Hydrophobic–Hydrophilic Janus Ceramic Membrane for Enhancing the Waste Heat Recovery from the Stripped Gas in the Carbon Capture Process

A novel hydrophilic–hydrophobic ceramic membrane was developed in this study for the waste heat recovery from the hot stripped gas (i.e., CO2 balanced by water vapor) in the CO2-rich solvent-split modified carbon capture process. This Janus ceramic membrane contained a layer of hydrophobic fluoroalkylsilane (FAS) molecules grafted on a hydrophilic Al2O3 ceramic membrane support. With the increase of FAS concentration, the carbon chain length in FAS molecules in addition to the grafting time, the water and solvent contact angles (CAs) of the hydrophobic side of the Janus membrane improved. The hydrophobic side of the Janus membrane also exhibited a good thermal stability under the typical CO2 regeneration temperature. Furthermore, this Janus ceramic membrane improved the waste heat recovery performance when compared with the conventional hydrophilic ceramic membrane. The hydrophobic side of the Janus membrane should orient toward the stripped gas for achieving a high heat recovery performance. With an increase in the water CA of the hydrophobic side of the Janus membrane, the waste heat recovery performance of the Janus membrane first increased and then declined. The optimal water CA was about 106 ± 1.3° in this study. Moreover, once the water CA for the hydrophobic side of the Janus membrane was fixed, the waste heat recovery performance of the Janus membrane was almost fixed no matter what the grafting conditions were adopted. The novel Janus ceramic membrane developed in this study exhibited a great potential to improve the waste heat recovery performance in the carbon capture process.