Experimental study on the stability of the ClHgSO3- in desulfurization wastewater.

Wet flue gas desulfurization technologies have received much concern for their superior performance on co-controlling the acid gases and mercury. However, high concentrations of mercury-containing desulfurization wastewater, which discharge from wet flue gas desulfurization system regularly, have received researchers' attention since it might generate the risk of secondary pollution. In this paper, the species of mercuric complexes in the desulfurization wastewater was investigated. It speculated that ClHgSO3- might determine the residual rate of Hg2+ in the desulfurization wastewater. Besides, the stability of ClHgSO3- on the condition of various wastewater features was also evaluated. The experiment revealed that the high temperature and high pH level promoted the decomposition of ClHgSO3-. SO32- could restrain the decomposition of ClHgSO3- gently; the Hg2+ residual rate was determined by the new mercury complexes which compounded by Hg2+ and SO32-. The decrease of SO42- and increase of Ca2+ concentrations could also stimulate the stability of ClHgSO3- in wastewater. Cu2+ and Fe2+ disturbed the stability of complexes for their catalysis and reduction activities. The study proposed that the ClHgSO3- probably decomposes and releases Hg0 in two pathways. Furthermore, changes of the water's features could disturb the balance of Hg2+-Cl--SO32- systems, which might stimulate the decomposition of ClHgSO3.