Nanostructured copper sulfide synthesized with the assistance of surfactant with nanoscale particle size and high Brunauer-Emmett-Teller surface area was for the first time applied for the capture of elemental mercury (Hg) from coal combustion flue gas. The optimal operation temperature of nano-CuS for Hg adsorption is 75 °C, which indicates that injection of the sorbent between the wet flue gas desulfurization and the wet electrostatic precipitator systems is feasible. This assures that the sorbent is free of the adverse influence of nitrogen oxides. Oxygen (O) and sulfur dioxide exerted a slight influence on Hg adsorption over the nano-CuS. Water vapor was shown to moderately suppress Hg capture efficiency via competitive adsorption. The simulated adsorption capacities of nano-CuS for Hg under pure nitrogen (N), N + 4% O, and simulated flue gas reached 122.40, 112.06, and 89.43 mgHg/g nano-CuS, respectively. Compared to those of traditional commercial activated carbons and metal sulfides, the simulated adsorption capacities of Hg over the nano-CuS are at least an order of magnitude higher. Moreover, with only 5 mg loaded in a fixed-bed reactor, the Hg adsorption rate reached 11.93-13.56 μg/g min over nano-CuS. This extremely speedy rate makes nano-CuS promising for a future sorbent injection technique. The anisotropic growth of nano-CuS was confirmed by X-ray diffraction analysis and provided a fundamental aspect for nano-CuS surface reconstruction and polysulfide formation. Further X-ray photoelectron spectroscopy and Hg temperature-programmed desorption tests showed that the active polysulfide, S-S dimers, and copper-terminated sites contributed primarily to the extremely high Hg adsorption capacity and rate. With these advantages, nano-CuS appears to be a highly promising alternative to traditional sorbents for Hg capture from coal combustion flue gas.
Abatement of mercury emission from coal-fired power plants remains a serious task for public health and environmental societies. Selenium functionalized metal−organic framework MIL-101 (Se/MIL-101) was prepared for mercury removal from power plants. The Se/MIL-101 exhibited a remarkable mercury adsorption capacity of 148.19 mg•g −1 , which was about 154 to 705 times larger than that of commercial activated carbons exclusively applied for mercury removal from power plants. The initial mercury adsorption rate for Se/MIL-101 reached up to 44.8 μg•g −1 •min −1 , which was 89to 1659-fold higher than those of mercury sorbents reported in the literature. The Se/MIL-101 maintained an excellent mercury adsorption stability under simulated flue gas atmosphere containing SO 2 , NO, and H 2 O. Gaseous elemental mercury (Hg 0 ) converted on the Se/MIL-101 to stable and water-insoluble mercury selenide (HgSe), which guaranteed a minimum re-emission even sequestration of mercury. Moreover, the mercury-laden Se/MIL-101 could also immobilize mercury in gypsum and efficiently capture mercury ions from desulfurization effluent to an undetectable level (<0.0035 μg•L −1 ). With these advantages, Se/MIL-101 appears to be a promising material for efficient and permanent sequestration of mercury from power plants.
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