The Role and Stabilization Behavior of Heavy Metal Ions in Eco-Friendly Porous Semi-Vitrified Ceramics for Construction Application

Generally, safety and environmental friendliness have been the major factors for the wide application of waste-based ceramic materials. Vitrified ceramic materials have an outstanding ability to solidify heavy metal ions, which may become a potential product for recycled waste. However, the role of different types of heavy metal ions in waste-based vitrified ceramics is not clear, as well as their stabilization behavior. Hence, electrical insulators waste and red mud-based porous semi-vitrified ceramics are prepared and used as host materials to investigate the influence of heavy metal ions (different types and contents) on the phase composition, pore structure and physical-mechanical performance of the prepared samples, including the stabilization behavior and mechanism of heavy metal ions. The obtained results show that the added three heavy metal ions can act as modify ions and lead the softening temperature of samples to decrease, resulting in the obvious variations in the structure and performance of the prepared samples. The stabilization behavior illustrates that the added heavy metal ions are selectively solidified in the glassy phase (solidifying Cd2+) and crystalline phase (solidifying Cu2+ and Zn2+) of the prepared samples, causing its leaching rate to be much lower than the regulatory standard limits. Moreover, the formed “gas-liquid-solid phase” structure can effectively protect the solid matrix from the corrosion of the acidic solution, ensuring that heavy metal ions are well kept in the matrix, even under acidic conditions. The results illustrated that the stabilization of different types of heavy metal elements is selective, providing theoretical support for the safe application of waste-based porous semi-vitrified ceramics which can be used as a competitive eco-friendly construction material.