title: Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).
abstract: The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.
authors.affiliation: Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan.
authors.forename: Po-Hsiang
authors.initials: PH
authors.lastname: Chang
authors.affiliation: Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan. Electronic address: atwtj@mail.ncku.edu.tw.
authors.forename: Wei-Teh
authors.initials: WT
authors.lastname: Jiang
authors.affiliation: Department of Geosciences, University of Wisconsin - Parkside, 900 Wood Road, Kenosha, WI 53144, USA. Electronic address: li@uwp.edu.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Public Health, College of Health Care and Management, Chung Shan Medical University, No. 110, Sec. 1, Chien-kuo N Road, Taichung 40242, Taiwan.
authors.forename: Chung-Yih
authors.initials: CY
authors.lastname: Kuo
authors.affiliation: Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan.
authors.forename: Jiin-Shuh
authors.initials: JS
authors.lastname: Jean
authors.affiliation: Department of Environmental Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan.
authors.forename: Wan-Ru
authors.initials: WR
authors.lastname: Chen
authors.affiliation: School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China.
authors.forename: Guocheng
authors.initials: G
authors.lastname: Lv
mesh_terms: D000327:Adsorption; D000639:Amitriptyline / Q000737:chemistry* / Q000302:isolation & purification; D001546:Bentonite / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D002412:Cations; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D012989:Soil Pollutants / Q000737:chemistry* / Q000302:isolation & purification; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods*
chemical_list: D002412:Cations; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D001546:Bentonite; D000639:Amitriptyline; D002118:Calcium
keywords: Amitriptyline; Cation exchange; FTIR; Intercalation; Montmorillonite; Sorption