Remediation of chromium(VI) at polypyrrole-coated titanium

The application of conducting polypyrrole (PPy) and polyaniline (PAni) coated substrates in remediation of chromium, Cr(VI), is an area of considerable interest. Here, we discuss the implementation of PPy-coated titanium as a new material for the reduction of Cr(VI) to the less toxic trivalent state, Cr(III). An alkaline-peroxide based etching process was used to ensure the adhesion of the PPy coatings to the underlying titanium. The PPy films showed excellent resistance to acidic Cr(VI) solutions and remained adherent after continuous exposure to the solutions. In order to optimise the remediation process a number of experimental parameters were investigated, including the thickness of the PPy coating, the reduction potential used in pre-treatment of the PPy and the degree of solution agitation. The durability of the materials on exposure to the Cr(VI) test solutions made them suitable for repeated remediation experiments. Following several test-runs, the cleanup efficiency of the material was found to decrease slightly, however, increasing the exposure/experiment time resulted in significantly improved cleanup ability

Electrochemical formation of N–substituted polypyrrole nanowires, microwires and open microtubes and their decoration with copper structures

The substituted pyrrole monomer, N–(2–cyanoethyl)pyrrole, was electropolymerised in a 70% water and 30% ethanol solution with ClO4– and H2PO4– as the dopant species to give nanowires at short electropolymerisation times and microwires at longer deposition periods. On adding toluene to the electropolymerisation solution, hollow microtubes were formed. This was attributed to the adsorption of toluene droplets at the electrode surface which served to separate the dopants from the monomer, with the monomer being highly soluble in the toluene droplet and the inorganic dopants soluble in the water/ethanol mixture. As a result electropolymerisation was confined to the toluene-water/ethanol interface. These polymer systems exhibit redox activity with the oxidation wave centred at about 0.40 V vs SCE, and the broader reduction wave positioned between 0.75 V and 0.25 V vs SCE. Although N-substitution reduces the conductivity of the polymer, various copper deposits, including cubes, leaves and hierarchical structures were deposited at the microwires and microtubes using high overpotentials. The hierarchical structures were wrapped around the microtubes at considerable distances, typically 3–4 µm, from the substrate

Remediation of chromium(VI) at polypyrrole-coated titanium

The application of conducting polypyrrole (PPy) and polyaniline (PAni) coated substrates in remediation of chromium, Cr(VI), is an area of considerable interest. Here, we discuss the implementation of PPy-coated titanium as a new material for the reduction of Cr(VI) to the less toxic trivalent state, Cr(III). An alkaline-peroxide based etching process was used to ensure the adhesion of the PPy coatings to the underlying titanium. The PPy films showed excellent resistance to acidic Cr(VI) solutions and remained adherent after continuous exposure to the solutions. In order to optimise the remediation process a number of experimental parameters were investigated, including the thickness of the PPy coating, the reduction potential used in pre-treatment of the PPy and the degree of solution agitation. The durability of the materials on exposure to the Cr(VI) test solutions made them suitable for repeated remediation experiments. Following several test-runs, the cleanup efficiency of the material was found to decrease slightly, however, increasing the exposure/experiment time resulted in significantly improved cleanup ability

Remediation of chromium(VI) at polypyrrole-coated titanium

The application of conducting polypyrrole (PPy) and polyaniline (PAni) coated substrates in remediation of chromium, Cr(VI), is an area of considerable interest. Here, we discuss the implementation of PPy-coated titanium as a new material for the reduction of Cr(VI) to the less toxic trivalent state, Cr(III). An alkaline-peroxide based etching process was used to ensure the adhesion of the PPy coatings to the underlying titanium. The PPy films showed excellent resistance to acidic Cr(VI) solutions and remained adherent after continuous exposure to the solutions. In order to optimise the remediation process a number of experimental parameters were investigated, including the thickness of the PPy coating, the reduction potential used in pre-treatment of the PPy and the degree of solution agitation. The durability of the materials on exposure to the Cr(VI) test solutions made them suitable for repeated remediation experiments. Following several test-runs, the cleanup efficiency of the material was found to decrease slightly, however, increasing the exposure/experiment time resulted in significantly improved cleanup ability

Remediation of chromium(VI) at polypyrrole-coated titanium

The application of conducting polypyrrole (PPy) and polyaniline (PAni) coated substrates in remediation of chromium, Cr(VI), is an area of considerable interest. Here, we discuss the implementation of PPy-coated titanium as a new material for the reduction of Cr(VI) to the less toxic trivalent state, Cr(III). An alkaline-peroxide based etching process was used to ensure the adhesion of the PPy coatings to the underlying titanium. The PPy films showed excellent resistance to acidic Cr(VI) solutions and remained adherent after continuous exposure to the solutions. In order to optimise the remediation process a number of experimental parameters were investigated, including the thickness of the PPy coating, the reduction potential used in pre-treatment of the PPy and the degree of solution agitation. The durability of the materials on exposure to the Cr(VI) test solutions made them suitable for repeated remediation experiments. Following several test-runs, the cleanup efficiency of the material was found to decrease slightly, however, increasing the exposure/experiment time resulted in significantly improved cleanup ability

Facile template-free electrochemical preparation of poly[N-(2-cyanoethyl)pyrrole] nanowires

In this paper the first synthesis of poly[N-(2-cyanoethyl)pyrrole] (PPyEtCN) in a nanowire morphology is reported. The method employed is a facile, one step electrochemical growth, which does not require the use of any templates or surfactants. Using optimised conditions the nanowires nucleate to give a homogeneous film across the electrode surface, with lengths of approximately 2 μm and diameters of approximately 150 nm. Structural information on the nanowires was obtained using vibrational spectroscopy. Evidence is presented to support an instantaneous 3-D nucleation and growth mechanism for the nanowires

Electrochemical Deposition of Hollow N‑Substituted Polypyrrole Microtubes from an Acoustically Formed Emulsion

We outline an electrodeposition procedure from an emulsion to fabricate novel vertically aligned open and closed-pore microstructures of poly(N-(2-cyanoethyl)pyrrole) (PPyEtCN) at an electrode surface. Adsorbed toluene droplets were employed as soft templates to direct polymer growth. The microstructures developed only in the presence of both ClO4– and H2PO4– doping ions due to a slower rate of polymer propagation in this electrolyte. Two sonication methods (probe and bath) were used to form the emulsion, producing significantly different microstructure morphologies. Control over microtube diameter can be achieved by simply altering the emulsion sonication time or the amount of toluene added to form the emulsion. Electrochemical characterization indicated the PPyEtCN microtube morphology had an increased electrochemical response compared to its bulk counterpart. TEM analysis of individual closed-pore microtubes identified a hollow interior at the base within which the toluene droplet was encapsulated. This cavity may be used to entrap other compounds making these materials useful in a range of applications. The methodology was also applied to form microstructures of poly(3,4-ethylenedioxythiophene) and polypyrrole

Electrochemical Deposition of Hollow N‑Substituted Polypyrrole Microtubes from an Acoustically Formed Emulsion

We outline an electrodeposition procedure from an emulsion to fabricate novel vertically aligned open and closed-pore microstructures of poly­(<i>N</i>-(2-cyanoethyl)­pyrrole) (PPyEtCN) at an electrode surface. Adsorbed toluene droplets were employed as soft templates to direct polymer growth. The microstructures developed only in the presence of both ClO₄^– and H₂PO₄^– doping ions due to a slower rate of polymer propagation in this electrolyte. Two sonication methods (probe and bath) were used to form the emulsion, producing significantly different microstructure morphologies. Control over microtube diameter can be achieved by simply altering the emulsion sonication time or the amount of toluene added to form the emulsion. Electrochemical characterization indicated the PPyEtCN microtube morphology had an increased electrochemical response compared to its bulk counterpart. TEM analysis of individual closed-pore microtubes identified a hollow interior at the base within which the toluene droplet was encapsulated. This cavity may be used to entrap other compounds making these materials useful in a range of applications. The methodology was also applied to form microstructures of poly­(3,4-ethylenedioxythiophene) and polypyrrole