Using non-thermal plasma to improve elemental mercury removal efficiency of copper-containing brominated pyrolytic chars derived from waste printed circuit boards

Brominated flame retardants (BFRs) in waste printed circuit boards (WPCBs) can lead to severe environmental pollution. However, brominated materials have been demonstrated to play a substantial role in elemental mercury (Hg 0 ) removal. In our preceding research, WPCB-derived chars were successfully prepared for the removal of Hg 0 from flue gas with decent performance. On this foundation, this work employed a non-thermal plasma (NTP) reactor to modify WPCB-derived chars with the objective of further improving Hg 0 removal efficiency. Various characterizations and adsorption tests were conducted to investigate the effects of modification power, time, and atmosphere on Hg 0 removal efficiency. Under the optimal condition, the Hg 0 removal efficiency of NTP-modified chars was increased by 20%. However, an extended modification period and the high power resulted in the deterioration of active functional groups and carbon erosion, leading to a notable reduction in Hg 0 adsorption efficiency. The NTP modification incorporated oxygen atoms onto the surface of modified char to form C(O)-O-C functional groups. Additionally, NTP modification promoted the formation of active CuO sites in copper-containing pyrolytic chars. The adsorption kinetics and mechanisms indicated that NTP modification primarily promoted chemisorption. The CuO and C(O)-O-C functional groups were the main oxidation active sites that significantly improved the Hg 0 removal performance.