title: Effects of copper, lead, and cadmium on the sorption and desorption of atrazine onto and from carbon nanotubes.
abstract: There are currently few studies on the dual effects of metal ions on the sorption of atrazine and conversely of atrazine on metal adsorption on multiwalled carbon nanotubes (MWCNTs). While a number of sorption models were considered to describe the sorption of atrazine on MWCNTs, the Polanyi-Manes model (PMM) fit the sorption isotherms well with the lowest mean weighted square errors. Atrazine was mainly adsorbed onto the surface and micropores of MWCNTs bundles or aggregates. Hydrogen bonding between azo and amino nitrogen of atrazine and functional groups on MWCNTs also occurred. Oxygenated functionalities, mainly carboxylic groups on MWCNTs surface, decreased the sorption of atrazine. Metal cations Cu2+, Pb2+, and Cd2+ diminished the sorption of atrazine depending on the oxygenated functionalities densities. The mechanisms ascribed were due to the formation of surface or inner-sphere complexes of Cu2+, Pb2+, and Cd2+ through carboxylic groups and hydration, which may occupy part of the surface of MWCNTs-O. The large hydration shell of metal cations may intrude or shield the hydrophobic and hydrophilic sites and indirectly compete with atrazine for surface sites, leading to the inhibition of atrazine adsorption around the metal-complexed moieties.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
authors.forename: Guang-Cai
authors.initials: GC
authors.lastname: Chen
authors.forename: Xiao-Quan
authors.initials: XQ
authors.lastname: Shan
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Wang
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Pei
authors.forename: Xiu-E
authors.initials: XE
authors.lastname: Shen
authors.forename: Bei
authors.initials: B
authors.lastname: Wen
authors.forename: Gary
authors.initials: G
authors.lastname: Owens
mesh_terms: D015502:Absorptiometry, Photon; D000327:Adsorption; D001280:Atrazine / Q000737:chemistry*; D002104:Cadmium / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006860:Hydrogen Bonding; D007854:Lead / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D037742:Nanotubes, Carbon; D002104:Cadmium; D007854:Lead; D003300:Copper; D001280:Atrazine