Behavior of mercury release from iron ores during temperature-programmed heat treatment in air.

The behavior of Hg release from iron ores during temperature-programmed heat treatment (TPHT) in air is studied, primarily using an online monitoring method. The Hg release behavior during TPHT depends significantly on the type of ore being processed, involving the evolved forms, Hg0 and Hg2+, and those that remain thermally stable up to 950 °C. Furthermore, TPHT experiments for model Hg compounds suggest the presence of several types of Hg forms (HgCl2, Hg2Cl2, HgS, HgO, HgSO4, and associated mineral Hg) in the considered iron ores. The findings of this study provide insights for designing an efficient method for the removal of Hg from iron ore and gaseous Hg.

Production of Silicone Tetrachloride from Rice Husk by Chlorination and Performance of Mercury Adsorption from Aqueous Solution of the Chlorinated Residue.

The production of silicone tetrachloride (SiCl4) from rice husk char by chlorination was investigated, and the effect of the char preparation temperature on SiCl4 volatilization and the coexisting element species in the char was examined. The behavior of chlorine (Cl) and the change in pore properties during char chlorination were analyzed, and the reaction mechanism was discussed. The performance of Hg ion removal of the chlorination residue was also investigated. At 1000 °C chlorination, the optimum rice husk pyrolysis temperature for attaining high ash-release extent was 800 °C. Ash volatilization during char chlorination with heat treatment mainly occurred at >300 °C and reached a release extent of ∼75% by 1000 °C. Si and P volatilization started at >300 °C and reached 70-75% by 1000 °C. In contrast, Na and K the volatilization occurred at >700 °C, with a 50% volatilization extent by 1000 °C. Mg and Ca had a volatilization rate of <20% by 1000 °C. When the char was held at 1000 °C, the release extent of Si and P reached 75-80% by 10 min. Na and K volatilized almost completely by 10 min, and the release extent of Mg and Ca increased with increasing holding time and became 10-50% by 60 min. The Cl content in the residue obtained at each chlorination temperature increased from 300 to 700 °C and then decreased with increasing temperature. The majority of Cl taken up in the residue was an H2O insoluble form. The surface area and pore volume of the chlorinated residue tended to increase with increasing chlorination temperature, with the former increasing to 335 m2/g at 1000 °C and 10 min holding. The maximum mercury adsorption amount of the chlorinated residue obtained at 1000 °C, 10 min holding was 620 mg/g, indicating the mercury ion adsorption performance of the chlorinated residue.