title: Sorption of thallium(I) onto geological materials: influence of pH and humic matter.
abstract: The sorption behaviour of the severely toxic heavy metal thallium (Tl) as a monovalent cation onto three representative materials (goethite, pyrolusite and a natural sediment sampled from a field site) was examined as a function of pH in the absence and presence of two natural humic acids (HAs), using 204Tl(I) as a radiotracer. In order to obtain a basic understanding of trends in the pH dependence of Tl(I) sorption with and without HA, sorption of HAs and humate complexation of Tl(I) as a function of pH were investigated as well. In spite of the low complexation between Tl(I) and HAs, the presence of HAs results in obvious alterations of Tl(I) sorption onto pyrolusite and sediment. An influence on Tl(I) sorption onto goethite was not observed. Predictions of Kd (distribution coefficient) for Tl(I) on goethite in the presence of HAs, based on a linear additive model, agree well with the experimental data, while a notable disagreement occurs for the pyrolusite and sediment systems. Accordingly, it is suggested that HAs and goethite may act as a non-interacting sorbent mixture under the given conditions, but more complex interactions may take place between the HAs and the mineral phases of pyrolusite or sediment.
authors.affiliation: Guangzhou University (GU), Key Laboratory of Waters Safety & Protection in the Pearl River Delta, Ministry of Education, 510006 Guangzhou, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Liu
authors.forename: Holger
authors.initials: H
authors.lastname: Lippold
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Johanna
authors.initials: J
authors.lastname: Lippmann-Pipke
authors.forename: Yongheng
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D002414:Cations, Monovalent / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D058085:Iron Compounds / Q000737:chemistry*; D017895:Manganese Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D008956:Models, Chemical; D010087:Oxides / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D013793:Thallium / Q000737:chemistry*
chemical_list: D002414:Cations, Monovalent; D006812:Humic Substances; D058085:Iron Compounds; D017895:Manganese Compounds; D008903:Minerals; D010087:Oxides; D012987:Soil; D012989:Soil Pollutants; C094886:goethite; D013793:Thallium; C016552:manganese dioxide