Development of ceramic filtering membranes based on Tunisian clay and phosphate sludge in wastewater treatment

Abstract

In order to fully exploit the Tunisian clays of the El Haria formation (Paleocene), and the phosphate washing sludge in the Gafsa region of Tunisia, and to obtain finished products using less expensive materials such as ceramic filtration membranes, four samples were studied to evaluate their suitability for industrial use. Different methods of identification were used, including: X-ray diffraction; chemical analysis; Fourier Transform InfraRed Spectroscopy; determination of the specific surface; thermal analysis; particle size analysis; plasticity. The results of these analyses indicate that the clays contain smectites and kaolinites associated with quartz, gypsum, calcite, and dolomite. The phosphate sludge had a low density (1.88 g cm−3), was plastic (plasticity limit of 22.09) and was mainly composed of fluoroapatite (48 %), calcite (32 %) and clay. The present work aims at developing new porous and flat ceramic membranes based on clay and sludge in percentages that vary from 10 % to 30 %, and in the form of disk with a diameter of 40 mm and a thickness of 3–5 mm. These membranes heated at temperatures between 800 °C and 1100 °C, are characterized by their physical properties (water absorption, porosity), mechanical properties (resistance to compression) and morphology (scanning electron microscopy). The results show porous membranes with pore sizes ranging from a few microns to tens of microns (1–20 μm). They show a good elimination efficiency of pollutants from wastewater. The integration of sludge improves the properties of the ceramic membranes and the management of large quantities of phosphate waste and thus minimizes its harmful impact on the environment.