Elution of Hg-containing substances from CeO2-MnO2/TiO2 adsorbent in H2S atmosphere by CuCl2 solution

Abstract

Mercury (Hg) pollution in syngas has received increasing attention. The adsorbent can effectively remove Hg from syngas, and the removal of Hg-containing substances before the landfill of spent adsorbent can avoid Hg secondary pollution effectively. H2S was the main resource for the generation of stable and insoluble HgS in syngas. In this work, the elution of Hg-containing substances from the spent CeO2-MnO2/TiO2 (Ce-Mn/Ti) adsorbent in H2S atmosphere by CuCl2 solution was studied. The optimum temperature for Ce-Mn/Ti to remove Hg0 in H2S atmosphere was 160 °C. The Hg-containing substances were HgS (black), HgS (red), and HgO (yellow), in which both the proportion and elution difficulty followed the descending order of HgS(black) > HgS(red) > HgO(yellow). The elution was basically completed within 2 min with excellent efficiency of 98.38 %. Higher concentration, higher temperature, and lower pH were conducive to the elution, and the optimum concentration and temperature were 1.0 mol/L and 45 °C respectively. The elution followed the first-order two-domain model, in which HgO and HgS were the rapid and slow part respectively. The elution not only retained the favorable mesoporous structure, but also enabled the eluted Ce-Mn/Ti adsorbent to have a higher efficiency and a better stability on Hg removal by loading the active component of CuCl2. This study demonstrated that CuCl2 could be a good eluent for the elution of Hg-containing species and the reutilization of metal oxide-based adsorbent.