Capture of elemental mercury from flue gas over a magnetic and sulfur-resistant sorbent prepared from Fe-containing sewage sludge activated with sulfuric acid. (15th September 2021) - Li, Honghu
Highlights: The sorbent prepared from sewage sludge was used for Hg 0 capture from flue gas. Sulfuric acid activation greatly improved the Hg 0 removal activity of the sorbent. Fe2 O3 and ferric polysulfide over the sorbent contributed to Hg 0 removal. The sorbent showed magnetic property, good SO2 resistance and excellent performance. 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 Fe 3+, Oβ and polysulfide and promoted the redox activity of the sorbent, leading to the enhanced Hg 0 removal activity. Both active oxygen and sulfur species derived from Fe2 O3 and ferric polysulfide were the active sites for Hg 0 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 Hg 0 with SO2 presence. The Hg 0 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.