Hg 0 oxidative absorption by K 2S 2O 8 solution catalyzed by Ag + and Cu 2+

Abstract

The aqueous phase oxidation of gaseous elemental mercury (Hg 0) by potassium persulfate (K 2S 2O 8, KPS) catalyzed by Ag + and Cu 2+ was investigated using a glass bubble column reactor. Concentrations of gaseous Hg 0 and aqueous Hg 2+ were measured by cold vapor generation atomic absorption spectrometry (CVAAS). The effects of several experimental parameters on the oxidation were studied; these include different types of catalysts, pHs and concentrations of potassium persulfate, temperatures, Hg 0 inlet concentrations and tertiary butanol (TBA). The results showed that the removal efficiency of Hg 0 increased with increasing concentration of potassium persulfate and catalysts Ag +, Cu 2+ and Ag + provided better catalytic effect than Cu 2+. For example, in the presence of 5.0 mmol l −1 KPS, the mercury removal efficiency could reach 75.4 and 97.0% for an Ag + concentration of 0.1 and 0.3 mmol l −1, respectively, and 69.8 and 81.9% for 0.1 and 0.3 mmol l −1 Cu 2+. On the other hand, high temperature and the introduction of TBA negatively affect the oxidation. Furthermore, the removal efficiency of Hg 0 was much greater in neutral solution than in either acidic or alkaline solution. But the influence of pH was almost eliminated upon the addition of Ag + and Cu 2+, and high Hg 0 inlet concentration also has positive impact on the removal efficiency of Hg 0. The possible catalytic oxidation mechanism of gaseous mercury by KPS was also proposed.