M. Bazzaoui

New single-step electrosynthesis process of homogeneous and strongly adherent polypyrrole films on iron electrodes in aqueous medium

Homogeneous and strongly adherent polypyrrole (PPy) films were electrochemically synthesized on iron electrodes in sodium tartrate (Na2C4O6H4 0.2 M) aqueous solution. This one step pyrrole electropolymerization process has been successfully achieved under different electrochemical techniques, such as potentiodynamic, galvanostatic and potentiostatic modes. During the first stage of the electrochemical process the tartrate counterion slows down the iron dissolution by leading to the formation of a passivation layer on the working electrode surface, and the pyrrole electropolymerization takes place. The electrosynthesized polymer deposit has been characterized by several microscopic and spectroscopic techniques. Any iron traces have been detected by X-ray photoelectron spectroscopy (XPS) on the outer side of the PPy films, which confirms the compactness and the homogeneity of the polymeric coating. Scanning electronic microscopy (SEM) imaging showed uniform and compact PPy coatings with cauliflower-like structure. Infra-red (IR) and Raman spectroscopies proved that the obtained PPy films have the same vibrational properties as those electrodeposited on noble Pt plates.

Electrosynthesis of homogeneous and adherent polypyrrole coatings on iron and steel electrodes by using a new electrochemical procedure

Abstract A single-step electropolymerization of pyrrole (Py) on iron and steel surfaces has been performed in aqueous medium in the presence of malate (C 4 H 4 O 5 2− ) as supporting electrolyte. The malate counter-ion slows down the iron dissolution by leading to the formation of a passivation layer on the working electrode surface, and the Py electropolymerization starts on. The polypyrrole (PPy) films electrosynthesized under different electrochemical techniques are uniform and adherent. The polymer coatings performed galvanostatically have a cauliflower-like structure and are thicker than those obtained by potentiodynamic mode. The adherence of PPy layers to the iron electrodes was estimated at 100% according to the standard sellotape test. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) analysis showed that the obtained coatings have the same structure and morphological properties as those electrodeposited on Pt electrodes.

Pyrrole electropolymerization on copper and brass in a single-step process from aqueous solution

The electrosynthesis of polypyrrole (PPy) on copper and brass (Cu–Zn alloy) electrodes was performed by anodic oxidation of pyrrole in a sodium tartrate (C4H4Na2O6 0.2 M) aqueous solution. The tartrate counter-ions slow the dissolution of the working electrode by leading to formation of a passivation layer on its surface, and pyrrole electropolymerization takes place. Strongly adherent and homogeneous polypyrrole films were electrodeposited on Cu and Cu–Zn alloy electrodes using different electrochemical techniques, such as potentiodynamic, galvanostatic and potentiostatic modes. The current densities of electropolymerization on brass are generally greater than those observed on copper. The corrosion behaviour of copper-coated electrodes, electrochemically modified by PPy films, was estimated by DC polarization and weight loss at different current densities in 0.1 M HCl solution. The synthesized polypyrrole films were characterised by several microscopic and spectroscopic techniques such as scanning electron microscopy, X-ray photo electron spectroscopy, Fourier transform infrared and Raman analysis. Galvanostatically deposited PPy films are shown to be an alternative to common black-nickel or black-chromium as a decorative top-coating.

Electrochemical synthesis of adherent polypyrrole films on zinc electrodes in acidic and neutral organic media

The electrodeposition of polypyrrole on zinc electrodes has been performed by anodic oxidation of pyrrole in acetonitrile, nitrobenzene and propylene carbonate media in the presence of para-toluene sulfonate counter-ions. When the zinc electrode has preferably undergone a chemical treatment by aqueous sodium sulfide solution, homogeneous and adherent PPy films are obtained. While, no PPy film grows (in the case of C6H5NO2 and PC) or a non-homogeneous and poorly adherent PPy–zinc oxide composite forms (in the case of CH3CN) when the zinc surface is simply polished. Among the electrochemical techniques used in these experiments, the galvanostatic mode was proved to be better adapted to perform the electropolymerization of pyrrole on the pretreated zinc electrodes using low applied current densities. The polypyrrole films synthesized by this technique has been characterized by several microscopic and spectroscopic techniques. In particular, SEM, XPS, FT-IR and Raman analyses showed that the obtained coatings have the same structure and morphological properties as those electrodeposited on Pt electrodes.

New electrochemical procedure for elaborating homogeneous and strongly adherent PPy films on zinc electrodes

Electropolymerization of pyrrole on zinc was investigated in sodium tartrate aqueous solution in order to obtain homogeneous and adherent polypyrrole films. The tartrate counter-anions inhibit the working electrode dissolution by leading to the formation of a passivation layer on its surface. Consequently, homogeneous and strongly adherent polypyrrole coating has been successfully achieved with different electrochemical techniques, such as potentiodynamic, galvanostatic and potentiostatic modes. Polypyrrole coatings electrosynthesized on zinc electrodes have been characterized by several microscopic and spectroscopic techniques. Particularly, scanning electron microscopy (SEM) analysis has revealed a compact, homogeneous and thick polypyrrole film. X-ray photoelectron spectroscopy (XPS), IR and Raman analyses proved that the coatings obtained have globally the same structural features and elementary composition as those electrosynthesized on noble metals.

Electropolymerization of pyrrole on zinc–lead–silver alloys electrodes in acidic and neutral organic media

Abstract Electropolymerization of pyrrole on zinc–lead–silver (Zn–Pb–Ag) alloys was carried out in acetonitrile, nitrobenzene and propylene carbonate (PC) organic media in the presence of para -toluene sulfonate counter ions. Adherent and homogeneous PPy films have been obtained on zinc alloy electrodes (65% Zn, 10% Pb and 25% Ag) prealably treated with aqueous sodium sulfide solution. Among the electrochemical techniques used in these experiments, the galvanostatic mode was proved to be better adapted to perform the electrosynthesis of polypyrrole using low applied current densities. The PPy coatings have been characterized by different microscopic and spectroscopic techniques. Scanning electron microscopy (SEM) showed that PC (DN=15.1) is the most suitable solvent for elaborating high-quality and thick PPy films. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) analysis proved that the obtained coatings have the same structure properties as those electrodeposited on noble Pt plates.

Morphology of Copper Coatings Electroplated in an Ultrasonic Field

This paper reports the study of ultrasonic effects on some physicochemical properties of electroplated copper on iron subtracts from an acid sulphate bath. The bath efficiency for three stirring processes has been also studied as a function of the time and the current density applied. The bath efficiency, the hardness, the brightness and the adherence of the electrodeposits increase with the ultrasonic agitation, in comparison with the same coatings produced from still or magnetic stirred baths. Scanning electron microscopy (SEM) analysis has revealed a compact and more order structure in the coatings performed under ultrasonic waves at high current densities, conversely to free and dusty obtained with still bath.

Study of congo red adsorption on the polyaniline and polypyrrole

ABSTRACT Polyaniline (PANI) and polypyrrole (PPY) were synthesized via in situ chemical oxidative polymerization and are used as adsorbents for removal of Congo Red (CR) dye from aqueous solution. The effects of various experimental parameters including pH of the solution, contact time, initial concentration, adsorbent dosage, and temperature on adsorption of CR by PANI and PPY were systematically investigated. The experimental results showed that the adsorption efficiency was increased with contact time and adsorbent dosage. The maximum removal efficiency was found after 45 minutes of solid/liquid contact with adsorbent doses of 0.4 and 1.73 g/L for PANI and PPY, respectively. The kinetic data were best fitted by the pseudo-second-order model. The adsorption equilibrium results were well fitted by the Langmuir isotherm model. These results suggest that the PANI and PPY can be used as alternative adsorbents for the treatment of wastewaters containing dyes. GRAPHICAL ABSTRACT

Comparative adsorption of nitrate ions on the polypyrrole and polyaniline from aqueous solution

ABSTRACT The objective of this study was to compare the adsorption of nitrate ions using two conducting polymers—polypyrrole (PPy) and polyaniline (PANi)—as adsorbents. The effects of different adsorption parameters including contact time, pH, temperature, initial concentration, adsorbent dosage, and presence of orthophosphate ions were investigated in batch experiments. Kinetic studies indicated that the adsorption process follow pseudo-second-order kinetic model. The Langmuir model fitted the experimental data much better than the Freundlich and Temkin models. The PANi showed higher adsorption capacity to nitrate ions than that of PPy. The adsorption of ions onto the PANi and PPy was spontaneous and exothermic. GRAPHICAL ABSTRACT

Electrochemical Synthesis of Polythiophene Coatings on Zinc and a Zinc Alloy in Organic Media

The electropolymerization of thiophene on zinc and a zinc alloy has been achieved in nitrobenzene and dichloromethane in the presence of 0.1 M NBu4PF6 supporting electrolyte and 0.5 M thiophene. The obtained polythiophene coating has been characterized by different microscopic and spectroscopic techniques. The micrographs performed by SEM have proved that among the electrochemical techniques the galvanostatic polarization leads to the formation of thick polythiophene films and improves their homogeneity. X-ray photoelectron spectroscopy (XPS), infrared (IR) and Raman analyses have shown that the obtained coatings have the same elementary composition and structural properties as those electrodeposited on noble electrodes.