Preparation and Characterization of Composite Membranes for Ultrafiltration Applications

Abstract

Water is an important aspect of living and nurturing. The advancements in the living style has led to increased and rapid industrialization which consequently increased the water pollution. There are various types of contaminants which pollute the water and numerous techniques have been evolved for water treatment. Membrane separation process is more propitious than other water treatment techniques due to its ease of operation and selective removal/concentration of target specie. The present work focuses on the preparation of low-cost ceramic membrane which can be used for microfiltration and as a support to the polymeric membrane during fabrication of polymer–ceramic composite ultrafiltration membrane, having positive attributes of both ceramic and polymeric membranes. The prepared ultrafiltration composite membranes can replace the use of nanofiltration and reverse osmosis by using polymer enhanced ultrafiltration (PEUF) and micellar enhanced ultrafiltration (MEUF) techniques. In the present work, the ceramic supports were prepared using paste method by sintering them at 900ºC and polymer–ceramic composite membranes were prepared using dip coating technique. The prepared membranes were characterized using TGA, XRD, SEM-EDAX, pycnometry analysis, gravimetric analysis, mechanical strength, corrosion test, FTIR analysis, gas permeation and liquid permeation analyses to find out their pore size, porosity, permeability, pore size distribution, mechanical strength, corrosion resistivity and polymer layer thickness. The effect of carbonates on the properties of kaolin based ceramic supports were studied by varying the amounts of the sodium carbonate (0–40 wt.%) and calcium carbonate (0–40 wt.%). The supports prepared using calcium carbonates had high porosity and liquid permeability as compared to those prepared using Na2CO3. Among all the prepared supports, the support C2 (20% CaCO3), with 0.5 µm pore size, 37% porosity and 48 MPa flexural strength was best to use for further fabrication of polymer–ceramic composite membranes and microfiltration applications. The application of the optimized ceramic support (C2) and polymer ceramic composite membrane was investigated for treatment of oil-in-water emulsions (100 mg/L and 200 mg/L). The copper and chromium ions were rejected using MEUF and PEUF membrane separation techniques.