Abstract: The sponge powder bismuth replaced by powder iron is low grade. In order to overcome such problem, new approach for producing sponge powder bismuth is developed with the use of iron plates under micro-current. The grade of the obtained sponge powder bismuth is over 90%, which is replaced by iron plates with the use of iron plates as the anode, graphite as the cathode, and the current density is 5×10-3 A/cm2 at a temperature of 40 ℃. Studies on the replacement process have shown that the replacement process meets the first-order reaction rate law, with the activation energy Ea=13.72 kJ/mol, and the reaction is diffusion-controlled. The reaction rate equation is v=3.2470×c(Bi3+)exp(-13720/RT). Electrochemical analysis shows that the micro-current promotes the replacement process, and the obtained sponge powder bismuth is high grade with fewer impurities, in particular, the lead content is significantly reduced.

Key words: Micro-current, iron plates, replacement, sponge bismuth, dynamics