Seawater as a promising absorption solvent in sustainable carbon capture and utilization

Given that geographic proximity between CO 2 sources and carbon capture and utilization (CCU) facilities minimizes transportation costs, developing specialized CCU technologies for coastal industrial complexes is imperative. Current wet carbon capture relies on freshwater; however, increasing scarcity necessitates sustainable alternatives. This study addresses this challenge by proposing a Seawater-Based Carbon Capture (SBCC) system that utilizes seawater as a promising solvent. While the SBCC process leveraged pH-buffering mechanisms to achieve a 54–86% increase in total carbon capture relative to freshwater solvents, it necessitated a proportional rise in NaOH consumption. Previous studies have primarily attributed the lower CO 2 absorption capacity of seawater to excessive OH − consumption during Mg(OH) 2 precipitation; in contrast, the proposed SBCC process achieved a substantial increase in net carbon capture (NCC) by 54–84%. Regarding the absorption capacity per unit of NaOH, seawater exhibited a marginal reduction of less than 6% compared to freshwater, despite the formation of carbonate precipitates such as MgCO 3 and CaCO 3 . Notably, this slight efficiency tradeoff is considered manageable and can be further offset by the valorization of these mineral precipitates as high-value resources. This study addresses the need for sustainable alternatives by proposing an SBCC system utilizing seawater as a promising solvent. These results validate that substituting freshwater with seawater can significantly enhance NCC by maximizing pH-buffering effects within the pH-buffer zone created by alkaline absorbent dosage at the Primary pH-control zone.