Consolidation of mine tailings through geopolymerization at ambient temperature

Mine tailings-based geopolymers were prepared at ambient temperature. The evolution of their microstructure and the immobilization of lead were studied. Characterizations include measurements in compressive strength, scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and toxicity characteristic leaching procedure (TCLP) tests. With increasing the ratio of metakaolin from 0% to 50%, geopolymer gel in the mine tailings-based geopolymers increased from 33.92% to 79.45%, leading to the compressive strength that increased from 2 to 15.5 MPa. With addition of Pb(NO3)(2), a three-stepped changes in the compressive strength and microstructure of the geopolymers were observed. As increasing Pb(NO3)(2) dosage from 0% to 6%, geopolymer gel was kept constant, while lead silicate glass increased from 0% to 10.51%, and Si sites in calcium silicate hydrate (CSH) gel decreased from 20.55% to 11.3%. Pb2+ was effectively immobilized in the geopolymers. This study first presents the evolution of geopolymer gel, belite, lead silicate glass, and CSH gel in mine tailings-based geopolymers as the functions of metakaolin and Pb(NO3)(2) additions.