电厂烟气中SO2对活性炭吸附单质铅(Pb0)的影响机理

利用密度泛函理论系统研究了SO_2对活性炭吸附单质铅(Pb~0)的影响,其中,结构优化与频率计算采用B3LYP/def2-SVP级别方法和基组,单点能计算采用B3LYP/def2-TZVP级别方法和基组.同时,利用玻尔兹曼分布函数分析了SO_2与Pb~0在活性炭表面的竞争吸附关系,结果表明,Pb~0在纯净活性炭上的吸附能力大于SO_2.此外,本研究发现,SO_2的预吸附会增强活性炭对Pb~0的吸附效果.通过静电势分布揭开了SO_2促进活性炭吸附Pb~0的深层原因,结果发现,吸附SO_2以后活性炭表面静电势极大值增大,极小值减小,吸附剂吸附能力因此增强.最后,利用电子密度差分图揭示出SO_2改性活性炭在吸附Pb~0时,SO_2对Pb~0吸附的影响可以分为直接影响和间接影响两种.

The effect of SO2 on adsorption of element lead (Pb0) toward activated carbon in coal-fired power plants

In this work,we investigated the effect of SO₂ molecule on adsorption of element lead (Pb⁰) toward the surface of activated carbon systematically,using density functional theory.Optimization of configuration as well as frequency analysis was carried out at B3LYP/def2-SVP level,and single point energy was calculated at B3LYP/def2-TZVP level,respectively.The competitive adsorption analysis between SO₂ and Pb⁰ was performed using Boltzmann distribution function (B_df),and the result suggested that the adsorption interaction of Pb⁰ on carbonaceous materials was stronger than that of SO₂.Besides,it was found that the pre-adsorption of SO₂ on activated carbon could promote the adsorption of Pb⁰ obviously.In addition,electrostatic potential distribution (ESP) analysis evidenced that the local maximum of ESP on activated carbon surface was enlarged and the local minimum of ESP was decreased after SO₂ was adsorbed,indicating the activity of sorbent rose due to SO₂ adsorption.The electronic density difference plot during Pb⁰ adsorption was acquired,and it indicated SO₂ molecule can impact Pb⁰ adsorption directly or indirectly.