Physico-chemical processes of environmentally friendly ceramics formation by hazardous electroplating and automotive industry waste application

Environmentally friendly red ceramics were developed from traditional mixtures of natural clay- sand mix with the inclusion of 3–10% hazardous waste sludge from the RENAULT plant and 5–10% electroplating waste. The ceramics were fired at temperatures of 700°, 750°, 800°, 850°, 900° and 950° C. The flexural strength of the test samples reached 17.6 MPa, water absorption after 950° C firing was 6,53–10,45%, shrinkage coefficient values between 5,3–13,8%, density 2,7–3,2 g/cm³. The study of the developed materials structure formation processes using a complex of physicochemical methods showed the synthesis of mullite Al6Si2O13, Na-thenardite Na2SO4, and anorthite (Ca, Na) (Si,Al)4O8 with the appearance of a very high content of amorphous new formations. The used industrial wastes played the role of accelerators of the structuring processes of the developed ceramic materials. Studies of the dissolution and leaching of heavy metals by atomic absorption analysis have shown their very strong chemical binding into a chemically insoluble state. In accordance with the Brazilian standarts, the developed materials can be used for the industrial production of environmentally friendly building materials such as tiles, bricks, blocks and similar products.