Solidification of heavy metals in lead smelting slag and development of cementitious materials

Abstract

Lead smelting slag (LSS) is a hazardous waste containing heavy metals (Cr, Ni, Cu, Zn, As, and Pb) and its improper disposal may cause irreparable damage to the ecosystem. Cementitious materials prepared with LSS can be used in construction fields and hazardous heavy metals are also solidified in prepared cementitious materials. In this study, the effects of particle sizes of LSS (8.30, 12.54, and 19.04 μm) on the compressive strength of prepared with high-volume LSS multiple coupling excitation cementitious materials were explored. According to the composition of LSS, activators were set as 6% MgO, 6% bischofite, 7% CaO, 1% CaCl2, and 8% cement, respectively. Decreasing the particle size of LSS could significantly improve the compressive strength of cementitious materials, especially in the early stage. The sample containing LSS with the particle size of 8.30 μm showed the highest compressive strength (47.1 MPa) and activity index (78.2%) among the samples containing LSS with different particle sizes. LSS with three particle sizes was analyzed with Fourier transform infrared spectroscope (FTIR) and X-ray diffractometer (XRD). The analysis results indicated that decreasing the particle size of LSS increased the specific surface areas (SSAs) and decreased the degree of crystallinity . Moreover, the microscopic analysis of cementitious materials implied that decreasing the particle size enhanced the degree of reaction and gelation , thus resulting in the denser structure of blocks. The results confirmed the compressive strength of LSS-based cementitious materials. • Heavy metals in LSS were effectively solidified in cementitious materials. • A hydration model for LSS-based cementitious materials is proposed. • The paper presents early strength could be significantly improved with decreasing particle size. • LSS-based cementitious materials can be used in the field of prefabricated construction industrial.