Industrial sewage slurry utilization for red ceramics production

This paper reports on ceramic materials based on hazardous industrial sewage slurry containing galvanic glass waste and clay-sand mixture. The slurry waste has high contents of heavy metals (Ni - 3.24%, Zn - 5.28%, Pb - 1.32%, Sn - 0.67%, Cr - 4.28% and Cu - 3.78%), organic components (pitches, oils, paints, inks, etc.), and water (56.35%). The ceramics is sintered at temperatures of 700, 750, 800 and 850 °C to provide flexural strengths of up to 12.5 MPa, coefficients of thermal expansion 6.1-9.0% and water absorption of 11.95-13.20%. The minerals that survive sintering are only Quartz SiO2 and Hematite Fe2O3. Analyses of ceramic samples demonstrate their amorphous glassy nature, presence of Na-Anortite (Ca,Na)(Si,Al)4O8, Thenardite Na2SO4 and Mullite Al6Si2O13, and strong chemical binding of the heavy metals within insoluble structures (leaching and solubility tests).