Remediation of Micro-Pollution in an Alkaline Washing Solution of Fly Ash Using Simulated Exhaust Gas: Parameters and Mechanism

Abstract

Currently, there is an urgent need to remediate heavy metals (HMs) and high alkalinity in the washing solution of fly ash (FA). This study investigated the remediation with simulated exhaust gases of two CO2 partial pressure and revealed the removal efficiency of target pollutants, mainly including Pb ions. The results verify that under the preferred conditions of 25 °C and 15 mL/min flow rate, bubbling two kinds of simulated flue gases could efficiently remove 97.9–99.2% of Pb ions. Moreover, the initial 40 min removal of Pb ions fits in a way with a pseudo-first-order equation. Based on the thermodynamic parameters, we infer that the removal of Pb ions was a spontaneous, exothermic, and entropy-decreasing process. Furthermore, residual HMs and terminal pH after remediation of the FA washing solution basically met the regulatory threshold values of the integrated wastewater discharge standard in China (GB 8978−1996). Additionally, the particles obtained from the washing solution of FA were identified as CaCO3, which was mainly composed of vaterite and calcite crystalline. This study provides a fundamental guide for remediating multiple pollutants in the washing solution of FA and simultaneously sequestrating carbon emissions from power plants and industries.