Biswajit Saha

Enhanced Adsorption of Hexavalent Chromium onto Magnetic Calcium Ferrite Nanoparticles: Kinetic, Isotherm, and Neural Network Modeling

Calcium ferrite nanoparticles with super-paramagnetic behavior were synthesized via simple chemical precipitation method for effective removal of hexavalent chromium from aqueous media. The properties of synthesized nanoparticles were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM) measurements. The ferrite nanoparticles have shown polycrystalline nature and high BET specific surface area (229.83 m2/g) with active functional groups on the surface. The adsorption process follows second-order kinetics with the involvement of intra-particle diffusion and adsorption capacity as much as 124.11 mg/g was determined from the Langmuir isotherm. The thermodynamic analysis revealed that the adsorption process was feasible, spontaneous, and exothermic in nature. A three-layer feed-forward back-propagation artificial neural network (ANN) model was employed to predict the removal (%) of Cr(VI) ions as output. Optimal ANN network (4:8:1) shows the minimum mean squared error (MSE) of 0.00161 and maximum coefficient of determination (R2) of 0.984. The adsorption process is mostly influenced by solution pH and followed by adsorbent dosage, initial Cr(VI) concentration, and contact time as illustrated by sensitivity analysis. With small size and high surface area, biocompatibility, ecofriendly nature, easy magnetic separation, and enhanced adsorption capacity towards Cr(VI), calcium ferrite nanoparticles will find its potential application in wastewater remediation. GRAPHICAL ABSTRACT

Simple Chemical Route Synthesis of Fe2O3 Nanoparticles and its Application for Adsorptive Removal of Congo Red from Aqueous Media: Artificial Neural Network Modeling

Nanocrystalline Fe2O3 powder was synthesized by a simple chemical route involving FeCl3 and NaOH. The Fe2O3 powder thus prepared was characterized using x-ray diffraction study, scanning electron microscopy, and Fourier transform infrared spectroscopy. The adsorption properties of crystalline Fe2O3 powder have been investigated with an aim to explore a possible low cost and efficient way to remove Congo red (CR) from waste water. Fe2O3 powder was found as an excellent adsorbent for CR from aqueous medium. Adsorption capacity as much as 203.66 mg g−1 is reported at room temperature. Effect of different experimental parameters such as reaction pH, initial CR dye concentration, adsorbent dose, and reaction temperature were studied on adsorption capacity of Fe2O3 powder and modeled by artificial neural network (ANN). Optimal ANN structure (4–5–1) shows minimum mean squared error (MSE) of 0.00235 and determination coefficient (R2) of 0.991 with Levenberg–Marquardt algorithm. Isotherm analysis of experimental data exhibited better fit to the Langmuir isotherm. The adsorption process was found to follow second-order kinetics as depicted by the analysis of experimental results. Thermodynamic study shows that the adsorption process is endothermic, spontaneous, and thermodynamically favorable in the temperature range of 27°C to 60°C. GRAPHICAL ABSTRACT

Tuning of electrical and optical properties of polyaniline incorporated functional paper for flexible circuits through oxidative chemical polymerization

An organic semiconductor material made of polyaniline with outstanding physical properties was prepared on a flexible paper substrate. Oxidative chemical polymerization, a straightforward and cost effective technique for large scale synthesis has been employed for the preparation of the polymer on the paper substrate. CuCl2 has been chosen as a polymerizing agent for the oxidative chemical polymerization process. The prepared polymer semiconductor has become an ideal system to explore this outstanding recipe of chemistry and physics. Formation of polaron and bipolaron defect energy states in the polymer lattice facilitates exceptional electrical hole transport through the polymer chain, providing an electrical sheet resistance varying from 5.0 × 105 Ω □−1 to 2.8 × 107 Ω □−1. The optical band gap as obtained from the absorbance study was found to be in the range of 2.49 eV to 2.62 eV, which is suitable for the design of semiconductor devices. Most importantly, this article reports an effective way of tuning the optical and electrical properties of the prepared semiconductor, achieved through controlling the degree of oxidation during polymerization and thus bringing a control over the defect energy states. Along with the controllable electrical and optical properties, the flexibility of the paper substrates provides an extra merit to such polymer systems for designing paper based low cost flexible devices.

Spectroscopic Studies on Interaction of Congo Red with Ferric Chloride in Aqueous Medium for Wastewater Treatment

Absorption spectroscopic studies of Congo red (CR) in interaction with FeCl3 in aqueous medium have been reported in this article. The interaction of CR with FeCl3 has been investigated with an aim to explore a possible low cost and efficient way to remove CR from industrial waste water. The removal mechanism is based on the formation of a complex of iron with anionic part of the CR molecule in interaction with FeCl3. An exceptionally high removal rate of 2670 mg/g has been observed at 100 mg/L initial CR concentration and enhanced removal rate was found with increasing initial CR concentration.

Synthesis of MnFe2O4 and Mn3O4 magnetic nano-composites with enhanced properties for adsorption of Cr(VI): artificial neural network modeling

This study reports adsorptive removal of Cr(VI) by magnetic manganese ferrite and manganese oxide nano-particles (MnF-MO-NPs) composite from aqueous media. The X-ray diffraction pattern of MnF-MO-NPs revealed a polycrystalline nature with nanoscale crystallite size. The prepared adsorbent with high Brunauer-Emmett-Teller specific surface area of 100.62 m2/g and saturation magnetization of 30.12 emu/g exhibited maximum Cr(VI) removal at solution pH 2.0 and was easily separated from water under an external magnetic field. Adsorption capacity as much as 91.24 mg/g is reported and electrostatic interaction between positively charged adsorbent surface and anionic metal ion species is the main driving force in this adsorption. Adsorption experimental data followed Langmuir isotherm and second order kinetics. Partial involvement of intra-particle diffusion was also observed due to the mesoporous nature of MnF-MO-NPs. The thermodynamic studies revealed that the process was favorable, spontaneous and exothermic in nature. An artificial neural network model was developed for accurate prediction of Cr(VI) ions removal with minimum mean squared error (MSE) of 15.4 × 10-4 and maximum R2 of 0.98. Owing to large surface to volume ratio, advantage of easy magnetic separation, and high adsorption capacity towards Cr(VI), the reported MnF-MO-NPs appear to be a potential candidate in Cr(VI) contaminated wastewater remediation.

Magnetoelectric coupling of xZn0.5Co0.5Fe2O4 - (1-x) PbZr0.58Ti0.42O3 (x = 0.3 and 0.4) nanocomposites

Multiferroic magnetoelectric composites have gained lots of interest from past few years due to its application in the magnetic field sensors device, data-storage media, multiple - state memories etc. In this context, we have been prepared series of xZn0.5Co0.5Fe2O4 - (1-x)PbZr0.58Ti0.42O3 (x = 0.3 and 0.4) nanocomposites. Structural characterizations have been carried out through x-ray diffraction technique. We have studied room temperature low frequency magnetoelectric coupling of all those nanocomposites in transverse and longitudinal configurations. The observed magnetoelectric coefficient is may be due to Joules magnetostriction of the magnetostrictive materials.

Room temperature magnetoelectric coupling and electrical properties of Ni doped Co - ferrite – PZT nanocomposites

Multiferroic magnetoelectric materials are very interesting for the researcher for the potential application in device preparation. We have prepared 0.3Ni0.5Co0.5Fe2O4 – 0.7PbZr0.58Ti0.42O3 magnetoelectric nanocomposites through chemical pyrophoric reaction process followed by solid state reaction and represented magnetoelectric coupling coefficient, thermally and magnetically tunable AC electrical properties. For the structural characterization XRD pattern and SEM micrograph have been analyzed. AC electrical properties reveal that the grain boundaries resistances are played dominating role in the conduction process in the system. Dielectric studies are represents that the dielectric polarization is decreased with frequency as well as magnetic field where it increases with increasing temperature. The dielectric profiles also represents the electromechanical resonance at a frequency of ∼183 kHz. High dielectric constant and low dielectric loss at room temperature makes the material very promising for the application of magnetic field sensor devices.Multiferroic magnetoelectric materials are very interesting for the researcher for the potential application in device preparation. We have prepared 0.3Ni0.5Co0.5Fe2O4 – 0.7PbZr0.58Ti0.42O3 magnetoelectric nanocomposites through chemical pyrophoric reaction process followed by solid state reaction and represented magnetoelectric coupling coefficient, thermally and magnetically tunable AC electrical properties. For the structural characterization XRD pattern and SEM micrograph have been analyzed. AC electrical properties reveal that the grain boundaries resistances are played dominating role in the conduction process in the system. Dielectric studies are represents that the dielectric polarization is decreased with frequency as well as magnetic field where it increases with increasing temperature. The dielectric profiles also represents the electromechanical resonance at a frequency of ∼183 kHz. High dielectric constant and low dielectric loss at room temperature makes the material very promising for the a...

Mesoporous Iron-Manganese Magnetic Bimetal Oxide for Efficient Removal of Cr(VI) from Synthetic Aqueous Solution

A facile co-precipitation method was established for synthesis of mesoporous iron-manganese magnetic bimetal oxide (MIMO) and its adsorption property was studied for removal of toxic metal ion hexavalent chromium from aqueous solution. XRD pattern of MIMO confirms the existence of Fe2O3 and Mn3O4 particle, out of which Mn3O4 is ferrimagnetic in nature. Synthesized MIMO has shown high saturation magnetization (23.08 emu/g), high BET surface area (178.27 m2/g) and high pore volume (0.484 cm3/g), which makes it a potential adsorbent. Adsorption process followed second order kinetic and Langmuir isotherm model. Involvement of intra-particle diffusion is also confirmed from kinetic data, which can be attributed to the mesoporous nature of the MIMO. Cr(VI) adsorption shows high pH dependency and maximum adsorption capacity of 116.25 mg/g is reported at pH 2.0. Electrostatic attraction between anionic chromium species and protonated MIMO surface is the predominant mechanism in this adsorption process.

Facile additive-free synthesis of hematite nanoparticles for enhanced adsorption of hexavalent chromium from aqueous media: Kinetic, isotherm, and thermodynamic study

ABSTRACT Facile additive-free synthesis of hematite nanoparticles via a chemical co-precipitation technique is reported for adsorptive removal of Cr(VI) from aqueous media, and adsorption capacity as much as 43.05 mg/g at solution pH 2.0 is observed. Langmuir isotherm model was fitted nicely with adsorption experimental data, whereas kinetic studies reveal that both surface adsorption and intra-particle diffusion are involved in the adsorption mechanism. Thermodynamic studies established the favorability, spontaneity, and exothermic nature of the adsorption process. Regeneration studies revealed the stability of the adsorbent up to three consecutive cycles, indicating it as a potential adsorbent for Cr(VI)-contaminated wastewater remediation.

DISPERSION IN IMPEDANCE SPECTRA OF ISOTYPE CdO–ZnO THIN FILM HETEROSTRUCTURE ON APPLIED DC BIAS

Radio frequency magnetron sputtering technique has been used to prepare n–n isotype heterostructure of CdO–ZnO thin film on glass substrate. The energy band structure analysis shows the formation of charge accumulation and charge depletion region created near the interface of CdO–ZnO n–n isotype heterostrucure which leads to the formation of a junction capacitance. The impedance spectroscopic studies of CdO–ZnO isotype heterostructure show an excellent dispersion in the impedance spectra as observed in the Nyquist plot depending on applied DC bias voltage. The frequency response of impedances has been explained from band structure and equivalent electrical circuit model of the heterostructure. These studies will be highly significant in exploring the possibility of application of such isotype interfaces in optimizing the functionality of organic and inorganic electronic devices and solar cells.