Effects of the Sintering Temperature on the Properties of Porous Ceramic Membrane Support Made of Fly Ash, Kaolin, and Claystone

Barbora Thomasová,Lucie Gembalová,Jan Thomas

doi:10.35180/gse-2020-0044

Abstract

In this article, the influence of the sintering temperature on the properties of porous ceramic membrane support made of low-cost inorganic materials is reported. Fly ash was used as a dominant component since it presents cheap, abundant waste material and can be activated by alkalis to form porous structure with great mechanical resistance. Fly ash from coal combustion and additives, which consist of natural kaolin and claystone, were mixed with 5M NaOH solution to make a paste suitable for extrusion. Properties of created tubular porous supports, sintered at temperature ranging from 900 to 1100 °C, were characterized using a number of methods. Tubes sintered at 1000 °C were selected for microfiltration purpose. The morphology of the surface of these samples, studied by scanning emission microscopy (SEM) show homogeneous and crack free structure. Mercury porosimetry indicates uniform pore size distribution with average pore size value of 2.5 μm and pore volume of 38 % and show good mechanical resistance (7.7 MPa). These properties make fly ash-based ceramics suitable as membranes supports for microfiltration membranes technology. Keywords: Ceramics; Fly ash; Membrane support; Sintering. DOI 10.35180/gse-2020-0044

Highlights

Ceramic membranes systems, used for industrial wastewater treatment, recovery and reuse, represent one of the most important technologies that have gained popularity over past two decades There is lot of data proving ceramic membranes dominance over polymeric ones especially when hot, corrosive, or oily wastewaters are treated [1,2,3].Ceramic membranes for effluent filtration usually consist of three filtration layers, porous support, which provides mechanical strength to a membrane layer, interlayer, and a top separation layer
The alkaline activation of aluminosilicates can be defined as a chemical process that leads to a rapid change in the specific structure – partially or totally amorphous which is very similar to the chemistry involved in the synthesis of large group of zeolites [4,5]
The main goal of this study was to evaluate and optimize the sintering temperature in the preparation of porous ceramic membrane supports made of cheap inorganic materials

Summary

Introduction

Ceramic membranes systems, used for industrial wastewater treatment, recovery and reuse, represent one of the most important technologies that have gained popularity over past two decades There is lot of data proving ceramic membranes dominance over polymeric ones especially when hot, corrosive, or oily wastewaters are treated [1,2,3].Ceramic membranes for effluent filtration usually consist of three filtration layers, porous support, which provides mechanical strength to a membrane layer, interlayer, and a top separation layer. All layers are of different densities and decreasing thickness and can be made of the same or different material. Despite mentioned benefits, their wider application is limited mainly by the high prices of input materials and the cost of sintering processes. Coal combustion product (fly ash) and natural materials (kaolin and claystone powders), all produced in the Czech Republic, were chosen as input materials in this study. The chemical composition of selected solid powder materials is mainly composed of silicon oxides (SiO2) and aluminium (Al2O3) compounds. These aluminosilicates, in presence of alkali solution, are subject to geopolymerization process described by Davidovits [4]. It was found that fly ash based geopolymer matrix after heat treatment to 1000 °C creates

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