Multiscale Dynamic Diffusion Model for Ions in Micro- and Nano-Porous Structures of Fly Ash: Mineralization Experimental Research

Abstract

The leaching concentration of alkaline ions plays a crucial role in the efficiency of the CO2 mineralization reaction in fly ash. The multi-scale structural characteristics of micro–nano pores in fly ash are the primary factors that control the leaching and diffusion rate of alkaline ions. However, the existing theoretical models do not account for the multi-scale pore structure, leading to challenges in accurately describing the ion diffusion in fly ash and predicting the reaction rate and efficiency of CO2 mineralization. To address this issue, a multi-scale dynamic diffusion model of ions was developed based on the micro–nano pore structure of fly ash. This model established the relationship between the ionic leaching rate and pore structure, as well as macroscopic changes over time, which were validated through experiments. Mineralization experiments with varying soaking times and uniaxial compression experiments on mineralized specimens were conducted to investigate the relationships among soaking time, ion leaching concentration, mineralization degree, and mechanical strength. The results elucidated the impact of alkaline ion concentration on the mineralization degree and mechanical strength of fly ash materials, offering theoretical insights to enhance mineralization and material properties.