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Ceramic membranes are widely used to purify, separate, fractionate, and concentrate aggressive solutions and mixtures of components of different compositions and chemistry. Microfiltration membranes can be obtained by different methods in ceramics technology and powder metallurgy by varying the forming technique (pressing of powders, slip casting, etc.), the dispersity of the initial components, and production conditions. When relatively large flat ceramic microfiltration membranes are being made, it is difficult to attain a high porosity with a narrow pore-size distribution and achieve good permeability along with satisfactory mechanical properties. We have developed a technology for producing such membranes by using dispersed powders of aluminum oxide. Different forming methods are used in the process.

1. The process of precipitation of dispersed bismuth on the cathode was investigated, and the optimum conditions for the formation of a fine powder were determined. The maximum powder current efficiency lies in the region of limiting current densities. 2. It was observed that precipitation of dispersed bismuth into the organic bath layer occurs at the potentials of SAA desorption from the cathode. The presence of cyclohexanone in the organic layer decreases cathode polarization. 3. To produce a fine bismuth powder, it is necessary to ensure a sufficient degree of cathode polarization, which may be achieved by adding polarizing agents to the electrolyte.

1. The proposed method can be employed only in those cases where the impregnating material has no magnetic properties and the skeleton is a ferromagnetic material; apart from this, the porosity should be relatively even. 2. The method is quite simple and reliable, and gives accurate and reproducible results.