Micropatterning of alumina tubular membranes via laser carving for enhanced direct air capture

An approach for preparing and applying micropatterned alumina tubular membranes was developed for improved gas-liquid contact at low air pressure drop in direct air capture application. The paper demonstrated that the laser carving of micropatterns on the outer surface of the alumina tubular membranes could greatly increase their outer surface area and enhance gas-liquid turbulence for a reduced diffusion mass transfer resistance. Six kinds of micropattern configurations were fabricated and studied, including random and regular micropatterns. By introducing a 500-µm solid grid micropattern, the outer surface area doubles and enhances carbon dioxide capture efficiency from 61% to 97% after the membrane was hydrophobically modified with fluoroalkylsilane. The air pressure drop through the tube lumen remained low even when the packing density increased from 382 to 906 m²/m³. The liquid entry pressure of this micropatterned membrane was the same after testing for 220 h running with the help of periodic drying.