Tubular TiO2/Al2O3 composite membranes: preparation, characterization, and performance in electrofiltration of oxide-CMP wastewater

In this work, inside-out tubular TiO2/Al2O3 composite membranes were prepared, characterized, and used for electrofiltration of oxide-CMP (chemical mechanical polishing) wastewater obtained from a wafer fab in Taiwan. The extrusion method and sol-gel/slip-casting method were employed for fabricating the membrane layer of TiO2 inside of the tubular substrate of Al2O3. A process of firing followed. Scanning electron microscopy, X-ray diffractometry, permporometry, and molecular weight cut-off determinations have verified the prepared tubular products were indeed inside-out tubular TiO2/Al2O3 composite membranes suitable for ultrafiltration applications. Experimental results of electrofiltration have shown that the prepared tubular TiO2/Al2O3 composite membranes are capable of removing a great extent of water quality criteria of concern from the target wastewater to yield permeate with a turbidity of lower than 0.75 NTU. Permeate thus obtained could be used for make-up water of cooling towers and other purposes.