This study addresses the challenge of efficient elemental mercury (Hg0) removal from coal-fired flue gas by proposing an optimized fly ash adsorbent based the on heavy liquid separation coupled with halide modification. A series of novel fly ash-based adsorbents are prepared by using heavy liquid separation coupled with halide modification, and the Hg0removal performance of the adsorbents is investigated. The effects of heavy liquid separation and halide modification on Hg0  removal are explored. Furthermore, several characterization techniques, including ICP, BET, XRD and SEM, are used to characterize the physicochemical properties of different adsorbents. The results demonstrate that heavy liquid separation can effectively enhance the Hg0  adsorption performance of FA, and the Hg0 adsorption performance can be further  enhanced by halide modification. The optimal Hg0  removal efficiency (nearly 100% within 90 min) can be achieved over the FA treated by 1.89×103 kg/m3 heavy liquid separation coupled with NaI modification. The kinetic analysis and characterization results confirm that heavy liquid separation can change the physicochemical properties of raw FA, which can promote the diffusion behavior of Hg0 on the adsorbent surface. Meanwhile, halide modification can increase the active 

sites as well as the specific surface area and pore structure, thus enhancing the Hg0 adsorption capacity of adsorbent. This study has confirmed that the coupling of heavy liquid separation and NaI modification can significantly improve the Hg0 adsorption capacity of fly ash, providing a new idea for the resource utilization of fly ash and the control of Hg0 pollution from coal-fired flue gas.