Novel process design of desalination wastewater recovery for CO₂ and SO_X utilization

Desalination is one of the most effective methods of supplying industrial water. Desalination has evolved into a feasible water supply alternative that allows the use of ocean water, and desalination plants operate in many countries, including in arid areas. Therefore, a large amount of desalination wastewater is generated, which is discharged into the sea. Since highly concentrated mineral ions in desalination wastewater are useful substitutes for carbon dioxide (CO₂) and sulfur oxide (SO_x) utilization compared with limited feedstock, such as high-grade limestone, it is crucial to improve the utilization of metal ions by recovering desalination wastewater. This study presents a novel process of desalination wastewater recovery CO₂ and SO_x utilization. The proposed process model comprises the following four systems based on validated experimental data: electrolysis, metal ion separation, SO_x capture and utilization (SCU), and CO₂ capture and utilization (CCU). First, desalination wastewater was electrolyzed to obtain a strong basic solution through electrolysis. Second, during metal ion separation, magnesium and calcium ions in the wastewater were precipitated in the form of a metal hydroxide and separated by the basic solution. Third, the separated Ca(OH)₂ was used for desulfurization and produced gypsum in the SCU system. Finally, CO₂ in the desulfurized flue gas was captured by the strong basic solution and utilized as CaCO₃ and MgCO₃ in the CCU procedures. Consequently, about 91% CO₂ is captured and utilized from flue gas, and the desulfurization efficiency is 99%. In addition, the maximum net profit of the proposed process is $ 73.23 per tonne of CO₂, and it is profitable and suitable for large-capacity processes, compared with other alternative CCU processes.