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

Abstract 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 (SOx) 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 SOx utilization. The proposed process model comprises the following four systems based on validated experimental data: electrolysis, metal ion separation, SOX 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.