ABSTRACT

Electrochemical synthesis of polypyrrole (PPy) and polypyrrole/activated carbon (PPy/AC)-composite films, with a thickness between 0.5 and 15 μm were performed in a three electrode cell containing 0.1 mol dm-3 Py, 0.5 mol dm-3 NaClO 4 dissolved in ACN, and dispersed particles of AC (30 g dm-3). Electrochemical characterization of PPy and PPy/AC composites was performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The linear dependences of the capacitance (q C), redox capacitance (q red), and limiting capacitance (C L) of PPy and PPy/AC-composite films on their thickness (L), obtained by electrochemical and impedance analysis, indicate a nearly homogeneous distribution of the incorporated AC particles in the composite films (correlation coefficient between 0.991 and 0.998). The significant enhancement of q C , q red and C L , was observed for composite films (for 40±5%) in respect to that of the "pure" PPy. The decreased values of a volume resistivity in the reduced state of the composite film, ρ = 1.3×10 6 Ω cm (for L = 7.5 µm), for two orders of magnitude, compared to that of PPy-film with the same thickness, ρ ≈ 10 8 Ω cm, were also noticed.

Adsorption is considered as one of the most effective and cost efficient methods in water effluents purification. Frequently used adsorbent for heavy metals removal is activated carbon. The adsorption of lead ions from wastewater model solutions on activated carbon has been studied by a batch adsorber. Experiments were performed at constant temperature, while the concentration of lead ions in the solutions has been varied. Using the MatLab software the parameters for the Langmuir and Freundlich adsorption isotherms were determined. The experimental data obeys the Langmuir isotherm, and the maximum sorption capacity determined was 17.09 mg g-1. The impact of the quantity of activated carbon and the initial concentration of lead ion on adsorption kinetics has been studied. The kinetics models for the first, pseudo-first, second and pseudo-second-order reaction were fitted to the experimentally obtained data by MatLab software. Data obtained by the kinetics study of Pb 2+ adsorption on activated carbon, might be useful in the selection of the most probable mechanism of the adsorption process. It has been shown that the pseudo-second-order model explains the experimental data the best.

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