Intensification Of Pulse Electric Field On The Performances Of Manganese Electrodeposition

Pure metallic manganese is a good alloy element, which is used in certain types ofsteel, particularly high-strength steels, and in nonferrous alloys. Similarly, it has beenextensively used in medicine, chemistry, and so on. At present, electrolysis is the mainway to refine manganese. However, because of the very negative potential of theMn²⁺/Mn couple in aqueous solution, reduction to Mn²⁺to Mn is always accompaniedby hydrogen evolution, which reduces the current efficiencies. On the other hand, manybranchses grow on the surface of cathode in metallic manganese deposition, which maybring down the current efficiencies and output of manganese, make the short circuitbetween anode and cathode, result in exceptional manufacture. So, a new technology ofenergy saving and emission reduction for electrolytic manganese metal is a hot researchtopic.This paper studied the preparation of manganese from a sulfate bath by pulsecurrent. The main content of the dissertation are as follows:①Linear sweep voltammetry （LSV） technique was used to investigate influenceof the electrolyte component to the manganese electrodeposition. Combine the industrypractice, the ideal compose of the electrolyte was30g·L^-1Mn²⁺、120g·L^-1（NH₄）₂SO₄、0.03g·L^-1SeO₂.②Chronopotentiometry was carried out to investigate the influence of pulsecurrent to cathode voltage. The results showed that, with the periodic variation ofcurrent, the cathode potential waved periodicity. At the same current density, aprogressive enhancement of the cathode polarization was observed, and theoverpotential of pulse electrodeposition was bigger than traditional directelectrodeposition for90～110mV.③The grain size and surface morphology of manganese deposits were studied byoptical microscope and scanning electron microscopy. At the initial stage ofelectrodeposition, there were many spherical grain （the radius was about10μm）growing on the surface because of a small quantity of hydrogen adsorbed on the cathode,when decreasing the pulse duty cycle, the spherical grain gradually reduced. At constantpulse current density and frequency, the grain size increased asymptotically withincreasing duty cycle. And at appropriate electrodeposition parameters, pulseelectrodeposition of manganese deposits resulted in ca. threefold reduction in the grain size in comparison with direct current electrodeposited samples.④Pulse electrodeposition of manganese by simulating the industry process inorganic glass electrobathes, investigated the influence of pulse parameters, i.e. currentdensity, frequency and duty cycle on the current efficiency, product quality and surfacemorphology in manganese electrodeposited. The results show that the ideal pulseparameters were frequency1000Hz, duty cycle50%and current density350A/m², andthe current efficiency achieved82.6%from the electrolysis experiment of8h.⑤In order to fit realistic industry produce, the pulse electrodeposition techniquewas put into industry process. The results show that the new method has betterperformance in current efficiency than the traditional electrodeposition technique for6%.