PREPARATION AND CHARACTERIZATION OF CERAMIC MEMBRANES ON THE BASE OF HALLOYSITE CLAY AND LIMESTONE
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2020-01-01
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Abstract
The development of ceramic membranes based on natural raw materials such as kaolins, clays, zeolites, lime-stones, dolomites, feldspars, quartzs and others appears an efficient solution to purification of water at a low cost. The ceramic membranes are prepared in the form of disks of a size of 3,0 cm x 0,4 cm by dry pressing of a homog-enized batch from halloysite clay and limestone of different quantities at pressure of 50 MPa. They are fired for 2 h at 1100°C. The properties of the sintered ceramic membranes such as shrinkage, water absorption, an apparent density, an apparent porosity and a mechanical bending strength are determined by standard methods. Mercury porosimetry is used to determine the pore size distribution and the average pores size. The phase composition is identified by XRD analysis. The microstructure is observed using SEM. The increase of the limestone content results in an increase of the water absorption and the apparent porosity and a decrease of the shrinkage, the apparent den-sity and the compressive strength. The average pore size equals 2,32 µm, while the total porosity amounts to 45,00 % for the ceramic membrane containing 60 wt.% of halloysite clay and 30 wt.% of limestone. The main crystalline phases found in the sintered ceramic samples refer to anorthite (CaO.Al2O2.2SiO2) gehlenite (2CaO.Al2O3.SiO2) mullite (2Al2O3.SiO2) and wollastonite (CaO.SiO2).