Chemical forms of lead immobilization in alkali-activated binders based on mine tailings

The present work studies the immobilization forms of lead in alkali-activated cementitious binders (AACBs) based on mine tailings. Through deconvolution of Pb 4f XPS spectra of the mine tailings-based binders, the immobilization forms of lead in network, and lead in silicate glass of PbO·3SiO2 and PbO·7SiO2 were first quantitatively presented. The 29Si NMR spectra of the binders synthesized with Pb(NO3)2 additions from 0 to 6% give the ratios of silicates involved in the formation of lead silicate glass, ranging from 0 to 10.56%. In addition, images of scanning electron microscope (SEM) equipped with X-ray microanalytical mapping and results of zeta potential measurements confirmed the immobilization forms in the mine tailings-based binders. It not only gives fundamentals for the solidification/stabilization (S/S) of mine tailings through alkaline activation process, but also enriches the understanding on the immobilization of heavy metals in AACBs.