title: Effective adsorption of hexavalent chromium through a three center (3c) co-operative interaction with an ionic liquid and biopolymer.
abstract: Biopolymers as well as ionic liquids are known for their potential applications. In this work, we report the utility of chitosan as an excellent platform for impregnating the ionic liquid, tetraoctylammonium bromide by ultrasonication and its subsequent adsorption for chromium(VI). The effective mass transfer due to sonication coupled with the hydrogen bonding interaction between chitosan-ionic liquid and the electrostatic interaction involving the amino groups in chitosan and hexavalent chromium governs this three center (3c) co-operative mechanism. The adsorption followed a pseudo second order kinetics with a Langmuir adsorption capacity of 63.69 mg g(-1). Various isotherm models were used to correlate the experimental data and the adsorption process is exothermic with a decreased randomness at the solid-solution interface. The thermodynamics of the spontaneous adsorption process could be explained through a positive co-operative effect between the host (chitosan) and the guest (ionic liquid). The adsorbed chromium(VI) could be converted to ammonium chromate using ammonium hydroxide, thereby regenerating the adsorbent. The method could be translated into action in the form of practical application to a real sample containing chromium.
authors.affiliation: Department of Chemistry, Birla Institute of Technology and Science, Pilani-Hyderabad Campus, Jawahar Nagar, Shameerpet Mandal, R.R. Dist, 500 078 AP, India.
authors.forename: A Santhana
authors.initials: AS
authors.lastname: Krishna Kumar
authors.forename: Timsi
authors.initials: T
authors.lastname: Gupta
authors.forename: Shruti Singh
authors.initials: SS
authors.lastname: Kakan
authors.forename: S
authors.initials: S
authors.lastname: Kalidhasan
authors.lastname: Manasi
authors.forename: Vidya
authors.initials: V
authors.lastname: Rajesh
authors.forename: N
authors.initials: N
authors.lastname: Rajesh
mesh_terms: D000327:Adsorption; D048271:Chitosan / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D052578:Ionic Liquids; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; C520892:tetraoctylammonium bromide; D048271:Chitosan