Wetting Kinetics of Lithium-Sodium Orthoborate on Nickel and Stainless Steel under CO₂-Lean and Saturated Conditions

Contact angle measurements were conducted on lithium-sodium orthoborate, an alkali-metal borate-based high-temperature carbon capture sorbent, in contact with nickel and stainless steel under air, N₂, and CO₂ atmospheres at 600 °C in order to assess the compatibility of this innovative sorbent with packed-bed reactors, typically used in the commercial carbon capture industry. On nickel, the results reveal the melt to be wetting (contact angle θ ≤ 90°), albeit with a contact angle reaching an apparent equilibrium over the experimental time considered. It was found that θ was lower under N₂ than under CO₂, which was explained as a consequence of the oxide-ion activity difference between the CO₂-lean and saturated melts. On stainless steel, however, the melt rapidly spreads, tending toward complete wetting of the metal sheet (θ = 0°) in all atmospheres. For the two metals investigated, the results indicate high to very high wettability, hence the adequacy of using lithium-sodium orthoborate in conventional gas-liquid contactors, further backing this sorbent as a potential alternative to existing sorbents for CO₂ capture.