scholarly journals Comparative Study of the Adsorption of Acid Blue 40 on Polyaniline, Magnetic Oxide and Their Composites: Synthesis, Characterization and Application

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2854 ◽  
Author(s):  
Muhammad ◽  
Shah ◽  
Bilal
Keyword(s):  
Free Energy ◽  
Comparative Study ◽  
Gibbs Free Energy ◽  
Electrostatic Interactions ◽  
Solution Temperature ◽  
Maximum Adsorption Capacity ◽  
Aqueous Environment ◽  
Magnetic Oxide ◽  
Vis Spectroscopy ◽  
Acid Blue

Conducting polymers (CPs), especially polyaniline (PANI) based hybrid materials have emerged as very interesting materials for the adsorption of heavy metals and dyes from an aqueous environment due to their electrical transport properties, fascinating doping/de-doping chemistry and porous surface texture. Acid Blue 40 (AB40) is one of the common dyes present in the industrial effluents. We have performed a comparative study on the removal of AB40 from water through the application of PANI, magnetic oxide (Fe3O4) and their composites. Prior to this study, PANI and its composites with magnetic oxide were synthesized through our previously reported chemical oxidative synthesis route. The adsorption of AB40 on the synthesized materials was investigated with UV-Vis spectroscopy and resulting data were analyzed by fitting into Tempkin, Freundlich, Dubinin–Radushkevich (D–R) and Langmuir isotherm models. The Freundlich isotherm model fits more closely to the adsorptions data with R2 values of 0.933, 0.971 and 0.941 for Fe3O4, PANI and composites, respectively. The maximum adsorption capacity of Fe3O4, PANI and composites was, respectively, 130.5, 264.9 and 216.9 mg g−1. Comparatively good adsorption capability of PANI in the present case is attributed to electrostatic interactions and a greater number of H-bonding. Effect of pH of solution, temperature, initial concentration of AB40, contact time, ionic strength and dose of adsorbent were also investigated. Adsorption followed pseudo-second-order kinetics. The activation energy of adsorption of AB40 on Fe3O4, PANI and composites were 30.12, 22.09 and 26.13 kJmol−1 respectively. Enthalpy change, entropy change and Gibbs free energy changes are −6.077, −0.026 and −11.93 kJ mol−1 for adsorption of AB40 on Fe3O4. These values are −8.993, −0.032 and −19.87 kJ mol−1 for PANI and −10.62, −0.054 and −19.75 kJ mol−1 for adsorption of AB40 on PANI/Fe3O4 composites. The negative sign of entropy, enthalpy and Gibbs free energy changes indicate spontaneous and exothermic nature of adsorption.

Preparation of titanate nanoflower for sorption of 75Se(IV) radioisotope from aqueous solution: Equilibrium, kinetic and thermodynamic studies

2015 ◽  
Vol 103 (12) ◽  
Author(s):  
Sahar El-Sayed Abd El-Kader Sharaf El-Deen ◽  
Karam Fatwhi Allan ◽  
Mohamed Holeil ◽  
Gehan El-Sayed Abd El-Kader Sharaf El-Deen
Keyword(s):  
Aqueous Solution ◽  
Electrostatic Interactions ◽  
Outer Sphere ◽  
Solution Temperature ◽  
Isotherm Models ◽  
Maximum Adsorption Capacity ◽  
Order Kinetic ◽  
X Ray ◽  
Adsorptive Removal ◽  
Order Kinetic Model

AbstractIn this study, the adsorptive removal of selenium (IV) from aqueous solution by titanate nanoflower (TNF) was prepared via alkaline hydrothermal method. The morphology and crystal phase of the TNF were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscope (EDX), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR) and specific surface area. This study was conducted to determine the influence of various operating parameters such as pH, adsorbate weight, initial anion concentration, contact time and solution temperature on the adsorptive removal of selenium (IV). Equilibrium adsorption data were analyzed using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) isotherm models. The results demonstrated that the adsorption was well described by the Langmuir adsorption isotherm with the maximum adsorption capacity up to 46.52 mg/g at pH 3.5. The adsorption of Se(IV) anions onto the surface of TNF may proceed through outer sphere electrostatic interactions and/or inner-sphere complexation interaction. The kinetic data indicated that the adsorption fit well with the pseudo-second-order kinetic model. The thermodynamic parameters implied that the adsorption process was spontaneous and endothermic in nature.

scholarly journals PnBA-b-PNIPAM-b-PDMAEA Thermo-Responsive Triblock Terpolymers and Their Quaternized Analogs as Gene and Drug Delivery Vectors

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2361
Author(s):  
Athanasios Skandalis ◽  
Dimitrios Selianitis ◽  
Stergios Pispas
Keyword(s):  
Electrostatic Interactions ◽  
Structural Characteristics ◽  
Ethyl Acrylate ◽  
Intrinsic Fluorescence ◽  
Solution Temperature ◽  
Hydrophobic Drug ◽  
Micellar Aggregates ◽  
Vis Spectroscopy ◽  
Triblock Terpolymers

In this work, the ability of thermo-responsive poly [butyl acrylate-b-N-isopropylacrylamide-b-2-(dimethylamino) ethyl acrylate] (PnBA-b-PNIPAM-b-PDMAEA) triblock terpolymer self-assemblies, as well as of their quaternized analogs (PnBA-b-PNIPAM-b-QPDMAEA), to form polyplexes with DNA through electrostatic interactions was examined. Terpolymer/DNA polyplexes were prepared in three different amine over phosphate group ratios (N/P), and linear DNA with a 2000 base pair length was used. In aqueous solutions, the terpolymers formed aggregates of micelles with mixed PNIPAM/(Q)PDMAEA coronas and PnBA cores. The PnBA-b-PNIPAM-b-PDMAEA terpolymers’ micellar aggregates were also examined as carriers for the model hydrophobic drug curcumin (CUR). The complexation ability of the terpolymer with DNA was studied by UV–Vis spectroscopy and fluorescence spectroscopy by investigating ethidium bromide quenching. Fluorescence was also used for the determination of the intrinsic fluorescence of the CUR-loaded micellar aggregates. The structural characteristics of the polyplexes and the CUR-loaded aggregates were investigated by dynamic and electrophoretic light scattering techniques. Polyplexes were found to structurally respond to changes in solution temperature and ionic strength, while the intrinsic fluorescence of encapsulated CUR was increased at temperatures above ambient.

scholarly journals Magnesium aluminium silicate-metformin hydrochloride complexes - The use of isothermal calorimetry in probing the understanding of clay and drug nanocomplexations

2021 ◽  
Vol 18 ◽  
Author(s):  
Ana-Maria Totea ◽  
Irina Dorin ◽  
Peter R. Laity ◽  
Barbara R. Conway ◽  
Laura Waters ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Electrostatic Interactions ◽  
Isothermal Calorimetry ◽  
Metformin Hydrochloride ◽  
Digital Microscopy ◽  
Total Change ◽  
Liquid Form ◽  
Release Drug ◽  
Aluminium Silicate

: This study reports the use of Isothermal Calorimetry (ITC) in understanding the complexation process occurring between Magnesium Aluminium Silicate (MAS) and metformin hydrochloride (MET), as a potential controlled release drug delivery system. The calorimetric results confirmed the binding between MET and MAS at various pHs (5, 7 and 9) and temperatures (25 ºC and 37 ºC). The overall change in enthalpy was found to be exothermic with a comparatively small entropic contribution to the total change in Gibbs free energy, implying that the binding was an enthalpically driven process. These findings suggest that the binding process was dominated by hydrogen bonding and electrostatic interactions. pH and temperature variation did not have a great impact on the binding, as observed from the similarity in enthalpy (ΔH), entropy (ΔS) or Gibbs free energy (ΔG), with the reaction being only slightly more exothermic at pH 5 and at 37 ºC. MAS and MET complex dispersions and particles were also formulated and analysed successfully using DSC, XRPD, ATR-FTIR, SEM/EDX, digital microscopy. 2D-SAXS. 2D-SAXS was able to differentiate between MAS particulates and MAS-MET complexes when analysed in their liquid form suggesting the importance of appropriate methodology and instrumentation used in characterisation.

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

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