Removal of mercury from flue gas using sewage sludge-based adsorbents

Mercury from coal-fired utility boilers, as the largest atmospheric mercury emission source, imposes serious environmental risks and health concerns. In order to explore the possibility of reducing costs of activated carbon injection, we investigated the most promising mercury control technology, Hg⁰ removal using ZnCl₂-impregnated adsorbents derived from sewage sludge. The results demonstrated that sludge-based adsorbents (SBAs) had fairly high mercury adsorption capacity over a wide range of temperatures (80–170 °C). Oxidizing atmosphere could improve the adsorption of Hg⁰ and weaken the inhibition of SO₂ on mercury adsorption to some extent. NO exhibited no obvious impact on mercury removal performance. In addition, to clarify whether oxygen- or chlorine-containing functional groups attributed to good mercury adsorption capacity of SBAs, the oxygen-containing functional groups were removed using Boehm’s method, and a temperature-programmed decomposition desorption experiment was conducted. The results suggest that chlorine-containing functional groups played a significant role in the removal process of mercury from flue gas using SBAs.