Selenium-modified activated coke: a high-capacity and facile designed Hg⁰ adsorbent for coal-fired flue gas

The substantial amount of mercury emissions from coal-fired flue gas causes severe environmental contamination. With the Minamata Convention now officially in force, it is critical to strengthen mercury pollution control. Existing activated carbon injection technologies suffer from poor desulfurization performance and risk secondary-release risks. Therefore, considering the potential industrial application of adsorbents, we selected cost-effective and readily available activated coke (AC) as the carrier in this study. Four metal selenides—copper, iron, manganese, and tin—were loaded onto the AC to overcome the application problems of existing technologies. After 120 min of adsorption, the CuSe/AC exhibited the highest efficiency in removing Hg⁰, surpassing 80% according to the experimental findings. In addition, the optimal adsorption temperature window was 30–120 °C, the maximum adsorption rate was 2.9 × 10⁻² mg·g⁻¹·h⁻¹, and the effectiveness of CuSe/AC in capturing Hg⁰ only dropped by 5.2% in the sulfur-containing atmosphere. The physicochemical characterization results indicated that the AC surface had a uniform loading of CuSe with a nanosheet structure resembling polygon and that the Cu-to-Se atomic ratio was close to 1:1. Finally, two possible Hg⁰ reaction pathways on CuSe/AC were proposed. Moreover, it was elucidated that the highly selective binding of Hg⁰ with ligand-unsaturated Se⁻ was the key factor in achieving high adsorption efficiency and sulfur resistance in the selenium-functionalized AC adsorbent. This finding offers substantial theoretical support for the industrial application of this adsorbent.