Chemical Engineering

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Shiv Nadar University

The present work explores the synthesis and characterization of antipyrine crowned Organosilatranes from a condensation reaction between antipyrine and amino silane followed by transesterification reaction with tripodal ligand. A highly selective chemosensor based on the prepared antipyrine crowned Organosilatrane exhibited remarkable selectivity and sensitivity towards Fe2+ and Hg2+ ions. The sensor binds to these ions at 1 : 1 stoichiometry and with high affinity as determined by Jobs plot and apparent from binding constant values of 4.05 ×105 M−1and 3.79 ×105 M−1 respectively. The structure of newly synthesized silanes and Organosilatranes were corroborated by numerous spectroscopic techniques. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

World University root node

(SoE) School of Engineering

ChemistrySelect

First Report on the Synthesis of Antipyrine Crowned Siloxy Framework: Optical Recognition of Fe2+ and Hg2+ Ions

The present manuscript reports the synthesis of multistimulus-responsive smart supramolecular hydrogels derived by in situ coating of silver nanoparticles (Ag NPs) on colloidal cytidine-5′-monophosphate-capped β-FeOOH nanohybrids (β-FeOOH@5′-CMP) under physiological conditions forming a polycrystalline building block (Ag-coated β-FeOOH@5′-CMP). The presence of Ag in the binary nanohybrids induces the puckering of ribose sugar, bringing a change in its conformation from C2′-endo to C3′-endo, which enhanced the supramolecular interactions among different moieties of other building blocks to construct a porous network of hydrogels in the self-assembly via the formation of a micellar structure. Such a supramolecular network in hydrogel is also evidenced by the reversible sol⇌gel transformation under multistimulus-responsiveness in a narrow range of pH, temperature, and sonication, as well as by the manifestation of rapid self-healing and injectability features. As-synthesized hydrogels exhibiting shear-thinning behavior under higher strain and converting back into the sol under low strain, suggests their potential for localized drug delivery. The presence of Ag NPs in the hydrogel enhanced its viscoelastic properties, % swelling (580) and loading capabilities (590 mg g-1) for methylene blue (MB), and its controlled release over days (∼2-30) as a function of pH. It displayed excellent surface-enhanced Raman spectroscopy activity allowing to detect MB-like drug molecules at ≤10-12 M. Thus, the as-synthesized hydrogels represent a unique superparamagnetic nanosystem consisting of all greener components (5′-CMP/β-FeOOH/Ag) with superior viscoelastic, sensing, and antimicrobial properties, displaying multistimulus-responsiveness (pH/temperature/sonication), thereby suggesting their vast potential for biomedical and environmental applications. © 2020 American Chemical Society.

Fulltext

ACS Omega

Multistimulus-Responsive Supramolecular Hydrogels Derived by in situ Coating of Ag Nanoparticles on 5′-CMP-Capped β-FeOOH Binary Nanohybrids with Multifunctional Features and Applications

The development of low molecular weight molecule-mediated biocompatible soft supramolecular hydrogels, considered to be next-generation materials for biomedical applications, is a challenging task. In this context, the present work reports the synthesis of the hybrid hydrogel (CISZ2H) comprising ternary nanohybrids (Zn2+-Ag NPs@β-FeOOH@5′-CMP), consisting of greener components as a building block with hydrophobic tail (containing Zn2+ ions, Ag NPs, and β-FeOOH) and hydrophilic head (5′-cytidine monophosphate (5′-CMP)). The presence of Zn2+ ions and Ag NPs in the nanohybrids introduces new coordination sites and induces the puckering of the ribose sugar in 5′-CMP to generate the solid-like network in the self-assembly via micellar formation involving building blocks. Extensive cross-linking among organic and inorganic moieties provide these hydrogels with unique physicochemical features of improved mechanical strength (∼71 000 Pa), large water retention capability (600%), self-healing, and injectability as arrived at by thixotropic measurements, low toxicity, and enhanced drug/dye loading capabilities. Thus, the co-doped Zn2+ ions and Ag NPs in CISZ2H impart it with enhanced mechanical stability, shear thinning, external stimuli-responsiveness (pH and temperature), sustained slow drug release, surface enhanced Raman scattering (SERS) activity, and antibacterial features, thereby making this hydrogel safer for drug delivery, wound healing, sensing, and tissue engineering. The excellent features of the as-synthesized hydrogels make it a smart soft material for advanced applications with enormous future potential. © The Royal Society of Chemistry.

Dalton Transactions

Smart soft supramolecular hybrid hydrogels modulated by Zn2+/Ag NPs with unique multifunctional properties and applications

The numerical investigation of free radical polymerization (FRP) of methyl methacrylate under mixed feed condition at inlet is made for three microtubular reactor geometries, namely, straight tube, coiled tube, and coil flow inverter reactor. The effect of variation of fluid thermophysical properties (FTPP) (density, viscosity, and thermal conductivity) with reaction along with discrete variation of chemical species diffusion coefficient is studied. Predicted values of monomer conversion, number-average chain length (DPn), and polydispersity index (PDI) are found to be systematically lower for variable FTPP case compared to constant FTPP case. But contrary to expectations, results are found to be independent of reactor geometry for either case. Results clearly show the importance of modeling the variation of FTPP especially with respect to conversion. One case of varying diffusion coefficient of each chemical species based on free volume theory with constant FTPP is also simulated. Here again, the results are found to be independent of reactor geometry. Constant thermal conductivity and isothermal reactor condition are found to be good assumptions. This study clearly establishes the need not only for variable FTPP, thus coupling transport processes, but also for incorporating varying diffusion coefficient along with conversion in modeling of FRP in microreactors for better predictions. © 2020 Wiley-VCH GmbH

Macromolecular Theory and Simulations

Numerical Investigations of Perfectly Mixed Condition at the Inlet of Free Radical Polymerization Tubular Microreactors of Different Geometries

The present study examines the stability of a thinning straight jet in electrospinning process. The linear stability analysis is carried out to obtain the growth/decay rate of axisymmetric disturbance imposed on the thinning jet. The analysis captures the role of solvent evaporation in the stability behavior of the linear path of the electrospinning jet. In contrast to many prior stability analyses which consider the jet as a cylindrical filament with uniform radius, the present study analyzes the stability of a jet which exhibits thinning under realistic electrospinning conditions. Two different polymeric solutions are considered: the poly-isobutene (PIB) Boger fluid with low electrical conductivity and the highly conductive poly-ethylene oxide (PEO) solution in ethanol/water. At low extensional deformation, the rheology of the unentangled PIB-based Boger fluid is described by the Oldroyd-B model. The PEO solution, on the other hand, experiences a very high elongation rate due to the development of strong axial electric stress. The nonlinear rheology of the entangled PEO solution is appropriately described by the eXtended Pom–Pom (XPP) model, a variant of the classical tube model. The analysis reveals that the instability in low conductivity fluid is driven by the capillary forces, whereas the high conductivity fluid exhibits oscillatory conducting mode of instability driven by the coupled effect of axial electric field and surface charges. For both the reference fluids, the increase in solvent evaporation tends to decrease the disturbance growth rate to the extent that the axisymmetric instability is completely suppressed for a strong enough evaporation. The stabilizing role of solvent evaporation is attributed to the enhancement in fluid viscosity and elasticity due to increased polymer concentration upon evaporation. Thus, by suppressing the onset of axisymmetric instability during the straight jet path, solvent evaporation potentially helps produce smooth fibers without bead formation. © 2020 Elsevier Ltd

Polymer

Electrospinning of polymer solutions: An analysis of instability in a thinning jet with solvent evaporation

Pulp and paper industry generates large wastewater volumes containing recalcitrant and toxic compounds in various forms. These compounds are highly toxic and standard primary/secondary treatments are unable to filter heavy metal contaminants besides organic species. An emerging demand of advance level treatment is the motivation of current work that explores possibility of using thick sand of deep aquifers as an adsorbent to remove inorganic and organic contaminants simultaneously from wastewater besides desalination. Popular ultrasonic cavitation is used to accelerate degradation of toxic organic effluent into less toxic open ring structures besides curing heavy metals to form new bonds during adsorption. Because of extreme local environment due to cavitation, heavy metals coagulate in silicon-aluminum atomic meshes and carbon nano tubes for less toxic new crystalline structure. Significant changes in physico-chemical investigations like pH, chemical oxygen demand and colour towards drinkable water standards indicate effective adsorption resulting into wastewater purification. © 2019

Physics

(SoNS) School of Natural Sciences

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Ultrasonic cavitation tailored wastewater purification and desalination using thick sand of highly permeable deep aquifer

Chitosan is a linear natural polymer obtained by deacetylation of chitin using sodium hydroxide. Depending on the manufacturing process as well as its source, chitosan is commercially available in various types and grades with molecular weights (MW) ranging from 38 to 200 kDa and degree of deacetylation (DD) with a range between 60 to 100%. In this work, chitosan films of different degrees of deacetylation (DD) and molecular weights (MW) were prepared by the solution casting method at concentrations of 1%, 2%, and 3%. The influence of DD and MW were studied on the prepared films using various characterization techniques such as dressing pH, water absorption capacity, water vapour transmission rate (WVTR), porosity, and water contact angle (WCA). The water absorption capacity, water vapour transmission rate (WVTR), and porosity results showed that there were significant effects of DD, MW, and concentration on the above-mentioned films. © 2020 Scientific Publishers. All rights reserved.

Journal of the Indian Chemical Society

Effect of degree of deacetylation and molecular weight on physicochemical properties of chitosan films

Carbon dioxide permeation studies were conducted on polyether-sulfone (PES) microspheres fabricated using phase-inversion technique by loading various amine-functionalized imidazolium cation ILs with a common anion bis-trifluoromethylsulfonylamide ([TF2N]−) on PES-polymer matrix. The cations include: Aminopropyl-butyl-imidazolium [APBIM], Diethyl-aminoethyl-imidazolium [DEAEBIM], Diaminopropyl-butyl-imidazolium [DMAPBIM]. Breakthrough adsorption of CO2 and CH4 was studied with a feed composition of 20\% CO2, 20\% CH4 and 60\% N2 by weight (4.835 mmol/L of CO2, 13.296 mmol/L of CH4 and 22.794 mmol/L of N2), at flow rates of 22 and 36 mL/min (superficial gas velocities are 0.29 cm/s and 0.47 cm/s). Among the ILs studied, [APBIM] showed maximum CO2 permeation. Results indicate that pore size and porosity are crucial for better CO2 absorption and need of further modification to microspheres morphology. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Adsorption

Ionic liquid loaded polyether sulfone microspheres for CO2 separation

Two tubular microreactor geometries—straight tube reactor (STR) and coil flow inverter reactor (CFIR)—are numerically studied with unmixed feed condition for the synthesis of poly(methyl methacrylate) and poly(styrene) by free radical polymerization. A new transformation rendering model dimensionless in terms of concentration is used during computational fluid dynamics modeling. For decoupled case of constant fluid thermo-physical properties (FTPP) (density, viscosity, and thermal conductivity), significant differences between the two types of reactor are observed. CFIR is found to achieve higher number-average chain lengths (DPn) while keeping polydispersity index (PDI) lower compared to STR. For the case of coupled FTPP variables with conversion (XM) and temperature, XM and DPn are found to have similar trends as in decoupled case but have systematically higher values while PDI values follows a different trend. CFIR is found to show better mixing compared to STR under similar conditions, thus allowing a better control over PDI under unmixed feed condition. An anomalous case of increased mixing in STR at low diffusion coefficient for coupled case is also observed. Overall, the importance of modeling the coupled case is clearly emphasized. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim