Sustainable materials from hazardous lead ore flotation waste in composites with spent foundry sand and clay

The aim of this study was the experimental tests of the mechanical properties and structure formation processes of sustainable ceramics from hazardous lead ore flotation waste, spent foundry sand, and natural red clay to produce sustainable ceramics. The lead was mined on a large scale from lead ores in the city of Adrianópolis, Brazil, for 58 years. The wastes from this activity bequeathed profound environmental and social impacts. The mechanical characteristics of twenty compositions of the ceramics were analyzed through the flexural resistance, water absorption, apparent density, and linear shrinkage; the study of the physicochemical processes of the ceramics’ mineral composite transitions and structure formation during sintering at 900–1250 °C was accomplished using XRD, SEM, EDS, AAS, and LAMMA methods. All ceramics presented flexural resistance (until 10.08 MPa) in comparison with the values established in the Brazilian national standards (> 1.5 MPa), with low water absorption and shrinkage. Ceramics with 7% of the flotation waste and 10% spent foundry sand, whose resistance reached from 3.7 to 10.1 MPa, showed the best mechanical properties. Leaching and solubility analyses by AAS method showed that there is no environmental jeopardy in using these compositions to produce sustainable ceramics.