title: Adsorption of mercury on lignin: combined surface complexation modeling and X-ray absorption spectroscopy studies.
abstract: Adsorption of mercury (Hg) on lignin was studied at a range of pH values using a combination of batch adsorption experiments, a surface complexation model (SCM) and synchrotron X-ray absorption spectroscopy (XAS). Surface complexation modeling indicates that three types of acid sites on lignin surfaces, namely aliphatic carboxylic-, aromatic carboxylic- and phenolic-type surface groups, contributed to Hg(II) adsorption. The bond distance and coordination number of Hg(II) adsorption samples at pH 3.0, 4.0 and 5.5 were obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy analysis. The results of SCM and XAS combined reveal that the predominant adsorption species of Hg(II) on lignin changes from HgCl(2)(0) to monodentate complex -C-O-HgCl and then bidentate complex -C-O-Hg-O-C- with increasing pH value from 2.0 to 6.0. The good agreement between SCM and XAS results provides new insight into understanding the mechanisms of Hg(II) adsorption on lignin.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors.forename: Jitao
authors.initials: J
authors.lastname: Lv
authors.forename: Lei
authors.initials: L
authors.lastname: Luo
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Peter
authors.initials: P
authors.lastname: Christie
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D052918:Environmental Restoration and Remediation / Q000295:instrumentation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D008031:Lignin / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008031:Lignin; D008628:Mercury