title: Effects of bloom-forming cyanobacterial extracellular polymeric substances on the adsorption of cadmium onto kaolinite: behaviors and possible mechanisms.
abstract: Cyanobacterial blooms result in high level of cyanobacterial extracellular polymeric substances (EPS) in water. The effects of bloom-forming cyanobacterial EPS on the distribution of Cd(II) in the interface between sediment and water is unknown. Clay is a main component in sediment. The effects of EPS, originated from a typical bloom-forming cyanobacterium Microcystis aeruginosa, on the adsorption and desorption characteristics of Cd(II) by kaolinite were investigated in this study. Results of XRD analysis indicated that cyanobacterial EPS bound on the surface of kaolinite. The composite of kaolinite + EPS showed higher adsorption capacity toward Cd(II) than pure kaolinite, and hydroxyl groups were involved in the adsorption processes. The data for the adsorption of Cd(II) by kaolinite are well fitted by both Langmuir model and Freundlich model, whereas only Freundlich model well describes the adsorption data of Cd(II) by the composite of kaolinite + EPS. The adsorption of Cd(II) onto kaolinite was an exothermic process, but it became an endothermic process after EPS incorporation. Results of desorption showed that EPS incorporation increased the adsorption of kaolinite toward Cd(II) through physical adsorption, ion exchange and complexation.
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Kuang
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Jihai
authors.initials: J
authors.lastname: Shao
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Anwei
authors.initials: A
authors.lastname: Chen
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Si
authors.initials: S
authors.lastname: Luo
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Peng
authors.affiliation: College of Resources and Environment, Hunan Agricultural University, Changsha, 410128 People's Republic of China.
authors.forename: Genyi
authors.initials: G
authors.lastname: Wu
authors.affiliation: Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Agricultural University, Changsha, 410128 People's Republic of China ; Laboratory of Environmental Microbiology and Toxicology, School of Biological Sciences, The University of Hong Kong, Hong Kong SAR, People's Republic of China.
authors.forename: Ji-Dong
authors.initials: JD
authors.lastname: Gu
keywords: Cadmium; Extracellular polymeric substances; Kaolinite; Microcystisaeruginosa