Development and Characterization of Low Cost Ceramic Membrane for Liquid Phase separation Applications

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A porous membrane support is prepared with low cost ceramic materials by a simple uniaxial compaction method. The effect of sintering temperature (850-1000DC) on porosity, mean pore size, pore size distribution, shrinkage, flexural strength and pure water permeability was investigated. The raw materials and sintered supports were characterized using thermo gravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD) and scanning electron micrograph (SEM) analysis. Based on the characterization results, the support sintered at 950DC (porosity = 44%, flexural strength = 28 MPa, average pore diameter = 1.01 Dm, and water permeability = 4.46D10-6 m/s kPa) is considered as the optimum support (referred as support-I) for membrane applications. Subsequently, the effect of TiO2 (3g and 6g) addition on the properties of the optimized support (support-I) is also examined and no substantial changes is observed for the TiO2 added membrane supports. All the membrane supports are investigated for the separation of oil and BSA from its solution. A higher rejection value of 90-99% is obtained for separation of oil through these supports. However, less rejection is observed for BSA. To improve the separation performance, a selective D-Al2O3 layer (thickness = 2.6 Dm, pore diameter = 5.4-13.6 nm) is developed on the support-I by dip-coating using a stable boehmite sol (davg =30.9 nm) synthesized from inexpensive aluminium chloride. The boehmite sol and the D-Al2O3- clay (clay refers to support-I) composite membrane are characterized with TGA, XRD, SEM, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and liquid displacement techniques. The separation performance of the membrane is investigated using BSA and electrolyte (AlCl3 and MgCl2) solution by varying the process parameters such as pH, applied pressure and feed concentration. The separation results confirm that the rejection and permeability mainly depend on electrostatic attraction/repulsion between the membrane and the solute molecules (BSA, electrolyte). The intrinsic rejection is estimated using Spiegler-Kedem model and the higher rejection (99% for BSA, 72% for MgCl2 and 88% for AlCl3) and permeate flux (3.4D10-5 m/s for BSA, 9.6D10-5 m/s for MgCl2 and 4.4D10-5 m/s for AlCl3) values confirm that the fabricated D-Al2O3-clay composite membrane is potential for liquid phase separation applications. The estimated cost of the membrane (26.04 $/m2) suggests that this could be an alternate for high cost commercial ceramic membranes..
Supervisor: G. Pugazhenthy