of salts in response to the change in PW concentration and temperature in the MD operation. [ABSTRACT FROM AUTHOR]

Published
2021
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30. Stable ion-exchange membranes for water desalination by electrodialysis

Author

Chakrabarty, Tina, Rajesh, A. Michael, Jasti, Amaranadh, Thakur, Amit K., Singh, Ajay K., Prakash, S., Kulshrestha, Vaibhav, and Shahi, Vinod K.

Subjects
*ION-permeable membranes, *SALINE water conversion, *ELECTRODIALYSIS, *POLYVINYL alcohol, *CROSSLINKED polymers, *SULFONATION, *HIGH temperatures, *ENERGY consumption
Abstract

Abstract: In this manuscript, we are using sulfonated poly (ethersulfone) (SPES) based cation-exchange membrane (CEM) and polyvinyl alcohol-4-vinylpyridine (4-VP) based cross-linked based anion-exchange membrane (AEM) for water desalination by electrodialysis (ED). These membranes were characterized for their electrochemical and physicochemical properties such as membrane conductivity, counter-ion transport number, ion-exchange capacity and water content. Prepared ion-exchange membranes (IEMs) showed good stabilities under severe conditions such as high temperature and strong oxidizing conditions. ED experiments in recirculation mode of operation were performed for water desalination. Energy consumption and current efficiency values confirmed suitability of these IEMs for desalination of water by ED. [Copyright &y& Elsevier]

Published
2011
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