title: Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash.
abstract: The mutual effects of metal cations (Cu2+, Pb2+, Zn2+, and Cd2+) and p-nitrophenol (NP) on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2+, Pb2+, and Zn2+ diminished the adsorption and increased the desorption of NP remarkably, while Cd2+ had no such effect. In contrast, NP diminished the adsorption of Cu2+, Pb2+, and Zn2+ onto ash, however, this suppression effect depended on the initial concentrations of metal cations. NP had no effect on Cd2+ adsorption on ash. Fourier transform infrared (FT-IR) and X-ray absorption spectroscopic (XAS) studies suggested the following mechanisms responsible for the metal suppression effect on NP adsorption: (1) large hydrated Cu2+, Pb2+, and Zn2+ shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; (2) Cu2+, Pb2+, and Zn2+ may block the micropores of ash, resulting in decreased adsorption of NP; (3) complexation of Cu2+, Pb2+, and Zn2+ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a "soft acid", Cd2+ is less efficient in the complexation of oxygen-containing acid groups than Cu2+, Pb2+, and Zn2+. Thus, Cd2+ had no effect on the adsorption of NP on wheat ash.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Beijing 100085, China. wangyushengly@163.com
authors.forename: Yusheng
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Pei
authors.forename: Xiaoquan
authors.initials: X
authors.lastname: Shan
authors.forename: Guangcai
authors.initials: G
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Yaning
authors.initials: Y
authors.lastname: Xie
authors.forename: Lirong
authors.initials: L
authors.lastname: Zheng
mesh_terms: D000327:Adsorption; D001673:Biodegradation, Environmental; D002412:Cations; D003300:Copper / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007854:Lead / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D019216:Metals, Heavy / Q000737:chemistry*; D009596:Nitrophenols / Q000302:isolation & purification*; D012015:Reference Standards; D017550:Spectroscopy, Fourier Transform Infrared; D014908:Triticum / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D015032:Zinc / Q000737:chemistry
chemical_list: D002412:Cations; D019216:Metals, Heavy; D009596:Nitrophenols; D007854:Lead; D003300:Copper; D015032:Zinc; C024836:4-nitrophenol