Porous Ceramic Materials Obtained from Industrial Waste with Filtration Applications

This paper presents experimental results regarding the feasibility of producing porous ceramic filters through the valorization of two types of industrial waste, i.e., an aluminum-rich material derived from treated black aluminum dross, and coal ashes recovered from an old landfill. To enhance the open, interconnected porosity of the ceramic filters, glucose was employed as a pore-forming agent in two dosages (20% and 40%). The results show that by controlling the thermal treatment parameters together with the composition of the raw mix, it is possible to achieve a microstructure and filtration performance suitable for ceramic filter applications. X-ray diffraction (XRD) analyses confirmed the presence of corundum (αAl2O3) and MgAl2O4 spinel in the ceramics based on aluminum-rich material, phases well-suited for filtration applications due to their chemical and mechanical properties. When kaolin is used as a raw material in combination with the aluminum-rich material, mullite (3Al2O3·2SiO2) can form, enhancing the mechanical strength of the ceramic. However, filters sintered at higher temperatures exhibit reduced filtration efficiency due to the decrease in porosity. In comparison, ceramic filters containing coal ashes, benefiting from the presence of fluxing oxides and gas-releasing components (unburnt fossil fuel and carbonates), develop higher open porosity at lower sintering temperatures. Microstructural analysis of the obtained ceramics revealed an interconnected pore network whose size and distribution depend on the raw-mix composition, glucose content, and sintering temperature. Increasing the glucose content from 20% to 40% significantly enhanced the open porosity and filtration flow rate, but at the expense of mechanical strength and ionic retention capacity. The filtration data confirmed that all investigated materials function effectively as gravity-driven filters without the need for applied pressure. The obtained results underline the strong potential of using waste-derived porous ceramics as sustainable and cost-effective filtration materials for wastewater treatment applications.