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Mercury (II) Reduction and Sulfite Oxidation in Aqueous Systems: Kinetic Study and Speciation Modeling
The re-emission of mercury (Hg), as a consequence of the formation and dissociation of the unstable complex HgSO3, is a problem encountered in flue gas desulphurization (FGD) treatment in coal-fired power plants. A model following a pseudo-second-order rate law for Hg2+ reduction was derived as a function of [SO3 2-], [H+] and temperature and fitted with experimentally obtained data to generate kinetic rate values of (0.120 Â± 0.04, 0.847 Â± 0.07, 1.35 Â± 0.4) mM-1 for 40Â°, 60Â°, and 75Â°C, respectively. The reduction of Hg2+ increases with a temperature increase but shows an inverse relationship with proton concentration. Plotting the model-fitted kinetic rate constants yields ÎH = 61.7 Â± 1.82 kJ mol-1, which is in good agreement with literature values for the formation of Hg0 by SO32-. The model could be used to better understand the overall Hg2+ re-emission by SO32- happening in aquatic systems such as FGD wastewaters.
EN16169 Accepted 16 December 2016
© CSIRO 2016