Galvanic Cr-Zn and spent foundry sand waste application as valuable components of sustainable ceramics to prevent environment pollution

The purpose of this study was to develop new composites of glass-ceramics from hazardous Cr-Zn galvanic sludge (up to 30%), spent foundry sand (25%), glass rejects from metal surface cleaning (20%), and natural red clay (25%) to produce environmentally clean ceramics. All the raw materials and the developed ceramics were analyzed by XRF, XRD, DTA and TGA, SEM, AAS, and LAMMA. The ceramics showed very high flexural resistance (up to 22.84 MPa) and low values of linear shrinkage (5.02%), water absorption (3.20%), and bulk density (2.00 g/cm3) after sintering at temperatures of 950–1200 °C for 1 h. The solubility and leaching of heavy metals from the developed composites with 75% of industrial wastes were far below Brazilian standards, which makes them eco-friendly materials. Such properties allow the use of the ceramics for the production of facing tiles, roof tiles, blocks, and bricks with high economic efficiency.