Study on Mercury Adsorption and Desorption on Different Modified Biochars.

To develop high-performance biochar adsorbents, the adsorption ability and rate of untreated (BC-CK) and six modified biochars with amino (BC-NH), epoxy (BC-C2H2O), ethoxy (BC-C2H5O), hydrosulfuryl (BC-SH), selenium (BC-Se), and chitosan (BC-Chitosan) on Hg(II) and MeHg were investigated by simulated experiment. The results indicated that the some modified biochars (BC-NH, BC-C2H2O, BC-C2H5O and BC-Chitosan) showed lower adsorption capacity than the untreated, possibly due to the decreased specific surface area and pore volume. Whereas, BC-SH and BC-Se was improved immensely by forming stable -SH-Hg and Hg-Se with the adsorption capacity 1.26 and 1.51 times as much as BC-CK, respectively. In spite of that, Hg desorption capacities and rates of all biochars were extremely low, exhibiting great adsorption stability of biochars on Hg in another way. In addition, BC-Chitosan performed the highest adsorption speed. These provided insights on the adsorption effectiveness for Hg in the aqueous solution that was critical for evaluating the application of modified biochars.