Recycle of ceramic substrate of PDMS/ceramic composite membranes towards alcohol-permselective pervaporation

Nowadays, membrane recycling has received increasing attention in water treatment, gas separation and pervaporation. Compared with polymeric substrates, inorganic substrates possess higher mechanical and thermal stability, which can be reused to balance the high cost. In this work, for the first time, we studied the recycle of inorganic substrate that was used for fabricating polymeric composite membranes. A facile approach was proposed to recycle ceramic substrate from PDMS/ceramic composite membranes with thermal degradation followed by ultrasonic cleaning. The thermal degradation compositions of PDMS membrane under air or nitrogen atmosphere were investigated by using TGA-IR, XRD and XPS analysis. Influence factors of the recycle approach including degradation conditions, cleaning approach and multi-recycle process were explored to optimize the transport properties of ceramic substrate and PDMS/ceramic composite membrane. The interfacial morphologies and adhesion of the PDMS membrane coated on the recycled ceramic substrate were characterized by SEM and nano-scratch measurement. The results demonstrated that PDMS composite membrane fabricated on the ceramic substrate with 10 times recycle by thermal degradation in nitrogen at 800 °C for 4 h and ultrasonic cleaning could still achieve >92% separation performance and interfacial adhesive force of the fresh PDMS/ceramic composite membrane. Specifically, the membrane exhibited stable flux of 1.2 kg/m²h and separation factor of 8.1 for 120 h continuous pervaporation separation of 5 wt% ethanol/water at 40 °C. Additionally, ∼75% energy saving relative to synthesizing fresh ceramic substrate was estimated for applying the feasible recycle approach.