Manufacturing of sustainable ceramics with improved mechanical properties from hazardous car paint waste to prevent environment pollution

Paint waste sludge (PWS) is one of the most polluted wastes of automobile construction industry. The main objective of this study was the experimental control of the neutralization of hazardous PWS (up to 20 wt%) in kaolin clay composites during the sintering of their mixtures at temperatures of 1000 °C, 1050 °C, 1100 °C, 1150 °C, 1200 °C, 1250 °C, and 1300 °C in order to manufacture environmentally clean white ceramics. These raw materials and the developed ceramics were characterized by following methods: X-ray diffraction, X-ray fluorescence, atomic absorption spectroscopy, energy-dispersive spectroscopy, and laser micro-mass analyses. The flexural resistance of the ceramics reached 12.77 MPa, the linear shrinkage varied between − 3.32 and 11.29%, the water absorption values ranged between 1.61 and 3.02%, and the density diverged from 1.53 to 1.62 g/cm³. These numbers significantly exceeded the values of the control samples without PWS during ceramics sintering at all temperatures. The decomposition of the crystalline structures of kaolin, gibbsite, muscovite, barite, and calcite was determined; instead, small amounts of mullite and cristobalite crystals with a high prevalence of glass-like amorphous material appeared. The values of the experimental leaching and solubility tests of heavy metals from the developed ceramics were significantly lower than those permitted by Brazilian standards. So, high values of mechanical and chemical properties of the developed ceramics permit to utilize PWS as valuable raw material for production of environmentally clean white bricks, blocks, and tiles and to decrease ecological damage of automobile industry.