Influência da geometria catódica sobre a transferência de massa e potencial catódico durante a eletrólise da água em meio alcalino.

Abstract

The search of geometries that make possible the easy detachment of bubbles of hydrogen in the process from brine electrolysis seeking to increase the efficiency of the electrochemical processes wakes up interest on the part of many researchers. This work has as main objective the experimental study of the mass transfer and the reduction of cathodic potential for two different geometries, perforated plate and screen, of the commercial alloy SAE 1020 used in industrial electrochemical processes. In this study a cell electrochemistry was used in scale of having supported for soda - chlorine production for the process to diaphragm with two separate compartments for a diaphragm composed by asbestos and polymer SM2 with electrodes of DSA® for the anode and as cathode the alloy SAE 1020. The study of the mass transfer was accomplished through the determination of the medium coefficient of mass transfer combined using the voltametric method with the following operational parameters: feeding flow varying between 2 x 10-6 and 8 x 10-6 ml.min-1; time of electrolysis of 20 minutes and intensity of applied current of 13 A (equivalent used her industrially). The experimental measures of cathodic potential were taken in relation to the reference electrode Hg/HgO/NaOH, (1,0 M) for several current densities. Inside of the conditions of this work it can be concluded that to obtain a better mass transfer the two geometries are favorable, depending on the percolating velocity of work. With relation to the reduction of cathodic potential the geometry of the type screen presented a larger reduction.