Preparation and interface state of phosphate tailing-based geopolymers

The long-term storage of phosphate tailings will occupy a large amount of land, pollute soil and groundwater, thus, it is crucial to achieve the harmless disposal of phosphate tailings. In this study, high-performance geopolymers with compressive strength of 38.8 MPa were prepared by using phosphate tailings as the main raw material, fly ash as the active silicon-aluminum material, and water glass as the alkaline activator. The solid content of phosphate tailings and fly ash was 60% and 40%, respectively, and the water-cement ratio was 0.22. The results of XRD, FTIR, SEM-EDS and XPS show that the reactivity of phosphate tailings with alkaline activator is weak, and the silicon-aluminum material can react with alkaline activator to form zeolite and gel, and encapsulate/cover the phosphate tailings to form a dense phosphate tailings-based geopolymer. During the formation of geopolymers, part of the aluminum-oxygen tetrahedron replaced the silicon-oxygen tetrahedron, causing the polycondensation reaction between geopolymers and increasing the strength of geopolymers. The leaching toxicity test results show that the geopolymer has a good solid sealing effect on heavy metal ions. The preparation of geopolymer from phosphate tailings is an important way to alleviate the storage pressure and realize the resource utilization of phosphate tailings.