Environment friendly ceramics from hazardous industrial wastes

This paper reports on recycling mixed industrial wastes (exhaust metallurgical dust, spent foundry sands, galvanic glass microspheres, and acid inertization salt) into environmentally friendly composite ceramic materials. The only natural component of the compositions developed is clay and sand mixture, which is a traditional raw material of local brick factories. All industrial wastes under study have high contents of heavy metals, such as Pb, Br, Sr and Cr. The main goal of this research is development of eco-friendly construction materials based on hazardous industrial wastes to reduce waste disposal at dumps that chemically contaminate the environment. This would prolong service life of industrial landfills and essentially reduce exploitation of natural raw materials. Samples containing 75–85% of industrial wastes fabricated at 950–1010 °C have flexural strength values of up to 14 MPa. The values of leaching and solubility of the heavy metals are hundreds of times less than those permitted the national standards of Brazil. Physicochemical studies of the samples confirm the formation of a glassy structure with inclusion of newly formed minerals (Sodium Anortite, Thenardite, Hematite and Mullite). This structure can explain the mechanical and chemical characteristics of the new ceramic materials.