The adsorption mechanism of elemental mercury by HNO3-modified bamboo char

The oxidizing agent (HNO3) was applied to modify bamboo char (BC) and then the samples were tested for mercury adsorption. The adsorption tests were conducted using a fixed-bed reactor under a mixed gas (N2 + O2) atmosphere at the temperature of 120 °C-160 °C. The physical and chemical properties of the samples were investigated by various techniques such as scanning electron microscope (SEM), ultimate analysis, Brunauer-Emmett-Teller analysis (BET), Fourier Transform Infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The mercury adsorption tests show that the modified BC samples have a better performance than the unmodified one, especially the sample modified by a higher concentration of modifier. Compared with specific surface area and total pore volume, oxygen functional groups on BC are supposed to play a more important role in mercury removal. The oxygen functional groups such as carboxyl, carboxylate and carbonyl groups were observed on the modified BC. In addition, water vapor is believed to play an active role in the modified BC samples. Pseudo-second-order model was applied to affirm the fact that chemisorption worked mainly in Hg0 capture for the HNO3 modified of bamboo char.