Preparation of Foamed Ceramics from Graphite Tailings Using A Self-Foaming Method

Graphite tailings were used as the raw materials for the preparation of foamed ceramics via a high-temperature self-foaming method. The residual carbon in the tailings acted as the foaming agent and no additional foaming agents were required. The residual carbon reacted with Fe2O3 and produced gas that was wrapped by the liquid phase to form a porous structure. The effects of sintering temperature, holding time, carbon content, flux on the bulk density, water absorption, and mean pore size of the foamed ceramics were investigated. The bulk density, compressive strength, thermal conductivity, and water absorption of the foamed ceramic prepared using the optimal sample D100 (100 wt% graphite tailings) and sintered at 1200 °C for 20 min were 1.36 g/cm3, 0.35%, 12.03 MPa, and 0.51 W/(m·K), respectively. The raw material contained CaO, Fe2O3, and SiO2, which formed augite with a low fusibility point. In contrast, the molten decomposition products of potassium feldspar and CaSiO3 ions formed anorthite, which has a high fusibility point. Therefore, potassium feldspar is not recommended for use as a flux in tailing systems with high calcium content. Foamed ceramics were prepared using up to 100 wt% graphite tailings. This is a new approach for the economical disposal of graphite tailings.