Research on leaching kinetics and reactivity evaluation of copper tailings as precursor for alkali-activated materials

Copper tailings are by-products of copper mining, and because of their rich content of SiO2 and Al2O3, it is considered as a possible raw material for the preparation of geopolymer composites. In this paper, the leaching kinetics and reactivity of reactive elements Si and Al in copper tailings under alkali hydrothermal environment are investigated, and the reasons for the difference in reactivity between copper tailings and granulated blast furnace slag (GBFS), fly ash (FA) are also introduced. The results show that the leached Si and Al in the precursor materials are involved in the formation of N/C-A-S-H. Similar to FA and GBFS, the leaching behavior of reactive elements in copper tailings is mainly controlled by the diffusion behavior through the surface product layer. Additionally, the activation energy of Al in the precursor materials is lower than that of Si, which makes the Al-O bond easier to break in alkaline environment, thus causing the leaching rate of Al in the raw materials to be higher than that of Si. Meanwhile, the activation energies of Si and Al in copper tailings are 69.29 kJ/mol and 33.91 kJ/mol, respectively, and higher elemental activation energy makes the efficiency of elemental dissolution lower, which is also the main reason for the lower reactivity of copper tailings. This study aims to elucidate the interrelationships between physicochemical properties, leaching behavior and reactivity of copper tailings. •The leaching characteristics of Si and Al from copper tailings are clarified.•The leaching rate of Si in copper tailings is consistently lower than that of Al.•The leaching process of copper tailings is influenced by the diffusion behavior of the surface product layer.•Higher dissolution activation energy of copper tailings reduces its reactivity.