Experimental studies on the durability and leaching properties of alkali-activated tailings subjected to different environmental conditions

This paper presents an investigation on the durability and leaching behavior of gold MTs-based geopolymer by conducting a series of experiments that included uniaxial compressive tests (UCT) and static monolithic leaching tests, considering submersion into three different reagent solutions: deionized (DI) water, salty water, and acidic water to mimic its resistance to different environmental impacts. The strength degradation of the geopolymer prior to and after immersion in different reagent solutions were measured by performing UCT tests. The interpretations of strength degradation were examined by conducting a series of experiments to investigate the ties between the material strength and microscopic insights. The leaching element concentrations were obtained by performing the Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses of the leachates. Results indicate that the strength degradation after immersion into three different reagent solutions were approximately equal to 50%. The strength degradation of the gold MTs-based geopolymer resulted from the hydrated minerals after immersion may have influenced the chemical process during solution immersion. The leaching analyses showed that the geopolymer was ineffective in immobilizing the As, Si, and S elements. The evolution of conductivity was consistent with the element concentrations with time. Leaching mechanism indicated that the leaching elements were mainly dominated by diffusion and surface wash-off. Finally, with the finding that only considers surface wash-off and diffusion, the first-order reaction/diffusion model (FRDM) can reasonably describe the leaching kinetics of the elements with immersion duration.