37 NOVEL, ALKALI-BONDED, CERAMIC FILTRATION MEMBRANES S. Mallicoat, P. Sarin, W. M. Kriven Department of Materials Science and Engineering University of Illinois at Urbana-Champaign Urbana, IL, 61801, USA ABSTRACT Ceramic filters allow operations at extreme pressures and pHs, high temperatures, and have longer operating lifetimes. However, costly ceramic filtration systems are often rejected in favor of polymeric filters. The primary cause for the high cost of ceramic filters is the expensive processing which includes powder synthesis and sintering cycles. The goal of our research is to develop a new type of ceramic filter using alkali bonded ceramics (ABCs). In this study, we present an update on our effort to create a ceramic membrane with interconnected porosity of controlled pore size using alkali bonded ceramics. Synthesis of ABC membranes can be separated into four main steps (a) synthesis of nanosize polymeric colloidal particles, (b) preparation of self-assembled templates using polystyrene (PS) nanospheres, (c) intrusion of the template with ABC slurry, which hardens at room temperature, and finally (d) dissolution of the template in a solvent. PS nanospheres of diameters 100 and 300 nanometers were synthesized and self-assembled to form templates of different shapes and sizes. Results on intrusion of ABC slurry into the template formed on a microporous nylon filter paper will be presented. INTRODUCTION Membranes used in filtration systems can be broadly classified into organic and inorganic filters. Organic filters, such as those made up of cellulose acetate, polyamides, and polysulfones, dominate the market today despite poorer performance in comparison to inorganic membranes in several aspects. In general, inorganic membranes, particularly those made of ceramics, offer superior chemical resistance, wider operational temperature limits, greater resistance to extreme pH conditions, higher pressure limits, longer operating lifetimes, and improved backflushing capabilities. Despite these benefits, inorganic membranes suffer from high fabrication costs primarily due to expensive powder processing and sintering at high temperatures. Alkali bonded ceramics (ABCs) are amorphous or nano-crystalline aluminosilicate materials. They are formed by reacting inexpensive aluminosilicate raw materials, such as natural clays and industrial by-products, with alkali silicate solutions. Some of the commonly used sources of aluminosilicate materials are metakaolin 1-8 , fly ash 9-13 , and slag. 14-17 Upon mixing of the aluminosilicate powders with the alkali silicate solutions, a slurry is formed which hardens at ambient temperatures and forms a rock-like material. ABCs are also referred to as geopolymers in the literature. 18 ABCs are comprised of a matrix of aluminosilicate material which encapsulates unreacted or filler particles that may be present in the system. The matrix is believed to be an amorphous analogue of zeolites and consists of a three-dimensional framework of linked SiO 4 and AlO 4 - tetrahedra. The excess negative charge, resulting from the AlO 4 - tetrahedra, is balanced by alkali cations. Porosimetry analysis (see Figure 1) has confirmed that the average pore size is less than four nanometers and that 95% of the internal surface area is present in pores of diameter less than ten nanometers. ABC’s are, however, impermeable materials, with a measured permeability value of 10 -9 cm/s. 19