title: Adsorption and desorption of 2,4,6-trichlorophenol onto and from ash as affected by Ag(+), Zn (2+), and Al (3+).
abstract: Metal cations and organic pollutants mostly co-exist in the natural environment. However, their interactions in adsorption processes have yet to be adequately addressed. In the current study, the effect of inorganic cations with different charges (Ag(+), Zn(2+), and Al(3+)) on the adsorption and desorption of 2,4,6-trichlorophenol (TCP) onto and from processed ash derived from wheat (Triticum aestivum L.) straw was investigated. The adsorption and desorption of TCP were both nonlinear; the isotherm and kinetics curves fitted well using the Freundlich equation and a pseudo-second-order model, respectively. The presence of Ag(+) promoted TCP adsorption, while Zn(2+) and Al(3+) reduced TCP adsorption onto ash. The desorption of TCP from ash showed obvious hysteresis, and the presence of Ag(+), Zn(2+), and Al(3+) caused the desorption to be less hysteretic. The suppression of TCP adsorption by Zn(2+) and Al(3+) was ascribed to the partial overlapping of adsorption groups between TCP and metal ions. Al(3+) had a stronger inhibition effect than that of Zn(2+) due to its higher binding capacity and larger hydrated ionic radius than those of Zn(2+). Enhanced adsorption of TCP onto ash by Ag(+) was ascribed to its ability to reduce the competitive adsorption of water molecules on ash surface by replacing the original ions, such as Na(+) and Ca(2+), and compressing the hydrated ionic radius of these metal ions. In addition, Ag(+) was able to bind with the aromatic organic compounds containing π-electrons, which resulted in a further increase of TCP adsorption by ash.
authors.affiliation: Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Fuyang, Zhejiang, 311400, China. guangcaichen@sohu.com.
authors.forename: Guangcai
authors.initials: G
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Yusheng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Pei
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D002412:Cations; D002733:Chlorophenols / Q000737:chemistry*; D060729:Coal Ash / Q000737:chemistry*; D007700:Kinetics; D008670:Metals / Q000737:chemistry*; D012834:Silver / Q000737:chemistry; D015032:Zinc / Q000737:chemistry
chemical_list: D002412:Cations; D002733:Chlorophenols; D060729:Coal Ash; D008670:Metals; D012834:Silver; D000535:Aluminum; D015032:Zinc; C024564:2,4,6-trichlorophenol
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