Inhibition Of Anode Electrochemical Oscillations For Electrolytic Manganese By Halide Ion

In electrolytic manganese metal processes,the electrochemical oscillations on the anode will increase the direct current consumption.Constructing electrochemical oscillation systems,studying the coupling behavior of electrochemical oscillations and further reduce the energy consumption were the important directions of the electrolytic manganese metal technology.In this work,halide ions were added to an aqueous manganese sulfate solution to investigate the effects of chloride ion and bromide ion on electrochemical oscillations in anodes.(1)When [Cl-] ranges from 0 mol/L to 0.303 mol/L,it found that electrodes could be effectively activated when [Cl-] was 0.075 mol/L,leading to a decrease of the power consumption and an increase of the manganese yield.Electrochemical experiments revealed that chloride ion could inhibit electrochemical oscillation on the anode.The amplitude and frequency decreased with the increase of [Cl-](?0.303 mol/L).Besides,the presence of the chloride could reduce the production of MnO2 mud on the anode surface.As the reaction time prolonged and the chloride ion concentration increased,ClO4-and some free ions in the solution formed an amorphous structure,which was insoluble in water.Subsequently,the MnO2 thin layer was covered by these complexes,preventing the further generation of the MnO2.In this manner,electrochemical oscillations were inhibited on the electrolytic manganese processing.Consequently,energy consumption was decreased and emissions were reduced.(2)After adding bromide ion to the electrolyte,it was that bromide ion inhibited electrochemical oscillations on the anode.Compared with chloride ion,its inhibitory effect was weaker.The amplitude was decreased with the increase of [Br-] from 0 mol/L to 0.263 mol/L,while the frequency showed a tendency of decreased first and then increased.The dynamical behavior of this system can be described as “periodic oscillation region-near-equilibrium linear region ”.The main reason of bromide ion inhibited electrochemical oscillations on the anode of electrolytic manganese was: H2O2 is the intermediate product that causes oxidation and turns Br-into Br2 in electrolytic manganese reaction.Hydrogen ion in the solution parts in the oxidation reaction,which leads to the increase of pH value.Under this condition,electrochemical oscillations are not easily to occur,and finally inhibits the electrochemical oscillation.Chloride ion and bromide ion show the varying degrees of inhibition on the anode of electrolytic manganese and the inhibitory action of chloride ion was stronger,besides,their inhibition mechanism are different.The reason for the inhibition of chloride ion was that the valence state of chloride ion has changed and the new substance was formed,which could not produce the oscillation of ?-MnO2 any more,effectively eliminated electrochemical oscillation.The same as chloride ion that the valence state of bromide ion also has changed that caused oxidation and turns Br-into Br2 in electrolytic manganese reaction,which leads to the increase of pH value.But it could still produce MnO2 which caused oscillation,and the inhibition effect become weaker.