Co-removal of CO2 and Hg using corn straw and pine biochar pretreated by hydrothermal technology

To reduce CO2 and Hg0 emission, the comparative research about CO2 and Hg0 co-removal performance of corn straw and pine biochar pretreated by hydrothermal technology was carried out. The results show that the specific surface area of corn straw and pine biochar can reach 448.24 m2/g and 397.86 m2/g, respectively. But in the range of 700–900 °C, pyrolysis temperature has opposite effects on the physical structure of the two types of biochar. Although iron ions can regulate the growth of ultra-micropores through the reduction reaction with matrix carbon during pyrolysis, too high pyrolysis temperature can also cause matrix collapse and ion sintering to hinder the construction of ultra-micropores of biochar. The ultra-microporous homogeneity and volume are main factors affecting the physical adsorption of CO2 and Hg0. The pine biochar prepared at 700 °C (PCH-700) performed the better CO2 adsorption capacity and mercury removal efficiency (5.35 wt% and around 100 %) at room temperature. The CO2 trapped on the biochar can be linked to the biochar matrix and form oxygen-containing functional groups, thereby promoting the release of free radical oxygen to achieve the co-removal of CO2 and Hg0.