Abstract
CuMn2O4 spinel has been regarded as a highly efficient sorbent for Hg0 capture from flue gas. The regenerability and recyclability of CuMn2O4 sorbent are mainly associated with the mercury speciation adsorbed on its surface. However, the effect mechanism of HCl on Hg0 transformation over CuMn2O4 sorbent is still elusive. Experiments were conducted to understand the effect of HCl on Hg0 transformation over CuMn2O4 sorbent. The results indicate that CuMn2O4 sorbent is a mesoporous material and possesses a good thermal stability. CuMn2O4 shows >95% Hg0 removal efficiency in a wide temperature window of 50–350°C. The favorable electron-transfer environment caused by the mixed valence states of Cu and Mn cations is responsible for the excellent Hg0 removal performance of CuMn2O4 sorbent. CuMn2O4 shows a higher Hg0 adsorption capacity of 4774.57 μg/g. Hg0 adsorption process over CuMn2O4 sorbent can be well described by the developed kinetic model. Hg0 removal efficiency of CuMn2O4 sorbent does not depend on the presence of HCl. Mercury species adsorbed on the CuMn2O4 sorbent in the presence of HCl mainly exist in the forms of HgO and HgCl2O8 · H2O. HCl shows a significant effect on mercury speciation over CuMn2O4 sorbent. Most of HgO species will be transformed into HgCl2O8 · H2O in the presence of HCl.
Highlights
Mercury is a toxic air pollutant with high volatility, and is harmful to human health and ecosystem [1–5]
Mercury species adsorbed on the CuMn2O4 surface in the presence of HCl mainly exist in the forms of HgO and HgCl2O8·H2O
The excellent Hg0 removal performance of CuMn2O4 sorbent is closely associated with the electron-transfer environment caused by the mixed valence states of Cu and Mn cations
Summary
Mercury is a toxic air pollutant with high volatility, and is harmful to human health and ecosystem [1–5]. Thermal power plant is considered to be a main source of gaseous anthropogenic mercury emissions in China [6–8]. The Minamata Convention on Mercury has officially come into force in August 2017 to restrict the global anthropogenic mercury emissions [9]. In order to meet the requirements of the Minamata Convention on Mercury, the mercury emission limit of thermal power plants in China will be set to 1 μg/m3 in 2030 [10]. Mercury emission control in thermal power plants becomes increasingly urgent. Mercury emission control technologies of thermal power plants mainly include: sorbent injection [11–16], catalytic oxidation [17–20] and bromide addition [21–23]. The technical strategy of catalytic oxidation and bromide addition is to oxidize Hg0 into Hg2+, which
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