Development of low-concentration mercury adsorbents from biohydrogen-generation agricultural residues using sulfur impregnation

Mercury adsorbents were derived from waste biohydrogen-generation barley husk and rice husk via carbonization, steam activation, and sulfur impregnation at 300-650 degrees C. The samples derived from agricultural residues showed a greater Hg-0 adsorption than that of a coal-based activated carbon, confirming the feasibility of resource recovery of these agricultural residuals for low-concentration gaseous Hg adsorption. Sulfur impregnation reduced both the surface area and pore volume of the samples, with lower temperature causing a greater decrease. Elevating the impregnation temperature increased the organic sulfur contents, suggesting that in addition to elemental sulfur, organic sulfur may also act as active sites to improve Hg-0 adsorption. Oxygen and sulfur functional groups accompanying the microporous structures may account for the enhancing Hg adsorption of the raw and sulfur-treated samples, respectively. The pseudo-second-order model can best describe the chemisorption characteristics, implying that Hg adsorption on the samples was in a bimolecular reaction form. (C) 2011 Elsevier Ltd. All rights reserved.