Efficient Hg Vapor Capture with Polysulfide Intercalated Layered Double Hydroxides

We report detailed studies showing that the novel layered polysulfide compounds S-x-LDH (S-x(2), polysulfides, x = 2, 4, 5; LDH, MgAl layered double hydroxides) can capture efficiently large quantities of mercury (Hg0) vapor. During the adsorption process, the interlayer polysulfides [S-x](2) react with Hg-0 through their SS bond to produce HgS. The structure of S-x-LDH before and after Hg-adsorption was characterized with X-ray diffraction, vibration spectroscopy, and scanning electron microscopy. The presence of adsorbed Hg was verified by weight gain, inductively coupled plasma atomic emission spectroscopy and X-ray photoelectron spectroscopy. Despite their relatively low surface areas, the S-2-LDH, S-4-LDH, and S-5-LDH samples show excellent Hg capture capacities of 4.9 x 10(5), 7.4 x 10(5), and 1.0 x 10(6) mu g/g, respectively, corresponding to 50-100% adsorption rates by weight, highlighting the potential of these materials in natural gas purification. The Hg-capture efficiency and mechanism in S-x-LDH are supported by control experiments with K2S4, S-8, LDH-NO3-CoS4, and MgAl-NO3-LDH.