Solidification of heavy metals in lead smelting slag-based cementitious materials via the hybrid binder method

Abstract

The hybrid binder method offers a possible solution for lead smelting slag (LSS) disposal and the immobilization of heavy metal technologies. In this study, in order to comprehend the effects of activators, solidification/stabilization solids (S/S solids) were prepared using different activators to excite LSS. The results showed that although using a single excitation source improved the compressive strengths of S/S solids, hybrid excitation can further enhance them, which 28d compressive strength could reach 73.2 MPa and increasing by 372%. Simultaneously, the leaching concentration of heavy metals decreased significantly. The mechanisms behind the significantly improved performance of S/S solids due to hybrid excitation were discussed based on the pH value and XRD, Fourier-transform infrared, TG, scanning electron microscope, and MIP results. The increase in the alkaline component due to the introduction of different activators provided a more extensive dissolution of active substances and deeper excitation. Thereby leads to the formation of new phases with cummingtonite and the variation of phases in LSS. The use of the hybrid excitation reduces the average pore diameter and porosity to 7.71 nm and 24.35% for hardened S/S solids, respectively, and significantly solidifies the heavy metals of LSS.