Janus ceramic membranes with asymmetric wettability for high-efficient microbubble aeration

Microbubbles have drawn increasing attention due to their wide applications in many fileds such as energy production, environmental remediation, and chemical and petrochemical industries. How to facilely and efficiently produce microbubbles is still keeps a great challenge. Herein, we report a Janus ceramic membrane with asymmetric wettability for high-efficient microbubble aeration. The pristine hydrophilic ceramic membrane was firstly modified by 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFTMS), and then functionalized through single-surface deposition of polydopamine (PDA) to achieve a Janus ceramic membrane with asymmetric surface wettability. Results highlight that the introduction of DA with suitable concentration and modification time is highly efficient for the control of surface wettability. Compared to the pristine and hydrophobic modified ceramic membranes, the use of the Janus ceramic membrane allows a uniform microbubble-in-liquid dispersion system at relatively low transmembrane pressure, and as a result, the dissolved oxygen concentration is effectively increased by 1.3 times. The bubble size is stable at about 160 μm in a 24 h continuous run, and the Janus ceramic membrane shows excellent stability. Our study demonstrates the effectiveness of fabricating Janus ceramic membranes and the advantages of Janus ceramic membranes in microbubble aeration.