Gaseous mercury capture using seaweed biochars modified by clean ultraviolet/hydrogen peroxide advanced oxidation process

Seaweed-based biochars stemmed from the solid wastes of seaweed-based biomass pyrolysis were used to reduce the emission of elemental mercury. An environmentally-friendly ultraviolet/hydrogen peroxide advanced oxidation process modification method was used to increase the active species over seaweed-based biochars for elemental mercury adsorption. Results suggest that the elemental mercury capture performance of seaweed-based biochars is greatly improved after the ultraviolet/hydrogen peroxide advanced oxidation process modification. The optimum adsorption temperature and hydrogen peroxide concentration are 120 °C and 4%, respectively. The characterization results display that the clean ultraviolet/hydrogen peroxide advanced oxidation process modification greatly enhances the rising of oxygen functional group on seaweed-based biochars surface. In particular, the presence of CO and COOH/COOC groups is conducive to Hg0 capture. The process of elemental mercury capture over the tested seaweed-based biochars accords with pseudo-second-order adsorption kinetic equation. Chemical sorption is the pivotal controlling link of the whole mercury capture process. The preparation costs of Sargassum-based biochar and Enteromorpha-based biochar are lower than that of chitosan adsorbent and commercial AC. In addition, the modified seaweed biochars have good regeneration performance, which is conducive to greatly reducing the cost of mercury removal. This research can provide new inspiration for the green modification of biochar and the development of clean mercury removal adsorbent.