JOURNAL of the Tunisian Chemical Society

serving the Research, the Education and the Industry

Hyperfiltration performances of cellulose acetate membranes

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CA membranes are prepared according to Manjikian technic. Two casting techniques are tested : manual and automatic. Membranes are characterized on a laboratory hyperfiltration cell. The variation of performances (represented by Water Permeation Rate and Salt Rejection) with constitution parameters of the casting solution and with characterization conditions are investigated.

E. Ferjani, M. Jedidi, M.S. Roudesli

Pages 223-232

Depassivation kinetics of a 17-8 stainless steel in H2SO4 aqueous solutions

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We have studied the dissolution kinetics of stainless steel 17-8 in various H2SO4 solutions with concentration varying from 0 to 100% by weight and having a temperature between 40 and 100°C. We find that the kinetics has a maximum corresponding to a [H2SO4] max which decreases from 55% at 40°C to 43% at 80°C. The first stage of attack corresponds to a preferential liberation of Cr and Ni. This occurs along a thickness of about 40 µm and can be explained by the continual formation of a passivation layer rich in Cr and Ni. This formation involves a migration of these elements from under layers to the surface.

N. Frini, M. El Maaoui

Pages 233-240

Modelisation of isothermal diffusion of steam on activated alumina

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Diffusion equation under conditions of diffusivity variation with concentration is solved numerically by Crank-Nicholson method. A simple exponential dependence of diffusion coefficient with concentration is assumed.Comparison of experiments with theory shows that the model describes the adsorption kinetics adequately and allows the knowledge of the diffusional coefficient parameter.

M. Baguenne, A. Bellagi

Pages 241-253

Flow pulsation on a tubular electrochemical reactor: 1. Distribution of concentration and transfer rate (New article)

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The effect of flow pulsations on the current reduction at a tubular cathode has been studied theoretically in the range of Reynolds number going up to 860, the amplitude and the frequency varying respectively from zero to 4.5 cm and 2 Hz. The most important result of the application of the model, of which the convenience has been tested in steady flow, is that the transfer rate is decreased at low frequencies and amplitudes compared to the value at steady state ; the improvement is more than 300% when the amplitude or the frequency increases.

A. Gadri, A. Ratel, S.S. Romdhane, G. Lacoste

Page 255-267

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