title: Adsorption of toxic metal ion Cr(VI) from aqueous state by TiO2-MCM-41: equilibrium and kinetic studies.
abstract: This paper deals with the immobilization of various weight percentage of TiO(2) on mesoporous MCM-41, characterization of the materials by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier Transform Infrared (FTIR) analysis, UV-vis diffuse reflectance spectroscopy (DRS) and evaluation of the adsorption capacity toward Cr(VI) removal. It is found that the MCM-41 structure retained after loading of TiO(2) but the surface area and pore diameter decreased due to pore blockage. Adsorption of Cr(VI) from aqueous state was investigated on TiO(2)-MCM-41 by changing various parameters such as pH, metal ion concentration, and the temperature. When TiO(2) loading was more than 20 wt.%, the adsorption activity (25)TiO(2)-MCM-41 reduced significantly due to considerable decrease in the surface area. It is also observed that TiO(2) and neat MCM-41 exhibits very less Cr(VI) adsorption compared to TiO(2)-MCM-41. The adsorption of Cr(VI) onto (20)TiO(2)-MCM-41 at pH~5.5 and temperature 323 K was 91% at 100mg/L Cr(VI) metal ion concentration in 80 min. The experimental data fitted well to Langmuir and Freundlich isotherms. The adsorption of Cr(VI) on TiO(2)-MCM-41 followed a second order kinetics with higher values of intra-particle diffusion rate. Thermodynamic parameters suggested that the adsorption process is endothermic in nature and desorption studies indicated a chemisorption mode.
authors.affiliation: Colloids and Material Chemistry Department, Institute of Minerals and Materials Technology (CSIR), Bhubaneswar 751013, Odisha, India. paridakulamani@yahoo.com
authors.forename: Kulamani
authors.initials: K
authors.lastname: Parida
authors.forename: Krushna Gopal
authors.initials: KG
authors.lastname: Mishra
authors.forename: Suresh Kumar
authors.initials: SK
authors.lastname: Dash
mesh_terms: D000327:Adsorption; D002857:Chromium / Q000302:isolation & purification* / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008962:Models, Theoretical; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013816:Thermodynamics; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000633:toxicity; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: C509968:MCM-41; C507641:TiO2-SiO2; D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D012822:Silicon Dioxide; D014025:Titanium