Experimental study on the oxidative absorption of Hg0 by KMnO4 solution

Abstract

The wet FGD system is widely recognized as the co-effective removal system for oxidized Hg vapor species and SO2. In this study, a purpose-built device was designed for this experiment and several factors potentially affecting the Hg0 removal efficiency were systematic investigated, including different types of oxidants, pHs and concentrations of potassium permanganate, reaction temperatures, Hg0 inlet concentrations, O2, SO2 and NO concentrations, and different types of absorption solutions. Results indicate that pHs and KMnO4 concentrations, reaction temperatures, SO2 and NO concentrations all have a strong influence on the removal of Hg0, and the inlet concentrations of Hg0 and O2 contribute little to the removal of Hg0. SO2 could significantly inhibit the removal of Hg0, the negative effect is serious especially at lower SO2 concentration, and SO2 could lead to the re-emission of Hg0. Hg0 could be removed effectively by using CaCO3+KMnO4 solution, when the KMnO4 concentration in the CaCO3+KMnO4 solution was 1.5mmol/L, the removal efficiencies of SO2, NO and Hg0 were 100%, 40.69% and 90.58%, respectively. So, considering the application to the practical engineering, adding 1.5–2mmol/L KMnO4 into limestone–gypsum flue gas desulfurization systems is necessary. This technology is a promising method for the simultaneous removal of NO, SO2 and Hg0.