Tubular ultrafiltration ceramic membrane based on titania nanoparticles immobilized on macroporous clay-alumina support: Elaboration, characterization and application to dye removal

Abstract

Abstract The development of new membranes with improved separation properties, high mechanical and thermal stability using inexpensive and naturally abundant materials is of utmost importance for sustainable development and environmental applications. Ceramic materials due to their high chemical, mechanical and thermal stability in combination to their facile surface functionalization have inspired material scientists to design innovative low-cost ceramic-based membrane supports. This study focuses on the preparation and characterization of novel asymmetric ultrafiltration ceramic membrane coated with single separation layer made of TiO2 nanoparticles, and its application to removal of alizarin dye from aqueous solutions. The membrane was prepared by a simple and one-step deposition of micrometer-thick titania layer on the internal surface of the tubular-shape porous clay-alumina membrane support from an aqueous colloidal suspension of titanium oxide (TiO2) nanoparticles with size of 10 nm. The colloidal suspension was prepared in the presence of 0.2 wt.% of Dolapix, and 30 g of an aqueous solution of polyvinyl alcohol at 12 wt.% and 66 mL of H2O. Microfiltration tubular supports of 10 mm/7 mm (outer/inner diameter) were prepared through an extrusion method followed by a sintering process using China Clay Rajmahal grade and alumina, as mineral precursors. The composition of 25% of clay and 75% of alumina was selected in this work as it showed a lower sintering temperature (Tf = 1350 °C) which could ensure low cost elaboration process, an average water flux of 850 L h−1 m−2 bar−1 as well as enhanced mechanical performance (≈37 MPa) and large porosity (48%) with an average pore diameter of 0.75 µm. SEM characterization showed that at the sintering temperature of 800 °C, the TiO2 nanoparticles coated densely and homogeneously the ceramic support forming a thin layer of about 4.2 µm in thickness and leading to a clear reduction of the mean pore size (50 nm approximatively) while providing a water permeability of 117 L h−1 m−2 bar−1. The so-designed ultrafiltration (UF) tubular ceramic membrane has proved efficient for alizarin red dye removal with a retention rate of 99% and a permeate flux of 70 L h−1 m−2 at pH 9 and a transmembrane pressure of 5 bar.