CuMn 2 O 4 spinel has been regarded as a highly efficient sorbent for Hg 0 capture from flue gas. The regenerability and recyclability of CuMn 2 O 4 sorbent are mainly associated with the mercury speciation adsorbed on its surface. However, the effect mechanism of HCl on Hg 0 transformation over CuMn 2 O 4 sorbent is still elusive. Experiments were conducted to understand the effect of HCl on Hg 0 transformation over CuMn 2 O 4 sorbent. The results indicate that CuMn 2 O 4 sorbent is a

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... s material and possesses a good thermal stability. CuMn 2 O 4 shows >95% Hg 0 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 Hg 0 removal performance of CuMn 2 O 4 sorbent. CuMn 2 O 4 shows a higher Hg 0 adsorption capacity of 4774.57 μg/g. Hg 0 adsorption process over CuMn 2 O 4 sorbent can be well described by the developed kinetic model. Hg 0 removal efficiency of CuMn 2 O 4 sorbent does not depend on the presence of HCl. Mercury species adsorbed on the CuMn 2 O 4 sorbent in the presence of HCl mainly exist in the forms of HgO and HgCl 2 O 8 • H 2 O. HCl shows a significant effect on mercury speciation over CuMn 2 O 4 sorbent. Most of HgO species will be transformed into HgCl 2 O 8 • H 2 O in the presence of HCl.