Electrofiltration of silica nanoparticle-containing wastewater using tubular ceramic membranes

In this work, two laboratory-prepared inside-out tubular TiO2/Al2O3 composite membranes with a molecular weight cut-off (MWCO) of 95 kDa were evaluated for their capabilities in treating silica nanoparticle-containing wastewater by crossflow electrofiltration. The silica nanoparticle-containing wastewater exemplified by oxide-CMP wastewater was obtained from a wafer fab and further characterized by various standard methods and apparatuses. The tested oxide-CMP wastewater was determined to have high contents of total solids and dissolved silica resulting in a high turbidity. The target wastewater also was found to have a rather high conductivity. Under a constant crossflow velocity, it was found that the filtration rate increased with increasing electric field strength and transmembrane pressure within some limits of magnitude. Experimental results have revealed that the laboratory-prepared tubular ceramic membranes are capable of removing a great extent of water quality criteria of concern to yield permeate with a turbidity of lower than 0.75 NTU. Thus, the filtrate is suitable for high-level recycling.