Synergy of copper vacancies and amorphous regions in copper sulfides enables superior capacity for Hg0 adsorption

Adsorption is a high-efficiency and low-cost approach to control elemental mercury emission from industrial flue gas. However, the adsorption capacity is unsatisfactory due to its surface-only adsorption. In this work, a facile method was used for preparing the crystalline-amorphous co-existed copper sulfides (CA-CuS) with an abundance of copper vacancies and amorphous regions through temperature-controlled ultrasonic cavitation. The CA-CuS was used in the flue gas wet scrubbing and displayed outstanding Hg0 capture performance, achieving a removal efficiency of 99.8% and an adsorption capacity up to 573.8 mg·g-1 with a sulfur atomic utilization ratio of 27.5%. Experimental results and density functional theory (DFT) calculation verified that the copper vacancies at di-coordinated sites led to the formation of robust mercury binding sites (i.e., S2-(CN=3)) and unsaturated coordinated oxidizing sites (i.e., S22-). Meanwhile, the amorphous regions facilitated the internal migration of adsorbed mercury on the surface and promote the exchange with Cu2+ in the interior of adsorbents. The synergistic effect of copper vacancies and amorphous regions enables superior mercury adsorption capability and high atomic utilization.