Stabilization of mercury in flue gas desulfurization gypsum from coal-fired electric power plants with additives

With the extensive utilization and disposal of flue gas desulfurization (FGD) gypsum, Hg0 re-emission and Hg2+ dissolution could cause severe atmospheric and groundwater contaminations. The present study employed two precipitating agents: sodium dithiocarbamate (DTCR) and 2,4,6-trimercaptotiazine, trisodium salt monohydrate (TMT) to prevent mercury in FGD gypsum from releasing into the environment as Hg0 and Hg2+. The results indicated that in the presence of DTCR and TMT, Hg2+ in leachate decreased to nearly 10%, while the amount of released Hg0 declined by over 2/3. Hence, it demonstrated an apparent effect of precipitants on the inhibition of Hg2+ dissolution and Hg0 re-emission. However, precipitation efficiencies represented better inhibitive performance of DTCR than that of TMT. Further increase of initial pH value and the precipitant dosage had an outstanding effect on the decline of total dissolved Hg2+, released Hg0 and Hg2+ remaining in leachate. Thus, in some severe conditions such as acid rain prone areas, the stabilization of mercury in FGD gypsum from dissolving and releasing could be extraordinarily controlled by the addition of DTCR and TMT, which is highly promising for future applications.