Chlorine Removal from Zinc Electrolyte-Ion Exchange Method

In the process of zinc electrolysis, when the concentration of chloride ions in the neutral leaching solution is high, dechlorination treatment of the neutral leaching solution is required. Currently, more than 75% of zinc in China is produced using the wet zinc smelting process. In the wet zinc smelting process, purification of the zinc solution is crucial, and harmful impurities such as copper, cadmium, cobalt, nickel, fluorine, and chlorine must be purified to below the allowable content.

Among them, the presence of chloride ions affects the normal progress of zinc electroplating process, which not only exacerbates the corrosion of lead anode, but also makes it difficult to strip zinc during electroplating operation; Moreover, the increase in electricity consumption of lead anodes also leads to an increase in lead content in cathode zinc; The increase of chlorine above the electrode slot deteriorates the operating conditions and seriously affects the health of workers. According to the process requirements, the chloride ion content in the zinc solution during electrolysis should be controlled below 200mg/l to ensure smooth production. Otherwise, it will cause inconvenience to the zinc electroplating and seriously affect the efficiency and quality of zinc electroplating products.

For a long time, the purification and separation of chloride ions in zinc electrolytes containing chlorine have mainly adopted the following methods:

The silver sulfate precipitation method involves adding silver sulfate to a chlorine containing solution to react with chloride ions, resulting in the formation of insoluble silver chloride precipitate; Although this method is simple to operate and has good chlorine removal effect, it is not suitable for large-scale application due to the high price of silver salts, low regeneration recovery rate of silver, and high cost.

Copper slag dechlorination method is based on the interaction between copper and copper ions with chloride ions in the solution, forming insoluble cuprous chloride precipitate. However, in order to generate cuprous chloride precipitate from chloride ions in the solution, it is necessary to establish an equilibrium point for copper and copper ions. In actual production, copper slag is difficult to establish an equilibrium point for sponge like copper and oxidized copper due to the different stacking times.

The dechlorination of zinc electrolyte was studied using Haipu resin products. When the initial chlorine content of zinc electrolyte was 1.36 g/L, the dechlorination efficiency after primary ion exchange was 31.74%.

When the liquid-solid ratio of regeneration is 4:1 and the concentration of SO42- in the regeneration solution is 250 g/L, the regeneration rate of the failed resin is 83.40%. The static exchange experiment results show that the kinetics of chlorine removal from zinc electrolyte by Haipu resin products are more in line with particle diffusion control.