Ultra-Fast CO₂ Gas Absorption Using Bubble-Manipulating Surfaces in Liquid Gas-Absorbing Systems.

Gas absorption by liquid media is an essential part of many large-scale industrial processes. When gas is injected into an absorber unit as discrete bubbles, as is the case for bubble column absorbers or gas sparging systems, the effectiveness of their reaction relies on careful control of the bubbles’ properties and flow. Here we demonstrate an efficient mode of gas absorption into a liquid by using engineered surfaces that manipulate bubbles and enhance the reaction rate between the phases. By integrating these surfaces into a liquid gas-absorbing system, we are able to increase the reaction rate by 2 orders of magnitude compared to a surfaceless gas-absorbing system. Experimentally we use carbon dioxide gas and a moderately alkaline potassium hydroxide absorbent solution. A surfaceless system suffers from two disadvantages: (1) bubble reaction rate decreases as they shrink and (2) the bubbles do not fully absorb due to product aggregation on their surface, blocking the gas/liquid reaction interface. However, our method overcomes the said challenges by (1) demonstrating the highest reaction rates for smaller bubbles, reversing the aforementioned trend, and (2) benefiting from the rapid timescales of bubble-manipulation relative to product aggregation, consequently avoiding the aggregation regime and leading to complete gas absorption. Finally, we offer to integrate bubble-manipulating surfaces in liquid gas-absorbing systems as an absorption technique with advantageous scaling for small-scale or distributed modular absorber designs.