燃煤烟气重金属与铈改性CaO的相互作用机理研究

Interaction mechanism between heavy metals and Ce-doped CaO in flue gas of coal combustion

氧化钙(CaO)作为一种吸附剂广泛应用于燃煤烟气重金属的净化,但其吸附效率有限,需要进一步改性提升。金属铈(Ce)改性可调整其表面电子分布,增强化学活性。基于此,本研究建立了Ce-CaO(100)周期性模型,研究了燃煤烟气中汞、硒、铅三类重金属污染物的吸附机理。结果表明,除Hg0在Ce-CaO(100)表面上的吸附为物理吸附外,其余重金属污染物均为化学吸附,Ce位点和O位点为重金属污染物的主要活性吸附位点,吸附分子与Ce-CaO(100)表面之间存在明显的电荷转移与强烈的相互作用。Ce掺杂改性提升了CaO(100)表面对重金属污染物的吸附能力,尤其对Se0、SeO2和HgCl2的捕集能力显著提高。

Calcium oxide(CaO)has been widely used as an adsorbent in the purification of heavy metals in coal-fired flue gas.However,the adsorption efficiency is limited and a further modification is needed.The cerium(Ce)modification can redistribute the surface electrons and enhance the chemical activity of CaO.Therefore,the Ce-CaO(100)periodic model was established to study the adsorption mechanism of mercury,selenium,and lead pollutants in the coal-fired flue gas.The results show that,except for the physical adsorption of Hg 0 on the Ce-CaO(100)surface,the other heavy metal pollutants are chemically adsorbed on the surface.The Ce-site and O-site are the main active adsorption sites of heavy metal pollutants.Intense charge transfer and strong interaction are observed between adsorption molecules and Ce-CaO(100).Moreover,the adsorption capacity of Ce-doped CaO(100)surface for heavy metal pollutants has been improved,especially the significantly increased capture capacity on Se0,SeO2 and HgCl2.