Gold Ore Tailings Solidified/Stabilized by a Green Waste-Based Composite Geopolymer

Solidification/stabilization (S/S) is a low-cost and efficient method to enhance the mechanical properties of gold ore tailings (GOTs) and to decontaminate contaminated tailings. However, the traditional cement-based stabilization method has problems of environmental pollution and questionable sustainability. In this study, the industrial waste residue was mixed with alkaline activators to prepare a green waste-based composite geopolymer (WCG) for stabilizing the GOTs. Their hydration mechanism, microstructure, mechanical properties and leaching characteristics were analyzed after curing periods of 3, 7, 14, 28 and 90 days. The tests included phase structure analysis (XRD), thermogravimetric analysis (TGA) and unconfined compression strength (UCS) tests to evaluate the hydration products and the strength of the stabilized-GOTs . The results showed that the increase of amorphous/unidentified content is not obvious after 28 days of curing, and that the stabilized tailings with the same content of WCG have higher mechanical strength than those stabilized with ordinary Portland cement (OPC, 32.5 MPa). Scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) and nitrogen adsorption test s were used to characterize the microstructure of the stabilized materials. These results indicated that the formation of C-(A)-S-H gels contributed to improve the degree of compaction in the stabilized samples. The i mmobilization mechanism of arsenic mainly included precipitation, physical encapsulation, adsorption and ion substitution . The stabilized materials had a dual pore fabric characterized by interaggregate and intra-aggregate pores. The properties of the leaching solution, including pH, electrical conductivity (EC), oxidation-reduction potential (ORP), and heavy metal ion leaching concentrations were determined to evaluate the leaching performance of the stabilized-GOTs. The relationship between the chemical properties of the leaching solution and the concentration of leaching ions was analyzed to help explain the immobilization mechanism for harmful elements. This paper provides a reference for the contamination remediation and sustainable management of gold ore tailings