Leaching mechanism of SiO2 in activated kaolinite clinker with low modulus sodium silicate solution

Abstract

ABSTRACT Preparation of high modulus solution and high Al/Si residue via leaching SiO2 is a key for large amount utilization of coal gangue based on ferric oxide assisted roasting – alkali leaching silica process. This work focuses on leaching mechanism of SiO2 in activated kaolinite clinker with low modulus sodium silicate solution. The results show that the lattice distorted cristobalite produced in the roasting process is readily soluble in sodium silicate solution, however the leaching of SiO2 was only 75% and the modulus of lixiviant reached 2.5 through leaching in sodium silicate solution with a modulus of ~1.0. The leaching kinetics and dissolution mechanism have also been analyzed by model fitting and microstructural observation. The leaching reaction was controlled by diffusion across the pore. The slit – shaped pores formed by the stacking of hercynite particles prevent the diffusion of the bulk solution, thus inhibiting the leaching of cristobalite inside the particles.