title: Comparison and evaluation of five types of imidazole-modified silica adsorbents for the removal of 2,4-dinitrophenol from water samples with the methyl group at different positions of imidazolium ring.
abstract: The objective of this work was to improve the understanding the influence of the methyl group at different positions of imidazolium ring on the adsorption behaviors of imidazole-modified silica adsorbents. Five adsorbents named as SilprImCl, SilprM₁ImCl, SilprM₂ImCl, SilprM₄ImCl and SilprM₁M₂ImCl were synthesized using imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 1,2-dimethylimidazole, respectively. These adsorbents were characterized by scanning electron microscope, infrared spectra, thermogravimetric analysis, elemental analysis and BET analysis. Firstly, phenol, 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) were used as adsorbates to investigate the selectivity of SilprImCl and its adsorption capacities followed the order of 2,4-DNP≫4-NP>2-NP≫3-NP>phenol. Therefore, 2,4-DNP was used to investigate the adsorption behaviors of the five adsorbents. It was inferred that the adsorbents are of primary anion-exchange and electrostatic nature. The electrostatic nature was affected significantly by the methyl group at different positions of imidazolium ring. The adsorbed amounts of 2,4-DNP decreased in the order of: SilprM₁M₂ImCl≈SilprM₁ImCl>SilprM4ImCl>SilprM₂ImCl>SilprImCl. The adsorption-elution experiments indicated that 2,4-DNP can be removed from aqueous solutions by a SilprM₄ImCl packed column and the recovery of 91.6% was obtained. The adsorbent could be regenerated and reused ten times at least by simple washings with HCl and water in turn.
authors.affiliation: School of Chemistry and Environmental Science, Henan Normal University, Henan Key Laboratory for Environmental Pollution Control, Key Laboratory for Yellow River and Huai River Water Environment and Pollution Control, Ministry of Education, Xinxiang 453007, China. wzk@htu.cn
authors.forename: Zhike
authors.initials: Z
authors.lastname: Wang
authors.forename: Cunling
authors.initials: C
authors.lastname: Ye
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Heping
authors.initials: H
authors.lastname: Wang
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
mesh_terms: D019297:2,4-Dinitrophenol / Q000032:analysis* / Q000737:chemistry; D000327:Adsorption; D002852:Chromatography, Ion Exchange; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D012822:Silicon Dioxide / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013696:Temperature; D013818:Thermogravimetry; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D018508:Water Purification / Q000379:methods
chemical_list: D007093:Imidazoles; D007477:Ions; D014874:Water Pollutants, Chemical; D014867:Water; D012822:Silicon Dioxide; D019297:2,4-Dinitrophenol; D006851:Hydrochloric Acid
keywords: 2,4-Dinitrophenol; Adsorption; Ionic liquid; Silica