Capture of elemental mercury from flue gas over a magnetic and sulfur-resistant sorbent prepared from Fe-containing sewage sludge activated with sulfuric acid

Abstract

By the pyrolysis of Fe-containing sewage sludge activated with sulfuric acid, a magnetic and sulfur-resistant sorbent (FSS-SA) was obtained, and it was used for capturing elemental mercury from flue gas. Sulfuric acid activation improved the pore structure, increased the contents of Fe3+, Oβ and polysulfide and promoted the redox activity of the sorbent, leading to the enhanced Hg0 removal activity. Both active oxygen and sulfur species derived from Fe2O3 and ferric polysulfide were the active sites for Hg0 removal. The increased surface acidity due to sulfuric acid activation suppressed the interaction of SO2 with FSS-SA and the polysulfide maintained the function of capturing Hg0 with SO2 presence. The Hg0 adsorption capacity of FSS-SA under simulated flue gas was estimated to be 14.8 mg/g. Meanwhile, FSS-SA exhibited superparamagnetic property with the saturation magnetization of 13.49 emu·g−1. It could be separated from fly ash mixture by using a magnetic separator. Utilizing the sludge for production of mercury sorbent can reduce the cost of sorbent and also help to find a way for resource utilization of the sewage sludge. FSS-SA might be a promising mercury sorbent due to its simple preparation method, low cost, magnetic property, good tolerance to SO2 and excellent performance.