烟气单质汞氧化去除过程络合反应机理

Study on the mechanism of complexation reaction in the process of mercury removal from flue gas

湿法氧化去除烟气Hg^0过程中产物Hg^2+易发生络合反应,络合产物可能改变氧化体系形成新反应机制,这一现象尚未被认识研究.为获得Hg^2+络合物生成及其对烟气脱汞影响机理,研究了配体阳离子、配体浓度、反应pH值、反应温度和摩尔比等对Hg^2+络合反应的影响和氧化去除烟气Hg0的络合反应机理.结果表明MgCl2、KCl、NiCl2和BaCl2配体均能与HgCl2形成络合物,而CuCl2和SnCl4则不能生成络合物.络合物生成量随配体浓度的增加先升高然后趋于平衡;络合反应在酸性环境下发生且不受pH值变化影响;碱性环境下络合反应不能进行;反应温度基本不影响络合反应效应;增加配体浓度可提高络合物产量,不同配体络合效应不同,但最大吸光度基本相同,为(4.20±0.03)A.配体对络合反应有响应区间,低于区间下限值时不能形成络合物,高于上限制值时络合物产量不随配体浓度而变化.HgCl2络合反应累积稳定常数β4=1015.07;[HgCl4]^2-可螯合Hg(aq)和O2(aq)使其与ClO-和Hg2Cl2反应,形成氧化-络合氧化反应新机理.

The product Hg^2+was prone to complexation during the process of wet oxidation to remove Hg0 from flue gas.The complexation product may change the oxidation mechanism to form a new reaction mechanism.This phenomenon has not been studied.The effects of ligand cation,ligand concentration,reaction pH,reaction temperature and molar ratio on the complexation reaction of Hg^2+and the complexation mechanism in the oxidation removal of Hg0 in flue gas were studied.The results showed that MgCl2,KCl,NiCl2 and BaCl2 could be complexed with HgCl2 but neither CuCl2 or SnCl4.The amount of complex formation increased first with ligand concentration increasing and then tended to be equilibrium.The acidic reaction environment was beneficial to the complexation reaction and not affected by the pH change.However,the complexation reaction could not occur in the alkaline reaction environment.The reaction temperature did not affect the complexation reaction.The absorbance of all the complexes produced was basically the same,this value was(4.20±0.03)A.The mercury complexation reaction had a response interval to the ligand concentration.When the ligand concentration was less than the lower limit of the interval,complex could not be formed.When the ligand concentration was more than the upper limit of the interval,the complex yield did not change with the ligand concentration.When the mercury atom sp orbit was recombined,it was difficult for the 6d empty orbit to participate in the hybridization to form a high-spin outer rail type complex.The cumulative stability constantβ4 was 1015.07.The complex[HgCl4]^2-had the ability to chelate Hg(aq)and O2(aq),then react with ClO-and Hg2Cl2.A new oxidation-complexation oxidation reaction mechanism was formed.