Control of mercury emissions from coal-combustion flue gases using CuCl2-modified zeolite and evaluating the cobenefit effects on SO2 and NO removal

•CuCl2 impregnation decreased surface area and pore volume of MCM-41.•CuCl2 impregnation enhanced Hg0 adsorption under both N2 and flue gas conditions.•Competitive adsorption for Hg and flue gas components caused smaller Hg capacities.•CuCl2-impregnated MCMs had greater potentials in removal of NO than SO2.•The main removal mechanisms of SO2 and NO may rely on catalytic oxidation.

The effects of CuCl2 impregnation on the physical and chemical properties and the Hg0 removal effectiveness of zeolite MCM-41 (MCM) were examined. Multipollutant removal potentials of the resulting samples on simultaneous capture of SO2 and NO were also evaluated. Overall, CuCl2 impregnation within 2–16% reduced the total surface area and pore volume of MCM. The introduced CuCl2 caused the impregnated MCM becoming a microporous adsorbent. The Hg0 adsorption capacities of CuCl2-impregnated MCMs were greater than those of the untreated sample under both N2 and simulated flue gas conditions. When the CuCl2 impregnation content was ≥ 8 wt%, however, the Hg0 adsorption capacity decreased because CuCl2 impregnation in excess amounts hindered certain active sites or blocked the pores. Hg0 oxidation tests showed that the average oxidation percentages of MCM-4% and MCM-16% were 26.7% and 53.7% respectively in the flue gas condition, compared to < 26% in the N2 condition. After CuCl2 impregnation, the SO2 removal of MCM samples decreased from 42.3% to approximately 38% but NO removal increased from 62.8% to up to 73%, showing that CuCl2-impregnated MCMs may have greater potentials in simultaneous removal of NO than SO2. Catalytic oxidation appeared to be important in SO2 and NO removal.