Department of Environmental Engineering, Zhejiang University , Hangzhou 310058, P. R. China.
Environ Sci Technol. 2014 Dec 2;48(23):14025-30. doi: 10.1021/es503837w. Epub 2014 Nov 11.
Recently, simultaneous removal of SO2, NOx and oxidized mercury in wet flue gas desulfurization (WFGD) scrubber has become a research focus. Mercury re-emission in traditional WFGD system has been widely reported due to the reduction of oxidized mercury by sulfite ions. However, in multipollutants simultaneous absorption system, the formation of a large quantity of nitrate and nitrite ions as NOx absorption might also affect the reduction of oxidized mercury in the aqueous absorbent. As such, this paper studied the effects of nitrate and nitrite ions on mercury re-emission and its related mechanism. Experimental results revealed that the nitrate ions had neglected effect on mercury re-emission while the nitrite ions could greatly change the mercury re-emission behaviors. The nitrite ions could initially improve the Hg(0)-emission through the decomposition of HgSO3NO2(-), but with a further increase in the concentration, they would then inhibit the reduction of bivalent mercury owing to the formation of Hg-nitrite complex [Hg(NO2)x(2-x)]. In addition, the subsequent addition of Cl(-) could further suppress the Hg(0) emission, where the formation of a stable Hg-SO3-NO2-Cl complex was assumed to be the main reason for such strong inhibition effect.
最近，在湿式烟气脱硫（WFGD）洗涤器中同时去除 SO2、NOx 和氧化态汞已成为研究热点。由于亚硫酸盐离子还原氧化态汞，传统的 WFGD 系统中的汞再排放已被广泛报道。然而，在多污染物同时吸收系统中，大量的硝酸盐和亚硝酸盐离子作为 NOx 吸收可能也会影响水相吸收剂中氧化态汞的还原。因此，本文研究了硝酸盐和亚硝酸盐离子对汞再排放及其相关机制的影响。实验结果表明，硝酸盐离子对汞再排放的影响可以忽略不计，而亚硝酸盐离子可以通过 HgSO3NO2(-)的分解来初步提高 Hg(0)-排放，但随着浓度的进一步增加，由于形成 Hg-亚硝酸盐络合物[Hg(NO2)x(2-x)]，它们会抑制二价汞的还原。此外，随后添加的 Cl(-)会进一步抑制 Hg(0)的排放，其中形成稳定的 Hg-SO3-NO2-Cl 络合物被认为是这种强烈抑制效应的主要原因。
