Participation influence of silicate on the temporal and spatial distribution of chloride electromigration in the electrokinetics of municipal solid waste incineration fly ashes

Abstract

The chloride (Cl) content in cement production and the other derivate products has been strictly restricted to avoid the corrosion of steels in building construction, which significantly narrows the possible utilization choices of Cl-abundant municipal solid waste incineration (MSWI) fly ashes. The reduction of soluble Cl from the source materials becomes an important prerequisite for efficient resource utilization of MSWI fly ashes. In this study, an electrochemical platform was constructed to investigate the potential pathways of the migration and transformation of Cl species in silicate-participated MSWI fly ashes during electrokinetic (EK) treatment. The factors including the operating time, voltage, and mass ratio of silicate to fly ashes were adjusted to evaluate the changes in pH, current, and Cl distribution. Each treated fly ash in the sampling area was evenly cut into 3 layers and 72 parts to accurately determine the distribution of Cl in the electrolyzer. More Cl- ions in the surface layer were electromigrated to the anode than those in the middle and bottom layers. The addition of silicate enhanced electromigration and improved the distribution uniformity of Cl species in the sampling area. The reduction in Ca2+ electromigration with the formation of C-S-H caused by the silicate guaranteed the continuous transfer and reactions of Cl- anions in the EK treatment.