Highly efficient Pb(II) and Hg(II) removal using coal gasification fine slag based functionalized porous silica

Coal gasification fine slag (CGFS) is a solid waste in the coal conversion process. In this study, CGFS-based functionalized porous silica (PS) adsorbents were synthesized. The amino (-NH2) and thiol groups (-SH) are successfully grafted onto the functionalized PS surface, and the grafting ability of PS to-NH2 is better than that of-SH. The addition of 2 % APTES and 2 % MPTMS during the functionalization process can promote-NH2-functionalized PS and-SH-functionalized PS to present efficient removal of Pb(II) and Hg(II). The removal efficiency of the two adsorbents at low dosages for Pb(II) and Hg(II) are more than 98 %, and show good cyclic stability. The results of adsorption kinetics, isothermal adsorption and adsorbent characterizations show that Pb (II) and Hg(II) are effectively captured on PS-N and PS-S surfaces through the interaction of complexation reaction, electrostatic attraction and surface physical adsorption, and the complexation reaction is the main reason.