Compared to land, the ocean is much richer in biomass resources. As an attempt to actively explore the utilization of these vast marine biomass resources, in this study, novel activated carbons were prepared from two representative seaweed species (sargassum and enteromorpha), and their efficiencies and mechanisms for Hg-0 removal were evaluated in a fixed bed reactor. The effects of modification methods, modification temperatures and reaction temperatures on Hg-0 removal were also studied. The experimental data were also tested with different adsorption kinetic models for the best fits, and standard thermodynamic parameters evaluated in order to elucidate Hg-0 adsorption mechanisms. The results appear to reveal that the performances of seaweed biomass-based activated carbons (denoted SAC and EAC, respectively) for Hg-0 removal, are by far more superior to those of seaweed biomass-based the same pyrolysis chars. The best activation temperature for both samples was found to be 800 degrees C (and hence denoted SAC-800 and EAC-800); and the Hg-0 removal efficiency of both samples also increased with increasing reaction temperature. The kinetic results show that the Hg-0 removal is controlled by the external mass transfer at 80 degrees C and controlled by the chemisorption at 120 degrees C and 160 degrees C. It was determined that the Hg-0 process was a combination of physisorption and chemisorption; with the excellent physical properties (specific surface area and pore structure), and the surface active sites (C-Cl groups and oxygen species) responsible for the physisorption and chemisorption, respectively.