Lead-Zinc Tailings-Based Construction Mortars/ Preparation, Performance and Stabilization Mechanism of Heavy Metals

Abstract

With the rapid development of technology in China, industrialisation has increased by leaps and bounds, resulting in the mining of large quantities of lead and zinc ores. The lead and zinc tailings that are discharged after beneficiation are discarded and piled up in large quantities in tailings ponds. Lead and zinc tailings are rich in resources and contain a variety of minerals, but they are often accompanied by many hazards, such as the heavy metals in lead and zinc tailings are extremely easy to migrate and transform, and the leachate produced causes serious pollution to the soil ecology, so attention needs to be paid to the resourceful use and harmless disposal of lead and zinc tailings. In this study, a high-strength hybrid mortar with not only good mechanical properties but also excellent solidification of Zn 2+ , Cu 2+ , Mn 2+ , Cr 3+ and Pb 2+ was prepared using Pb-Zn tailings. By analysis, the leaching concentrations of Zn 2+ , Cu 2+ , Mn 2+ , Cr 3+ and Pb 2+ in the mortar are well below the limit values. The influence of mortar composition on the solidification/stabilisation of heavy metals in tailings was also systematically analysed by introducing different levels of Zn 2+ , Cu 2+ , Mn 2+ , Cr 3+ and Pb 2+ (0%, 0.5%, 1.0% and 2.0 wt%) in the formulation and by using a modified BCR continuous extraction method for each form of the five heavy metals in the test blocks. Tailings-based mortars are mainly used for the solidification/stabilisation of heavy metals by mechanisms such as physical sequestration, precipitation, adsorption, ion exchange, lattice solidification, encapsulation and geopolymer reactions. This study provides a good strategy for the environmentally sound treatment of Pb-Zn tailings by not only achieving a strength of M25, but also curing five heavy metal ions, Zn 2+ , Cu 2+ , Mn 2+ , Cr 3+ and Pb 2+ with the best solidification/stabilization of Mn 2+ and Cr 3+ . This study provides a feasible strategy for the resource utilisation of Pb-Zn tailings by preparing a mixed mortar with special fixation ability for heavy metals, which is beneficial for the safe recycling of solid waste.

Keywords: lead zinc tailings, Solid waste, Solidification/Stabilization, Toxic leaching, Heavy metal speciation