Strength development and polymerization reaction mechanism of sulfur-tailings-based geopolymer produced with CaO and Na2SiO3 composite activator

Mining and beneficiation processes are accompanied by the discharge of large quantities of tailings, which occupy large areas of land and cause environmental pollution, which is a significant concern. This study prepared an environmentally friendly geopolymer using sulfur tailings and granulated blast furnace slag (GBFS) and characterized its performance and mechanism analysis. A low-cost and efficient CaO-Na2SiO3 composite activator and comprehensive utilization method for sulfur tailings have been proposed. The experimental results showed that the CaO-Na2SiO3 composite activator can improve the strength of STBG, especially the early strength. The highest 28d compressive strength of STBG can reach 32.2 MPa when the CaO content in the composite activators was 10%. However, when the CaO content in the activators was greater than 10%, the cumulative pore volume and harmful pore volumes of the STBG increased to 0.17 mg/L and 0.07 mg/L respectively, and the compressive strength developed slowly in the later period. In addition, the highest immobilization efficiency of STBG for Cu, Pb, and Mn can reach 99.9%, 93.9%, 91.6% respectively. The STBG can effectively immobilize heavy metals.