Technoeconomic Analysis of a Brine Purification Process─Combined Carbon Dioxide Mineralization and Hydromagnesite Recovery

A huge amount of brine purification sludge (BS) is discharged from soda plants every year, which results in serious environmental pollution and resource waste. In this work, a modified brine purification route is proposed. First, the brine is purified by adding lime, sodium sulfate, and soda ash sequentially to remove magnesium and calcium ions; meanwhile, the BS is produced. Then, CO2 is mineralized by the sludge through the carbonation reaction. Finally, magnesium sulfate, the product of the carbonation reaction, is used to produce hydromagnesite. The optimal reaction conditions were investigated, under which the magnesium ion leaching efficiency can reach up to 95.54% in the carbonation reaction step and the magnesium ion utilization efficiency can reach up to 99.05% in the hydromagnesite production step. The characterization results indicated that high-purity calcite and hydromagnesite were obtained. Based on the optimal operational condition, the economic analysis for the process was completed and the results showed that the modified route was economically feasible.