CO₂ Separation Using a Sonic Nozzle Flow and Ion-Induced Nucleation

Abstract

In this study, the feasibility of a CO₂ separation process based on ion-induced nucleation was investigated. Ion-induced nucleation is a heterogeneous nucleation process in which gas-phase molecules aggregate around an ion, allowing cluster formation under milder supersaturation conditions compared to homogeneous nucleation. First, the adsorption–desorption dynamics of vapor molecules on an ion surface were modeled using queueing theory, and the theoretical predictions were compared with molecular dynamics (MD) simulation results. The arrival-interval and binding-time distributions obtained from MD simulations showed good agreement with exponential distributions under low vapor pressure conditions. Next, ion-induced nucleation of CO₂ was investigated using MD simulations of CO₂–N₂ gas mixtures containing a single ammonium ion, representing the dilute ion limit. Under conditions where homogeneous nucleation was suppressed, the formation and growth of CO₂ nanoclusters around the ion were clearly observed. These results demonstrate that ion-induced nucleation can effectively lower the nucleation barrier and promote particle formation. The findings of this study suggest the potential of combining ion-induced nucleation with sonic nozzle separation to realize a low-energy and efficient CO₂ separation process.