Adsorptive removal of gas-phase mercury by oxygen non-thermal plasma modified activated carbon

• A non-chemical modified method of AC was investigated for Hg0 adsorption.
• Oxygen non-thermal plasma could promote mercury adsorption on activated carbon.
• The oxygen-containing groups of modified ACs surface were increased.
• External diffusion and chemisorption controlled Hg0 adsorption on modified ACs.

The effects of oxygen non-thermal plasma modification on the surface properties and mercury removal performance of activate carbon (AC) were investigated. The raw and modified ACs were characterized by N2 adsorption/desorption, scanning electron microscope (SEM), Boehm titration and Fourier Transform Infrared Spectrometer (FTIR). The results showed that the surface textual properties of the modified ACs were slightly damaged, but the surface chemistries such as the content of surface oxygen-containing groups were significantly changed. The elemental mercury removal performance of raw and modified ACs were also evaluated in a quartz tube fix-bed reactor under N2 atmosphere. The results indicated that the AC treated with oxygen non-thermal plasma had better elemental mercury removal performance compared to the raw AC. This reason was attributed to the oxygen non-thermal plasma treatment increasing the ester groups (CO), carbonyl groups (CO) and adsorption activate sites on AC surface, which played an important role in the adsorption of elemental mercury. The adsorption kinetic of raw and modified ACs could be best described by the Pseudo-first-order model and Pseudo-second-order model, which implied that external diffusion and chemisorption were the control step in the mercury adsorption process of raw and modified ACs.