Ahn et al. (2026): Direct ocean capture via a pH-swing integrated hollow fiber membrane contactor
Chihyuk Ahn, Sang Moon Shin and Tae-Hyun Bae, IN: Chemical Engineering Journal, https://doi.org/10.1016/j.cej.2026.165197
Direct ocean capture (DOC) has emerged as a promising negative-emissions pathway that exploits the ocean’s natural carbon reservoir to remove CO₂ from seawater rather than from air. Here, the authors demonstrate a DOC system that integrates a pH-swing process with a hollow fiber membrane contactor (HFMC), enabling continuous CO₂ extraction under ambient temperature and pressure. Acidification shifts the dissolved inorganic carbon equilibrium toward molecular CO₂, which is selectively removed across a gas-permeable, water-repellent membrane driven by a concentration gradient. The HFMC architecture provides a high specific interfacial area while maintaining complete phase separation, allowing stable operation in natural seawater without observable fouling. Combined experimental measurements and transport modeling elucidate the hydrodynamic dependence of gas–liquid mass transfer and quantify the relative contributions of liquid-, membrane-, and gas-side resistances, establishing a predictive framework for HFMC scale-up.