Preparation of calcium carbonate by ion-exchange membrane carbonization electrolysis of calcium-containing magnesium slag solution

Magnesium slag is a solid waste produced by Pidgeon process. It is found that there are a large number of CaO and Ca₂SiO₄ phases in magnesium slag, which is a good calcium source. The concentration of CaCl₂ solution obtained by adding hydrochloric acid to leach magnesium slag is about 250 g/L, and then converted into Ca(OH)₂ solution by electrolysis. Light CaCO₃ products can be prepared by introducing CO₂ into the cathode of the electrolytic cell. Therefore, in this paper, using 250 g/L CaCl₂ solution as the anode liquid, CaCO₃ product was obtained by cation exchange membrane electrolysis technology and CO₂ was introduced at the cathode. The effects of various factors on the electrolysis process were investigated by changing the cathode NaCl concentration, CO₂ flow rate, current density and electrolysis time. The results show that the electrolysis effect is the best when the experimental conditions are cathode NaCl concentration of 50 g/L, CO₂ flow rate of 50 mL/min, current density of 0.05 A/cm² and electrolysis time of 2 h. At this time, the mass of CaCO₃ product was 4.41 g, and the energy consumption per unit mass of electrolysis process was 2.79 kW·h/kg. Compared with direct electrolysis to obtain Ca(OH)₂, it was found that direct electrolysis had obvious mass loss and increased energy consumption, so it was necessary to introduce CO₂ into the cathode during the electrolysis process.