Comparative Assessment of Li–Na(CO₃/NO₃/OH) on Flux Performance of Ceramic–Salt Composite CO₂ Separation Membranes

In addition to the years of trials and innovations delivered in ceramic processing for high CO2 separation of membranes, acceleration of additional flux of oxide ions through the molten phase of the ceramic–salt composite has been a seeking complementary but most interesting topic of the research. The previous examinations on carbonate, nitrate, hydroxide salts, etc., with an additive, were independently carried out, and their merits were addressed. However, the unavailability of collective information and data on nitrate, hydroxide, and carbonate hinders the true comparison in optimizing the best competitor. In scope of the above drawback, the current study is dedicated to review the impact of nitrate, hydroxide, and carbonate salts together at a fixed Li-to-Na cationic molarity of 52:48. All assessments were performed in the asymmetric membrane geometry of the composite under identical synthesis and testing protocols, where 40 vol % porous support and ∼10 μm-thick matrices were prepared from Ce0.9Gd0.1O2−δ. However, the molten nitrate, hydroxide, and carbonate salts were impregnated, respectively, to the top thick-film matrix at 350 °C, 460 °C (in argon), and 650 °C (in air), i.e., 150 °C above the corresponding eutectic temperatures.