Promotional effect of NH3 on mercury removal over biochar thorough chlorine functional group transformation
2020
Zhang, Huicong | Wang, Tao | Zhang, Yongsheng | Sun, Baomin | Pan, Wei-Ping
The mercury removal performance of chlorine plasma-modified biochar was tested under NH₃ and NH₃ combined with a NO/SO₂ atmosphere. The addition of NH₃ promotes the mercury removal process of modified biochar, and the mercury removal efficiency can be increased by up to 17.5%. NH₃ can induce the conversion of chloride to C–Cl, making it easier to bind to Hg⁰. NO also exhibits a promoting effect on mercury removal. This is because Hg⁰ can be converted to HgO by the oxidation of NO. When the flue gas contains both NH₃ and NO, the mercury removal efficiency is not as good as when the two gases are present alone. It is due to that NO will be consumed with NH₃ at high temperatures and NO₃⁻ will be generated on the surface of biochar and occupy the active site. SO₂ inhibits mercury removal by modified biochar through competitive adsorption. Sulphates and sulphites are more likely to form on the surface of biochar in the case of the coexistence of NH₃ and SO₂. The deposition of the chemical salt on the surface of the biochar causes the pores to be blocked and the active sites to be occupied, thereby deteriorating the efficiency of mercury removal.
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