title: Adsorption of metal ions on lignin.
abstract: This study investigated the adsorption of the heavy metal ions Pb(II), Cu(II), Cd(II), Zn(II), and Ni(II) on a lignin isolated from black liquor, a waste product of the paper industry. Lignin has affinity with metal ions in the following order: Pb(II)>Cu(II)>Cd(II)>Zn(II)>Ni(II). The adsorption kinetic data can be described well with a pseudosecond-order model and the equilibrium data can be fitted well to the Langmuir isotherm. Metal ion adsorption was strongly dependent on pH and ionic strength. Surface complexation modelling was performed to elucidate the adsorption mechanism involved. This shows that lignin surfaces contain two main types of acid sites attributed to carboxylic- and phenolic-type surface groups and the phenolic sites have a higher affinity for metal ions than the carboxylic sites.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
authors.forename: Xueyan
authors.initials: X
authors.lastname: Guo
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Zhang
authors.forename: Xiao-quan
authors.initials: XQ
authors.lastname: Shan
mesh_terms: D000327:Adsorption; D002412:Cations / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008031:Lignin / Q000737:chemistry*; D019216:Metals, Heavy / Q000737:chemistry*; D008956:Models, Chemical; D013816:Thermodynamics
chemical_list: D002412:Cations; D019216:Metals, Heavy; D008031:Lignin