China Nonferrous Metallurgy

The acidpickling liquid produced by the smelter is mostly treated by lime neutralization method, resulting in a large amount of calcium chloride waste liquid. At present, the treatment process is complex, the cost is high, and the economy of calcium chloride recovery is not high.In this paper, the method of direct electrolysis of calcium chloride wastewater was proposed by referring to the treatment method of chlor-alkali industry, and the diaphragm electrolysis test was carried out with calcium chloride as raw material.The effects of current density, temperature and time on current efficiency and power consumption were investigated, andthe current efficiency was comparedbetween withandwithout carbon dioxideintheelectrolytic cell.The experimental results show thatafter the cathode is introduced with carbon dioxide,slightly soluble Ca(OH)₂ can be carbonized into insoluble CaCO₃, higher current efficiencywasobtainedcompared to direct preparation of calcium hydroxide by cationic membrane electrolysis. At a current density of 40mA·cm^-2, a temperature of 50℃ and an electrolysis time of 3h, the power consumption is lower, the current efficiency is higher and the economic efficiency is best.The median particle size of CaCO₃ produced by carbonization of calcium hydroxide is in the range of 16~23μm, and the particle size is more uniform.The method of cation membrane electrolysis-carbonization to prepare CaCO₃ has high current efficiency and high product purity, which provides a new idea for the treatment of calcium chloride waste liquid produced by steel acidpickling waste liquid by neutralization method.