ELECTROLYTIC MANGANESE-DIOXIDE FROM CHLORIDE ELECTROLYTE

The influence of various electrolytic parameters on the properties of electrolytic manganese dioxide (EMD), using a chloride electrolyte and a titanium substrate manganese dioxide (TSMD) coated anode, was inves tigated on a bench scale. Optimum conditions were arrived at. Subseque ntly, a pilot plant processing 20 kg/d was set up. It was found that t he chloride route mainly results in superior quality EMD, plus improve d physical, chemical, catalytic and electrochemical properties, as com pared with the conventional sulphate route. The properties of EMD depe nd much upon the conditions of preparation. Generally, the values of a vailable oxygen and x in MnO(x) are not much affected by the change in concentration of manganese chloride, but are markedly influenced by o ther parameters. Manganese dioxide contents and x values in MnO(x) inc rease with an increase in temperature, the increase being more pronoun ced above 70-degrees-C, but decrease with an increase in the anode cur rent density, the decrease being more pronounced up to 270 A/m2. The c alculated bound moisture content increases with increasing current den sity and decreasing temperature. The electrolyte composition appears n ot to influence the chemical properties of EMD appreciably, except at high concentrations of hydrochloric acid. However, the advantage of th e higher conductivity of increased concentrations of electrolyte is ma de use of in practical operations. The trend is for the density of the material to increase with increasing temperature and concentration of electrolyte. However, the reverse is true with anode current density. The change in surface area is mainly influenced by temperature and an ode current density. This is also reflected in the free moisture conte nt. It was observed that lower current density, higher temperature and higher concentration of electrolyte favour the formation of EMD of hi gher activity. So far as crystal structure is concerned, from XRD, it seems that temperature has a marked effect as compared to current dens ity and concentration of hydrochloric acid.