In this study, used refrigerator PU foam was converted into nitrogen-containing activated carbon by hydrothermal carbonization as a Hg sorbent in a fume hood. We investigate the co-hydrothermal reaction with wood sawdust, regarding the kinetics and performance of mercury removal. Our experimental results showed that the resulting activated carbon had a nitrogen content of 4% and a yield of 40%. Through the hydrothermal reaction of wood sawdust and waste refrigerator insulation foam, the self-derived pressure is mostly maintained at about 10 bar, and the yield of activated carbon is about 40%. The atomic nitrogen ratio in the obtained activated carbon was confirmed by FTIR spectra and XPS spectra. We established a reliable adsorption/desorption column system and evaluated the mercury vapor adsorption capacity of nitrogen-containing activated carbon and commercial sulfur-containing activated carbon to derive the kinetic parameters of mercury adsorption. The estimated saturated adsorption capacity of granular nitrogen-containing activated carbon is 433 g/g, and it is 76 g/g for granular sulfur-containing activated carbon. The kinetic curves of granular nitrogen-containing activated carbon and granular commercial sulfur-containing activated carbon are suitable for the fitting of Elovich equation. A resource recycling plant in Taoyuan was selected to implement the on-site mercury removal efficiency. Through the mercury desorption experiment, the monthly mercury adsorption amounts of the two activated carbons were measured, which were 110 g/g and 25g respectively within 5 months. The nitrogen-containing activated carbon has a significantly higher mercury adsorption capacity than commercial sulfur-containing activated carbon in the in-plant mercury adsorption device. This work not only reduces solid waste but also generates new resource.

Hydrothermal carbonization, Polyurethane wastes, Activated carbon