Influence of ball materials on the surface activation behavior of coal ash particles during a mechanochemical process

Abstract

In this study, the surfaces of coal ash particles were activated via a planetary ball mill-assisted mechanochemical process by utilizing balls that were made from different materials such as zirconia, alumina, and iron. The influence of ball materials on particle morphology, crystallinity, chemical structure, and elution of Si and Al ions in alkali solvents were systematically investigated for the first time, during when the impact energy and friction force induced on the coal ash surface was also clarified in details via the assistance of a self-constructed system. It was found that the mechanochemical process performed with zirconia and iron balls featured a preferred “grinding effect” with decreasing particle size and increasing specific surface area. This was due to the efficiently impact energy induced. In contrast, alumina balls featured an “activation effect” by inducing crystal distortion on the surface and thereby, promoting the ion elution within the alkaline solvents.