Characterization of an asymmetric ultrafiltration membrane prepared from TiO2-smectite nanocomposites doped with commercial TiO2 and its application to the treatment of textile wastewater

Inexpensive ultrafiltration ceramic membranes were prepared using three nanoparticle powders created by mixing synthetic TiO2-smectite nanocomposites with commercial TiO2 in various ratios: 95:5 (generating type 1 nanoparticle powder, "NP1"), 85:15 (type 2 nanoparticle powder, "NP2"), and 70:30 (type 3 nanoparticle powder, "NP3"). For each membrane, the active layer that performed the ultrafiltration was deposited on a previously prepared silty marl support ("M") in a layer-by-layer approach using a suspension of the nanoparticles in polyvinyl alcohol solution (PVA) and water. The morphologies and properties of the membranes obtained after sintering at 950 degrees C for 3 h were characterized by BET and SEM. It was observed that the active layers of the three membranes (NP1/M, NP2/M, and NP3/M) were homogeneously structured, exhibited no cracks, and had average pore diameters of 22.5 nm, 16 nm, and 5 nm, respectively. Water permeabilities ranged from 2100 L h(-1) m(-2) bar for the support before layer deposition to 181 L h(-1) m(-2) bar for the NP3/M membrane, which indicates that the latter membrane can be used for ultrafiltration. The performance of the NP3/M membrane was then investigated by studying pure water permeation through the membrane and by using NP3/M to filter pretreated and nonpretreated textile wastewaters. The results showed that ultrafiltration through NP3/M led to significant decreases in the turbidity, color, and chemical oxygen demand (COD) of the wastewaters, while the permeate flux was maintained at an acceptable level. Thus, the NP3/M ultrafiltration membrane developed in this work could be used for the remediation of industrial effluents.