School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240.
Environ Sci Technol. 2009 Nov 15;43(22):8610-5. doi: 10.1021/es901803s.
The equilibria and kinetics of the reaction between bromine (Br(2)) and chlorine (Cl(2)) to form bromine chloride (BrCl) at various temperatures were determined. BrCl was employed to oxidize elemental mercury (Hg(0)) under simulated flue gas conditions. The removal of Hg(0) from the gas phase by a homogeneous gas-phase oxidation reaction and the heterogeneous reactions involving flyash were investigated. The second-order gas phase rate constant was determined to be 2.3(+/-0.2) x 10(-17) cm(3).molecules(-1).s(-1) at 373K. The reaction of Hg(0)/BrCl was significantly accelerated in the presence of flyash, and the estimated Hg(0) removal efficiency in the presence of 0.6 ppmv BrCl and 20 g/m(3) flyash was up to 90%. Unexpectedly, the major product was found to be HgCl(2), rather than HgBr(2), indicating that bromine in part acted as the accelerant in Hg(0) oxidation in BrCl/Br(2)/Cl(2) system by facilitating the formation of intermediates. As a result, bromine consumption is much less than if only bromine gas is utilized alone. These results were helpful not only for understanding the mechanism of Hg(0) removal in coal-fired flue gas but also in any atmosphere in which bromine and chlorine species coexist.
测定了不同温度下溴（Br(2)）和氯（Cl(2)）之间形成溴化氯（BrCl）的反应平衡和动力学。在模拟烟道气条件下，使用 BrCl 氧化元素汞（Hg(0)）。研究了气相中均相气相氧化反应和涉及飞灰的多相反应中 Hg(0)的去除。在 373K 下，确定了第二级气相速率常数为 2.3(+/-0.2) x 10(-17) cm(3).molecules(-1).s(-1)。在飞灰存在下，Hg(0)/BrCl 的反应明显加速，在 0.6ppm BrCl 和 20g/m(3)飞灰存在下，Hg(0)的去除效率估计高达 90%。出乎意料的是，主要产物是 HgCl(2)，而不是 HgBr(2)，这表明溴在部分促进中间产物形成的情况下，作为 BrCl/Br(2)/Cl(2)体系中 Hg(0)氧化的加速剂。因此，溴的消耗远低于仅使用溴气的情况。这些结果不仅有助于理解燃煤烟道气中 Hg(0)去除的机制，而且有助于理解任何共存溴和氯物种的大气中的机制。
