Sustainable Recovery of Gaseous Mercury by Adsorption and Electrothermal Desorption Using Activated Carbon Fiber Cloth

The present work aims to develop a novel and sustainable approach to adsorb and recover low-concentration Hg-0 in the off-gas downstream a distillation/condensation system in the recycling processes for waste Hg-containing devices. Hg-0 adsorption and regeneration efficiencies of raw and HNO3-treated activated carbon fiber cloth (ACFC) were examined. The adsorption experiments were conducted with an initial Hg-0 concentration of 260-300 ktg/m(3) at room temperature. The regeneration of ACFC was done by an electrothermal swing process with 20, 40, and 60 W direct currents. The experimental results showed that the Hg-0 adsorption efficiency of raw ACFC increased to approximately 90% after the 60 W electrothermal regeneration. After HNO3 treatment, the content of oxygen functional groups on HNO3 treated ACFC increased, which enhanced the He adsorption performance and resulted in over 90% adsorption efficiency for the samples before and after electrothermal regeneration. Importantly, both raw and HNO3-treated ACFCs retained the high adsorption efficiency after nine cycles of adsorption/regeneration, indicating that both raw and HNO3-treated ACFCs were effective and renewable adsorbents for low-concentration Hg-0 adsorption and recovery. A Hg adsorption/regeneration mechanism was proposed to explain the increasing adsorption efficiency after electrothermal regeneration and the great adsorption efficiency of HNO3 -treated ACFC.