Preparation and characterization of membranes made of pottery clay

Abstract

Membrane separation works on the physical principle of size cut-off, wherein the particles larger in diameter cannot permeate while fluid (solvent) can. Membranes used in micro to ultra filtration have been prepared from refined inorganic materials. Some researchers have used low-cost natural materials such as clay, fly ash and apatite, these need lower firing temperature than metal oxide materials and have high flux performance to treat large volumes of process fluids. In this work, membranes with pore size lying in microfiltration regime were prepared using local pottery clay of Patiala. Two membranes sets were prepared by paste casting followed by sintering at different temperatures, viz. 850oC, 900oC, 1000oC varying the primary and porosity components compositions. Using 68% clay, 20% calcium carbonate, 10% sodium carbonate (membrane A) and the second one using 76% clay, 20% calcium carbonate (membrane B) with small amounts of sodium metasilicate. Both the membranes were characterized by TGA, SEM, XRD, porosity test with water as wetting liquid and acid–base treatment. The effect of sintering temperature on porosity and pore size has been studied, with pore size data taken from SEM imaging analysis. The composition of membrane is also important as amount of calcium carbonate determines amount of CO2 escaping per gram of membrane bulk, porosity increases with increase in CaCO3 amount/g of membrane, but larger CaCO3 concentration can be damaging as pressure of CO2 increases with increased percentage of CaCO3. From the experimental results, it was found that with the increase of sintering temperature, pore size was increasing while porosity was decreasing. The overall performance of membrane B was better than membrane A.