Oxidation Of Pyrrole Research Articles

In-Situ Coating of Iron with a Conducting Polymer, Polypyrrole, as a Promise for Corrosion Protection

Iron microparticles were coated with polypyrrole in situ during the chemical oxidation of pyrrole with ammonium peroxydisulfate in aqueous medium. A series of hybrid organic/inorganic core–shell materials were prepared with 30–76 wt% iron content. Polypyrrole coating was revealed by scanning electron microscopy, and its molecular structure and completeness were proved by FTIR and Raman spectroscopies. The composites of polypyrrole/carbonyl iron were obtained as powders and characterized with respect to their electrical properties. Their resistivity was monitored by the four-point van der Pauw method under 0.01–10 MPa pressure. In an apparent paradox, the resistivity of composites increased from the units Ω cm for neat polypyrrole to thousands Ω cm for the highest iron content despite the high conductivity of iron. This means that composite conductivity is controlled by the electrical properties of the polypyrrole matrix. The change of sample size during the compression was also recorded and provides a parameter reflecting the mechanical properties of composites. In addition to conductivity, the composites displayed magnetic properties afforded by the presence of iron. The study also illustrates the feasibility of the polypyrrole coating on macroscopic objects, demonstrated by an iron nail, and offers potential application in the corrosion protection of iron. The differences in the morphology of micro- and macroscopic polypyrrole objects are described.

Rod-shaped Mo(vi) trichalcogenide–Mo(vi) oxide decorated on poly(1-H pyrrole) as a promising nanocomposite photoelectrode for green hydrogen generation from sewage water with high efficiency

Abstract The synthesis of rod-shaped Mo(vi) trichalcogenide–Mo(vi) oxide, cleverly adorned on a poly(1-H pyrrole) (P1HP) matrix (MoS3–MoO3/P1HP), is achieved through a one-pot preparation method. This process occurs under the pyrrole oxidation employing the oxidizing agent Na2MoO4. Notably, this oxidation process facilitates the direct incorporation of the inorganic constituents into the polymer matrix. Of particular significance is the material’s bandgap, which is optimally situated at 1.4 eV, rendering it highly suitable for its intended applications. The material assumes a rod-like structure, characterized by an average length of 400 nm and width of 30 nm, further enhancing its desirability. In practice, this thin film serves as an exceptionally promising photoelectrode. It finds its forte in the generation of hydrogen from sewage water, achieving an impressive efficiency rate of 12.66%, specifically at 340 nm. In addition to that, it boasts a remarkable hydrogen generation rate of 1.2 moles·h−1·cm−2. Moreover, the material exhibits remarkable versatility in its response to light. Its sensitivity to monochromatic light across a broad optical spectrum (UV till IR), underscores its potential for hydrogen generation applications for industrial applications.

Enzymatic synthesis of biocompatible polypyrrole with enhanced electrochemical properties for supercapacitors

This study focuses on the biocompatible and ecofriendly enzymatic synthesis of conductive polypyrrole (PPy) using mediators for supercapacitor electrode material. The work investigates the effects of various mediator systems on laccase-catalyzed oxidation of pyrrole and is confirmed through Fourier transform infrared spectroscopy (FTIR) and Ultraviolet (UV) visible spectroscopy. The x-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis has revealed that both mediators and laccase can produce crystalline and amorphous PPy with agglomeration of globular-shaped particles. The PPy-ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) demonstrates higher decomposition temperatures, indicating superior thermal stability up to 400 °C. Electrochemical studies such as cyclic voltammetry (CV), galvanometric charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) revealed that PPy-ABTS possesses good electrochemical properties. Compared to other laccase-mediated materials synthesized PPy in this study, PPy-ABTS exhibits higher specific capacitance values (242 F g−1 by CV at 10 mV s−1 and 153 F g−1 by GCD at 1 A g−1), with a capacitance retention of nearly 90 % after 10000 cycles. Cytotoxicity study shows that PPy-ABTS has an IC50 value of 528 μg ml−1 against human breast adenocarcinoma (MCF-7) cells, indicating its biocompatibility. Consequently, PPy-ABTS emerges as a promising electrode material for high-performance supercapacitors. Its unreported biocompatibility opens up possibilities for diverse biomedical applications.

Relative Humidity Modulates the Physicochemical Processing of Secondary Brown Carbon Formation from Nighttime Oxidation of Furan and Pyrrole.

Light-absorbing secondary organic aerosols (SOAs), also known as secondary brown carbon (BrC), are major components of wildfire smoke that can have a significant impact on the climate system; however, how environmental factors such as relative humidity (RH) influence their formation is not fully understood, especially for heterocyclic precursors. We conducted chamber experiments to investigate secondary BrC formation from the nighttime oxidation of furan and pyrrole, two primary heterocyclic precursors in wildfires, in the presence of pre-existing particles at RH < 20% and ∼ 50%. Our findings revealed that increasing RH significantly affected the size distribution dynamics of both SOAs, with pyrrole SOA showing a stronger potential to generate ultrafine particles via intensive nucleation processes. Higher RH led to increased mass fractions of oxygenated compounds in both SOAs, suggesting enhanced gas-phase and/or multiphase oxidation under humid conditions. Moreover, higher RH reduced the mass absorption coefficients of both BrC, contrasting with those from homocyclic precursors, due to the formation of non-absorbing high-molecular-weight oxygenated compounds and the decreasing mass fractions of molecular chromophores. Overall, our findings demonstrate the unique RH dependence of secondary BrC formation from heterocyclic precursors, which may critically modulate the radiative effects of wildfire smoke on climate change.

One pot synthesizing of cobalt (III) and (IV) oxides/polypyrrole nanocomposite for light sensing in wide optical range

A highly porous potato-shaped nanocomposite, Co(111) and Co(IV) oxide/polypyrrole (Co2O3-Co3O4/Ppy), is synthesized employing a one-pot procedure involving the slow oxidation of pyrrole using Co(NO3)2. The exceptional physical characteristics of this nanocomposite are accompanied by impressive optical properties, marked by a bandgap of 1.72 eV. Its absorbance spans across the UV, visible (Vis), and infrared (IR) regions, making it a promising candidate for optoelectronic applications such as photodetectors designed for light sensing within this extensive optical range that encompasses a substantial portion of the electromagnetic spectrum. This Co2O3-Co3O4/Ppy thin film photodetector is subjected to electrical testing under varying light conditions, leading to the determination of the photocurrent density (Jph) value of 0.26 mA.cm−2. When evaluated under different monochromatic light sources ranging from 340 to 730 nm, distinct Jph values are observed for each wavelength, reflecting the nanocomposite’s ability to effectively interact with photons across this spectrum. The measured responsivity (R) and detectivity (D) values further underscore the photodetector’s efficiency. At 340 nm, the R and D values stand at 1.22 mA.W-1 and 0.275 × 109 Jones, respectively. Similarly, at 730 nm, these values are 1.21 mA.W−1 and 0.270 × 109 Jones. The combination of these favorable findings, including cost-effectiveness and high stability, position the Co2O3-Co3O4/Ppy nanocomposite as an optimal choice for a wide range of industrial applications, attesting to its potential impact in the field.

Atroposelective Synthesis of Axially Chiral Naphthylpyrroles by a Catalytic Asymmetric 1,3-Dipolar Cycloaddition/Aromatization Sequence.

A straightforward methodology for the enantioselective preparation of axially chiral 2-naphthylpyrroles has been developed. This protocol is based on a CuI/Fesulphos-catalyzed highly enantioselective 1,3-dipolar cycloaddition of an azomethine ylide followed by pyrrolidine alkylation and pyrrolidine to pyrrole oxidation. The mild conditions employed in the DDQ/blue light-mediated aromatization process facilitate an effective central-to-axial chirality transfer affording the corresponding pyrroles with high atroposelectivity.

Reaction Mechanism of Nitrogen-Containing Heterocyclic Compounds Affecting Coal Spontaneous Combustion.

To uncover the reaction mechanism of nitrogen-containing heterocyclic compounds affecting coal self-heating, quantum chemical calculations and X-ray photoelectron spectroscopy (XPS) experiments were applied to elucidate the reaction pathways and thermodynamic characteristics of pyrrole, pyridine, indole, quinoline, and carbazole. Results show that in pyrrole, pyridine, indole, quinoline, and carbazole, the reaction with O2 captures the H atom and leads to the formation of ·OOH and pyrrolyl, pyridinyl, indolyl, quinolinyl, and carbazolyl radicals, respectively. The activation energies are 118.15, 86.642, 34.132, 21.004, and 47.259 kJ/mol, respectively. ROO· formed by spontaneous adsorption of O2 by nitrogen-containing radicals undergoes self-reaction, and the O-O bond is broken and dehydrogenated to generate ·OH. Subsequently, at room temperature, ·OH reacts with pyrrole, pyridine, indole, quinoline, and carbazole, resulting in the formation of H2O and pyrrolyl, pyridinyl, indolyl, quinolinyl, and carbazolyl radicals, respectively, thereby forming a cyclic chain reaction. The XPS analysis yielded the following findings: (i) when the temperature rises to 70 °C, the N-5 and N-6 content decrease, which is attributed to the activation energy; (ii) when the temperature reaches 200 °C, the N-5 content decreases, which can be attributed to the activation energy required for the oxidation of pyrrole (118.5 kJ/mol).

Highly Uniform Spherical MoO2-MoO3/Polypyrrole Core-Shell Nanocomposite as an Optoelectronic Photodetector in UV, Vis, and IR Domains.

A highly uniform spherical MoO2-MoO3/polypyrrole core-shell nanocomposite has been successfully synthesized as an optoelectronic photon sensing material, capable of detecting light in the UV, Vis, and IR domains. The nanocomposite is prepared through the oxidation of pyrrole using Na2MoO4, resulting in a uniform spherical morphology that has been confirmed by TEM, theoretical modeling, and SEM analyses. This morphology contributes to its promising optical behavior, characterized by a small bandgap of 1.36 eV. The optoelectronic photosensing capability of the nanocomposite has been evaluated across the UV, Vis, and IR spectra, demonstrating high efficiency. The photoresponsivity R values indicate the ability of the nanocomposite to generate hot electrons in response to incident photons. With an R value of 4.15 mA·W-1 at 440 nm, this optoelectronic device exhibits considerable promise for integration into an advanced technological apparatus. The detection (D) value of 9.30 × 108 Jones at 440 nm further confirms the high sensitivity in the Vis region. The excellent stability of the device can be attributed to the inherent MoO2-MoO3 oxide and Ppy polymer materials. This stability has been demonstrated through reproducibility studies and current-voltage measurements under various optical conditions. The combination of stability, efficiency, and sensitivity makes this optoelectronic device well suited for light sensing applications in both industrial and commercial settings. Its promising performance opens up opportunities for advancements in various fields requiring accurate and reliable light detection.

Aqueous Processable One-Dimensional Polypyrrole Nanostructured by Lignocellulose Nanofibril: A Conductive Interfacing Biomaterial.

One-dimensional (1D) nanomaterials of conductive polypyrrole (PPy) are competitive biomaterials for constructing bioelectronics to interface with biological systems. Synergistic synthesis using lignocellulose nanofibrils (LCNF) as a structural template in chemical oxidation of pyrrole with Fe(III) ions facilitates surface-confined polymerization of pyrrole on the nanofibril surface within a submicrometer- and micrometer-scale fibril length. It yields a core-shell nanocomposite of PPy@LCNF, wherein the surface of each individual fibril is coated with a thin nanoscale layer of PPy. A highly positive surface charge originating from protonated PPy gives this 1D nanomaterial a durable aqueous dispersity. The fibril-fibril entanglement in the PPy@LCNFs facilely supported versatile downstream processing, e.g., spray thin-coating on glass, flexible membranes with robust mechanics, or three-dimensional cryogels. A high electrical conductivity in the magnitude of several to 12 S·cm-1 was confirmed for the solid-form PPy@LCNFs. The PPy@LCNFs are electroactive and show potential cycling capacity, encompassing a large capacitance. Dynamic control of the doping/undoping process by applying an electric field combines electronic and ionic conductivity through the PPy@LCNFs. The low cytotoxicity of the material is confirmed in noncontact cell culture of human dermal fibroblasts. This study underpins the promises for this nanocomposite PPy@LCNF as a smart platform nanomaterial in constructing interfacing bioelectronics.

Structure and electrochemical properties of magnetite and polypyrrole nanocomposites formed by pyrrole oxidation with magnetite nanoparticles

Nanocomposite of magnetic Fe3O4 nanoparticles and polypyrrole was prepared under sonication by a new chemical polymerization method during which Fe3O4 nanoparticles acted both as a pyrrole oxidant and as a component in the composite material. Synthesis of this nanocomposite was carried out in aqueous solution acidified to pH 2, a prerequisite for the formation of these types of material and to facilitate pyrrole oxidation by Fe3O4 nanoparticles. In this way, two kind of materials were produced: Fe3O4/PPy nanocomposite in which magnetite nanoparticles were dispersed in PPy matrix and Fe3O4-aggregates@PPy nanocomposite that exhibits structure in which aggregates of magnetite nanoparticles are surrounded by a layer of polymeric phase. In the latter case, the polymerization process took place in the presence of a surfactant. These nanocomposites were characterized by electron microscopy techniques, IR spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and thermogravimetry. Particular attention was focused on the study of the electrochemical properties of the formed composites. The composite of Fe3O4 and PPy exhibits reversible electrochemical behaviour upon oxidation. The electrode process of the polymeric component oxidation in organic solvents such as acetonitrile and dichloromethane is very similar to the process in an aqueous solution.

Enhancing electromagnetic absorption performance of Molybdate@Carbon by metal ion substitution

Transition metal molybdate (RMoO4) has been extensively studied in optics, electricity and catalysis due to its low cost and multivalent Mo atoms, while its poor electrical conductivity limits its application in electromagnetic wave absorption (EMA). Compounding molybdate with conductive materials is an effective way to improve its electrical conductivity. In this work, a homogeneous coating on the molybdate surface was achieved by utilizing a pyrrole oxidation polymerization mechanism, and then stabilized composites of Molybdate@Carbon (RMoO4@C) were obtained by high-temperature pyrolysis. The EMA properties of the nanocomposites were tuned by substituting the species of transition metal elements (RMoO4@C, R=Fe, Co, Cu). Among them, Fe2(MoO4)3@C has a minimum reflection loss of −60.62 dB at an ultra-low thickness of 1.7 mm, and the effective absorption bandwidth (EAB) can reach 4.75 GHz at 3.00 mm. This work expands the range of applications for molybdate and provides a new material basis for building high-performance EMA materials.

Electrochemical Deposition of Polypyrrole in the Presence of Silanes as Adhesion Promoters.

Polypyrrole adhesion to indium-tin oxide electrodes was improved by adding pre-hydrolyzed alkoxysilanes to the electrodeposition media. The pyrrole oxidation and film growth rates were studied by potentiostatic polymerization in acidic media. The morphology and thickness of the films were studied by contact profilometry and surface-scanning electron microscopy. The bulk and surface semiquantitative chemical composition was studied by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Finally, the adhesion was studied by scotch-tape adhesion test, where both alkoxysilanes showed a significant improvement in adhesion. We proposed a hypothesis for the improvement in adhesion, that involves the formation of siloxane material as well as in situ surface modification of the transparent metal oxide electrode.

Coating of Leather with Dye-Containing Antibacterial and Conducting Polypyrrole

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress.

Experimental and kinetic model studies on the low- to moderate-temperature oxidation of N-methyl pyrrole in a jet-stirred reactor

N-methyl pyrrole (NMP) is an important nitrogenous heterocyclic compound in bio-oils produced from biomass conversion. NMP can be used as surrogate model compound to clarify the combustion chemistry of nitrogenous fuels and NOX formation mechanism. The low- to moderate-temperature oxidation experiments of NMP are carried out in atmospheric pressure jet-stirred reactor for 0.5% NMP/oxygen/Argon mixtures at different equivalence ratios (0.5, 1.0, and 2.0) over the temperature range of 760 – 1030 K. More than twenty species, including reactants, nitrogen-containing species, and oxygenated products, are measured using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A detailed and comprehensive kinetic model for NMP oxidation is developed for the first time based on the pyrrole oxidation model developed by Pelucchi et al. and Chen et al.. Simulated results show that the present model can reasonably reproduce the experimental results. Rate of production analysis indicates that the H-abstraction reactions on the methyl group dominate in NMP oxidation at all equivalence ratios. NMP oxidation produces C4 and C5 nitrogen-containing compounds including pyridine and pyrrole. These species are found to be products of the primary reactions of NMP, and their formation pathways can be explained satisfactorily by the present model. The present work provides a basis to further understand the oxidation characteristics of nitrogen-containing heterocyclic fuels.

Conducting polypyrrole-coated leathers

Conducting polymers are promising materials applicable as interfaces in various functional materials given they intrinsically possess electronic and ionic conductivity. Herein, a conducting polymer, polypyrrole (PPy) was explored for surface modification of three different leathers via in-situ oxidation of pyrrole in the absence and the presence of two stabilizing polymers, hydroxypropylcellulose and poly(N-vinylpyrrolidone). Colloidal dispersed PPy assemblies were formed with colloidal stabilizers along with PPy-coated leathers and hampered the formation of PPy precipitates that would otherwise contaminate the leather surface. The surface-modified bio-based composites were characterized by FTIR and Raman spectroscopy, and optical and scanning electron microscopy. PPy was deposited on collagen fibers on both sides of the leather. The thickness of the PPy layer varied between 24 and 200 μm. Mechanical properties of the leathers manifested themselves by the decrease in tensile strength and elongation at break after the modification process. Sheet resistances were in the range of 100–103 kΩ/sq with the highest values observed for materials modified in the presence of the polymeric stabilizers. Different sheet resistances were obtained for the top and bottom sides of the leathers depending on the surface finishing. Furthermore, the modified leathers were subjected to cyclic bending tests and the variation in their resistivity was studied. The conductivity and electroactivity of the modified materials may serve as guidance for the rational design of intelligent leathers in the footwear, as heating elements, and in energy storage.

Oxidation study of n-propylamine with SVUV-photoionization molecular-beam mass spectrometry

This work reports the experimental results of n-propylamine (NPA) oxidation in a jet-stirred reactor at 1 atm within 625–875 K, equivalence ratios from 0.5 to 2.0. Oxidation products and intermediates were identified and quantified with synchrotron vacuum ultraviolet photoionization mass spectrometry. Apart from various hydrocarbons, oxygenated and nitrogenous species reported in previous studies of amines, several intermediates were newly detected, including formamide (H2NCHO), nitromethane (CH3NO2), nitrous acid (HNO2), 2-propen-1-ol (C3H5OH) and 2-propenal (C2H3CHO). A detailed kinetic model consisting of 277 species and 2314 reactions was developed with reasonable predictions against the measured data. The rate-of-production and sensitivity analyses results show that NPA oxidation at low temperatures is dominated by the reaction with HO2. Particular attention was paid to the main oxidation product HCN, because its formation is affected by both fuel structure and reaction temperature. The equivalence ratio changes have an opposite effect on HCN concentration in NPA oxidation compared with the pyrrole oxidation and ethylamine flame. In the current study, the peak mole fraction of HCN decreases with increasing equivalence ratio, because the formation of CN triple bond in HCN requires successive H-abstractions, dominantly controlled by the concentrations of OH/HO2 radicals and O2. In addition, a comparison between the experimental results of NPA oxidation and pyrolysis was performed to illustrate the effect of O2 concentration on reaction routes. Current results provide a preliminary insight into the combustion kinetics of more complicated aliphatic amines.

Conducting polypyrrole silicotungstate deposited on macroporous melamine sponge for electromagnetic interference shielding

Macroporous melamine/formaldehyde sponge was coated in situ during the oxidation of pyrrole with iron(III) chloride hexahydrate in aqueous medium. The reaction mixture contained a heteropolyacid, silicotungstic acid, which protonated polypyrrole. Polypyrrole/silicotungstate deposits were prepared either in globular form or as nanotubes. The resulting hybrid composites thus combine an organic conducting polymer with inorganic component known, e.g., for its proton conductivity and electrocatalytic activity. The specific surface area of all materials was of the order of tens m2g−1. The molecular structure is discussed on the basis of FTIR and Raman spectra. The resistivity of the sponges was recorded as a function of compression to 10 MPa and it decreased from the order of 10 Ω cm to 0.1 Ω cm. The sponges were tested in electromagnetic interference shielding and absorbed over 80% of 9 GHz radiation frequency. The shielding is based mainly on the radiation absorption efficiency, −8.2 dB for globular polypyrrole and −13.1 dB for nanotubes, afforded by silicotungstic component. Hybrid composite sponges were subsequently carbonized at 650 °C in inert atmosphere when they converted to a sponge-like macroporous carbons enriched with nitrogen atoms. Their resistivity increased by two orders of magnitude after this process. The absorption of electromagnetic radiation, however, fell below 10%. Original and carbonized hybrid sponges may be of interest in the construction of macroporous electrodes.

Chemical Structure Regulates the Formation of Secondary Organic Aerosol and Brown Carbon in Nitrate Radical Oxidation of Pyrroles and Methylpyrroles.

Nitrogen-containing heterocyclic volatile organic compounds (VOCs) are important components of wildfire emissions that are readily reactive toward nitrate radicals (NO3) during nighttime, but the oxidation mechanism and the potential formation of secondary organic aerosol (SOA) and brown carbon (BrC) are unclear. Here, NO3 oxidation of three nitrogen-containing heterocyclic VOCs, pyrrole, 1-methylyrrole (1-MP), and 2-methylpyrrole (2-MP), was investigated in chamber experiments to determine the effect of precursor structures on SOA and BrC formation. The SOA chemical compositions and the optical properties were analyzed using a suite of online and offline instrumentation. Dinitro- and trinitro-products were found to be the dominant SOA constituents from pyrrole and 2-MP, but not observed from 1-MP. Furthermore, the SOA from 2-MP and pyrrole showed strong light absorption, while that from 1-MP were mostly scattering. From these results, we propose that NO3-initiated hydrogen abstraction from the 1-position in pyrrole and 2-MP followed by radical shift and NO2 addition leads to light-absorbing nitroaromatic products. In the absence of a 1-position hydrogen, NO3 addition likely dominates the 1-MP chemistry. We also estimate that the total SOA mass and light absorption from pyrrole and 2-MP are comparable to those from phenolic VOCs and toluene in biomass burning, underscoring the importance of considering nighttime oxidation of pyrrole and methylpyrroles in air quality and climate models.

EMI Shielding and Absorption of Electroconductive Textiles with PANI and PPy Conductive Polymers and Numerical Model Approach

The paper presents the results and analysis of interdisciplinary research concerning electromagnetic field shielding, conductive polymers printed on textiles and numerical simulation using the finite element method (FEM). The use of conductive, layered textiles for shielding electromagnetic interference (EMI) has been proposed. After establishing the optimal conditions for deposition of polyaniline (PANI) and polypyrrole (PPy) on polyacrylonitrile (PAN) fabric, conductive composites were made by means of reactive inkjet printing. For this purpose, polyacrylonitrile (PAN) fabrics were coated with polyaniline or polypyrrole, obtained by chemical oxidation of aniline hydrochloride and pyrrole by ammonium peroxydisulfate. The morphology of the obtained coatings was observed using a scanning electron microscope (SEM). The conductive properties (surface resistance) of the fabrics were measured using the four-wire method, and the tests of the effectiveness of electromagnetic shielding were carried out using the waveguide method in the frequency range from 2.5 to 18 GHz. The results of experimental shielding effectiveness (SE) tests and numerical simulation showed that the composites of polyacrylonitrile with polyaniline PAN/PANI and polyacrylonitrile with polypyrrole PAN/PPy achieved very good and good EMI shielding efficiency, respectively. Moreover, the obtained measurement results were verified by numerical modeling with the use of FEM–ANSYS HFFS software.

Polypyrrole/zeolite composite – A nanoadsorbent for reactive dyes removal from synthetic solution

Synthetic dyes are among the common pollutants in the ecosystem. In the present study, polypyrrole/zeolite (PPy/Ze) nanocomposite was prepared and subsequently assessed for the removal of Reactive blue (RB) and Reactive red (RR) from synthetic solution. The polymeric PPy/Ze composite was synthesized by chemical oxidation of pyrrole in the presence of zeolite. Electron microscopic images (transmission and scanning) indicate that PPy/Ze nanocomposite was spherical in shape with an average size of 40–80 nm. The characteristic pyrrole and zeolite Fourier transform infrared spectrum peaks (1542 cm−1, 1463 cm−1, 1156 cm−1, 1054 cm−1, 879 cm−1 and 756 cm−1) in the nanocomposite confirmed zeolite integration with polypyrrole. Experimental variables such as PPy/Ze nanocomposite dose, initial RB and RR concentration, reaction temperature and pH were optimized. The PPy/Ze nanocomposite adsorbed 86.2% of RB and 88.3% of RR from synthetic solution at optimal conditions (pH 9, initial RR or RB concentration, 75 mg/l; PPy/Ze dose, 1.8 g/l; and temperature, 50 °C). Freundlich isotherm model and pseudo-second-order kinetics showed better fit for both RB and RR removal from synthetic solution. X-ray diffractogram confirmed the amorphous nature of PPy/Ze nanocomposite and that it was not altered even after dye adsorption. Adsorption–desorption studies showed that the composite has satisfactory adsorption potential for four cycles. The results show that the PPy/Ze nanocomposite could be used for the removal of dyes from wastewaters.