Magnetically recyclable CoS-modified graphitic carbon nitride-based materials for efficient immobilization of gaseous elemental mercury

Mercury pollution from coal-fired power plants poses a serious threat to human health and the ecological environment. In this work, a novel cobalt sulfide (CoS) modified graphite carbon nitride (g-C3N4) adsorbent was developed to capture Hg0 in flue gas at low temperature, aiming at the shortcomings of poor adsorption performance and slow adsorption rate of most traditional adsorbents. It was found that the addition of CoS can greatly improve the Hg0 removal effect of g-C3N4 monomer. Meanwhile, due to the magnetic characteristics of CoS, it can be recycled and reused under the action of an external magnetic field. Benefiting from the optimized performance, the composites loaded with 20 wt% CoS can maintain a mercury removal efficiency close to 90% for a long time, which is more than 4 times that of pure g-C3N4. In addition, the adsorption characteristics of CoS/g-C3N4 on Hg0 were analyzed by various kinetic models, and the maximum mercury adsorption capacity at 120celcius was calculated to be 15.22 mg/g. The XPS and Hg-TPD analysis showed that the adsorbed mercury mainly existed in the form of HgS on the surface of the adsorbent. The CoS/g-C3N4 composite designed in this study can be used as a good adsorbent to replace traditional activated carbon for elemental mercury removal in coal-fired power plants due to its excellent mercury removal performance and recyclability.