Synthesis of rare earth tailing-based geopolymer for efficiently immobilizing heavy metals

Rare earth tailing (RET) is a specific tailing containing high content of heavy metals. In this work, RET-based geopolymer was successfully prepared, which not only possesses good mechanical performance but also can immobilize the heavy metals well. The compressive strength of the optimized RET-based geopolymer after 7 d can reach over 35 MPa. XRD results showed that the RET-based geopolymer had a typical broadening diffraction peak corresponding to the amorphous geopolymer structure, which was also supported by SEM micromorphology. The incorporated RET played a role similar to aggregate and has a reinforcement effect on the overall mechanical strength of RET-based geopolymer. The immobilizing mechanism of heavy metals in the RET-based geopolymer was investigated by XRD, FTIR, XPS, etc. The introduced heavy metal cations (Pb2+ and Ba2+) were immobilized in the geopolymer by combining with unbridged oxygen or with the Si/Al chain-like framework thereby generating corresponding new phase of PbO/BaSiO3. This work provides a feasible strategy to utilize the RET solid waste through the preparation of geopolymer, which possesses extraordinary immobilizing ability on heavy metals and is conducive to the environmental-friendly waste management.