Fabrication of Composite Membranes for Filtration Applications

Abstract

Water is very essential for survival of all living things and is also critical in every aspect of economy. As the drinkable water resources are limited, removal of major contaminants from industrial effluents prior to disposal into water bodies has been enforced to reduce the pollution at source. Also, reuse of treated water in process industries helps in solving the water crisis. With the rapid industrialization and economic growth, the generation and discharge of wastewater from industrial/municipal sources also increased at the same pace, posing a serious concern on the environment. Among the different techniques for wastewater treatment, membrane separation is widely adopted because of its efficiency and reliability for continuous processing. Current membrane separation approaches emphasize the use of reverse osmosis, which is prohibitively expensive relative to microfiltration and ultrafiltration because of its high operating cost. Microfiltration and ultrafiltration membranes are composed of either expensive ceramic or low-durability polymeric materials. In the present work, low-cost ceramic membranes were prepared by using kaolin (KA), fly ash (FA) and dolomite. The effects of sintering temperature and raw materials composition (i.e., 0 100 wt% of KA in the mixture of KA + FA) on the membrane properties (strength, porosity, pore size, permeability, etc.) were studied. The raw material mixtures were subjected to TGA and the prepared membranes were characterized by SEM, XRD, liquid permeation, mechanical strength and chemical stability tests. The SEM analysis evidenced that the membranes were free of defects and had homogeneous surface structure with evenly distributed pores of similar sizes. A sintering temperature of 900 °C was found to be optimum for both kaolin-based and fly ash based membranes. Addition of 20% dolomite provided sufficient porosity to all membranes (28 51%). The porosity, strength and stability increased, while the pore diameter decreased with an increase in the kaolin content (M0 M100).